correl.github.io/blog.org

#+STARTUP: indent inlineimages hideblocks
#+HUGO_BASE_DIR: .
#+HUGO_SECTION: blog
#+OPTIONS: toc:nil num:nil todo:nil d:(not "HIDDEN")
#+PROPERTY: header-args :cache yes :eval never-export :output-dir static/ox-hugo/
#+COLUMNS: %TODO %50ITEM %CLOSED %EXPORT_FILE_NAME %CATEGORY %TAGS
#+LINK: relref file:{{< relref "%s.md" >}}

* DONE Potatoes and Portal Guns                                      :gaming:
CLOSED: [2011-04-26 Tue]
:PROPERTIES:
:EXPORT_FILE_NAME: potatoes-and-portal-guns
:END:

#+begin_export markdown
[<img src="/images/portal_2_logo-150x150.jpg" alt="Portal 2 Logo" title="Portal 2 Logo" width="150" height="150" style="float: right" />](/images/portal_2_logo.jpg) Got my hands on Portal 2 and finished a run through the single player campaign. Was a *lot* of fun, the characters were bursting with humor and personality. Just like the first game, it was hard to stop playing. *Unlike* the first game, it's got some length, so I stayed up late a couple nights with my eyes glued to the television. I already want to play through it again to find any little things I my tired eyes may have missed.

I'm itching to give co-op a try, so if you happen to have it on xbox or care to drop by, let me know.

**Update:** Played some co-op with Jen, had fun navigating puzzles together :)
#+end_export
* DONE Meh.php                                                  :programming:
CLOSED: [2011-04-27 Wed 00:00]
:PROPERTIES:
:EXPORT_FILE_NAME: meh-php
:END:
#+begin_export markdown
```php
<?php
if (!defined('meh')) define('meh', null);

class Meh {
    public function __set($name, $value) {
    }
    public function __get($name) {
        return meh;
    }
    public function __isset($name) {
        return true || false;
    }
    public function __unset($name) {
    }
    public function __call($name, $arguments) {
        return meh;
    }
    public function __callStatic($name, $arguments) {
        return meh;
    }
}

$bwuh = new Meh();
$bwuh->give_a_shit();
echo $bwuh->concerns;

class SuperDuperBillingProcessor extends Meh {}

$p = new SuperDuperBillingProcessor();
$p->calculateEverything();
$p->profit();
```
#+end_export


* DONE Transmission, RSS, and XBMC                       :programming:python:
CLOSED: [2011-04-27 Wed 00:01]
:PROPERTIES:
:EXPORT_FILE_NAME: transmission-rss-and-xbmc
:END:

#+begin_export markdown
I'm a huge fan of [XBMC](http://www.xbmc.org/). My pc (currently running Ubuntu 10.04) has taken root in my
living room, piping all my movies and tv shows straight to my HDTV.

While my pc is set up as a DVR using [MythTV](http://www.mythtv.org) to record shows off my FIOS box, it tends to be a little unreliable, which can suck when it's time to catch up on Daily Show and Colbert episodes.
I've had [Transmission](http://www.transmissionbt.com/) set up for a while for all my torrenting needs, and
I've even written an [XBMC script to manage torrents](https://github.com/correl/Transmission-XBMC), so I got to looking for
tools to track tv show torrent rss feeds.

<!--more-->

My first stop was [TED](http://ted.nu/). TED worked well enough, but would occasionally hang.
Since it's a GUI java app running in the taskbar, it would require me to dig
out my mouse and break out of full screen XBMC to fiddle with it. I eventually
got tired of dealing with TED and went back to prodding Myth.

Recently I've been itching to reliably watch my shows again, so I checked around
for a simple command-line utility to track rss feeds and download torrents.
Finding none, I loaded up vim and threw together a python script to handle it
all for me.

I also have another, simple script from when I was using TED (or just manually
downloading shows) which looks at completed torrents, compares their names with
the folders in my TV directory, and moves the shows into them for XBMC to see.

A couple cron jobs and a few rss feeds later, and I've got all my shows
automatically delivered straight to XBMC for my lazy evening viewing pleasure.

### trss.py
[Download](https://github.com/correl/trss/raw/master/trss.py)

```
Usage:
    trss.py add <rss-url> [<recent-items>]
        Adds an RSS feed to follow
        rss-url:        Full URL to the RSS feed
        recent-items:   (Optional) number of recent items to queue
                        for downloading
    trss.py remove <index>
        Remove an RSS feed
        index:          Numeric index of the feed to remove as
                        reported by the list command
    trss.py list
        Displays a list of followed feeds

    trss.py download
        Fetch all feeds and download new items

    trss.py set [<setting> [<value>]]
        Set or view configuration settings
        Call without any arguments to list all settings and their values
        Call with a setting and no value to see the current value for that setting

        Currently, the only used setting is 'download_dir', which allows you to set
        a directory to store all retrieved torrents, such as a directory your
        torrent application watches for new downloads. If 'download_dir' is not set,
        the current directory will be used.
```

### transmission-tv.py
```python
#!/usr/bin/python
import os
import re

import transmissionrpc

TV_PATH = '/media/Gaia/Video/TV/'

class TVShowCollection:
	def __init__(self, path):
		self.path = path
		self.shows = os.listdir(path)
		self.patterns = [[s.lower().replace(' ', '.?'), s] for s in sorted(self.shows, key=len, reverse=True)]
	def match(self, filename):
		for pattern, show in self.patterns:
			if re.findall(pattern, filename.lower()):
				return show
		return None

def move(self, ids, location):
	"""Move torrent data to the new location."""
	self._rpc_version_warning(6)
	args = {'location': location, 'move': True}
	self._request('torrent-set-location', args, ids, True)

if float(transmissionrpc.__version__) < 0.4:
	# The move function is not present in versions 0.3 and older
	transmissionrpc.Client.move = move

collection = TVShowCollection(TV_PATH)
client = transmissionrpc.Client()

torrents = client.info()
for i, torrent in torrents.iteritems():
	status = torrent.status
	if status not in ['seeding', 'stopped']:
		continue
	show = collection.match(torrent.name)
	if show is None:
		continue
	path = '{0}{1}/'.format(TV_PATH, show)
	if torrent.downloadDir.startswith(path):
		continue
	print 'Found {0} torrent \'{1}\' in show \'{2}\', moving...'.format(status, torrent.name, show)
	result = client.move(i, path)
	if status == 'seeding':
		print 'Re-starting torrent to continue seeding'
		client.start(i)
```
#+end_export
* DONE Learning Functional Programming, Part One         :programming:python:
CLOSED: [2012-04-09 Mon]
:PROPERTIES:
:EXPORT_FILE_NAME: learning-functional-programming-part-one
:END:
#+begin_export markdown
## Part One: Lambdas? In my Python?

Over the past few months, I've decided to take a stab at learning some
functional programming. I'd been doing python for a few years (and
completely falling in love with it), and so I'd been exposed to a few
functional concepts it offers - primarily higher-order functions and list
comprehensions, both of which allow for very clear, concise and powerful code.
Since that's where I started my journey, that's where my post will begin as
well.

<!--more-->

### Functions are objects, too

Having graduated to python from PHP and C/C++, perhaps the biggest new thing to
wrap my head around (besides readable code, whitespace-as-syntax,
[programming being fun again](http://xkcd.com/353/), and all that), is that in
python, functions (and classes!) are objects, just like anything else. They
can still be defined in the usual way, but they can also be assigned, passed
as arguments, even modified and replaced like any other value or object in your
program. 

```python
def do_a():
    print "Doing something"

do_b = do_a

do_b()

# Prints "Doing something"
```

Functions themselves no longer require formal definitions, either, they can be
created *[anonymously](http://en.wikipedia.org/wiki/Anonymous_function)*:

```python
my_send = lambda person, thing: send(person.upper(), thing, subject="Check this out!")
ucase_people = map(lambda name: name.upper(), ["Joe", "Mary", "Zach"])
```


### Abstracting behaviour

You'll find you can now start abstracting away common idioms. For
example, you probably very often find yourself looping over some list of items,
performing some set of actions on them, or passing them to some other function
or method:

```python
people = ["Joe", "Chris", "Matt", "Jennifer"]
for person in people:
    u_person = person.upper()
    send(person, super_fun_thing)
```

Instead of that, you could have a function that takes a list as one argument,
and a function to apply to each item in it as another:

```python
def dostuff(action, things):
    result = []
    for thing in things:
        result.append(action(thing))
    return result

dostuff(send, people)
```

The above example is actually just a simple definition of one of the most
common higher-order functions,
[map](http://docs.python.org/library/functions.html#map), which python already
provides for you. Another particularly useful higher-order function is
[filter](http://docs.python.org/library/functions.html#filter) which, given a
function that returns true of false if its criteria are met by the passed item,
will return the subset of the passed list that satisfy the filtering function:

```python
stuff = ["My notes.txt", "Matt's notes.txt",  "My music.pls"]
my_stuff = filter(lambda s: s.startswith("My "), stuff)

# my_stuff = ["My notes.txt", "My music.pls"]
```

[List comprehensions](http://docs.python.org/tutorial/datastructures.html#list-comprehensions)
provide a cleaner, easier to read way to perform mapping and/or filtering on a
list:

```python
stuff = ["My notes.txt", "Matt's notes.txt",  "My music.pls"]

my_stuff = [file for file in stuff if file.startswith("My ")]
# ["My notes.txt", "My music.pls"]

upper_stuff = [file.upper() for file in stuff]
# ["MY NOTES.TXT", "MATT'S NOTES.TXT", "MY MUSIC.PLS"]

music = [file.upper() for file in stuff if file.endswith(".pls")]
# ["MY MUSIC.PLS"]
```


### Tip of the iceberg

This is just a very small taste of functional programming concepts. Later, I'll
introduce a couple of functional languages, and explain what sets them apart
from object-oriented and imperative programming languages.
#+end_export
* DONE Erlang: The Movie                                 :programming:erlang:
CLOSED: [2013-11-27 Wed]
:PROPERTIES:
:EXPORT_FILE_NAME: erlang-the-movie
:END:

#+begin_export markdown
Hopping through [Joe Armstrong's blog](http://joearms.github.io/), I happened across Erlang: The Movie.
More programming languages need videos like this.

<iframe width="420" height="315" src="//www.youtube.com/embed/xrIjfIjssLE" frameborder="0" allowfullscreen></iframe>
#+end_export
* DONE Getting Organized with Org Mode           :emacs:org_mode:git:graphviz:
CLOSED: [2014-11-25 Tue]
:PROPERTIES:
:EXPORT_FILE_NAME: getting-organized-with-org-mode
:END:

#+begin_export markdown
<img src="/images/org-mode-unicorn-logo.png" alt="Org Mode logo" style="float: right" />
#+end_export

I've been using Emacs Org mode for nearly a year now. For a while I
mostly just used it to take and organize notes, but over time I've
discovered it's an incredibly useful tool for managing projects and
tasks, writing and publishing documents, keeping track of time and
todo lists, and maintaining a journal.

** Project Management
Most of what I've been using [[http://orgmode.org/][Org mode]] for has been breaking down large
projects at work into tasks and subtasks. It's really easy to enter
projects in as a hierarchy of tasks and task groupings. Using
[[http://orgmode.org/worg/org-tutorials/org-column-view-tutorial.html][Column View]], I was able to dive right into scoping them individually
and reporting total estimates for each major segment of work.

