{-
 - Copyright 2015 Egor Tensin <Egor.Tensin@gmail.com>
 - This file is licensed under the terms of the MIT License.
 - See LICENSE.txt for details.
-}

module Environment
    ( saveToRegistry
    , saveToRegistryWithPrompt
    , queryFromRegistry
    , wipeFromRegistry
    , wipeFromRegistryWithPrompt
    , getEnv
    , splitPaths
    , joinPaths
    , RegistryBasedEnvironment(..)
    ) where

import Control.Monad (liftM, when)
import Data.List (intercalate)
import Data.List.Split (splitOn)
import Data.Maybe (fromMaybe)
import qualified System.Environment (lookupEnv)
import System.IO.Error (catchIOError, isDoesNotExistError)

import qualified Registry
import qualified Utils (promptToContinue)

data RegistryBasedEnvironment
    = CurrentUserEnvironment
    | AllUsersEnvironment
    deriving (Eq, Show)

registrySubKeyPath :: RegistryBasedEnvironment -> String
registrySubKeyPath CurrentUserEnvironment = "Environment"
registrySubKeyPath AllUsersEnvironment = "SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Environment"

registryKey :: RegistryBasedEnvironment -> Registry.KeyHandle
registryKey CurrentUserEnvironment = Registry.hkcu
registryKey AllUsersEnvironment = Registry.hklm

registryKeyPath :: RegistryBasedEnvironment -> String
registryKeyPath CurrentUserEnvironment = "HKCU\\" ++ registrySubKeyPath CurrentUserEnvironment
registryKeyPath AllUsersEnvironment = "HKLM\\" ++ registrySubKeyPath AllUsersEnvironment

saveToRegistry :: RegistryBasedEnvironment -> String -> String -> IO ()
saveToRegistry env = Registry.setString (registryKey env) (registrySubKeyPath env)

saveToRegistryWithPrompt :: RegistryBasedEnvironment -> String -> String -> IO ()
saveToRegistryWithPrompt env name value = do
    putStrLn $ "Saving variable '" ++ name ++ "' to '" ++ registryKeyPath env ++ "'..."
    oldValue <- queryFromRegistry env name
    putStrLn $ "\tOld value: " ++ oldValue
    putStrLn $ "\tNew value: " ++ value
    agreed <- Utils.promptToContinue
    when agreed $ saveToRegistry env name value

queryFromRegistry :: RegistryBasedEnvironment -> String -> IO String
queryFromRegistry env name = catchIOError (Registry.getString (registryKey env) (registrySubKeyPath env) name) emptyIfDoesNotExist
  where
    emptyIfDoesNotExist :: IOError -> IO String
    emptyIfDoesNotExist e = if isDoesNotExistError e then return "" else ioError e

wipeFromRegistry :: RegistryBasedEnvironment -> String -> IO ()
wipeFromRegistry env name = catchIOError (Registry.delValue (registryKey env) (registrySubKeyPath env) name) ignoreIfDoesNotExist
  where
    ignoreIfDoesNotExist :: IOError -> IO ()
    ignoreIfDoesNotExist e = if isDoesNotExistError e then return () else ioError e

wipeFromRegistryWithPrompt :: RegistryBasedEnvironment -> String -> IO ()
wipeFromRegistryWithPrompt env name = do
    putStrLn $ "Deleting variable '" ++ name ++ "' from '" ++ registryKeyPath env ++ "'..."
    agreed <- Utils.promptToContinue
    when agreed $ wipeFromRegistry env name

getEnv :: String -> IO String
getEnv = liftM (fromMaybe "") . System.Environment.lookupEnv

pathSep :: String
pathSep = ";"

splitPaths :: String -> [String]
splitPaths = filter (not . null) . splitOn pathSep

joinPaths :: [String] -> String
joinPaths = intercalate pathSep . filter (not . null)