-- |
-- Copyright   : (c) 2015 Egor Tensin <Egor.Tensin@gmail.com>
-- License     : MIT
-- Maintainer  : Egor.Tensin@gmail.com
-- Stability   : experimental
--
-- Low-level utility functions for reading and writing registry values.

module Windows.Registry
    ( IsKeyPath(..)
    , RootKey(..)
    , KeyPath(..)

    , ValueName
    , ValueType
    , ValueData

    , open
    , close

    , deleteValue

    , queryValue
    , queryType

    , getValue
    , GetValueFlag(..)
    , getType

    , getExpandedString

    , setValue
    , setString
    , setExpandableString
    , setStringPreserveType
    ) where

import           Control.Exception     (bracket)
import           Control.Monad.Trans.Except (ExceptT(..), catchE, throwE)
import           Data.Bits             ((.|.))
import qualified Data.ByteString       as B
import           Data.List             (intercalate)
import           Data.Maybe            (fromJust)
import qualified Data.Text             as T
import           Data.Text.Encoding    (decodeUtf16LE, encodeUtf16LE)
import           Data.Tuple            (swap)
import           Foreign.ForeignPtr    (withForeignPtr)
import           Foreign.Marshal.Alloc (alloca, allocaBytes)
import           Foreign.Marshal.Array (peekArray, pokeArray)
import           Foreign.Storable      (peek, poke)
import           System.IO.Error       (catchIOError, isDoesNotExistError)
import qualified System.Win32.Types    as WinAPI
import qualified System.Win32.Registry as WinAPI

type Handle = WinAPI.HKEY

class IsKeyPath a where
    openUnsafe :: a -> IO Handle

close :: Handle -> IO ()
close = WinAPI.regCloseKey

open :: IsKeyPath a => a -> IO (Either IOError Handle)
open a = catchIOError (Right <$> openUnsafe a) $ return . Left

data RootKey = CurrentUser
             | LocalMachine
             deriving (Eq)

instance IsKeyPath RootKey where
    openUnsafe CurrentUser = return WinAPI.hKEY_CURRENT_USER
    openUnsafe LocalMachine = return WinAPI.hKEY_LOCAL_MACHINE

instance Show RootKey where
    show CurrentUser = "HKCU"
    show LocalMachine = "HKLM"

data KeyPath = KeyPath RootKey [String]

pathSep :: String
pathSep = "\\"

instance IsKeyPath KeyPath where
    openUnsafe (KeyPath root path) = do
        rootHandle <- openUnsafe root
        WinAPI.regOpenKey rootHandle $ intercalate pathSep path

instance Show KeyPath where
    show (KeyPath root path) = intercalate pathSep $ show root : path

type ValueName = String

data ValueType = TypeNone
               | TypeBinary
               | TypeDWord
               | TypeDWordBE
               | TypeQWord
               | TypeString
               | TypeMultiString
               | TypeExpandableString
               | TypeLink
               deriving (Eq, Show)

instance Enum ValueType where
    fromEnum = fromJust . flip lookup valueTypeTable
    toEnum = fromJust . flip lookup (map swap valueTypeTable)

valueTypeTable :: [(ValueType, Int)]
valueTypeTable =
    [ (TypeNone,     0)
    , (TypeBinary,   3)
    , (TypeDWord,    4)
    , (TypeDWordBE,  5)
    , (TypeQWord,   11)
    , (TypeString,   1)
    , (TypeMultiString,      7)
    , (TypeExpandableString, 2)
    , (TypeLink,     6)
    ]

type ValueData = (ValueType, B.ByteString)

encodeString :: String -> B.ByteString
encodeString str = encodeUtf16LE addLastZero
  where
    text = T.pack str
    addLastZero | T.null text = text
                | T.last text == '\0' = text
                | otherwise = T.snoc text '\0'

decodeString :: ValueData -> String
decodeString (_, bytes) = T.unpack dropLastZero
  where
    text = decodeUtf16LE bytes
    dropLastZero | T.null text = text
                 | otherwise = T.dropWhileEnd (== '\0') text

openCloseCatch :: IsKeyPath a => a -> (Handle -> IO b) -> ExceptT IOError IO b
openCloseCatch keyPath f = ExceptT $ catchIOError (openApplyClose >>= return . Right) $ return . Left
  where
    openApplyClose = bracket (openUnsafe keyPath) close f

