{-# LANGUAGE LambdaCase #-}

module ReadConfig where

import UnitConversions
import qualified Text.Read as TR
import Control.Exception
import Data.Typeable
import Data.Char (toLower)
import Data.List.Split
import Lang.Pirate
import Lang.French
import System.FilePath ((</>))
import System.Directory
import Paths_herms hiding (getDataDir) -- This module is generated by cabal

------------------------------
------- Config Types ---------
------------------------------

-- TODO Allow record synonyms with that fancy stuff

data ConfigInfo = ConfigInfo
  { defaultUnit           :: Conversion
  , defaultServingSize    :: Int
  , recipesFile           :: String
  , language              :: String
  } deriving (Read, Show)

data Config = Config
  { defaultUnit'        :: Conversion
  , defaultServingSize' :: Int
  , dataDir             :: String
  , configDir           :: String
  , recipesFile'        :: String
  , translator          :: String -> String
  }

data Language = English
              | Pirate
              | Portuguese
              | French

type Translator = String -> String

------------------------------
---- Exception Handling ------
------------------------------

data ConfigParseError = ConfigParseError
  deriving Typeable

instance Show ConfigParseError where
  show ConfigParseError = "Error parsing config.hs"

instance Exception ConfigParseError

------------------------------
------ Language Synonyms -----
------------------------------

-- Contributor's note: Make sure that all of these synonyms are lower-case as
-- we handle case-sensitivity by first converting the user's settings input
-- to all lower-case.

englishSyns = [ "english"
              , "en"
              , "en-us"
              , "\'murican"
              ]

pirateSyns = [ "pirate"
             , "pr"
             ]

portugueseSyns = [ "portuguese"
                 , "português"
                 , "portugues"
                 , "pt"
                 ]

frenchSyns = [ "french"
              , "fr"
              , "fr-fr"
              , "français"
              , "francais"
              ]


------------------------------
--------- Functions ----------
------------------------------

getLang :: ConfigInfo -> Language
getLang c
  -- | isIn portugueseSyns = Portuguese
  | isIn pirateSyns  = Pirate
  -- | isIn frenchSyns = French
  | isIn frenchSyns  = French
  | otherwise        = English
  where isIn = elem (map toLower $ language c)

getTranslator :: Language -> Translator
getTranslator lang = case lang of
                       Pirate    -> pirate
                       French    -> french
                       _         -> id :: String -> String

dropComments :: String -> String
dropComments = unlines . map (head . splitOn "--") . lines

processConfig :: FilePath -> FilePath -> ConfigInfo -> Config
processConfig dataDir configDir raw = Config
  { defaultUnit'        = defaultUnit raw
  , defaultServingSize' = defaultServingSize raw
  , recipesFile'        = dataDir </> recipesFile raw
  , translator          = getTranslator $ getLang raw
  , dataDir             = dataDir
  , configDir           = configDir
  }

-- | The directory of the config.hs file. Its location is dictated by
--   <http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html XDG
--   Base Directory Specification>.
getConfigDir :: IO FilePath
getConfigDir = getXdgDirectory XdgConfig "herms"

-- | The directory of the recipes.herms file.
getDataDir :: IO FilePath
getDataDir = getXdgDirectory XdgData "herms"

-- | Create a directory if it doesn't exist, ensure it is readable,
-- writable, and executable.
directoryWithPermissions :: FilePath -> IO ()
directoryWithPermissions dir = do
  createDirectoryIfMissing True dir
  setPermissions dir $
    setOwnerReadable True $
    setOwnerWritable True $
    setOwnerExecutable True
    emptyPermissions

writeDefaultFile :: String -> FilePath -> IO ()
writeDefaultFile name path = do
  putStrLn $ "Couldn't find " ++ path
  templatePath <- getDataFileName name
  putStrLn $ "Copying default from " ++ templatePath
  copyFile templatePath path

-- | @readFileOrDefault attempts to read a file from a path. If that file
-- doesn't exist, it copies a default version that was installed by cabal
-- with @writeDefaultFile.
readFileOrDefault :: String -> FilePath -> IO String
readFileOrDefault name path = 
  (try (readFile path) :: IO (Either IOError String)) >>=
    \case
      Left _ -> writeDefaultFile name path >> readFile path
      Right content -> return content

getConfig :: IO Config
getConfig = do

  -- Create configuration and data directories
  configDir <- getConfigDir
  dataDir   <- getDataDir
  mapM_ directoryWithPermissions [configDir, dataDir]

  -- Try to read configuration file
  contents  <- readFileOrDefault "config.hs" (configDir </> "config.hs")

  -- Parse the configuration
  let result = TR.readEither (dropComments contents) :: Either String ConfigInfo
  case result of
    Left  _ -> throw ConfigParseError
    Right r -> return (processConfig dataDir configDir r)