{-# LANGUAGE TupleSections              #-}

-- | Dealing with Cabal packages in Fay's own special way.

module Fay.Compiler.Packages where

import Fay.Types
import Fay.Compiler.Config

import Control.Applicative
import Control.Monad
import Control.Monad.Extra
import Data.Maybe
import Data.List
import Data.Version
import GHC.Paths
import Paths_fay
import System.Directory
import System.FilePath
import System.Process.Extra

-- | Given a configuration, resolve any packages specified to their
-- data file directories for importing the *.hs sources.
resolvePackages :: CompileConfig -> IO CompileConfig
resolvePackages config =
  foldM resolvePackage config (configPackages config)

-- | Resolve package.
resolvePackage :: CompileConfig -> String -> IO CompileConfig
resolvePackage config name = do
  desc <- describePackage (configPackageConf config) name
  case packageVersion desc of
    Nothing -> error $ "unable to find package version: " ++ name
    Just ver -> do
      let nameVer = name ++ "-" ++ ver
      shareDir <- if isJust (configBasePath config) && name == "fay-base"
                    then return . fromJust $ configBasePath config
                    else fmap ($ nameVer) getShareGen
      let includes = [shareDir,shareDir </> "src"]
      exists <- mapM doesSourceDirExist includes
      if or exists
         then return (addConfigDirectoryIncludes (map (Just nameVer,) includes) config)
         else error $ "unable to find (existing) package's share dir: " ++ name ++ "\n" ++
                      "tried: " ++ unlines includes ++ "\n" ++
                      "but none of them seem to have Haskell files in them."

-- | Does a directory exist and does it contain any Haskell sources?
doesSourceDirExist :: FilePath -> IO Bool
doesSourceDirExist path = do
  exists <- doesDirectoryExist path
  if not exists
     then return False
     else do files <- filter (\v -> v /= "." && v /= "..") <$> getDirectoryContents path
             sub   <- anyM doesSourceDirExist $ map (path </>) files
             return $ any ((==".hs") . takeExtension) files || sub

-- | Describe the given package.
describePackage :: Maybe FilePath -> String -> IO String
describePackage db name = do
  result <- readAllFromProcess ghc_pkg args ""
  case result of
    Left  (err,_out) -> error $ "ghc-pkg describe error:\n" ++ err
    Right (_err,out) -> return out

  where args = ["describe",name] ++ ["-f" ++ db' | Just db' <- [db]]

-- | Get the package version from the package description.
packageVersion :: String -> Maybe String
packageVersion = fmap (dropWhile (==' ')) . lookup "version:" . map (span (/=' ')) . lines

-- | Make a share directory generator.
getShareGen :: IO (String -> FilePath)
getShareGen = do
  dataDir <- getDataDir
  return $ \pkg ->
    joinPath (map (replace pkg . dropTrailingPathSeparator) (splitPath dataDir))

  where replace pkg component
          | component == nameVer = pkg
          | otherwise = component
        nameVer = "fay-" ++ intercalate "." (map show (versionBranch version))