foreign import ccall unsafe "Windows.h RegQueryValueExW"
    c_RegQueryValueEx :: WinAPI.PKEY -> WinAPI.LPCTSTR -> WinAPI.LPDWORD -> WinAPI.LPDWORD -> WinAPI.LPBYTE -> WinAPI.LPDWORD -> IO WinAPI.ErrCode

foreign import ccall unsafe "Windows.h RegSetValueExW"
    c_RegSetValueEx :: WinAPI.PKEY -> WinAPI.LPCTSTR -> WinAPI.DWORD -> WinAPI.DWORD -> WinAPI.LPBYTE -> WinAPI.DWORD -> IO WinAPI.ErrCode

foreign import ccall unsafe "Windows.h RegGetValueW"
    c_RegGetValue :: WinAPI.PKEY -> WinAPI.LPCTSTR -> WinAPI.LPCTSTR -> WinAPI.DWORD -> WinAPI.LPDWORD -> WinAPI.LPBYTE -> WinAPI.LPDWORD -> IO WinAPI.ErrCode

queryValue :: IsKeyPath a => a -> ValueName -> ExceptT IOError IO ValueData
queryValue keyPath valueName =
    openCloseCatch keyPath $ \keyHandle ->
    withForeignPtr keyHandle $ \keyHandlePtr ->
    WinAPI.withTString valueName $ \valueNamePtr ->
    alloca $ \valueSizePtr -> do
        poke valueSizePtr 0
        WinAPI.failUnlessSuccess "RegQueryValueExW" $
            c_RegQueryValueEx keyHandlePtr valueNamePtr WinAPI.nullPtr WinAPI.nullPtr WinAPI.nullPtr valueSizePtr
        valueSize <- fromIntegral <$> peek valueSizePtr
        alloca $ \valueTypePtr ->
            allocaBytes valueSize $ \bufferPtr -> do
                WinAPI.failUnlessSuccess "RegQueryValueExW" $
                    c_RegQueryValueEx keyHandlePtr valueNamePtr WinAPI.nullPtr valueTypePtr bufferPtr valueSizePtr
                buffer <- B.pack <$> peekArray valueSize bufferPtr
                valueType <- toEnum . fromIntegral <$> peek valueTypePtr
                return (valueType, buffer)

queryType :: IsKeyPath a => a -> ValueName -> ExceptT IOError IO ValueType
queryType keyPath valueName =
    openCloseCatch keyPath $ \keyHandle ->
    withForeignPtr keyHandle $ \keyHandlePtr ->
    WinAPI.withTString valueName $ \valueNamePtr ->
    alloca $ \valueTypePtr -> do
        WinAPI.failUnlessSuccess "RegQueryValueExW" $
            c_RegQueryValueEx keyHandlePtr valueNamePtr WinAPI.nullPtr valueTypePtr WinAPI.nullPtr WinAPI.nullPtr
        valueType <- toEnum . fromIntegral <$> peek valueTypePtr
        return valueType

data GetValueFlag = RestrictAny
                  | RestrictNone
                  | RestrictBinary
                  | RestrictDWord
                  | RestrictQWord
                  | RestrictString
                  | RestrictMultiString
                  | RestrictExpandableString
                  | DoNotExpand
                  deriving (Eq, Show)

instance Enum GetValueFlag where
    fromEnum = fromJust . flip lookup getValueFlagsTable
    toEnum = fromJust . flip lookup (map swap getValueFlagsTable)

getValueFlagsTable :: [(GetValueFlag, Int)]
getValueFlagsTable =
    [ (RestrictAny,    0x0000ffff)
    , (RestrictNone,   0x00000001)
    , (RestrictBinary, 0x00000008)
    , (RestrictDWord,  0x00000010)
    , (RestrictQWord,  0x00000040)
    , (RestrictString, 0x00000002)
    , (RestrictMultiString,      0x00000020)
    , (RestrictExpandableString, 0x00000004)
    , (DoNotExpand,    0x10000000)
    ]