#+ATTR_HTML: :alt Example projects org file
[[file:static/images/emacs-projects.png]]

Because Org Mode makes building and modifying an outline structure
like this so quick and easy, I usually build and modify the project
org document while planning it out with my team. Once done, I then
manually load that information into our issue tracker and get
underway. Occasionally I'll also update tags and progress status in
the org document as well as the project progresses, so I can use the
same document to plan subsequent development iterations.
** Organizing Notes and Code Exercises
More recently, I've been looking into various ways to get more
things organized with Org mode. I've been stepping through
[[http://sarabander.github.io/sicp/][Structure and Interpretation of Computer Programs]] with some other
folks from work, and discovered that Org mode was an ideal fit for
keeping my notes and exercise work together. The latter is neatly
managed by [[http://orgmode.org/worg/org-contrib/babel/intro.html][Babel]], which let me embed and edit source examples and
my excercise solutions right in the org document itself, and even
export them to one or more scheme files to load into my
interpreter.
** Exporting and Publishing Documents
Publishing my notes with org is also a breeze. I've published
project plans and proposals to PDF to share with colleagues, and
exported my [[https://github.com/correl/sicp][SICP notes]] to html and [[http://sicp.phoenixinquis.net/][dropped them into a site]] built
with [[http://jekyllrb.com/][Jekyll]]. Embedding graphs and diagrams into exported documents
using [[http://www.graphviz.org/][Graphviz]], [[http://www.mcternan.me.uk/mscgen/][Mscgen]], and [[http://plantuml.sourceforge.net/][PlantUML]] has also really helped with
putting together some great project plans and documentation. A lot of
great examples using those tools (and more!) can be found [[http://home.fnal.gov/~neilsen/notebook/orgExamples/org-examples.html][here]].
** Emacs Configuration
While learning all the cool things I could do with Org mode and Babel,
it was only natural I'd end up using it to reorganize my [[https://github.com/correl/dotfiles/tree/master/.emacs.d][Emacs
configuration]]. Up until that point, I'd been managing my configuration
in a single init.el file, plus a directory full of mode or
purpose-specific elisp files that I'd loop through and load. Inspired
primarily by the blog post, [[http://zeekat.nl/articles/making-emacs-work-for-me.html]["Making Emacs Work For Me"]], and later by
others such as [[http://pages.sachachua.com/.emacs.d/Sacha.html][Sacha Chua's Emacs configuration]], I got all my configs
neatly organized into a single org file that gets loaded on
startup. I've found it makes it far easier to keep track of what I've
got configured, and gives me a reason to document and organize things
neatly now that it's living a double life as a [[https://github.com/correl/dotfiles/blob/master/.emacs.d/emacs.org][published document]] on
GitHub. I've still got a directory lying around with autoloaded
scripts, but now it's simply reserved for [[https://github.com/correl/dotfiles/blob/master/.emacs.d/emacs.org#auto-loading-elisp-files][tinkering and sensitive
configuration]].
** Tracking Habits
Another great feature of Org mode that I've been taking advantage
of a lot more lately is the [[http://orgmode.org/manual/Agenda-Views.html][Agenda]]. By defining some org files as
being agenda files, Org mode can examine these files for TODO
entries, scheduled tasks, deadlines and more to build out useful
agenda views to get a quick handle on what needs to be done and
when. While at first I started by simply syncing down my google
calendars as org-files (using [[http://orgmode.org/worg/code/awk/ical2org.awk][ical2org.awk]]), I've started
managing TODO lists in a dedicated org file. By adding tasks to
this file, scheduling them, and setting deadlines, I've been doing
a much better job of keeping track of things I need to get done
and (even more importantly) /when/ I need to get them done.

#+ATTR_HTML: :alt Agenda view snippet
[[file:static/images/emacs-org-agenda.png]]

This works not only for one-shot tasks, but also [[http://orgmode.org/manual/Tracking-your-habits.html][habits and other
repetitive tasks]]. It's possible to schedule a task that should be
done every day, every few days, or maybe every first sunday of a
month. For example, I've set up repeating tasks to write a blog
post at least once a month, practice guitar every two to three
days, and to do the dishes every one or two days. The agenda view
can even show a small, colorized graph next to each repeating task
that paints a picture of how well (or not!) I've been getting
those tasks done on time.
** Keeping a Journal and Tracking Work
The last thing I've been using (which I'm still getting a handle
on) is using [[http://orgmode.org/manual/Capture.html][Capture]] to take and store notes, keep a journal, and
even [[http://orgmode.org/manual/Clocking-work-time.html][track time on tasks at work]].

#+BEGIN_SRC emacs-lisp :exports code
  (setq org-capture-templates
        '(("j" "Journal Entry" plain
           (file+datetree "~/org/journal.org")
           "%U\n\n%?" :empty-lines-before 1)
          ("w" "Log Work Task" entry
           (file+datetree "~/org/worklog.org")
           "* TODO %^{Description}  %^g\n%?\n\nAdded: %U"
           :clock-in t
           :clock-keep t)))

  (global-set-key (kbd "C-c c") 'org-capture)

  (setq org-clock-persist 'history)
  (org-clock-persistence-insinuate)
#+END_SRC

For my journal, I've configured a capture template that I can use
to write down a new entry that will be stored with a time stamp
appended into its own org file, organized under headlines by year,
month and date.

For work tasks, I have another capture template configured that
will log and tag a task into another org file, also organized by
date, which will automatically start tracking time for that
task. Once done, I can simply clock out and check the time I've
spent, and can easily find it later to clock in again, add notes,
or update its status. This helps me keep track of what I've gotten
done during the day, keep notes on what I was doing at any point
in time, and get a better idea of how long it takes me to do
different types of tasks.
** Conclusion
There's a lot that can be done with Org mode, and I've only just
scratched the surface. The simple outline format provided by Org mode
lends itself to doing all sorts of things, be it organizing notes,
keeping a private or work journal, or writing a book or technical
document. I've even written this blog post in Org mode! There's tons
of functionality that can be built on top of it, yet the underlying
format itself remains simple and easy to work with. I've never been
great at keeping myself organized, but Org mode is such a delight to
use that I can't help trying anyway. If it can work for me, maybe it
can work for you, too!

There's tons of resources for finding new ways for using Org mode, and
I'm still discovering cool things I can track and integrate with it. I
definitely recommend reading through [[http://sachachua.com/blog/][Sacha Chua's Blog]], as well as
posts from [[http://newartisans.com/2007/08/using-org-mode-as-a-day-planner/][John Wiegley]]. I'm always looking for more stuff to try
out. Feel free to drop me a line if you find or are using something
you think is cool or useful!

* DONE Adventuring Through SICP                            :programming:lisp:
CLOSED: [2015-01-01 Thu]
:PROPERTIES:
:EXPORT_FILE_NAME: sicp
:END:

Back in May, a coworker and I got the idea to start up a little
seminar after work every couple of weeks with the plan to set aside
some time to learn and discuss new ideas together, along with anyone
else who cared to join us.

** Learning Together
  Over the past several months, we've read our way through the first
  three chapters of the book, watched the [[http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-001-structure-and-interpretation-of-computer-programs-spring-2005/video-lectures/][related video lectures]], and
  did (most of) the exercises.
  
  Aside from being a great excuse to unwind with friends after work
  (which it is!), it's proved to be a great way to get through the
  material. Doing a section of a chapter every couple of weeks is an
  easy goal to meet, and meeting up to discuss it becomes something to
  look forward to. We all get to enjoy a sense of accomplishment in
  learning stuff that can be daunting or difficult to set aside time for
  alone.
  
  The best part, by far, is getting different perspectives on the
  material. Most of my learning tends to be solitary, so it's refreshing
  to do it with a group. By reviewing the different concepts together,
  we're able to gain insights and clarity we'd never manage on our
  own. Even the simplest topics can spur interesting conversations.

** SICP
Our first adventure together so far has been the venerable [[http://mitpress.mit.edu/sicp/][Structure
and Interpretation of Computer Programs]]. This book had been on my todo
list for a long time, but never quite bubbled to the top. I'm glad to
have the opportunity to go through it in this format, since there's
plenty of time to let really get into the excercises and let the
lessons sink in.

SICP was originally an introductory textbook for MIT computer
programming courses. What sets it apart from most, though, is that it
doesn't focus so much on learning a particular programming language
(while the book does use and cover MIT Scheme) as it does on
identifying and abstracting out patterns common to most programming
problems. Because of that, the book is every bit as useful and
illuminating as ever, especially now that functional paradigms are
re-entering the spotlight and means of abstracting and composing
systems are as important as ever.

** What's next?
We've still got plenty of SICP left to get through. We've only just
gotten through Chapter 4, section 1, which has us building a scheme
interpreter *in* scheme, so there's plenty of fun left to be had
there.

We're also staring to do some smaller, lunchtime review meetings
following the evening discussions to catch up the folks that can't
make it. I may also try sneaking in some smaller material, like
interesting blog posts, to keep things lively.

----------------------------------------------------------------------

If anyone's interested, I have the exercise work along with some notes
taken during the meetings [[http://sicp.phoenixinquis.net/][hosted online]]. I apologize for the lack of
notes early on, I've been trying to get better at capturing memorable
excerpts and conversation topics recently. I may have to put some more
posts together later on summarizing what we discussed for each
chapter; if and when I do, they'll be posted on the [[http://extreme-tech-seminar.github.io/][seminar website]].

* DONE Coders at Work                                     :programming:books:
CLOSED: [2015-01-28 Wed]
:PROPERTIES:
:EXPORT_FILE_NAME: coders-at-work
:END:
# Gather highlights from the book and write a post summarizing my
# thoughts on it, and what I took away from it.

A few days before leaving work for a week and a half of flying and
cruising to escape frigid Pennsylvania, I came across a [[armstrong-oop][Joe Armstrong
quote]] during my regularly scheduled slacking off on twitter and Hacker
News. I'd come across a couple times before, only this time I noticed
it had a source link. This led me to discovering (and shortly
thereafter, buying) Peter Seibel's "[[http://www.codersatwork.com/][Coders at Work -- Reflections on
the Craft of Programming]]". I loaded it onto my nook, and off I went.

The book is essentially a collection of interviews with a series of
highly accomplished software developers. Each of them has their own
fascinating insights into the craft and its rich history.

While making my way through the book, I highlighted some excerpts
that, for one reason or another, resonated with me. I've organized and
elaborated on them below.

** DONE Incremental Changes
CLOSED: [2015-01-20 Tue 20:59]
<<fitzpatrick-increments>>
#+BEGIN_QUOTE
I've seen young programmers say, "Oh, shit, it doesn't work," and then
rewrite it all. Stop. Try to figure out what's going on. *Learn how to
write things incrementally so that at each stage you could verify it.*\\
-- Brad Fitzpatrick
#+END_QUOTE

I can remember doing this to myself when I was still relatively new to
coding (and even worse, before I discovered source control!). Some
subroutine or other would be misbehaving, and rather than picking it
apart and figuring out what it was I'd done wrong, I'd just blow it
away and attempt to write it fresh. While I /might/ be successful,
that likely depended on the issue being some sort of typo or missed
logic; if it was broken because I misunderstood something or had a bad
plan to begin with, rewriting it would only result in more broken
code, sometimes in more or different ways than before. I don't think
I've ever rewritten someone else's code without first at least getting
a firm understanding of it and what it was trying to accomplish, but
even then, breaking down changes piece by piece makes it all the
easier to maintain sanity.

I do still sometimes catch myself doing too much at once when building
a new feature or fixing a bug. I may have to fix a separate bug that's
in my way, or I may have to make several different changes in various
parts of the code. If I'm not careful, things can get out of hand
pretty quickly, and before I know it I have a blob of changes strewn
across the codebase in my working directory without a clear picture of
what's what. If something goes wrong, it can be pretty tough to sort
out which change broke things (or fixed them). Committing changes
often helps tremendously to avoid this sort of situation, and when I
catch myself going off the rails I try to find a stopping point and
split changes up into commits as soon as possible to regain
control. Related changes and fixes can always be squashed together
afterwards to keep things tidy.

** DONE Specifications & Documentation
CLOSED: [2015-01-20 Tue 20:59]
<<bloch-customers>>
#+BEGIN_QUOTE
*Many customers won't tell you a problem; they'll tell you a
solution.* A customer might say, for instance, "I need you to add
support for the following 17 attributes to this system. Then you have
to ask, 'Why? What are you going to do with the system? How do you
expect it to evolve?'" And so on. You go back and forth until you
figure out what all the customer really needs the software to
do. These are the use cases.\\
-- Joshua Bloch
#+END_QUOTE

Whether your customer is your customer, or your CEO, the point stands:
customers are /really bad/ at expressing what they want. It's hard to
blame them, though; analyzing what you really want and distilling it
into a clear specification is tough work. If your customer is your
boss, it can be intimidating to push back with questions like "Why?",
but if you can get those questions answered you'll end up with a
better product, a better /understanding/ of the product, and a happy
customer. The agile process of doing quick iterations to get tangible
results in front of them is a great way of getting the feedback and
answers you need.

<<armstrong-documentation>>
#+BEGIN_QUOTE
The code shows me what it /does/. It doesn't show me what it's
supposed to do. I think the code is the answer to a problem.
*If you don't have the spec or you don't have any documentation, you have to guess what the problem is from the answer. You might guess wrong.*\\
-- Joe Armstrong
#+END_QUOTE

Once you've got the definition of what you've got to build and how
it's got to work, it's extremely important that you get it
documented. Too often, I'm faced with code that's doing something in
some way that somebody, either a customer or a developer reading it,
takes issue with, and there's no documentation anywhere on why it's
doing what it's doing. What happens next is anybody's guess. Code
that's clear and conveys its intent is a good start towards avoiding
this sort of situation. Comments explaining intent help too, though
making sure they're kept up to date with the code can be
challenging. At the very least, I try to promote useful commit
messages explaining what the purpose of a change is, and reference a
ticket in our issue tracker which (hopefully) has a clear accounting
of the feature or bugfix that prompted it.
** DONE Pair Programming
CLOSED: [2015-01-20 Tue 21:03]
<<armstrong-pairing>>
#+BEGIN_QUOTE
... *if you don't know what you're doing then I think it can be very
helpful with someone who also doesn't know what they're doing.* If you
have one programmer who's better than the other one, then there's
probably benefit for the weaker programmer or the less-experienced
programmer to observe the other one. They're going to learn something
from that. But if the gap's too great then they won't learn, they'll
just sit there feeling stupid.\\
-- Joe Armstrong
#+END_QUOTE

Pairing isn't something I do much. At least, it's pretty rare that I
have someone sitting next to me as I code. I *do* involve peers while
I'm figuring out what I want to build as often as I can. The tougher
the problem, the more important it is, I think, to get as much
feedback and brainstorming in as possible. This way, everybody gets to
tackle the problem and learn together, and anyone's input, however
small it might seem, can be the key to the "a-ha" moment to figuring
out a solution.

