import Control.Applicative
import Control.Arrow
import Control.Monad
import Data.List
import Data.Maybe
import System.Directory
import System.Environment
import System.FilePath
import System.Process

import Git


main :: IO ()
main = do
  (repos, args) <- reposAndArgs <$> getArgs
  cabalFiles <- mapM fetch repos
  cabalInstall (catMaybes cabalFiles) args


reposAndArgs :: [String] -> ([String], Maybe String)
reposAndArgs = second flags . span (/= "--")
 where
  flags [] = Nothing
  flags ["--"] = Nothing
  flags (_:xs) = Just $ unwords xs

fetch :: String -> IO (Maybe FilePath)
fetch urlAndMaybeRevision = do
  currentDir <- getCurrentDirectory
  newDir <- createNonExistentDirectory currentDir ("cabalg_" ++ repoName urlAndMaybeRevision)
  case maybeRevision of
    Just revision -> cloneRevision url revision newDir
    Nothing -> clone url newDir
  findCabalFile newDir
    where
      maybeRevision = case dropWhile (/= '@') urlAndMaybeRevision of
        '@':x -> Just x
        _ -> Nothing
      url = takeWhile (/= '@') urlAndMaybeRevision

cabalInstall :: [String] -> Maybe String -> IO ()
cabalInstall cabalFiles args = void $ readProcess "cabal" ("install" : cabalFiles ++ words (fromMaybe "" args)) []

repoName :: String -> String
repoName = takeWhile (/= '@') . lastSplitOn '/'
  where lastSplitOn :: Eq a => a -> [a] -> [a]
        lastSplitOn c = go []
          where
            go acc (x:xs) | x == c = go [] xs
                          | otherwise = go (acc ++ [x]) xs
            go acc [] = acc

createNonExistentDirectory :: FilePath -> String -> IO FilePath
createNonExistentDirectory currentDir dirname = do
  newDir <- generateNonExistentDirectory dirname Nothing
  createDirectory newDir
  return newDir
    where
      generateNonExistentDirectory :: FilePath -> Maybe Int -> IO FilePath
      generateNonExistentDirectory d suffix = let fullDirName = currentDir </> d ++ maybe "" show suffix in do
        exist <- doesDirectoryExist fullDirName
        if exist
          then generateNonExistentDirectory d $ return $ maybe 1 (+ 1) suffix
          else return fullDirName

findCabalFile :: FilePath -> IO (Maybe FilePath)
findCabalFile path = ((path </>) `fmap`) `fmap` find (".cabal" `isSuffixOf`) `fmap` getDirectoryContents path