{-# LANGUAGE DeriveGeneric #-}

module F2Md.Config
  ( getUserdata
  , FeedUserdata(..)
  , updateLastUpdated
  ) where

import Data.List
import F2Md.Utils
import F2Md.Types
import Data.Maybe
import Data.Text (Text)
import Data.Time
import GHC.Generics
import qualified Data.HashMap.Strict as HM
import Data.Aeson

data Config = Config
  { dbPath :: String
  , maildir :: String
  , feeds :: [Text]
  } deriving (Generic, Show)

instance FromJSON Config

data FeedUserdata = FeedUserdata
  { fuUrl :: Text
  , fuLastUpdated :: Maybe ZonedTime } deriving (Show)

getUserdata :: FilePath -> IO ([FeedUserdata], Maybe FilePath, Maybe FilePath)
getUserdata file = do
  config <- decodeFileStrict file
  case config of
    Nothing -> return ([], Nothing, Nothing)
    Just config' -> do
      feedData <- getUserdata' config'
      maildir' <- expandPath $ maildir config'
      dbPath' <- expandPath $ dbPath config'
      return (feedData, Just maildir', Just dbPath')

getUserdata' :: Config -> IO [FeedUserdata]
getUserdata' (Config dbPath _ feeds) = do
  decoded <- getLastUpdatedMap dbPath
  return $ map (\url -> FeedUserdata url $ HM.lookup url decoded) feeds

getLastUpdatedMap :: FilePath -> IO (HM.HashMap Text ZonedTime)
getLastUpdatedMap dbPath =
  fromMaybe (HM.fromList []) <$> (decodeFileStrict =<< expandPath dbPath)

updateLastUpdated :: FilePath -> [FeedUserdata] -> [[Message]] -> IO ()
updateLastUpdated path feeds feedMsgs = do
  decoded <- getLastUpdatedMap path
  encodeFile path $ foldl'
    (\hm (feed, msgs) ->
       case msgs of
         [] -> hm
         h : _ -> HM.insert (fuUrl feed)
                  (utcToZonedTime (zonedTimeZone $ mDate h) . maximum $
                    (zonedTimeToUTC . mDate) <$> msgs)
                  hm)
    decoded (zip feeds feedMsgs)
  --   HM.fromList $ 
  -- mapMaybe
  -- (\(feed, msgs) ->
  --     case msgs of
  --       [] -> fuLastUpdated feed >>= \date -> return (fuUrl feed, date)
  --       h : _ ->
  --         Just (fuUrl feed,
  --               utcToZonedTime (zonedTimeZone $ mDate h) . maximum $
  --                (zonedTimeToUTC . mDate) <$> msgs)) $ zip feeds feedMsgs