--   Copyright 2013 Mario Pastorelli (pastorelli.mario@gmail.com) Samuel Gélineau (gelisam@gmail.com)
--
--   Licensed under the Apache License, Version 2.0 (the "License");
--   you may not use this file except in compliance with the License.
--   You may obtain a copy of the License at
--
--       http://www.apache.org/licenses/LICENSE-2.0
--
--   Unless required by applicable law or agreed to in writing, software
--   distributed under the License is distributed on an "AS IS" BASIS,
--   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
--   See the License for the specific language governing permissions and
--   limitations under the License.

-- Extra steps to be performed if hawk was installed from a sandbox.
-- 
-- Extra steps are needed because the hawk binary needs runtime access
-- to the hawk library, but the hint library only knows about the globally-
-- installed libraries. If hawk has been installed with a sandbox, its
-- binary and its library will be installed in a local folder instead of
-- in the global location.
module System.Console.Hawk.Sandbox
    ( extraGhcArgs
    , runHawkInterpreter
    ) where

import Control.Applicative
import Data.List
import Language.Haskell.Interpreter (InterpreterT, InterpreterError)
import Language.Haskell.Interpreter.Unsafe (unsafeRunInterpreterWithArgs)
import System.Directory (getDirectoryContents)
import System.FilePath (pathSeparator)
import Text.Printf (printf)

-- magic self-referential module created by cabal
import Paths_haskell_awk (getBinDir)


data Sandbox = Sandbox
  { folder :: FilePath
  , packageFilePrefix :: String
  , packageFileSuffix :: String
  } deriving Show

cabalDev, cabalSandbox :: Sandbox
cabalDev = Sandbox "cabal-dev" "packages-" ".conf"
cabalSandbox = Sandbox ".cabal-sandbox" "" "-packages.conf.d"

-- all the sandbox systems we support.
sandboxes :: [Sandbox]
sandboxes = [cabalDev, cabalSandbox]


-- a version of isSuffixOf which returns the string stripped of its suffix.
isSuffixOf' :: String -> String -> Maybe String
isSuffixOf' suffix s = if suffix `isSuffixOf` s
                         then Just (take (n - m) s)
                         else Nothing
  where
    n = length s
    m = length suffix


-- convert slashes to backslashes if needed
path :: String -> String
path = map replaceSeparator where
    replaceSeparator '/' = pathSeparator
    replaceSeparator x = x


-- if hawk has been compiled by a sandboxing tool,
-- its binary has been placed in a special folder.
-- 
-- return something like (Just "/.../cabal-dev")
getSandboxDir :: Sandbox -> IO (Maybe String)
getSandboxDir sandbox = do
    dir <- Paths_haskell_awk.getBinDir
    let sandboxFolder = folder sandbox
    let suffix = path (sandboxFolder ++ "/bin")
    let basePath = suffix `isSuffixOf'` dir
    let sandboxPath = fmap (++ sandboxFolder) basePath
    return sandboxPath

-- something like "packages-7.6.3.conf"
isPackageFile :: Sandbox -> FilePath -> Bool
isPackageFile sandbox f = packageFilePrefix sandbox `isPrefixOf` f
                       && packageFileSuffix sandbox `isSuffixOf` f

-- something like "/.../cabal-dev/package-7.6.3.conf"
getPackageFile :: Sandbox -> String -> IO String
getPackageFile sandbox dir = do
    files <- getDirectoryContents dir
    case filter (isPackageFile sandbox) files of
      [file] -> return $ printf (path "%s/%s") dir file
      [] -> fail' "no package-db"
      _ -> fail' $ "multiple package-db's"
  where
    fail' s = error $ printf "%s found in sandbox %s" s (folder sandbox)

sandboxSpecificGhcArgs :: Sandbox -> IO [String]
sandboxSpecificGhcArgs sandbox = do
    sandboxDir <- getSandboxDir sandbox
    case sandboxDir of
      Nothing -> return []
      Just dir -> do packageFile <- getPackageFile sandbox dir
                     let arg = printf "-package-db %s" packageFile
                     return [arg]


extraGhcArgs :: IO [String]
extraGhcArgs = concat <$> mapM sandboxSpecificGhcArgs sandboxes

-- | a version of runInterpreter which can load libraries
--   installed along hawk's sandbox folder, if applicable.
-- 
-- Must be called inside a `withLock` block, otherwise hint will generate
-- conflicting temporary files.
-- 
-- TODO: Didn't we write a patch for hint about this?
--       Do we still need the lock?
runHawkInterpreter :: InterpreterT IO a -> IO (Either InterpreterError a)
runHawkInterpreter mx = do
    args <- extraGhcArgs
    unsafeRunInterpreterWithArgs args mx