{-# LANGUAGE RecordWildCards   #-}

module Handler.Shared where

import Import

import           Control.Concurrent.STM
import           Data.IntMap            (IntMap)
import qualified Data.IntMap            as IntMap

import Network.URI
import qualified Data.Text as T

import Database.Persist.Sql (ConnectionPool, runSqlPool, fromSqlKey)

import Control.Concurrent.Lifted (fork, threadDelay)

import qualified Crypto.Hash.SHA1 as CHS

import System.Process
import System.Exit
import System.Random

import System.Directory (renameDirectory)

import PersistSHA1

import qualified Data.ByteString as BS

atom = Control.Concurrent.STM.atomically

type Channel = TChan (Maybe Text)

arena :: FilePath
arena = "arena"

gitPath :: FilePath
gitPath = "/usr/bin/git"

runViewProgress :: (Channel -> Handler ()) -> Handler TypedContent
runViewProgress action = do
  App {..} <- getYesod
  jobId <- randomInt
  chan <- liftIO $ atom $ do
    chan <- newBroadcastTChan
    m <- readTVar jobs
    writeTVar jobs $ IntMap.insert jobId chan m
    return chan
  fork $ do
    liftIO $ threadDelay 1000000
    action chan
    liftIO $ atom $ do
      writeTChan chan $ Just "All done\n"
      writeTChan chan Nothing
      m <- readTVar jobs
      writeTVar jobs $ IntMap.delete jobId m
  redirect $ ViewProgressR jobId

msg :: Channel -> Text -> Handler ()
msg chan m = liftIO $ atom $ writeTChan chan $ Just (m ++ "\n")

err :: Channel -> Text -> Handler ()
err = msg

raw :: Channel -> Text -> Handler ()
raw = msg

doRepoCloning :: Text -> Text -> Channel -> Handler ()
doRepoCloning url branch chan = do
  msg chan "Did something"
  _ <- cloneRepo url branch chan
  return ()

validGitProtocols :: [String]
validGitProtocols = ["git", "http", "https", "ssh"]

validGitProtocolsAsText :: Text
validGitProtocolsAsText = T.pack $ intercalate ", " $ map (++"://") validGitProtocols

cloneRepo :: Text -> Text -> Channel -> Handler (Maybe (Key Repo))
cloneRepo url branch chan = do
  maybeRepo <- runDB $ getBy $ UniqueUrlBranch url branch
  case maybeRepo of
    Just _ -> do
      err chan "Repo already there"
      return Nothing
    Nothing -> cloneRepo' url branch chan

updateRepo :: Key Repo -> Channel -> Handler Bool
updateRepo repoId chan = do
  repo <- runDB $ get404 repoId
  let repoDir = getRepoDir repoId
  (exitCode, _) <- runProgram (Just repoDir) gitPath ["pull", "--progress"] chan
  case exitCode of
    ExitSuccess -> do
      maybeHeadCommit <- getHeadCommit repoDir chan
      case maybeHeadCommit of
        Just headCommit -> do
          runDB $ update repoId [RepoCurrentCommit =. headCommit]
          return True
        Nothing -> return False

getHeadCommit :: FilePath -> Channel -> Handler (Maybe SHA1)
getHeadCommit repoDir chan = do
  (exitCode, out) <- runProgram (Just repoDir) gitPath ["rev-parse", "HEAD"] chan
  case exitCode of
    ExitSuccess -> do
      msg chan $ concat ["HEAD commit is ", commitId]
      return $ Just commitRaw
        where commitId = T.replace "\n" "" out
              commitRaw = fromTextToSHA1 commitId
    ExitFailure _ -> do
      err chan "cannot determine HEAD commit"
      return Nothing