** DONE Peer Review
CLOSED: [2015-01-25 Sun 22:44]
<<crockford-reading>>
#+BEGIN_QUOTE
*I think an hour of code reading is worth two weeks of QA.* It's just
a really effective way of removing errors. If you have someone who is
strong reading, then the novices around them are going to learn a lot
that they wouldn't be learning otherwise, and if you have a novice
reading, he's going to get a lot of really good advice.\\
-- Douglas Crockford
#+END_QUOTE

Just as important as designing the software as a team, I think, is
reviewing it as a team. In doing so, each member of the team has an
opportunity to understand /how/ the system has been implemented, and
to offer their suggestions and constructive criticisms. This helps the
team grow together, and results in a higher quality of code overall.
This benefits QA as well as the developers themselves for the next
time they find themselves in that particular bit of the system.
** DONE Object-Oriented Programming
CLOSED: [2015-01-20 Tue 20:59]
<<armstrong-oop>>
#+BEGIN_QUOTE
I think the lack of reusability comes in object-oriented languages,
not in functional languages.
*Because the problem with object-oriented languages is they've got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle.*\\
-- Joe Armstrong
#+END_QUOTE

A lot has been written on why OOP isn't the great thing it claims to
be, or was ever intended to be. Having grappled with it myself for
years, attempting to find ways to keep my code clean, concise and
extensible, I've more or less come to the same conclusion as Armstrong
in that coupling data structures with behaviour makes for a terrible
mess. Dividing the two led to a sort of moment of clarity; there was
no more confusion about what methods belong on what object. There was
simply the data, and the methods that act on it. I am still struggling
a bit, though, on how to bring this mindset to the PHP I maintain at
work. The language seems particularly ill-suited to managing complex
data structures (or even simple ones -- vectors and hashes are
bizarrely intertwined).
** DONE Writing
CLOSED: [2015-01-28 Wed 22:42]
<<bloch-writing>>
#+BEGIN_QUOTE
You should read /[Elements of Style]/ for two reasons: The first is
that a large part of every software engineer's job is writing
prose. *If you can't write precise, coherent, readable specs, nobody
is going to be able to use your stuff.* So anything that improves your
prose style is good. The second reason is that most of the ideas in
that book are also applicable to programs.\\
-- Joshua Bloch
#+END_QUOTE

<<crockford-writing>>
#+BEGIN_QUOTE
*My advice to everybody is pretty much the same, to read and write.*\\
...\\
Are you a good Java programmer, a good C programmer, or whatever? I
don't care. I just want to know that you know how to put an algorithm
together, you understand data structures, and you know how to document
it.\\
-- Douglas Crockford
#+END_QUOTE

<<knuth-writing>>
#+BEGIN_QUOTE
This is what literate programming is so great for --\\
*I can talk to myself. I can read my program a year later and know
exactly what I was thinking.*\\
-- Donald Knuth
#+END_QUOTE

The more I've program professionally, the clearer it is that writing
(and communication in general) is a very important skill to
develop. Whether it be writing documentation, putting together a
project plan, or whiteboarding and discussing something, clear and
concise communication skills are a must. Clarity in writing translates
into clarity in coding as well, in my opinion. Code that is short, to
the point, clear in its intention, making good use of structure and
wording (in the form of function and variable names) is far easier to
read and reason about than code that is disorganized and obtuse.
** DONE Knuth
CLOSED: [2015-01-28 Wed 22:42]
<<crockford-knuth>>
#+BEGIN_QUOTE
I tried to make familiarity with Knuth a hiring criteria, and I was
disappointed that I couldn't find enough people that had read him. In
my view,
*anybody who calls himself a professional programmer should have read
Knuth's books or at least should have copies of his books.*\\
-- Douglas Crockford
#+END_QUOTE

<<steele-knuth>>
#+BEGIN_QUOTE
... Knuth is really good at telling a story about code. When you read
your way through /The Art of Computer Programming/ and you read your
way through an algorithm, he's explained it to you and showed you some
applications and given you some exercises to work, and *you feel like
you've been led on a worthwhile journey.*\\
-- Guy Steele
#+END_QUOTE

<<norvig-knuth>>
#+BEGIN_QUOTE
At one point I had /[The Art of Computer Programming]/ as my monitor
stand because it was one of the biggest set of books I had, and it was
just the right height. That was nice because it was always there, and
I guess then I was more prone to use it as a reference because it was
right in front of me.\\
-- Peter Norvig
#+END_QUOTE

I haven't read any of Knuth's books yet, which is something I'll have
to rectify soon. I don't think I have the mathematical background
necessary to get through some of his stuff, but I expect it will be
rewarding nonetheless. I'm also intrigued by his concept of literate
programming, and I'm curious to learn more about TeX. I imagine I'll
be skimming through [[http://brokestream.com/tex-web.html][TeX: The Program]] pretty soon now that I've
finished Coders at Work :)

* DONE Birthday Puzzle                                   :programming:prolog:
CLOSED: [2015-04-18 Sat]
:PROPERTIES:
:header-args:prolog: :system swipl :session *birthday* :goal true :exports both
:EXPORT_FILE_NAME: birthday-puzzle
:END:

This logic puzzle has been floating around the internet lately. When I
caught wind of it, I thought it would be a great exercise to tackle
using Prolog. I'm not especially good with the language yet, so it
added to the challenge a bit, but it was a pretty worthwhile
undertaking. When I got stumped, I discovered that mapping out the
birthdays into a grid helped me visualize the problem and ultimately
solve it, so I've included that with my prolog code so you can see how
I arrived at the answer.

** The Puzzle
  Albert and Bernard have just met Cheryl. “When is your birthday?”
  Albert asked Cheryl. Cheryl thought for a moment and said, “I won’t
  tell you, but I’ll give you some clues”. She wrote down a list of
  ten dates:


  - May 15, May 16, May 19
  - June 17, June 18
  - July 14, July 16
  - August 14, August 15, August 17

  “One of these is my birthday,” she said.


  Cheryl whispered in Albert’s ear the month, and only the month, of
  her birthday. To Bernard, she whispered the day, and only the
  day. “Can you figure it out now?” she asked Albert.


  Albert: “I don’t know when your birthday is, but I know Bernard
  doesn’t know, either.”

  Bernard: “I didn’t know originally, but now I do.”

  Albert: “Well, now I know, too!”

  /When is Cheryl’s birthday?/

** The Solution
*** The Dates

   To start off, i entered each of the possible birthdays as facts:

   #+BEGIN_SRC prolog :results silent
     possible_birthday(may, 15).
     possible_birthday(may, 16).
     possible_birthday(may, 19).
     possible_birthday(june, 17).
     possible_birthday(june, 18).
     possible_birthday(july, 14).
     possible_birthday(july, 16).
     possible_birthday(august, 14).
     possible_birthday(august, 15).
     possible_birthday(august, 17).
   #+END_SRC

   And here they are, mapped out in a grid:

   |    | <c> | <c>  | <c>  |  <c>   |
   |    | May | June | July | August |
   |----+-----+------+------+--------|
   | 14 |     |      |  X   |   X    |
   | 15 |  X  |      |      |   X    |
   | 16 |  X  |      |  X   |        |
   | 17 |     |  X   |      |   X    |
   | 18 |     |  X   |      |        |
   | 19 |  X  |      |      |        |

*** Albert's Statement
   #+BEGIN_QUOTE
   I don’t know when your birthday is,...
   #+END_QUOTE

   Albert only knows the month, and the month isn't enough to uniquely
   identify Cheryl's birthday.

   #+BEGIN_SRC prolog :results silent
     month_is_not_unique(M) :-
         bagof(D, possible_birthday(M, D), Days),
         length(Days, Len),
         Len > 1.
   #+END_SRC

   #+BEGIN_QUOTE
   ... but I know Bernard doesn’t know, either.
   #+END_QUOTE

   Albert knows that Bernard doesn't know Cheryl's
   birthday. Therefore, the day alone isn't enough to know Cheryl's
   birthday, and we can infer that the month of Cheryl's birthday does
   not include any of the unique dates.

   #+BEGIN_SRC prolog :results silent
     day_is_not_unique(D) :-
         bagof(M, possible_birthday(M, D), Months),
         length(Months, Len),
         Len > 1.

     month_has_no_unique_days(M) :-
         forall(possible_birthday(M,D),
                day_is_not_unique(D)).
   #+END_SRC

   Based on what Albert knows at this point, let's see how we've
   reduced the possible dates:

   #+HEADER: :goal findall((M,D), part_one(M,D), Results)
   #+BEGIN_SRC prolog
     part_one(M,D) :-
         possible_birthday(M,D),
         month_is_not_unique(M),
         month_has_no_unique_days(M),
         day_is_not_unique(D).
   #+END_SRC

   #+RESULTS:
   : Results = [ (july, 14), (july, 16), (august, 14), (august, 15), (august, 17)].

   So the unique days (the 18th and 19th) are out, as are the months
   that contained them (May and June).

   |    | <c>  | <c>    |
   |    | July | August |
   |----+------+--------|
   | 14 |  X   | X      |
   | 15 |      | X      |
   | 16 |  X   |        |
   | 17 |      | X      |

*** Bernard's Statement
   #+BEGIN_QUOTE
   I didn’t know originally, but now I do.
   #+END_QUOTE

   For Bernard to know Cheryl's birthday, the day he knows must be
   unique within the constraints we have so far.

   #+BEGIN_SRC prolog :goal findall((M,D), part_two(M,D), Results)
     day_is_unique(Month, Day) :-
         findall(M, part_one(M, Day), [Month]).
     part_two(Month, Day) :-
         possible_birthday(Month, Day),
         day_is_unique(Month, Day).
   #+END_SRC

   #+RESULTS:
   : Results = [ (july, 16), (august, 15), (august, 17)].

   Both July and August contain the 14th, so that row is out.

   |    | July | August |
   |----+------+--------|
   | 15 |      | X      |
   | 16 | X    |        |
   | 17 |      | X      |

*** Albert's Second Statement
   #+BEGIN_QUOTE
   Well, now I know, too!
   #+END_QUOTE

   Albert's month must be the remaining unique month:

   #+BEGIN_SRC prolog :goal findall((M,D), part_three(M,D), Results)
     month_is_not_unique(Month, Day) :-
         findall(D, part_two(Month, D), [Day]).
     part_three(Month, Day) :-
         possible_birthday(Month, Day),
         month_is_not_unique(Month, Day).
   #+END_SRC

   #+RESULTS:
   : Results = [ (july, 16)].

   August had two possible days, so it's now clear that the only
   possible unique answer is July 16th.

   |    | <c>  |
   |    | July |
   |----+------|
   | 15 |      |
   | 16 |  X   |
   | 17 |      |

*** Cheryl's Birthday
   #+BEGIN_SRC prolog :goal cheryls_birthday(Month, Day)
     cheryls_birthday(Month, Day) :-
         part_three(Month, Day).
   #+END_SRC

   #+RESULTS:
   : Month = july,
   : Day = 16.

   So, there we have it. Cheryl's birthday is July 16th!

   |    | <c>  |
   |    | July |
   |----+------|
   | 16 |  X   |
* DONE Keeping Files And Configuration In Sync                          :git:
CLOSED: [2015-04-20 Mon]
:PROPERTIES:
:EXPORT_FILE_NAME: syncing
:END:

I have a few computers I use on a daily basis, and I like to keep the
same emacs and shell configuration on all of them, along with my org
files and a handful of scripts. Since I'm sure other people have this
problem as well, I'll share what I'm doing so anyone can learn from
(or criticise) my solutions.

** Git for configuration and projects

  I'm a software developer, so keeping things in git just makes sense
  to me. I keep my org files in a privately hosted git repository, and
  [[https://www.gnu.org/software/emacs/][Emacs]] and [[http://www.zsh.org/][Zsh]] configurations in a [[https://github.com/correl/dotfiles][public repo on github]]. My blog is
  also hosted and published on github as well; I like having it cloned
  to all my machines so I can work on drafts wherever I may be.

