module State.Flagging
  ( loadFlaggedMessages
  , updateMessageFlag
  )
where

import           Prelude ()
import           Prelude.MH

import           Data.Function ( on )
import qualified Data.Set as Set
import           Lens.Micro.Platform

import           Network.Mattermost.Types

import           State.Common
import           Types


loadFlaggedMessages :: Seq FlaggedPost -> ChatState -> IO ()
loadFlaggedMessages prefs st = doAsyncWithIO Normal st $ do
  return $ Just $ do
      sequence_ [ updateMessageFlag (flaggedPostId fp) True
                | fp <- toList prefs
                , flaggedPostStatus fp
                ]


-- | Update the UI to reflect the flagged/unflagged state of a
-- message. This __does not__ talk to the Mattermost server, but
-- rather is the function we call when the Mattermost server notifies
-- us of flagged or unflagged messages.
updateMessageFlag :: PostId -> Bool -> MH ()
updateMessageFlag pId f = do
  if f
    then csResources.crFlaggedPosts %= Set.insert pId
    else csResources.crFlaggedPosts %= Set.delete pId
  msgMb <- use (csPostMap.at(pId))
  case msgMb of
    Just msg
      | Just cId <- msg^.mChannelId -> do
      let isTargetMessage m = m^.mMessageId == Just (MessagePostId pId)
      csChannel(cId).ccContents.cdMessages.traversed.filtered isTargetMessage.mFlagged .= f
      csPostMap.ix(pId).mFlagged .= f
      -- We also want to update the post overlay if this happens while
      -- we're we're observing it
      mode <- gets appMode
      case mode of
        PostListOverlay PostListFlagged
          | f ->
              csPostListOverlay.postListPosts %=
                addMessage (msg & mFlagged .~ True)
          -- deleting here is tricky, because it means that we need to
          -- move the focus somewhere: we'll try moving it _up_ unless
          -- we can't, in which case we'll try moving it down.
          | otherwise -> do
              selId <- use (csPostListOverlay.postListSelected)
              posts <- use (csPostListOverlay.postListPosts)
              let nextId = case getNextPostId selId posts of
                    Nothing -> getPrevPostId selId posts
                    Just x  -> Just x
              csPostListOverlay.postListSelected .= nextId
              csPostListOverlay.postListPosts %=
                filterMessages (((/=) `on` _mMessageId) msg)
        _ -> return ()
    _ -> return ()