module Material.Textfield where

{-| From the [Material Design Lite documentation](http://www.getmdl.io/components/#textfields-section):

> The Material Design Lite (MDL) text field component is an enhanced version of
> the standard HTML `<input type="text">` and `<input type="textarea">` elements.
> A text field consists of a horizontal line indicating where keyboard input
> can occur and, typically, text that clearly communicates the intended
> contents of the text field. The MDL text field component provides various
> types of text fields, and allows you to add both display and click effects.
>
> Text fields are a common feature of most user interfaces, regardless of a
> site's content or function. Their design and use is therefore an important
> factor in the overall user experience. See the text field component's
> [Material  Design specifications page](https://www.google.com/design/spec/components/text-fields.html)
> for details.
>
> The enhanced text field component has a more vivid visual look than a standard
> text field, and may be initially or programmatically disabled. There are three
> main types of text fields in the text field component, each with its own basic
> coding requirements. The types are single-line, multi-line, and expandable.

This implementation provides only single-line.


# Configuration
@docs Kind, Label

# Component
@docs Action, Model, model, update, view
-}

import Html exposing (..)
import Html.Attributes exposing (..)
import Html.Events exposing (..)

import Material.Aux exposing (..)


-- MODEL


{-| Label configuration. The `text` is the text of the label;
the label floats if `float` is True.
-}
type alias Label =
  { text : String
  , float : Bool
  }


{-| Kind of textfield. Currently supports only single-line inputs.
-}
type Kind
  = SingleLine
  {-
  | MultiLine (Maybe Int) -- Max no. of rows or no limit
  -- TODO. Should prevent key event for ENTER
  -- when number of rows exceeds maxrows argument to constructor:

  MaterialTextfield.prototype.onKeyDown_ = function(event) {
    var currentRowCount = event.target.value.split('\n').length;
    if (event.keyCode === 13) {
      if (currentRowCount >= this.maxRows) {
        event.preventDefault();
      }
    }
  };
  -}


{-| Model. The textfield is in its error-state if `error` is not `Nothing`.
The contents of the field is `value`.
-}
type alias Model =
  { label : Maybe Label
  , error : Maybe String
  , kind : Kind
  , isDisabled : Bool
  , isFocused : Bool
  , value : String
  }


{-| Default model. No label, error, or value.
-}
model : Model
model =
  { label = Nothing
  , error = Nothing
  , kind = SingleLine
  , isDisabled = False
  , isFocused = False
  , value = ""
  }


-- ACTIONS, UPDATE


{-| Component actions. `Input` carries the new value of the field.
-}
type Action
  = Input String
  | Blur
  | Focus


{-| Component update.
-}
update : Action -> Model -> Model
update action model =
  case action of
    Input str ->
      { model | value = str }

    Blur ->
      { model | isFocused = False }

    Focus ->
      { model | isFocused = True }


-- VIEW


{-| Component view.
-}
view : Signal.Address Action -> Model -> Html
view addr model =
  let hasFloat = model.label |> Maybe.map .float |> Maybe.withDefault False
      hasError = model.error |> Maybe.map (always True) |> Maybe.withDefault False
  in
    filter div
      [ classList
          [ ("mdl-textfield", True)
          , ("mdl-js-textfield", True)
          , ("is-upgraded", True)
          , ("mdl-textfield--floating-label", hasFloat)
          , ("is-invalid", hasError)
          , ("is-dirty", model.value /= "")
          , ("is-focused", model.isFocused && not model.isDisabled)
          , ("is-disabled", model.isDisabled)
          ]
      ]
      [ Just <| input
          [ class "mdl-textfield__input"
          , style [ ("outline", "none") ]
          , type' "text"
          , disabled model.isDisabled
          , value model.value
          , Html.Events.on "input" targetValue (\s -> Signal.message addr (Input s))
          , onBlur addr Blur
          , onFocus addr Focus
          ]
          []
      ,   model.label |> Maybe.map (\l ->
            label [class "mdl-textfield__label"]  [text l.text])
      ,   model.error |> Maybe.map (\e ->
            span [class "mdl-textfield__error"] [text e])
      ]