  My [[https://github.com/correl/dotfiles/blob/master/.zshrc][.zshrc]] installs [[https://github.com/robbyrussell/oh-my-zsh][oh-my-zsh]] if it isn't installed already, and sets
  up my shell theme, path, and some other environmental things.

  My [[https://github.com/correl/dotfiles/blob/master/.emacs.d/emacs.org][Emacs configuration]] behaves similarly, making use of John
  Wiegley's excellent [[https://github.com/jwiegley/use-package][use-package]] tool to ensure all my packages are
  installed if they're not already there and configured the way I like
  them.

  All I have to do to get running on a new system is to install git,
  emacs and zsh, clone my repo, symlink the files, and grab a cup of
  tea while everything installs.

** Bittorrent sync for personal settings & books

  For personal configuration that doesn't belong in and/or is too
  sensitive to be in a public repo, I have a folder of dotfiles and
  things that I sync between my machines using [[https://www.getsync.com/][Bittorrent Sync]]. The
  dotfiles are arranged into directories by their purpose:

  #+BEGIN_EXAMPLE
    [correlr@reason:~/dotenv]
    % tree -a -L 2
    .
    ├── authinfo
    │   └── .authinfo.gpg
    ├── bin
    │   └── .bin
    ├── emacs
    │   ├── .bbdb
    │   └── .emacs.local.d
    ├── mail
    │   ├── .gnus.el
    │   ├── .signature
    ├── README.org
    ├── .sync
    │   ├── Archive
    │   ├── ID
    │   ├── IgnoreList
    │   └── StreamsList
    ├── tex
    │   └── texmf
    ├── xmonad
    │   └── .xmonad
    └── zsh
        └── .zshenv
  #+END_EXAMPLE

  This folder structure allows my configs to be easily installed using
  [[https://www.gnu.org/software/stow/][GNU Stow]] from my =dotenv= folder:

  : stow -vvS *

  Running that command will, for each file in each of the directories,
  create a symlink to it in my home folder if there isn't a file or
  directory with that name there already.

  Bittorrent sync also comes in handy for syncing my growing [[http://calibre-ebook.com/][Calibre]] ebook
  collection, which outgrew my [[https://www.dropbox.com/][Dropbox]] account a while back.
* DONE Drawing Git Graphs with Graphviz and Org-Mode :emacs:org_mode:git:graphviz:
CLOSED: [2015-07-12 Sun]
:PROPERTIES:
:EXPORT_FILE_NAME: git-graphs
:header-args:emacs-lisp: :results silent
:header-args:dot: :exports both
:END:

  #+begin_export html
  <style type="text/css">
   svg text {
       fill: white;
   }
   svg path,
   svg polygon,
   svg ellipse {
       stroke: white;
   }
  </style>
  #+end_export

Digging through Derek Feichtinger's [[https://github.com/dfeich/org-babel-examples][org-babel examples]] (which I came
across via [[http://irreal.org/blog/?p%3D4162][irreal.org]]), I found he had some great examples of
displaying git-style graphs using graphviz. I thought it'd be a fun
exercise to generate my own graphs based on his graphviz source using
elisp, and point it at actual git repos.

** Getting Started

I started out with the goal of building a simple graph showing a
mainline branch and a topic branch forked from it and eventually
merged back in.

Using Derek's example as a template, I described 5 commits on a master
branch, plus two on a topic branch.

#+NAME: git-graphs-example
#+begin_src dot :file git-graphs-example.svg
  digraph G {
          rankdir="LR";
          bgcolor="transparent";
          node[width=0.15, height=0.15, shape=point, color=white];
          edge[weight=2, arrowhead=none, color=white];
          node[group=master];
          1 -> 2 -> 3 -> 4 -> 5;
          node[group=branch];
          2 -> 6 -> 7 -> 4;
  }
#+end_src

The resulting image looks like this:
#+RESULTS[a7cf21cb99be72abc22593af68f374b04297803c]: git-graphs-example
[[file:static/ox-hugo/git-graphs-example.svg]]

*** Designing the Data Structure

The first thing I needed to do was describe my data structure. Leaning
on my experiences reading and working through [[https://www.google.com/url?sa%3Dt&rct%3Dj&q%3D&esrc%3Ds&source%3Dweb&cd%3D1&cad%3Drja&uact%3D8&ved%3D0CB8QFjAA&url%3Dhttps%253A%252F%252Fmitpress.mit.edu%252Fsicp%252F&ei%3DlH6gVau5OIGR-AG8j7yACQ&usg%3DAFQjCNHTCXQK7qN-kYibdy_MqRBWxlr8og&sig2%3DLu9WIhyuTJS92e8hxne0Aw&bvm%3Dbv.97653015,d.cWw][SICP]], I got to work
building a constructor function, and several accessors.

I decided to represent each node on a graph with an id, a list of
parent ids, and a group which will correspond to the branch on the
graph the commit belongs to.

#+begin_src emacs-lisp
  (defun git-graph/make-node (id &optional parents group)
    (list id parents group))

  (defun git-graph/node-id (node)
    (nth 0 node))

  (defun git-graph/node-parents (node)
    (nth 1 node))

  (defun git-graph/node-group (node)
    (nth 2 node))
#+end_src

*** Converting the structure to Graphviz

Now that I had my data structures sorted out, it was time to step
through them and generate the graphviz source that'd give me the
nice-looking graphs I was after.

The graph is constructed using the example above as a template. The
nodes are defined first, followed by the edges between them.

#+name: git-graph/to-graphviz
#+begin_src emacs-lisp
  (defun git-graph/to-graphviz (id nodes)
    (string-join
     (list
      (concat "digraph " id " {")
      "bgcolor=\"transparent\";"
      "rankdir=\"LR\";"
      "node[width=0.15,height=0.15,shape=point,fontsize=8.0,color=white,fontcolor=white];"
      "edge[weight=2,arrowhead=none,color=white];"
      (string-join
       (-map #'git-graph/to-graphviz-node nodes)
       "\n")
       (string-join
        (-uniq (-flatten (-map
                          (lambda (node) (git-graph/to-graphviz-edges node nodes))
                          nodes)))
        "\n")
        "}")
     "\n"))
#+end_src

For the sake of readability, I'll format the output:

#+name: git-graph/to-graphviz
#+begin_src emacs-lisp
  (defun git-graph/to-graphviz-pretty (id nodes)
    (with-temp-buffer
      (graphviz-dot-mode)
      (insert (git-graph/to-graphviz id nodes))
      (indent-region (point-min) (point-max))
      (buffer-string)))
#+end_src


Each node is built, setting its group attribute when applicable.

#+begin_src emacs-lisp
  (defun git-graph/to-graphviz-node (node)
    (let ((node-id (git-graph/to-graphviz-node-id
                    (git-graph/node-id node))))
      (concat node-id
              (--if-let (git-graph/node-group node)
                  (concat "[group=\"" it "\"]"))
              ";")))
#+end_src

Graphviz node identifiers are quoted to avoid running into issues with
spaces or other special characters.

#+name: git-graph/to-graphviz-nodes
#+begin_src emacs-lisp
  (defun git-graph/to-graphviz-node-id (id)
    (format "\"%s\"" id))
#+end_src

For each node, an edge is built connecting the node to each of its
parents.

#+name: git-graph/to-graphviz-edges
#+begin_src emacs-lisp
  (defun git-graph/to-graphviz-edges (node &optional nodelist)
    (let ((node-id (git-graph/node-id node))
          (parents (git-graph/node-parents node))
          (node-ids (-map #'git-graph/node-id nodelist)))
      (-map (lambda (parent)
              (unless (and nodelist (not (member parent node-ids)))
                (git-graph/to-graphviz-edge node-id parent)))
            parents)))

  (defun git-graph/to-graphviz-edge (from to)
    (concat
     (git-graph/to-graphviz-node-id to)
     " -> "
     (git-graph/to-graphviz-node-id from)
     ";"))
#+end_src

With that done, the simple graph above could be generated with the
following code:

#+name: git-example
#+begin_src emacs-lisp :results silent
  (git-graph/to-graphviz-pretty
   "example"
   (list (git-graph/make-node 1 nil "master")
         (git-graph/make-node 2 '(1) "master")
         (git-graph/make-node 3 '(2) "master")
         (git-graph/make-node 4 '(3 7) "master")
         (git-graph/make-node 5 '(4) "master")
         (git-graph/make-node 6 '(2) "branch")
         (git-graph/make-node 7 '(6) "branch")))
#+end_src

Which generates the following graphviz source:

#+NAME: git-graphs-generated-example
#+begin_src dot :noweb yes :file "git-graphs-generated-example.svg"
  <<git-example()>>
#+end_src

The generated image matches the example exactly:

#+RESULTS[124faae6db8992b9cf42cabab4d1493f973aa6c5]: git-graphs-generated-example
[[file:static/ox-hugo/git-graphs-generated-example.svg]]

** Adding Labels

The next thing my graph needed was a way of labeling nodes. Rather
than trying to figure out some way of attaching a separate label to a
node, I decided to simply draw a labeled node as a box with text.

#+begin_src dot :file "git-graphs-labels.svg"
  digraph G {
          rankdir="LR";
          bgcolor="transparent";
          node[width=0.15, height=0.15, shape=point,fontsize=8.0,color=white,fontcolor=white];
          edge[weight=2, arrowhead=none,color=white];
          node[group=main];
          1 -> 2 -> 3 -> 4 -> 5;
          5[shape=box,label=master];
          node[group=branch1];
          2 -> 6 -> 7 -> 4;
          7[shape=box,label=branch];
  }
#+end_src

#+RESULTS[2d1e27579abf3bcd67093d101de7b9f6ec61eb52]:
[[file:static/ox-hugo/git-graphs-labels.svg]]

*** Updating the Data Structure

I updated my data structure to support an optional label applied to a
node. I opted to store it in an associative list alongside the group.

#+name: git-graph/structure
#+begin_src emacs-lisp
  (defun git-graph/make-node (id &optional parents options)
    (list id parents options))

  (defun git-graph/node-id (node)
    (nth 0 node))

  (defun git-graph/node-parents (node)
    (nth 1 node))

  (defun git-graph/node-group (node)
    (cdr (assoc 'group (nth 2 node))))

  (defun git-graph/node-label (node)
    (cdr (assoc 'label (nth 2 node))))
#+end_src

*** Updating the Graphviz node generation

The next step was updating the Graphviz generation functions to handle
the new data structure, and set the shape and label attributes of
labeled nodes.

#+name: git-graph/to-graphviz-nodes
#+begin_src emacs-lisp
  (defun git-graph/to-graphviz-node (node)
    (let ((node-id (git-graph/to-graphviz-node-id (git-graph/node-id node))))
      (concat node-id
              (git-graph/to-graphviz-node--attributes node)
              ";")))

  (defun git-graph/to-graphviz-node--attributes (node)
    (let ((attributes (git-graph/to-graphviz-node--compute-attributes node)))
      (and attributes
           (concat "["
                   (mapconcat (lambda (pair)
                                (format "%s=\"%s\""
                                        (car pair) (cdr pair)))
                              attributes
                              ", ")
                   "]"))))

  (defun git-graph/to-graphviz-node--compute-attributes (node)
    (-filter #'identity
             (append (and (git-graph/node-group node)
                          (list (cons 'group (git-graph/node-group node))))
                     (and (git-graph/node-label node)
                          (list (cons 'shape 'box)
                                (cons 'label (git-graph/node-label node)))))))
#+end_src

I could then label the tips of each branch:

#+name: graph-example-labels
#+begin_src emacs-lisp :exports code :results silent
  (git-graph/to-graphviz-pretty
   "labeled"
   (list (git-graph/make-node 1 nil '((group . "master")))
         (git-graph/make-node 2 '(1) '((group . "master")))
         (git-graph/make-node 3 '(2) '((group . "master")))
         (git-graph/make-node 4 '(3 7) '((group . "master")))
         (git-graph/make-node 5 '(4) '((group . "master")
                                       (label . "master")))
         (git-graph/make-node 6 '(2) '((group . "branch")))
         (git-graph/make-node 7 '(6) '((group . "branch")
                                       (label . "branch")))))
#+end_src

#+begin_src dot :file "git-graphs-labels-generated.svg" :noweb yes :exports results
  <<graph-example-labels()>>
#+end_src

#+RESULTS[e5a194d1f4c737ff465c20d6b063ab58f9530a72]:
[[file:static/ox-hugo/git-graphs-labels-generated.svg]]

** Automatic Grouping Using Leaf Nodes

Manually assigning groups to each node is tedious, and easy to
accidentally get wrong. Also, with the goal to graph git repositories,
I was going to have to figure out groupings automatically anyway.

To do this, it made sense to traverse the nodes in [[https://en.wikipedia.org/wiki/Topological_sorting][topological order]].