getValue :: IsKeyPath a => a -> ValueName -> [GetValueFlag] -> ExceptT IOError IO ValueData
getValue keyPath valueName flags =
    openCloseCatch keyPath $ \keyHandle ->
    withForeignPtr keyHandle $ \keyHandlePtr ->
    WinAPI.withTString valueName $ \valueNamePtr ->
    alloca $ \valueSizePtr -> do
        poke valueSizePtr 0
        WinAPI.failUnlessSuccess "RegGetValueW" $
            c_RegGetValue keyHandlePtr WinAPI.nullPtr valueNamePtr rawFlags WinAPI.nullPtr WinAPI.nullPtr valueSizePtr
        bufferCapacity <- fromIntegral <$> peek valueSizePtr
        alloca $ \valueTypePtr ->
            allocaBytes bufferCapacity $ \bufferPtr -> do
                WinAPI.failUnlessSuccess "RegGetValueW" $
                    c_RegGetValue keyHandlePtr WinAPI.nullPtr valueNamePtr rawFlags valueTypePtr bufferPtr valueSizePtr
                bufferSize <- fromIntegral <$> peek valueSizePtr
                buffer <- B.pack <$> peekArray bufferSize bufferPtr
                valueType <- toEnum . fromIntegral <$> peek valueTypePtr
                return (valueType, buffer)
  where
    rawFlags = fromIntegral $ foldr (.|.) 0 $ map fromEnum flags

getType :: IsKeyPath a => a -> ValueName -> [GetValueFlag] -> ExceptT IOError IO ValueType
getType keyPath valueName flags =
    openCloseCatch keyPath $ \keyHandle ->
    withForeignPtr keyHandle $ \keyHandlePtr ->
    WinAPI.withTString valueName $ \valueNamePtr ->
    alloca $ \valueTypePtr -> do
        WinAPI.failUnlessSuccess "RegGetValueW" $
            c_RegGetValue keyHandlePtr WinAPI.nullPtr valueNamePtr rawFlags valueTypePtr WinAPI.nullPtr WinAPI.nullPtr
        valueType <- toEnum . fromIntegral <$> peek valueTypePtr
        return valueType
  where
    rawFlags = fromIntegral $ foldr (.|.) 0 $ map fromEnum $ DoNotExpand : flags

getExpandedString :: IsKeyPath a => a -> ValueName -> ExceptT IOError IO String
getExpandedString keyPath valueName = do
    valueData <- getValue keyPath valueName [RestrictString]
    return $ decodeString valueData

setValue :: IsKeyPath a => a -> ValueName -> ValueData -> ExceptT IOError IO ()
setValue keyPath valueName (valueType, valueData) =
    openCloseCatch keyPath $ \keyHandle ->
    withForeignPtr keyHandle $ \keyHandlePtr ->
    WinAPI.withTString valueName $ \valueNamePtr ->
    allocaBytes bufferSize $ \bufferPtr -> do
        pokeArray bufferPtr buffer
        WinAPI.failUnlessSuccess "RegSetValueExW" $
            c_RegSetValueEx keyHandlePtr valueNamePtr 0 rawValueType bufferPtr (fromIntegral bufferSize)
  where
    rawValueType = fromIntegral $ fromEnum valueType
    buffer = B.unpack valueData
    bufferSize = B.length valueData

setString :: IsKeyPath a => a -> ValueName -> String -> ExceptT IOError IO ()
setString keyPath valueName valueData =
    setValue keyPath valueName (TypeString, encodeString valueData)

setExpandableString :: IsKeyPath a => a -> ValueName -> String -> ExceptT IOError IO ()
setExpandableString keyPath valueName valueData =
    setValue keyPath valueName (TypeExpandableString, encodeString valueData)

setStringPreserveType :: IsKeyPath a => a -> ValueName -> String -> ExceptT IOError IO ()
setStringPreserveType keyPath valueName valueData = do
    valueType <- getType keyPath valueName [RestrictString, RestrictExpandableString] `catchE` stringByDefault
    setValue keyPath valueName (valueType, encodeString valueData)
  where
    stringByDefault e | isDoesNotExistError e = return TypeString
                      | otherwise = throwE e

deleteValue :: IsKeyPath a => a -> ValueName -> ExceptT IOError IO ()
deleteValue keyPath valueName =
    openCloseCatch keyPath $ \keyHandle ->
    withForeignPtr keyHandle $ \keyHandlePtr ->
    WinAPI.withTString valueName $ \valueNamePtr ->
    WinAPI.failUnlessSuccess "RegDeleteValueW" $
        WinAPI.c_RegDeleteValue keyHandlePtr valueNamePtr