{-# 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"