Repeating the example above,
#+begin_src dot :file git-graphs-topo.svg
  digraph G {
          rankdir="LR";
          bgcolor="transparent";
          node[width=0.15, height=0.15, shape=circle, color=white, fontcolor=white];
          edge[weight=2, arrowhead=none, color=white];
          node[group=main];
          1 -> 2 -> 3 -> 4 -> 5;
          node[group=branch1];
          2 -> 6 -> 7 -> 4;
  }
#+end_src

#+RESULTS[277f98904b151a521fcdb45b5a77568f481639c1]:
[[file:static/ox-hugo/git-graphs-topo.svg]]

These nodes can be represented (right to left) in topological order as
either ~5, 4, 3, 7, 6, 2, 1~ or ~5, 4, 7, 6, 3, 2, 1~.

Having no further children, ~5~ is a leaf node, and can be used as a
group. All first parents of ~5~ can therefore be considered to be in
group ~5~.

~7~ is a second parent to ~4~, and so should be used as the group for
all of its parents not present in group ~5~.

#+name: git-graph/group-topo
#+begin_src emacs-lisp
  (defun git-graph/group-topo (nodelist)
    (reverse
     (car
      (-reduce-from
       (lambda (acc node)
         (let* ((grouped-nodes (car acc))
                (group-stack (cdr acc))
                (node-id (git-graph/node-id node))
                (group-from-stack (--if-let (assoc node-id group-stack)
                                      (cdr it)))
                (group (or group-from-stack node-id))
                (parents (git-graph/node-parents node))
                (first-parent (first parents)))
           (if group-from-stack
               (pop group-stack))
           (if (and first-parent (not (assoc first-parent group-stack)))
               (push (cons first-parent group) group-stack))
           (cons (cons (git-graph/make-node node-id
                                      parents
                                      `((group . ,group)
                                        (label . ,(git-graph/node-label node))))
                       grouped-nodes)
                 group-stack)))
       nil
       nodelist))))
#+end_src

While iterating through the node list, I maintained a stack of pairs
built from the first parent of the current node, and the current
group. To determine the group, the head of the stack is checked to see
if it contains a group for the current node id. If it does, that group
is used and it is popped off the stack, otherwise the current node id
is used.

The following table illustrates how the stack is used to store and
assign group relationships as the process iterates through the node
list:

#+caption: Progressing through the nodes
| Node | Parents | Group Stack     | Group |
|------+---------+-----------------+-------|
|    5 | (4)     | (4 . 5)         |     5 |
|    4 | (3 7)   | (3 . 5)         |     5 |
|    3 | (2)     | (2 . 5)         |     5 |
|    7 | (6)     | (6 . 7) (2 . 5) |     7 |
|    6 | (2)     | (2 . 5)         |     7 |
|    2 | (1)     | (1 . 5)         |     5 |
|    1 |         |                 |     5 |


*** Graph without automatic grouping

#+name: graph-no-auto-grouping
#+begin_src emacs-lisp :exports code :results silent
  (git-graph/to-graphviz-pretty
   "nogroups"
   (list (git-graph/make-node 5 '(4) '((label . master)))
         (git-graph/make-node 4 '(3 7))
         (git-graph/make-node 3 '(2))
         (git-graph/make-node 7 '(6) '((label . develop)))
         (git-graph/make-node 6 '(2))
         (git-graph/make-node 2 '(1))
         (git-graph/make-node 1 nil)))
#+end_src

#+begin_src dot :noweb yes :file git-graphs-no-auto-grouping.svg :exports results
  <<graph-no-auto-grouping()>>
#+end_src

#+RESULTS[91bedd3cab2a02d3083d10217462e07aa8eb0be0]:
[[file:static/ox-hugo/git-graphs-no-auto-grouping.svg]]

*** Graph with automatic grouping

#+name: graph-with-auto-grouping
#+begin_src emacs-lisp :exports code :results silent
  (git-graph/to-graphviz-pretty
   "autogroups"
   (git-graph/group-topo
    (list (git-graph/make-node 5 '(4) '((label . master)))
          (git-graph/make-node 4 '(3 7))
          (git-graph/make-node 3 '(2))
          (git-graph/make-node 7 '(6) '((label . develop)))
          (git-graph/make-node 6 '(2))
          (git-graph/make-node 2 '(1))
          (git-graph/make-node 1 nil))))
#+end_src

#+begin_src dot :noweb yes :file git-graphs-with-auto-grouping.svg :exports results
  <<graph-with-auto-grouping()>>
#+end_src

#+RESULTS[fa116b45cd590ae9cb00517bb3ed51dbab357592]:
[[file:static/ox-hugo/git-graphs-with-auto-grouping.svg]]

** Graphing a Git Repository

Satisfied that I had all the necessary tools to start graphing real
git repositories, I created an example repository to test against.

*** Creating a Sample Repository

Using the following script, I created a sample repository to test
against. I performed the following actions:

- Forked a develop branch from master.
- Forked a feature branch from develop, with two commits.
- Added another commit to develop.
- Forked a second feature branch from develop, with two commits.
- Merged the second feature branch to develop.
- Merged develop to master and tagged it.

#+begin_src sh :exports results :results silent
  rm -rf /tmp/test.git
#+end_src
#+begin_src sh :exports both :results silent
  mkdir /tmp/test.git
  cd /tmp/test.git
  git init
  touch README
  git add README
  git commit -m 'initial'
  git commit --allow-empty -m 'first'
  git checkout -b develop
  git commit --allow-empty -m 'second'
  git checkout -b feature-1
  git commit --allow-empty -m 'feature 1'
  git commit --allow-empty -m 'feature 1 again'
  git checkout develop
  git commit --allow-empty -m 'third'
  git checkout -b feature-2
  git commit --allow-empty -m 'feature 2'
  git commit --allow-empty -m 'feature 2 again'
  git checkout develop
  git merge --no-ff feature-2
  git checkout master
  git merge --no-ff develop
  git tag -a 1.0 -m '1.0!'
#+end_src
*** Generating a Graph From a Git Branch

The first order of business was to have a way to call out to git and
return the results:

#+name: git-graph/from-git
#+begin_src emacs-lisp
  (defun git-graph/git-execute (repo-url command &rest args)
    (with-temp-buffer
      (shell-command (format "git -C \"%s\" %s"
                             repo-url
                             (string-join (cons command args)
                                          " "))
                     t)
      (buffer-string)))
#+end_src

Next, I needed to get the list of commits for a branch in topological
order, with a list of parent commits for each. It turns out git
provides exactly that via its =rev-list= command.

#+name: git-graph/from-git
#+begin_src emacs-lisp
  (defun git-graph/git-rev-list (repo-url head)
    (-map (lambda (line) (split-string line))
          (split-string (git-graph/git-execute
                         repo-url
                         "rev-list" "--topo-order" "--parents" head)
                        "\n" t)))
#+end_src

I also wanted to label branch heads wherever possible. To do this, I
looked up the revision name from git, discarding it if it was relative
to some other named commit.

#+name: git-graph/from-git
#+begin_src emacs-lisp
  (defun git-graph/git-label (repo-url rev)
    (let ((name (string-trim
                 (git-graph/git-execute repo-url
                                        "name-rev" "--name-only" rev))))
      (unless (s-contains? "~" name)
        name)))
#+end_src

Generating the graph for a single branch was as simple as iterating
over each commit and creating a node for it.

#+name: git-graph/from-git
#+begin_src emacs-lisp
  (defun git-graph/git-graphs-head (repo-url head)
    (git-graph/group-topo
     (-map (lambda (rev-with-parents)
             (let* ((rev (car rev-with-parents))
                    (parents (cdr rev-with-parents))
                    (label (git-graph/git-label repo-url rev)))
               (git-graph/make-node rev parents
                                    `((label . ,label)))))
           (git-graph/git-rev-list repo-url head))))
#+end_src

Here's the result of graphing the =master= branch:

#+name: graph-git-branch
#+begin_src emacs-lisp
  (git-graph/to-graphviz-pretty
   "git"
   (git-graph/git-graphs-head
    "/tmp/test.git"
    "master"))
#+end_src

#+begin_src dot :file git-graphs-branch.svg :noweb yes
  <<graph-git-branch()>>
#+end_src

#+RESULTS[e971f68020b770b27fa6d08eaaec85798e8da4a2]:
[[file:static/ox-hugo/git-graphs-branch.svg]]

*** Graphing Multiple Branches

To graph multiple branches, I needed a function for combining
histories. To do so, I simply append any nodes I don't already know
about in the first history from the second.

#+name: git-graph/adder
#+begin_src emacs-lisp
  (defun git-graph/+ (a b)
    (append a
            (-remove (lambda (node)
                       (assoc (git-graph/node-id node) a))
                     b)))
#+end_src

From there, all that remained was to accumulate the branch histories
and output the complete graph:

#+name: git-graph/from-git
#+begin_src emacs-lisp
  (defun git-graph/git-load (repo-url heads)
    (-reduce #'git-graph/+
             (-map (lambda (head)
                     (git-graph/git-graphs-head repo-url head))
                   heads)))
#+end_src

And here's the example repository, graphed in full:

#+name: graph-git-repo
#+begin_src emacs-lisp
  (git-graph/to-graphviz-pretty
   "git"
   (git-graph/git-load
    "/tmp/test.git"
    '("master" "feature-1")))
#+end_src

#+begin_src dot :file git-graphs-repo.svg :noweb yes
  <<graph-git-repo()>>
#+end_src

#+RESULTS[0d4e90afa31090ce57eeb60b7f40c0579e3fbc1e]:
[[file:static/ox-hugo/git-graphs-repo.svg]]

** Things I may add in the future
*** Limiting Commits to Graph

Running this against repos with any substantial history can make the
graph unwieldy. It'd be a good idea to abstract out the commit list
fetching, and modify it to support different ways of limiting the
history to display.

Ideas would include:
- Specifying commit ranges
- Stopping at a common ancestor to all graphed branches (e.g., using
  =git-merge-base=).
- Other git commit limiting options, like searches, showing only merge
  or non-merge commits, etc.

*** Collapsing History

Another means of reducing the size of the resulting graph would be to
collapse unimportant sections of it. It should be possible to collapse
a section of the graph, showing a count of skipped nodes.

The difficult part would be determining what parts aren't worth
drawing. Something like this would be handy, though, for concisely
graphing the state of multiple ongoing development branches (say, to
get a picture of what's been going on since the last release, and
what's still incomplete).

#+begin_src dot :file git-graphs-long.svg
  digraph G {
          rankdir="LR";
          bgcolor="transparent";
          node[width=0.15,height=0.15,shape=point,color=white];
          edge[weight=2,arrowhead=none,color=white];
          node[group=main];
          1 -> 2 -> 3 -> 4 -> 5;
          node[group=branch];
          2 -> 6 -> 7 -> 8 -> 9 -> 10 -> 4;
  }
#+end_src

#+caption: A graph with multiple nodes on a branch.
#+RESULTS[6d6237fcc49d1bbc21685b447d7065ba1faf907e]:
[[file:static/ox-hugo/git-graphs-long.svg]]


#+begin_src dot :file git-graphs-collapsed.svg
    digraph G {
            rankdir="LR";
            bgcolor="transparent";
            node[width=0.15,height=0.15,shape=point,color=white];
            edge[weight=2,arrowhead=none,color=white,fontcolor=white];
            node[group=main];
            1 -> 2 -> 3 -> 4 -> 5;
            node[group=branch];
            2 -> 6;
            6 -> 10[style=dashed,label="+3"];
            10 -> 4;
    }
#+end_src

#+caption: The same graph, collapsed.
#+RESULTS[4bf40f7b350a8d92ddc70098eb48d8a0d50f432b]:
[[file:static/ox-hugo/git-graphs-collapsed.svg]]


*** Clean up and optimize the code a bit

Some parts of this (particularly, the grouping) are probably pretty
inefficient. If this turns out to actually be useful, I may take
another crack at it.

** Final Code

In case anyone would like to use this code for anything, or maybe just
pick it apart and play around with it, all the Emacs Lisp code in this
post is collected into a single file below:

#+begin_src emacs-lisp :noweb yes :exports code :tangle "static/files/git-graph.el"
  ;;; git-graph.el --- Generate git-style graphs using graphviz

  ;; Copyright (c) 2015 Correl Roush <correl@gmail.com>

  ;;; License:

  ;; This program is free software; you can redistribute it and/or modify
  ;; it under the terms of the GNU General Public License as published by
  ;; the Free Software Foundation; either version 3, or (at your option)
  ;; any later version.
  ;;
  ;; This program is distributed in the hope that it will be useful,
  ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  ;; GNU General Public License for more details.
  ;;
  ;; You should have received a copy of the GNU General Public License
  ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  ;; Boston, MA 02110-1301, USA.

