{-# LANGUAGE FlexibleContexts      #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings     #-}
{-# LANGUAGE PartialTypeSignatures #-}
{-# LANGUAGE RankNTypes            #-}
{-# LANGUAGE TypeFamilies          #-}
module Core (
  markAsUnprocessed,
  subscribe,
  unsubscribe,
  listFeeds,
  describeFeed,
  importOPML,
) where

-- {{{ Imports
import           Control.Exception.Safe
import           Data.Conduit
import qualified Data.Map                as Map
import qualified Data.Set                as Set
import           Data.Tree
import qualified Imm.Database.Feed       as Database
import           Imm.Feed
import           Imm.Logger              as Logger
import           Imm.Pretty
import           Refined
import           Text.OPML.Conduit.Parse
import           Text.OPML.Types         as OPML
import           Text.XML                as XML ()
import           Text.XML.Stream.Parse   as XML (def, force, parseBytes)
-- }}}


markAsUnprocessed :: MonadThrow m
                  => Logger.Handle m
                  -> Database.Handle m
                  -> FeedQuery
                  -> m ()
markAsUnprocessed logger database query = Database.resolveEntryKey database query
  >>= mapM_ (Database.markAsUnprocessed logger database)

-- | Print database status for given feed(s)
describeFeed :: MonadThrow m => Logger.Handle m -> Database.Handle m -> FeedQuery -> m ()
describeFeed logger database feedQuery = do
  entries <- Database.fetchQuery database (Database.matching feedQuery)
  flushLogs logger
  forM_ (Map.toList entries) $ \(index, entry) ->
    log logger Info $ pretty index <+> Database.prettyEntry entry

-- | Register the given set of feeds in database
subscribe :: MonadCatch m => Logger.Handle m -> Database.Handle m -> FeedLocation -> Set Text -> m ()
subscribe logger database feedLocation tags = do
  index <- Database.register logger database feedLocation tags
  log logger Info $ "Subscribed with index" <+> pretty index

-- | Un-register the given set of feeds from database
unsubscribe :: MonadThrow m
            => Logger.Handle m
            -> Database.Handle m
            -> FeedQuery
            -> m ()
unsubscribe logger database query = Database.resolveEntryKey database query
  >>= Database.delete logger database

-- | List all subscribed feeds and their status
listFeeds :: MonadCatch m => Logger.Handle m -> Database.Handle m -> m ()
listFeeds logger database = do
  entries <- Database.fetchAll database
  flushLogs logger
  when (null entries) $ log logger Warning "No subscription"
  forM_ (zip [0..] $ Map.elems entries) $ \(i, entry) ->
    log logger Info $ pretty (i :: Int) <+> Database.prettyShortEntry entry


-- | 'subscribe' to all feeds described by the OPML document provided in input
importOPML :: MonadCatch m => Logger.Handle m -> Database.Handle m -> ConduitT () ByteString m () -> m ()
importOPML logger database input = do
  opml <- runConduit $ input .| XML.parseBytes def .| force "Invalid OPML" parseOpml
  forM_ (opmlOutlines opml) $ importOPML' logger database mempty

importOPML' :: MonadCatch m => Logger.Handle m -> Database.Handle m -> Set Text -> Tree OpmlOutline -> m ()
importOPML' logger database _ (Node (OpmlOutlineGeneric b _) sub) = mapM_ (importOPML' logger database (Set.singleton . unrefine $ OPML.text b)) sub
importOPML' logger database c (Node (OpmlOutlineSubscription _ s) _) = void $ subscribe logger database (FeedDirectURI $ xmlUri s) c
importOPML' _ _ _ _ = return ()