Created a route to fetch recent modifications as a csv to allow creating clients

src/Handler/Api.hs

@@ -0,0 +1,52 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+module Handler.Api where
+
+import Import
+import Database.Persist.Sql (rawSql)
+import Data.Time.Clock.POSIX (posixSecondsToUTCTime, utcTimeToPOSIXSeconds)
+import qualified Data.Text as Text
+getApiR :: Int -> Handler TypedContent
+getApiR time = do
+    -- TODO: use only one runDB
+    userId <- getUserId
+    -- We get all groups no matter what, since else we can't know which groups have been deleted
+    groups <- getGroups userId
+    let utcTime = posixSecondsToUTCTime (fromIntegral time)
+    let sqlLists = "select ?? from todolist join group_user on todolist.group_id = group_user.group_id and group_user.user = ? join \"group\" on todolist.group_id = \"group\".id and \"group\".last_modified > ?;"
+    lists <- runDB $ rawSql sqlLists [toPersistValue userId, toPersistValue utcTime]
+    let a = lists :: [Entity Todolist]
+    let sqlItems = "select ?? from todolist join group_user on todolist.group_id = group_user.group_id and group_user.user = ? join \"group\" on todolist.group_id = \"group\".id and \"group\".last_modified > ? join todolist_item on todolist_item.todolist_id = todolist.id;"
+    items <- runDB $ rawSql sqlItems [toPersistValue userId, toPersistValue utcTime]
+    let t = unlines $ map groupToCSV groups <> map todolistToCSV lists <> map todolistItemToCSV items
+    return $ TypedContent typePlain $ toContent t
+
+todolistItemToCSV :: Entity TodolistItem -> Text
+todolistItemToCSV item = "i," <> fieldToText item
+todolistToCSV :: Entity Todolist -> Text
+todolistToCSV list = "l," <> fieldToText list
+groupToCSV :: Entity Group -> Text
+groupToCSV group = "g," <> fieldToText group
+
+-- TODO: error management ? (maybe use Either Text Text and then propagate left to handler and send error ?)
+fieldToText :: PersistEntity record => Entity record -> Text
+fieldToText field = Text.intercalate "," (map persistValueToText $ entityValues field)
+
+persistValueToText :: PersistValue -> Text
+persistValueToText (PersistText s) = s
+persistValueToText (PersistInt64 i) = Text.pack $ show i
+persistValueToText (PersistUTCTime d) = Text.pack $ show $ floor (utcTimeToPOSIXSeconds d)
+persistValueToText (PersistBool b) = if b then "T" else "F"
+persistValueToText _ = error  "Wrong input type"
+
+getText :: Text
+getText = do
+    -- GET EVERY GROUP THAT HAS BEEN MODIFIED SINCE TIMESTAMP FROM USER
+
+    -- GET EVERY TODOLIST THAT HAS BEEN MODIFIED SINCE TIMESTAMP
+    -- GET EVERY ITEM FROM THESE TODOLISTS
+    -- ENCODE ALL OF THEM IN THE TEXTFILE
+    -- SEND IT !
+    -- DONE :)
+    error "not done yet"