From 19980acc0c0103e13ca411c3f1b4fe5e0b921b7f Mon Sep 17 00:00:00 2001
From: Correl <correl@gmail.com>
Date: Wed, 13 Jul 2022 00:04:35 -0400
Subject: [PATCH] WIP: Pagination

---
 src/Tutor/Api.hs        | 12 +++++++++---
 src/Tutor/Database.hs   | 13 ++++++++-----
 src/Tutor/Pagination.hs | 12 ++++++++++++
 src/Tutor/Select.hs     |  2 +-
 4 files changed, 30 insertions(+), 9 deletions(-)
 create mode 100644 src/Tutor/Pagination.hs

diff --git a/src/Tutor/Api.hs b/src/Tutor/Api.hs
index f2699fb..5202464 100644
--- a/src/Tutor/Api.hs
+++ b/src/Tutor/Api.hs
@@ -27,9 +27,11 @@ import GHC.Generics (Generic)
 import qualified Paths_tutor as PT
 import Servant
 import Servant.OpenApi (HasOpenApi (toOpenApi))
+import qualified Tutor.Pagination as Pagination
 import Tutor.Card
 import Tutor.Config
 import Tutor.Database
+import Data.Maybe (fromMaybe)
 
 data Status = Status
   { apiVersion :: T.Text,
@@ -176,6 +178,8 @@ type SearchCards =
     :> QueryParam' '[Description "Query string"] "q" T.Text
     :> QueryParam' '[Description "Sorting method"] "sort_by" T.Text
     :> QueryParam' '[Description "Search across collection or all cards"] "in_collection" T.Text
+    :> QueryParam' '[Description "Pagination limit"] "limit" Int
+    :> QueryParam' '[Description "Pagination offset"] "offset" Int
     :> Get '[JSON] [Card]
 
 type TutorAPI =
@@ -206,9 +210,11 @@ openapi =
 tutorServer :: Config -> Server TutorAPI
 tutorServer config = status config :<|> searchCards (tutorDatabase config)
   where
-    searchCards :: FilePath -> Maybe T.Text -> Maybe T.Text -> Maybe T.Text -> Handler [Card]
-    searchCards dbFile q sortBy inCollection =
-      liftIO $ Tutor.Database.searchCards dbFile q sortBy inCollection
+    searchCards :: FilePath -> Maybe T.Text -> Maybe T.Text -> Maybe T.Text -> Maybe Int -> Maybe Int -> Handler [Card]
+    searchCards dbFile q sortBy inCollection limit offset =
+      liftIO $ Pagination.items <$> Tutor.Database.searchCards dbFile q sortBy inCollection pagination
+      where pagination = Pagination.Pagination (fromMaybe 10 limit) (fromMaybe 0 offset)
+
 
 docsServer :: Server DocsAPI
 docsServer = return openapi
diff --git a/src/Tutor/Database.hs b/src/Tutor/Database.hs
index 7ba9ebc..58fe9ea 100644
--- a/src/Tutor/Database.hs
+++ b/src/Tutor/Database.hs
@@ -14,12 +14,13 @@ import Database.SQLite.Simple.Internal
 import Database.SQLite.Simple.Ok
 import Database.SQLite.Simple.QQ
 import Tutor.Card
+import qualified Tutor.Pagination as Pagination
 import qualified Tutor.Search as Search
 import Tutor.SearchParser
 import Tutor.Select
   ( Select (..),
     join,
-    limit,
+    limitOffset,
     orderBy,
     parameter,
     selectSimple,
@@ -198,14 +199,16 @@ instance FromRow Card where
               }
         }
 
-searchCards :: FilePath -> Maybe T.Text -> Maybe T.Text -> Maybe T.Text -> IO [Card]
-searchCards dbFile q sortBy inCollection =
+searchCards :: FilePath -> Maybe T.Text -> Maybe T.Text -> Maybe T.Text -> Pagination.Pagination -> IO (Pagination.Page Card)
+searchCards dbFile q sortBy inCollection pagination =
   withConnection dbFile $ \conn ->
-    queryNamed
+    asPage <$> queryNamed
       conn
       (toQuery query)
       (selectParameters query)
   where
+    asPage results =
+      Pagination.Page Nothing Nothing results
     baseQuery =
       selectSimple
         [ "cards.scryfall_id",
@@ -234,7 +237,7 @@ searchCards dbFile q sortBy inCollection =
              ELSE cards.color_identity END ASC|]
         <> orderBy "cards.name ASC"
         <> parameter ":last_update_key" ("last_update" :: T.Text)
-        <> limit 10
+        <> limitOffset (Pagination.limit pagination) (Pagination.offset pagination)
     query =
       mconcat $
         catMaybes
diff --git a/src/Tutor/Pagination.hs b/src/Tutor/Pagination.hs
new file mode 100644
index 0000000..38bbda1
--- /dev/null
+++ b/src/Tutor/Pagination.hs
@@ -0,0 +1,12 @@
+module Tutor.Pagination (Pagination(..), Page(..)) where
+
+data Pagination = Pagination
+  { limit :: Int
+  , offset :: Int
+  }
+
+data Page a = Page
+  { previous :: Maybe Pagination
+  , next :: Maybe Pagination
+  , items :: [a]
+  }
diff --git a/src/Tutor/Select.hs b/src/Tutor/Select.hs
index 3aae492..55820ff 100644
--- a/src/Tutor/Select.hs
+++ b/src/Tutor/Select.hs
@@ -96,7 +96,7 @@ toQuery select =
       [] -> Nothing
       xs -> Just $ "ORDER BY " <> sqlJoin ", " xs
     sqlLimitOffset = case (selectLimit select, selectOffset select) of
-      (Just l, Just o) -> Just "LIMIT :__limit, :__offset"
+      (Just l, Just o) -> Just "LIMIT :__limit OFFSET :__offset"
       (Just l, Nothing) -> Just "LIMIT :__limit"
       _ -> Nothing