  ;;; Commentary:

  ;;; Code:

  (require 'dash)

  <<git-graph/structure>>

  <<git-graph/adder>>

  <<git-graph/to-graphviz>>

  <<git-graph/to-graphviz-nodes>>

  <<git-graph/to-graphviz-edges>>

  <<git-graph/group-topo>>

  <<git-graph/from-git>>

  (provide 'git-graph)
  ;;; git-graph.el ends here
#+end_src

Download: [[file:/files/git-graph.el][git-graph.el]]
* DONE Use a different theme when publishing Org files       :emacs:org_mode:
CLOSED: [2016-02-23 Tue]
:PROPERTIES:
:EXPORT_FILE_NAME: org-publish-with-theme
:END:
#+KEYWORDS: emacs org-mode themes

I've been using [[https://github.com/cpaulik/emacs-material-theme][material-theme]] lately, and I sometimes switch around,
but I've found that [[https://github.com/bbatsov/solarized-emacs][solarized]] produces the best exported code block
results. To avoid having to remember to switch themes when exporting,
I wrote a quick wrapper for org-export to do it for me:

#+BEGIN_SRC emacs-lisp :exports code
  (defun my/with-theme (theme fn &rest args)
    (let ((current-themes custom-enabled-themes))
      (mapcar #'disable-theme custom-enabled-themes)
      (load-theme theme t)
      (let ((result (apply fn args)))
        (mapcar #'disable-theme custom-enabled-themes)
        (mapcar (lambda (theme) (load-theme theme t)) current-themes)
        result)))

  (advice-add #'org-export-to-file :around (apply-partially #'my/with-theme 'solarized-dark))
  (advice-add #'org-export-to-buffer :around (apply-partially #'my/with-theme 'solarized-dark))
#+END_SRC

Voilà, no more bizarrely formatted code block exports from whatever
theme I might have loaded at the time :)
* DONE Recursive HTTP Requests with Elm                     :programming:elm:
CLOSED: [2018-01-22 Mon]
:PROPERTIES:
:EXPORT_FILE_NAME: recursive-http-requests-with-elm
:END:

So I got the idea in my head that I wanted to pull data from the
GitLab / GitHub APIs in my Elm app. This seemed straightforward
enough; just wire up an HTTP request and a JSON decoder, and off I go.
Then I remember, oh crap... like any sensible API with a potentially
huge amount of data behind it, the results come back /paginated/. For
anyone unfamiliar, this means that a single API request for a list of,
say, repositories, is only going to return up to some maximum number
of results. If there are more results available, there will be a
reference to additional /pages/ of results, that you can then fetch
with /another/ API request. My single request decoding only the
results returned /from/ that single request wasn't going to cut it.

I had a handful of problems to solve. I needed to:

- Detect when additional results were available.
- Parse out the URL to use to fetch the next page of results.
- Continue fetching results until none remained.
- Combine all of the results, maintaining their order.

** Are there more results?

The first two bullet points can be dealt with by parsing and
inspecting the response header. Both GitHub and GitLab embed
pagination links in the [[https://www.w3.org/wiki/LinkHeader][HTTP Link header]]. As I'm interested in
consuming pages until no further results remain, I'll be looking for a
link in the header with the relationship "next". If I find one, I know
I need to hit the associated URL to fetch more results. If I don't
find one, I'm done!

#+CAPTION: Example GitHub Link header
#+BEGIN_SRC http
  Link: <https://api.github.com/user/repos?page=3&per_page=100>; rel="next",
    <https://api.github.com/user/repos?page=50&per_page=100>; rel="last"
#+END_SRC

Parsing this stuff out went straight into a utility module.

#+BEGIN_SRC elm
  module Paginated.Util exposing (links)

  import Dict exposing (Dict)
  import Maybe.Extra
  import Regex


  {-| Parse an HTTP Link header into a dictionary. For example, to look
  for a link to additional results in an API response, you could do the
  following:

      Dict.get "Link" response.headers
          |> Maybe.map links
          |> Maybe.andThen (Dict.get "next")

  -}
  links : String -> Dict String String
  links s =
      let
          toTuples xs =
              case xs of
                  [ Just a, Just b ] ->
                      Just ( b, a )

                  _ ->
                      Nothing
      in
          Regex.find
              Regex.All
              (Regex.regex "<(.*?)>; rel=\"(.*?)\"")
              s
              |> List.map .submatches
              |> List.map toTuples
              |> Maybe.Extra.values
              |> Dict.fromList
#+END_SRC

A little bit of regular expression magic, tuples, and
=Maybe.Extra.values= to keep the matches, and now I've got my
(=Maybe=) URL.

** Time to make some requests

Now's the time to define some types. I'll need a =Request=, which will
be similar to a standard =Http.Request=, with a /slight/ difference.

#+BEGIN_SRC elm
  type alias RequestOptions a =
      { method : String
      , headers : List Http.Header
      , url : String
      , body : Http.Body
      , decoder : Decoder a
      , timeout : Maybe Time.Time
      , withCredentials : Bool
      }


  type Request a
      = Request (RequestOptions a)
#+END_SRC

What separates it from a basic =Http.Request= is the =decoder= field
instead of an =expect= field. The =expect= field in an HTTP request is
responsible for parsing the full response into whatever result the
caller wants. For my purposes, I always intend to be hitting a JSON
API returning a list of items, and I have my own designs on parsing
bits of the request to pluck out the headers. Therefore, I expose only
a slot for including a JSON decoder representing the type of item I'll
be getting a collection of.

I'll also need a =Response=, which will either be =Partial=
(containing the results from the response, plus a =Request= for
getting the next batch), or =Complete=.

#+BEGIN_SRC elm
  type Response a
      = Partial (Request a) (List a)
      | Complete (List a)
#+END_SRC

Sending the request isn't too bad. I can just convert my request into
an =Http.Request=, and use =Http.send=.

#+BEGIN_SRC elm
  send :
      (Result Http.Error (Response a) -> msg)
      -> Request a
      -> Cmd msg
  send resultToMessage request =
      Http.send resultToMessage <|
          httpRequest request


  httpRequest : Request a -> Http.Request (Response a)
  httpRequest (Request options) =
      Http.request
          { method = options.method
          , headers = options.headers
          , url = options.url
          , body = options.body
          , expect = expect options
          , timeout = options.timeout
          , withCredentials = options.withCredentials
          }


  expect : RequestOptions a -> Http.Expect (Response a)
  expect options =
      Http.expectStringResponse (fromResponse options)
#+END_SRC

All of my special logic for handling the headers, mapping the decoder
over the results, and packing them up into a =Response= is baked into
my =Http.Request= via a private =fromResponse= translator:

#+BEGIN_SRC elm
  fromResponse :
      RequestOptions a
      -> Http.Response String
      -> Result String (Response a)
  fromResponse options response =
      let
          items : Result String (List a)
          items =
              Json.Decode.decodeString
                  (Json.Decode.list options.decoder)
                  response.body

          nextPage =
              Dict.get "Link" response.headers
                  |> Maybe.map Paginated.Util.links
                  |> Maybe.andThen (Dict.get "next")
      in
          case nextPage of
              Nothing ->
                  Result.map Complete items

              Just url ->
                  Result.map
                      (Partial (request { options | url = url }))
                      items
#+END_SRC

** Putting it together

Now, I can make my API request, and get back a response with
potentially partial results. All that needs to be done now is to make
my request, and iterate on the results I get back in my =update=
method.

To make things a bit easier, I add a method for concatenating two
responses:

#+BEGIN_SRC elm
  update : Response a -> Response a -> Response a
  update old new =
      case ( old, new ) of
          ( Complete items, _ ) ->
              Complete items

          ( Partial _ oldItems, Complete newItems ) ->
              Complete (oldItems ++ newItems)

          ( Partial _ oldItems, Partial request newItems ) ->
              Partial request (oldItems ++ newItems)
#+END_SRC

Putting it all together, I get a fully functional test app that
fetches a paginated list of repositories from GitLab, and renders them
when I've fetched them all:

#+BEGIN_SRC elm
  module Example exposing (..)

  import Html exposing (Html)
  import Http
  import Json.Decode exposing (field, string)
  import Paginated exposing (Response(..))


  type alias Model =
      { repositories : Maybe (Response String) }


  type Msg
      = GotRepositories (Result Http.Error (Paginated.Response String))


  main : Program Never Model Msg
  main =
      Html.program
          { init = init
          , update = update
          , view = view
          , subscriptions = \_ -> Sub.none
          }


  init : ( Model, Cmd Msg )
  init =
      ( { repositories = Nothing }
      , getRepositories
      )


  update : Msg -> Model -> ( Model, Cmd Msg )
  update msg model =
      case msg of
          GotRepositories (Ok response) ->
              ( { model
                  | repositories =
                      case model.repositories of
                          Nothing ->
                              Just response

                          Just previous ->
                              Just (Paginated.update previous response)
                }
              , case response of
                  Partial request _ ->
                      Paginated.send GotRepositories request

                  Complete _ ->
                      Cmd.none
              )

          GotRepositories (Err _) ->
              ( { model | repositories = Nothing }
              , Cmd.none
              )


  view : Model -> Html Msg
  view model =
      case model.repositories of
          Nothing ->
              Html.div [] [ Html.text "Loading" ]

          Just (Partial _ _) ->
              Html.div [] [ Html.text "Loading..." ]

          Just (Complete repos) ->
              Html.ul [] <|
                  List.map
                      (\x -> Html.li [] [ Html.text x ])
                      repos


  getRepositories : Cmd Msg
  getRepositories =
      Paginated.send GotRepositories <|
          Paginated.get
              "http://git.phoenixinquis.net/api/v4/projects?per_page=5"
              (field "name" string)
#+END_SRC

** There's got to be a better way

I've got it working, and it's working well. However, it's kind of a
pain to use. It's nice that I can play with the results as they come
in by peeking into the =Partial= structure, but it's a real chore to
have to stitch the results together in my application's =update=
method. It'd be nice if I could somehow encapsulate that behavior in
my request and not have to worry about the pagination at all in my
app.

It just so happens that, with Tasks, I can.

/Feel free to check out the full library documentation and code
referenced in this post [[http://package.elm-lang.org/packages/correl/elm-paginated/1.0.1][here]]./

/Continue on with part two, [[relref:cleaner-recursive-http-with-elm-tasks][Cleaner Recursive HTTP Requests with Elm
Tasks]]./

* DONE Cleaner Recursive HTTP Requests with Elm Tasks       :programming:elm:
CLOSED: [2018-01-23 Tue]
:PROPERTIES:
:EXPORT_FILE_NAME: cleaner-recursive-http-with-elm-tasks
:END:
/Continued from part one, [[relref:recursive-http-requests-with-elm][Recursive HTTP Requests with Elm]]./

In [[relref:recursive-http-requests-with-elm][my last post]], I described my first pass at building a library to
fetch data from a paginated JSON REST API. It worked, but it wasn't
too clean. In particular, the handling of the multiple pages and
concatenation of results was left up to the calling code. Ideally,
both of these concerns should be handled by the library, letting the
application focus on working with a full result set. Using Elm's
Tasks, we can achieve exactly that!

** What's a Task?

A [[http://package.elm-lang.org/packages/elm-lang/core/5.1.1/Task][Task]] is a data structure in Elm which represents an asynchronous
operation that may fail, which can be mapped and *chained*. What this
means is, we can create an action, transform it, and chain it with
additional actions, building up a complex series of things to do into
a single =Task=, which we can then package up into a [[http://package.elm-lang.org/packages/elm-lang/core/5.1.1/Platform-Cmd#Cmd][Cmd]] and hand to
the Elm runtime to perform. You can think of it like building up a
[[https://en.wikipedia.org/wiki/Futures_and_promises][Future or Promise]], setting up a sort of [[https://en.wikipedia.org/wiki/Callback_(computer_programming)][callback]] chain of mutations
and follow-up actions to be taken. The Elm runtime will work its way
through the chain and hand your application back the result in the
form of a =Msg=.

So, tasks sound great!

** Moving to Tasks

Just to get things rolling, let's quit using =Http.send=, and instead
prepare a simple =toTask= function leveraging the very handy
=Http.toTask=. This'll give us a place to start building up some more
complex behavior.

#+BEGIN_SRC elm
  send :
      (Result Http.Error (Response a) -> msg)
      -> Request a
      -> Cmd msg
  send resultToMessage request =
          toTask request
          |> Task.attempt resultToMessage


  toTask : Request a -> Task Http.Error (Response a)
  toTask =
      httpRequest >> Http.toTask
#+END_SRC

** Shifting the recursion

Now, for the fun bit. We want, when a request completes, to inspect
the result. If the task failed, we do nothing. If it succeeded, we
move on to checking the response. If we have a =Complete= response,
we're done. If we do not, we want to build another task for the next
request, and start a new iteration on that.

