-- | Threads.hs
-- A module which runs threads for downloading and parsing pages and
-- then send messages via xmpp.

module Threads (
    runLoop,
    q
) where

import Config
import DB
import DBState
import HTTP
import Parsers

import Happstack.State
import Control.Concurrent hiding (Chan)
import Control.Concurrent.MVar
import Control.Concurrent.QSem
import System.IO.Unsafe
import Network
import Network.XMPP

import Data.List
import Text.Regex.Posix


-- | Do some prepares and running loop.
runLoop :: TCPConnection -> Config -> Chans -> IO ()
runLoop c cf chans = do
    mvars <- mapM (const newEmptyMVar) [1..cthreads cf]
    runLoop' c mvars chans


q :: QSem
q = unsafePerformIO $ do
    qq <- newQSem 0
    signalQSem qq
    return qq


runLoop' :: TCPConnection -> [MVar Bool] -> Chans -> IO ()
runLoop' c mvars chans = do
    putStrLn "---"
    -- get pages for downloading and parsing
    db <- query GetDB
    let urls = getList db
    -- run threads
    mapM_ runThread urls
    putStrLn "---"
    -- big timeout before running new cycle
    threadDelay 10000000

    runLoop' c mvars chans
  where
    runThread url = do
      threadDelay 100000 -- small timeout for scatter threads spawn
      mmvar <- findEmptyMVar mvars
      case mmvar of
        Just mvar -> do
          putMVar mvar True
          forkIO $ doThreadUpdates url mvar
        _ -> runThread url

    findEmptyMVar [] = return Nothing
    findEmptyMVar (mvar:mvars) = do
      isEmpty <- isEmptyMVar mvar
      if isEmpty
        then return $ Just mvar
        else findEmptyMVar mvars

    doThreadUpdates url@(URL u) mvar = do
      -- try to find parser for url in DB
      case find (\(r,_) -> u =~ r) chans of
        Just (_, chan) -> do
          -- download page
          putStrLn $ "INFO: fetching "++u
          resp <- downloadPage chan url
          -- matching response
          case resp of
            Left SomeError ->
              putStrLn $ "WARNING: some error while downloading "++u
            Left PageDeleted -> do
              update $ DelThreadAll' url
              putStrLn $ "WARNING: 404 at "++u++", deleting from DB"
            Right body -> do
              putStrLn $ "INFO: got "++u++", parsing"
              
              db <- query GetDB              
              let (lastPost, jids) = getThread url db
              
              result <- parsePage chan lastPost body
              case result of
                Just (lastPost', msg) | lastPost' > lastPost -> do
                  update $ UpdateThread' url lastPost'
                  putStrLn $ "INFO: "++u++" has new posts"
                  sendToXMPP c url jids msg
                _ ->
                  putStrLn $ "INFO: "++u++" hasn't new posts"

        Nothing ->
          putStrLn $ "ERROR: can't find chan for "++u

      -- release mvar
      a <- takeMVar mvar
      return ()

-- | Send info about update in thread via xmpp.
sendToXMPP :: TCPConnection -> URL -> [JID] -> String -> IO ()
sendToXMPP c url@(URL u) jids msg = do
    -- block
    waitQSem q
    -- send msgs
    db <- query GetDB
    runXMPP c $ mapM_ (processJID db) jids
    -- unblock
    signalQSem q
  where
    -- send message with description and wait a little
    processJID db jid@(JID j) = do
      let descr = getDescription url jid db
      sendMessage j ("*"++descr++"* \n"++u++"\n"++msg)
      liftIO $ threadDelay 200000