cloneRepo' :: Text -> Text -> Channel -> Handler (Maybe (Key Repo))
cloneRepo' url branch chan = do
      msg chan $ concat ["Preparing to clone repo ", url]
      if checkRepoUrl url
       then do
        msg chan "Cloning..."
        r <- randomInt
        let tmpRepoDir = arena </> ("t" ++ show r)
        (exitCode, _) <- runProgram Nothing gitPath ["clone",
                                                     "--progress",
                                                     "--branch",
                                                     T.unpack branch,
                                                     T.unpack url,
                                                     tmpRepoDir] chan
        case exitCode of
          ExitSuccess -> do
            maybeHeadCommit <- getHeadCommit tmpRepoDir chan
            case maybeHeadCommit of
              Just commitRaw -> do
                userId <- requireAuthId
                time <- liftIO getCurrentTime
                repoId <- runDB $ insert $ Repo {
                  repoUrl=url,
                  repoBranch=branch,
                  repoCurrentCommit=commitRaw,
                  repoOwner=userId,
                  repoReady=True,
                  repoStamp=time }
                let repoDir = getRepoDir repoId
                liftIO $ renameDirectory tmpRepoDir repoDir
                msg chan $ concat ["Repo is in ", (T.pack repoDir)]
                return $ Just repoId
              Nothing -> do
                return Nothing
          ExitFailure _ -> do
            err chan "git failed"
            return Nothing
       else do
        err chan $ concat ["Wrong URL to a Git repo (note that one of the following protocols must be specified: ", validGitProtocolsAsText]
        return Nothing


getRepoDir :: Key Repo -> FilePath
getRepoDir repoId = arena </> ("r" ++ repoIdAsString)
                    where repoIdAsString = show $ fromSqlKey repoId

checkRepoUrl :: Text -> Bool
checkRepoUrl url = case parsedURI of
                      Just uri -> (uriScheme uri) `elem` (map (++":") validGitProtocols)
                      Nothing -> False
                   where parsedURI = parseURI $ T.unpack url

getViewProgressR :: Int -> Handler TypedContent
getViewProgressR jobId = do
    App {..} <- getYesod
    mchan <- liftIO $ atom $ do
        m <- readTVar jobs
        case IntMap.lookup jobId m of
            Nothing -> return Nothing
            Just chan -> fmap Just $ dupTChan chan
    case mchan of
        Nothing -> notFound
        Just chan -> respondSource typePlain $ do
            let loop = do
                    mtext <- liftIO $ atom $ readTChan chan
                    case mtext of
                        Nothing -> return ()
                        Just text -> do
                            sendChunkText text
                            sendFlush
                            loop
            loop

runProgram :: Maybe FilePath -> FilePath -> [String] -> Channel -> Handler (ExitCode, Text)
runProgram workingDir programPath args chan = do
  (_, Just hout, Just herr, pid) <-
       liftIO $ createProcess (proc programPath args){ std_out = CreatePipe,
                                                       std_err = CreatePipe,
                                                       cwd = workingDir}
  (code, out) <- gatherOutput pid hout herr chan
  _ <- liftIO $ waitForProcess pid
  return (code, out)


processOutput :: Text -> ([Text], Text)
processOutput = processOutput' . lines
                where processOutput' [] = ([], "")
                      processOutput' out = (init out, last out)
                      init [] = []
                      init [x] = []
                      init (x:xs) = (x:(init xs))
                      last [x] = x
                      last (_:xs) = last xs


gatherOutput :: ProcessHandle -> Handle -> Handle -> Channel -> Handler (ExitCode, Text)
gatherOutput ph hout herr chan = work mempty mempty
  where
    work accout accerr = do
        -- Read any outstanding input.
        resterr <- takeABit herr accerr
        restout <- takeABit hout accout
        threadDelay 1000000
        -- Check on the process.
        s <- liftIO $ getProcessExitCode ph
        -- Exit or loop.
        case s of
            Nothing -> work restout resterr
            Just ec -> do
                -- Get any last bit written between the read and the status
                -- check.
                _ <- takeFinalBit herr resterr
                all <- takeFinalBit hout restout
                return (ec, all)
    takeABit h acc = do
      bs <- liftIO $ BS.hGetNonBlocking hout (64 * 1024)
      let acc' = acc <> (decodeUtf8 bs)
      let (fullLines, rest) = processOutput acc'
      mapM_ (msg chan) fullLines
      return rest
    takeFinalBit h rest = do
      last <- liftIO $ BS.hGetContents h
      let all = rest <> (decodeUtf8 last)
      mapM_ (msg chan) $ lines all
      return all

randomInt :: Handler Int
randomInt = liftIO $ randomIO

gatherSHA1ForCollectionOfFiles :: [FilePath] -> IO ByteString
gatherSHA1ForCollectionOfFiles files = do
  contentss <- mapM readFile $ sort files
  return $ CHS.finalize $ foldl' CHS.update CHS.init contentss