All that needs to be done here is to chain our response handling using
=Task.andThen=, and either recurse to continue the chain with the next
=Task=, or wrap up the final results with =Task.succeed=!

#+BEGIN_SRC elm
  recurse :
      Task Http.Error (Response a)
      -> Task Http.Error (Response a)
  recurse =
      Task.andThen
          (\response ->
              case response of
                  Partial request _ ->
                      httpRequest request
                          |> Http.toTask
                          |> recurse

                  Complete _ ->
                      Task.succeed response
          )
#+END_SRC

That wasn't so bad. The function recursion almost seems like cheating:
I'm able to build up a whole chain of requests /based/ on the results
without actually /having/ the results yet! The =Task= lets us define a
complete plan for what to do with the results, using what we know
about the data structures flowing through to make decisions and tack
on additional things to do.

** Accumulating results

There's just one thing left to do: we're not accumulating results yet.
We're just handing off the results of the final request, which isn't
too helpful to the caller. We're also still returning our Response
structure, which is no longer necessary, since we're not bothering
with returning incomplete requests anymore.

Cleaning up the types is pretty easy. It's just a matter of switching
out some instances of =Response a= with =List a= in our type
declarations...

#+BEGIN_SRC elm
  send :
      (Result Http.Error (List a) -> msg)
      -> Request a
      -> Cmd msg


  toTask : Request a -> Task Http.Error (List a)


  recurse :
      Task Http.Error (Response a)
      -> Task Http.Error (List a)
#+END_SRC


...then changing our =Complete= case to return the actual items:

#+BEGIN_SRC elm
                  Complete xs ->
                      Task.succeed xs
#+END_SRC

The final step, then, is to accumulate the results. Turns out this is
*super* easy. We already have an =update= function that combines two
responses, so we can map /that/ over our next request task so that it
incorporates the previous request's results!

#+BEGIN_SRC elm
                  Partial request _ ->
                      httpRequest request
                          |> Http.toTask
                          |> Task.map (update response)
                          |> recurse
#+END_SRC

** Tidying up

Things are tied up pretty neatly, now! Calling code no longer needs to
care whether the JSON endpoints its calling paginate their results,
they'll receive everything they asked for as though it were a single
request. Implementation details like the =Response= structure,
=update= method, and =httpRequest= no longer need to be exposed.
=toTask= can be exposed now as a convenience to anyone who wants to
perform further chaining on their calls.

Now that there's a cleaner interface to the module, the example app is
looking a lot cleaner now, too:

#+BEGIN_SRC elm
  module Example exposing (..)

  import Html exposing (Html)
  import Http
  import Json.Decode exposing (field, string)
  import Paginated


  type alias Model =
      { repositories : Maybe (List String) }


  type Msg
      = GotRepositories (Result Http.Error (List String))


  main : Program Never Model Msg
  main =
      Html.program
          { init = init
          , update = update
          , view = view
          , subscriptions = \_ -> Sub.none
          }


  init : ( Model, Cmd Msg )
  init =
      ( { repositories = Nothing }
      , getRepositories
      )


  update : Msg -> Model -> ( Model, Cmd Msg )
  update msg model =
      case msg of
          GotRepositories result ->
              ( { model | repositories = Result.toMaybe result }
              , Cmd.none
              )


  view : Model -> Html Msg
  view model =
      case model.repositories of
          Nothing ->
              Html.div [] [ Html.text "Loading" ]

          Just repos ->
              Html.ul [] <|
                  List.map
                      (\x -> Html.li [] [ Html.text x ])
                      repos


  getRepositories : Cmd Msg
  getRepositories =
      Paginated.send GotRepositories <|
          Paginated.get
              "http://git.phoenixinquis.net/api/v4/projects?per_page=5"
              (field "name" string)
#+END_SRC

So, there we have it! Feel free to check out the my complete
=Paginated= library on the [[http://package.elm-lang.org/packages/correl/elm-paginated/latest][Elm package index]], or on [[https://github.com/correl/elm-paginated][GitHub]]. Hopefully
you'll find it or this post useful. I'm still finding my way around
Elm, so any and all feedback is quite welcome :)
* DONE How Does The Phillips Hue Wake-Up Feature Work?      :home_automation:
CLOSED: [2018-03-13 Tue]
:PROPERTIES:
:EXPORT_FILE_NAME: hue-wake-up
:header-args:http: :post anonymize(json=*this*) :resolve bridge:80:192.168.1.199 :var username="uCpPPhYlWIJdOvGuyrsM2EtmaeiVvcTX0WEdAn0P" :pretty :exports both :wrap SRC js
:END:
#+name: anonymize
#+BEGIN_SRC emacs-lisp :var json="" :exports none :results silent
  ;; Anonymize user/manufacturer IDs
  (->>
   json
   (s-replace "oV5vUaXuBwEAA6sjnvqr8n6fBLlzWLjG4x4SIyD8"
              "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx")
   (s-replace "oV5vUaXuBwEAA6sjnvqr8n6fBLlzWLjG"
              "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"))
#+END_SRC

I recently got myself a set of Phillips Hue White and Color Ambiance
lights. One of the features I was looking forward to in particular
(besides playing with all the color options) was setting a wake-up
alarm with the lights gradually brightening. This was pretty painless
to get set up using the phone app. I'm pretty happy with the result,
but there's certainly some things I wouldn't mind tweaking. For
example, the initial brightness of the bulbs (at the lowest setting)
still seems a bit bright, so I might want to delay the bedside lamps
and let the more distant lamp start fading in first. I also want to
see if I can fiddle it into transitioning between some colors to get
more of a sunrise effect (perhaps "rising" from the other side of the
room, with the light spreading towards the head of the bed).

Figuring out how the wake-up settings that the app installed on my
bridge seemed a good first step towards introducing my own
customizations.

Information on getting access to a Hue bridge to make REST API calls
to it can be found in the [[https://www.developers.meethue.com/documentation/getting-started][Hue API getting started guide]].

** My wake-up settings
My wake-up is scheduled for 7:00 to gradually brighten the lights with
a half-hour fade-in each weekday. I also toggled on the setting to
automatically turn the lights off at 9:00.

#+BEGIN_CENTER
[[file:static/images/Screenshot_20180313-182434.png]] [[file:static/images/Screenshot_20180313-182438.png]]
#+END_CENTER

** Finding things on the bridge

The most natural starting point is to check the schedules. Right off
the bat, I find what I'm after:

*** The schedule ...

#+BEGIN_SRC http
  GET http://bridge/api/${username}/schedules/1
#+END_SRC

#+RESULTS[185c8bd9c6da61034cb699944dfb1827d2d08282]:
#+BEGIN_SRC js
{
  "name": "Wake up",
  "description": "L_04_fidlv_start wake up",
  "command": {
    "address": "/api/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/sensors/2/state",
    "body": {
      "flag": true
    },
    "method": "PUT"
  },
  "localtime": "W124/T06:30:00",
  "time": "W124/T10:30:00",
  "created": "2018-03-11T19:46:54",
  "status": "enabled",
  "recycle": true
}
#+END_SRC

This is a recurring schedule item that runs every weekday at 6:30. We
can tell this by looking at the =localtime= field. From the
documentation on [[https://www.developers.meethue.com/documentation/datatypes-and-time-patterns#16_time_patterns][time patterns]], we can see that it's a recurring time
pattern specifying days of the week as a bitmask, and a time (6:30).

#+CAPTION: Unraveling the weekday portion
| <l>                         |
| =0MTWTFSS=                  |
| =01111100= (124 in decimal) |

Since this schedule is enabled, we can be assured that it will run,
and in doing so, will issue a =PUT= to a sensors endpoint, setting a
flag to true.

*** ... triggers the sensor ...

#+BEGIN_SRC http
  GET http://bridge/api/${username}/sensors/2
#+END_SRC

#+RESULTS[6660e5539302c8863c2d7cd9417e3996c35b2b87]:
#+BEGIN_SRC js
{
  "state": {
    "flag": false,
    "lastupdated": "2018-03-13T13:00:00"
  },
  "config": {
    "on": true,
    "reachable": true
  },
  "name": "Sensor for wakeup",
  "type": "CLIPGenericFlag",
  "modelid": "WAKEUP",
  "manufacturername": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
  "swversion": "A_1801260942",
  "uniqueid": "L_04_fidlv",
  "recycle": true
}
#+END_SRC

The sensor is what's /really/ setting things in motion. Here we've got
a [[https://www.developers.meethue.com/documentation/supported-sensors#clipSensors][generic CLIP flag sensor]] that is triggered exclusively by our
schedule. Essentially, by updating the flag state, we trigger the
sensor.

*** ... triggers a rule ...

#+BEGIN_SRC http
  GET http://bridge/api/${username}/rules/1
#+END_SRC

#+RESULTS[449d90a31c32d4630701c75e4655ccb6378d8655]:
#+BEGIN_SRC js
{
  "name": "L_04_fidlv_Start",
  "owner": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
  "created": "2018-03-11T19:46:51",
  "lasttriggered": "2018-03-13T10:30:00",
  "timestriggered": 2,
  "status": "enabled",
  "recycle": true,
  "conditions": [
    {
      "address": "/sensors/2/state/flag",
      "operator": "eq",
      "value": "true"
    }
  ],
  "actions": [
    {
      "address": "/groups/1/action",
      "method": "PUT",
      "body": {
        "scene": "7GJer2-5ahGIqz6"
      }
    },
    {
      "address": "/schedules/2",
      "method": "PUT",
      "body": {
        "status": "enabled"
      }
    }
  ]
}
#+END_SRC

Now things are happening. Looking at the conditions, we can see that
this rule triggers when the wakeup sensor updates, and its flag is set
to =true=. When that happens, the bridge will iterate through its
rules, find that the above condition has been met, and iterate through
each of the actions.

*** ... which sets the scene ...

The bedroom group (=/groups/1= in the rule's action list) is set to
the following scene, which turns on the lights at minimum brightness:

#+BEGIN_SRC http
  GET http://bridge/api/${username}/scenes/7GJer2-5ahGIqz6
#+END_SRC

#+RESULTS[acf0f0fd18efd18cdf94d2c1175f148f9cd85733]:
#+BEGIN_SRC js
{
  "name": "Wake Up init",
  "lights": [
    "2",
    "3",
    "5"
  ],
  "owner": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
  "recycle": true,
  "locked": true,
  "appdata": {},
  "picture": "",
  "lastupdated": "2018-03-11T19:46:50",
  "version": 2,
  "lightstates": {
    "2": {
      "on": true,
      "bri": 1,
      "ct": 447
    },
    "3": {
      "on": true,
      "bri": 1,
      "ct": 447
    },
    "5": {
      "on": true,
      "bri": 1,
      "ct": 447
    }
  }
}
#+END_SRC

*** ... and schedules the transition ...
Another schedule (=/schedules/2= in the rule's action list) is enabled
by the rule.

#+BEGIN_SRC http
  GET http://bridge/api/${username}/schedules/2
#+END_SRC

#+RESULTS[b408558373a001cc2354c960171b21df2669ab85]:
#+BEGIN_SRC js
{
  "name": "L_04_fidlv",
  "description": "L_04_fidlv_trigger end scene",
  "command": {
    "address": "/api/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/groups/0/action",
    "body": {
      "scene": "gXdkB1um68N1sZL"
    },
    "method": "PUT"
  },
  "localtime": "PT00:01:00",
  "time": "PT00:01:00",
  "created": "2018-03-11T19:46:51",
  "status": "disabled",
  "autodelete": false,
  "starttime": "2018-03-13T10:30:00",
  "recycle": true
}
#+END_SRC

/This/ schedule is a bit different from the one we saw before. It is
normally disabled, and it's time pattern (in =localtime=) is
different. The =PT= prefix specifies that this is a timer which
expires after the given amount of time has passed. In this case, it is
set to one minute (the first 60 seconds of our wake-up will be spent
in minimal lighting). Enabling this schedule starts up the timer. When
one minute is up, another scene will be set.

This one, strangely, is applied to group =0=, the meta-group including
all lights, but since the scene itself specifies to which lights it
applies, there's no real problem with it.

*** ... to a fully lit room ...

#+BEGIN_SRC http
  GET http://bridge/api/${username}/scenes/gXdkB1um68N1sZL
#+END_SRC

#+RESULTS[d73d2de48bbff9ac73185999ff3671ddf159dc0d]:
#+BEGIN_SRC js
{
  "name": "Wake Up end",
  "lights": [
    "2",
    "3",
    "5"
  ],
  "owner": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
  "recycle": true,
  "locked": true,
  "appdata": {},
  "picture": "",
  "lastupdated": "2018-03-11T19:46:51",
  "version": 2,
  "lightstates": {
    "2": {
      "on": true,
      "bri": 254,
      "ct": 447,
      "transitiontime": 17400
    },
    "3": {
      "on": true,
      "bri": 254,
      "ct": 447,
      "transitiontime": 17400
    },
    "5": {
      "on": true,
      "bri": 254,
      "ct": 447,
      "transitiontime": 17400
    }
  }
}
#+END_SRC

This scene transitions the lights to full brightness over the next 29
minutes (1740 seconds), per the specified =transitiontime= (which is
specified in deciseconds).

*** ... which will be switched off later.
Finally, an additional rule takes care of turning the lights off and
the wake-up sensor at 9:00 (Two and a half hours after the initial
triggering of the sensor).

#+BEGIN_SRC http
  GET http://bridge/api/${username}/rules/2
#+END_SRC

#+RESULTS[68cbdf0c611d00ec6d86daa820d2dbe672f1d452]:
#+BEGIN_SRC js
{
  "name": "Wake up 1.end",
  "owner": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
  "created": "2018-03-11T19:46:51",
  "lasttriggered": "2018-03-13T13:00:00",
  "timestriggered": 2,
  "status": "enabled",
  "recycle": true,
  "conditions": [
    {
      "address": "/sensors/2/state/flag",
      "operator": "eq",
      "value": "true"
    },
    {
      "address": "/sensors/2/state/flag",
      "operator": "ddx",
      "value": "PT02:30:00"
    }
  ],
  "actions": [
    {
      "address": "/groups/2/action",
      "method": "PUT",
      "body": {
        "on": false
      }
    },
    {
      "address": "/sensors/2/state",
      "method": "PUT",
      "body": {
        "flag": false
      }
    }
  ]
}
#+END_SRC

Unlike the first rule, this one doesn't trigger immediately. It has an
additional condition on the sensor state flag using the special =ddx=
operator, which (given the timer specified) is true *two and a half
hours after* the flag has been set. As the schedule sets it at 6:30,
that means that this rule will trigger at 9:00, turn the lights off in
the bedroom, and set the sensor's flag to =false=.

** Where to go from here

The wake-up config in the phone app touched on pretty much every major
aspect of the Hue bridge API. Given the insight I now have into how it
works, I can start constructing my own schedules and transitions, and
playing with different ways of triggering them and even having them
trigger each other.

If I get around to building my rolling sunrise, I'll be sure to get a
post up on it :)

* DONE Automating My Apartment With Home Assistant          :home_automation:
CLOSED: [2019-06-27 Thu 18:13]
:PROPERTIES:
:EXPORT_FILE_NAME: automating-my-apartment-with-home-assistant
:END:

A while ago, I [[relref:hue-wake-up][posted about]] my experiments with the Phillips Hue API
to create an automated morning sunrise effect. The end result was
nice, but all that mucking about with their HTTP APIs was a hassle any
time I wanted to tweak something. I wanted to define what I wanted in
a more declarative style, and have all the API calls managed behind
the scenes. [[https://www.home-assistant.io/][Home Assistant]] allowed me to do exactly that, and more.

While the Home Assistant docs are geared heavily towards setting up a
raspberry pi appliance to run everything 24/7, I don't own one, and I
already have a server going. I opted instead to get the home assistant
server running using [[https://www.home-assistant.io/docs/installation/docker/][Docker]], and setting up a git repository to hold
my configuration.

** A Brand New Day
Setting up my sunrise was actually /really/ easy. I already had the
scenes I wanted from my [[relref:hue-wake-up][previous attempt]], so it was just a matter of
codifying them in the YAML config. I split them into four scenes - a
start (dawn) and end (daylight) pair for the standing lamp at the wall
beyond the foot of the bed, and a pair for the two nightstand lights.
The end scenes include the transition time to fade in (30 minutes).

#+begin_src yaml
  scene:
    - name: Dawn Sun
      entities:
        light.standing_lamp:
          state: on
          brightness: 1
          xy_color: [0.6042, 0.3739]
    - name: Dawn Daylight
      entities:
        light.correls_nightstand:
          state: on
          brightness: 1
          xy_color: [0.2376, 0.1186]
        light.stephanies_nightstand:
          state: on
          brightness: 1
          xy_color: [0.2376, 0.1186]
    - name: Sunrise Sun
      entities:
        light.standing_lamp:
          state: on
          transition: 1800
          brightness: 254
          xy_color: [0.3769, 0.3639]
    - name: Sunrise Daylight
      entities:
        light.correls_nightstand:
          state: on
          transition: 1800
          brightness: 203
          xy_color: [0.2698, 0.295]
        light.stephanies_nightstand:
          state: on
          transition: 1800
          brightness: 203
          xy_color: [0.2698, 0.295]
#+end_src

Breaking them apart this way means I can trigger the "sun" first for a
splash of orange, then start up the nightstand "daylight" lights a
little bit later! This worked out well, too, since even at the lowest
brightness, having them turn on right at the start when the room is
totally dark had a tendency to jolt me awake. Staggering them produces
a much gentler effect. Scripting all of this took very little work...

#+begin_src yaml
  script:
    sunrise:
      alias: Sunrise
      sequence:
        - service: scene.turn_on
          data:
            entity_id: scene.dawn_sun
        - service: scene.turn_on
          data:
            entity_id: scene.sunrise_sun
        - delay:
            seconds: 180
        - service: scene.turn_on
          data:
            entity_id: scene.dawn_daylight
        - service: scene.turn_on
          data:
            entity_id: scene.sunrise_daylight
#+end_src

... and the end result really is quite pleasant:

#+begin_src ditaa :file ha-lights-1.png :exports none
         +----+
         |cA20|
         |    |
         |{o} |
         +----+






  +----+    Z   +----+
  |cBLK|   z    |cBLK|
  |    |  z     |    |
  |{o} |        |{o} |
  +----+        +----+

         6꞉30 AM
#+end_src

#+RESULTS[bb260c3d0d038bb1fdcd6cba2076efeff57bad80]:
[[file:static/ox-hugo/ha-lights-1.png]]

#+begin_src ditaa :file ha-lights-2.png :exports none
       +----+
       |cB50|
       |    |
       |{o} |
       +----+






+----+        +----+
|c327|   z    |c327|
|    |  z     |    |
|{o} |        |{o} |
+----+        +----+

       6꞉33 AM
#+end_src

#+RESULTS[07189ab694076463b9a88997b2f8be6427ea6950]:
[[file:static/ox-hugo/ha-lights-2.png]]

#+begin_src ditaa :file ha-lights-3.png :exports none
       +----+
       |cFFD|
       |    |
       |{o} |
       +----+


        \o/
         | 
         | 
        / \
+----+        +----+
|cDDF|        |cDDF|
|    |        |    |
|{o} |        |{o} |
+----+        +----+

       7꞉00 AM
#+end_src

#+RESULTS[b22835dedc7d706f3f8ff6826040349decbb5d1a]:
[[file:static/ox-hugo/ha-lights-3.png]]

#+begin_center
[[file:static/ox-hugo/ha-lights-1.png]]
[[file:static/ox-hugo/ha-lights-2.png]]
[[file:static/ox-hugo/ha-lights-3.png]]
#+end_center

That just leaves the automation, which fires a half an hour before the
/actual/ sunrise, so long as the lights aren't already on and somebody
is home (using a binary sensor I defined elsewhere based on phones
detected in the house plus an override toggle).

#+begin_src yaml
  automation:
    - alias: Sunrise
      action:
        - service: script.sunrise
          data: {}
      trigger:
        - platform: sun
          event: sunrise
          offset: '-00:30:00'
      condition:
        - condition: state
          entity_id: binary_sensor.occupied
          state: 'on'
        - condition: state
          entity_id: group.bedroom_lights
          state: 'off'
#+end_src

I later extended the automation with some configuration inputs, which
tie into some new triggers and conditions. I added a "latest start
time" to make sure it always gets me up in time for me to get ready
for work, and an option to disable the wake-up on weekends.

#+begin_src yaml
  input_select:
    sunrise_days:
      name: Days to wake up
      options:
        - Every Day
        - Weekdays
      initial: Every Day
      icon: mdi:weather-sunset
  input_datetime:
    sunrise_time:
      name: Latest start time
      has_date: false
      has_time: true
      initial: '06:30'
  automation:
    - alias: Sunrise
      action:
        - service: script.sunrise
          data: {}
      trigger:
        - platform: sun
          event: sunrise
          offset: '-00:30:00'
        - platform: template
          value_template: >-
            {{ states('sensor.time') == (
                 states.input_datetime.sunrise_time.attributes.timestamp
                 | int | timestamp_custom('%H:%M', False)
               )
            }}
      condition:
        - condition: state
          entity_id: binary_sensor.occupied
          state: 'on'
        - condition: state
          entity_id: group.bedroom_lights
          state: 'off'
        - condition: or
          conditions:
            - condition: state
              entity_id: input_select.sunrise_days
              state: Every Day
            - condition: and
              conditions:
                - condition: state
                  entity_id: input_select.sunrise_days
                  state: Weekdays
                - condition: time
                  weekday:
                    - mon
                    - tue
                    - wed
                    - thu
                    - fri
#+end_src

Sprinkle in some groups, and I've got a nice panel in my Home
Assistant UI to manage everything:

#+CAPTION: The completed sunrise panel
#+ATTR_ORG: :width 800
[[file:static/images/ha-sunrise-ui.png]]

** Keep It Down!

Determined to find more things to automate, I realized that since I
have my TV audio going through a Sonos sound bar, I could very easily
automate the rather annoying ritual of leaping for the app on my phone
to turn on night mode when a movie I'm watching is getting explodey
and I realize it's a bit late in the evening to be shaking my
neighbor's walls.

#+begin_src yaml
  automation:
    - alias: Toggle Sonos night mode
      action:
        - service: media_player.sonos_set_option
          entity_id: media_player.den
          data_template:
            night_sound: >-
              {{ now().hour >= 22 }}
      trigger:
        - platform: time
          at: '22:30:00'
        - platform: time
          at: '08:00:00'
#+end_src

Boom. Happier neighbors, and I can fall asleep in front of movies
without worry!

Just because I could, I also added some configurability to this
automation as well. The logic got a bit tricky, since I wanted to
configure a window that crosses a 24-hour boundary. I also added a
binary sensor so I could see when night mode was enabled from Home
Assistant.

#+begin_src yaml
  automation:
    - alias: Toggle Sonos night mode
      action:
        - service: media_player.sonos_set_option
          entity_id: media_player.den
          data_template:
            night_sound: >-
              {% set start = states.input_datetime.sonos_nightmode_start.attributes %}
              {% set end = states.input_datetime.sonos_nightmode_end.attributes %}
              {% set now_ = (now().hour, now().minute, now().second) %}
              {% set start_ = (start.hour, start.minute, start.second) %}
              {% set end_ = (end.hour, end.minute, end.second) %}
              {% if start_ > end_ -%}
                {{ now_ >= start_ or now_ < end_ }}
              {%- else -%}
                {{ now_ >= start_ and now_ < end_ }}
              {%- endif -%}
      trigger:
        - platform: template
          value_template: "{{ states('sensor.time') == (states.input_datetime.sonos_nightmode_start.attributes.timestamp | int | timestamp_custom('%H:%M', False)) }}"
        - platform: template
          value_template: "{{ states('sensor.time') == (states.input_datetime.sonos_nightmode_end.attributes.timestamp | int | timestamp_custom('%H:%M', False)) }}"
  sensor:
    - platform: time_date
      display_options:
        - time
  input_datetime:
    sonos_nightmode_start:
      name: Start Night Mode
      has_date: false
      has_time: true
      initial: '22:30'
    sonos_nightmode_end:
      name: End Night Mode
      has_date: false
      has_time: true
      initial: '08:00'
  binary_sensor:
    - platform: template
      sensors:
        den_night_mode:
          friendly_name: Sonos Den Night Mode
          value_template: >-
            {{ state_attr('media_player.den', 'night_sound') }}
#+end_src

And, voilà, a dashboard for my speakers, which I pretty much never
need to look at anymore!

[[file:static/images/ha-sonos-ui.png]]

** But Wait, There's More!

It's a too much to cover in a single blog post, but there's plenty
more going on in my config. Over time, I've tweaked and added to my
device tracking to make sure Home Assistant knows when someone's home.
I set up some text-to-speech to announce the weather in the morning,
and welcome the first person to get home. I even re-purposed an old
phone as a webcam so I can check on the cat while I'm out. My config
is on my personal gitlab server, feel free to check it out and see if
there's anything there you can use or learn from:
http://git.phoenixinquis.net/correlr/home-assistant

* TODO Types in Python                                   :programming:python:
:PROPERTIES:
:EXPORT_FILE_NAME: types-in-python
:END:

** TODO Why Use Types?
** TODO Success Typing
** TODO Running Mypy
** TODO Specifying Types