{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE PatternSynonyms #-}
{-# LANGUAGE LambdaCase #-}
-----------------------------------------------------------------------------
--
-- Module      :  Language.Javascript.JSaddle.WebSockets
-- Copyright   :  (c) Hamish Mackenzie
-- License     :  MIT
--
-- Maintainer  :  Hamish Mackenzie <Hamish.K.Mackenzie@googlemail.com>
--
-- |
--
-----------------------------------------------------------------------------
module Language.Javascript.JSaddle.WebKit2GTK (
  -- * Running JSM in a WebView
    run
  , runInWebView
  ) where

import Control.Monad (void)
import Control.Monad.IO.Class (MonadIO(..), MonadIO)
import Control.Concurrent (forkIO, yield)

import System.Posix.Signals (installHandler, keyboardSignal, Handler(Catch))
import System.Directory (getCurrentDirectory)

import Data.Monoid ((<>))
import Data.ByteString.Lazy (toStrict, fromStrict)
import qualified Data.ByteString.Lazy as LB (ByteString)
import Data.Aeson (encode, decode)
import Data.Text (Text)
import qualified Data.Text as T (pack)
import Data.Text.Foreign (fromPtr)
import Data.Text.Encoding (decodeUtf8, encodeUtf8)

import Foreign.Ptr (castPtr, nullPtr)

import Data.GI.Base.BasicTypes (GObject)
import Data.GI.Base.Signals
       (connectSignalFunPtr, SignalConnectMode(..), SignalConnectMode,
        SignalHandlerId)
import Data.GI.Base.ManagedPtr (withManagedPtr)

import GI.GLib (timeoutAdd, idleAdd, pattern PRIORITY_HIGH, pattern PRIORITY_DEFAULT)
import qualified GI.Gtk as Gtk (main, init)
import GI.Gtk
       (windowSetPosition, windowSetDefaultSize, windowNew,
        scrolledWindowNew, noAdjustment, containerAdd,
        WindowType(..), WindowPosition(..), widgetDestroy,
        widgetGetToplevel, widgetShowAll, onWidgetDestroy,
        mainQuit)
import GI.Gio (noCancellable)
import GI.JavaScriptCore (Value(..), GlobalContext(..))
import GI.WebKit2
       (WebView, setSettingsEnableWriteConsoleMessagesToStdout,
        setSettingsEnableJavascript,
        webViewNewWithUserContentManager, userContentManagerNew,
        userContentManagerRegisterScriptMessageHandler,
        javascriptResultGetValue, javascriptResultGetGlobalContext,
        webViewGetUserContentManager,
        mk_UserContentManagerScriptMessageReceivedCallback,
        wrap_UserContentManagerScriptMessageReceivedCallback,
        webViewRunJavascript, LoadEvent(..),
        UserContentManagerScriptMessageReceivedCallback, webViewLoadHtml,
        onWebViewLoadChanged, setSettingsEnableDeveloperExtras,
        webViewSetSettings, webViewGetSettings)

import Graphics.UI.Gtk.WebKit.JavaScriptCore.JSBase
       (JSValueRef, JSContextRef)
import Graphics.UI.Gtk.WebKit.JavaScriptCore.JSStringRef
       (jsstringgetcharactersptr, jsstringgetlength, jsstringrelease)
import Graphics.UI.Gtk.WebKit.JavaScriptCore.JSValueRef
       (jsvaluetostringcopy)

import Language.Javascript.JSaddle (JSM, Results)
import Language.Javascript.JSaddle.Run (runJavaScript)
import Language.Javascript.JSaddle.Run.Files (initState, runBatch, ghcjsHelpers)

quitWebView :: WebView -> IO ()
quitWebView wv = postGUIAsync $ do w <- widgetGetToplevel wv --TODO: Shouldn't this be postGUISync?
                                   widgetDestroy w

installQuitHandler :: WebView -> IO ()
installQuitHandler wv = void $ installHandler keyboardSignal (Catch (quitWebView wv)) Nothing

postGUIAsync :: IO () -> IO ()
postGUIAsync action =
  void . idleAdd PRIORITY_DEFAULT $ action >> return False

withJSContextRef :: GlobalContext -> (JSContextRef -> IO a) -> IO a
withJSContextRef (GlobalContext ctx) f = withManagedPtr ctx (f . castPtr)

withJSValueRef :: Value -> (JSValueRef -> IO a) -> IO a
withJSValueRef (Value ptr) f = withManagedPtr ptr (f . castPtr)

valueToText :: JSContextRef -> JSValueRef -> IO Text
valueToText ctxRef s = do
    jsstring <- jsvaluetostringcopy ctxRef s nullPtr
    l <- jsstringgetlength jsstring
    p <- jsstringgetcharactersptr jsstring
    result <- fromPtr (castPtr p) (fromIntegral l)
    jsstringrelease jsstring
    return result

run :: JSM () -> IO ()
run main = do
    _ <- Gtk.init Nothing
    window <- windowNew WindowTypeToplevel
    _ <- timeoutAdd PRIORITY_HIGH 10 (yield >> return True)
    windowSetDefaultSize window 900 600
    windowSetPosition window WindowPositionCenter
    scrollWin <- scrolledWindowNew noAdjustment noAdjustment
    contentManager <- userContentManagerNew
    webView <- webViewNewWithUserContentManager contentManager
    settings <- webViewGetSettings webView
    -- setSettingsEnableUniversalAccessFromFileUris settings True
    setSettingsEnableDeveloperExtras settings True
    setSettingsEnableJavascript settings True
    setSettingsEnableWriteConsoleMessagesToStdout settings True
    webViewSetSettings webView settings
    window `containerAdd` scrollWin
    scrollWin `containerAdd` webView
    _ <- onWidgetDestroy window mainQuit
    widgetShowAll window
    pwd <- getCurrentDirectory
    void . onWebViewLoadChanged webView $ \case
        LoadEventFinished -> runInWebView main webView
        _ -> return ()
    webViewLoadHtml  webView "" . Just $ "file://" <> T.pack pwd <> "/"
    installQuitHandler webView
    Gtk.main

runInWebView :: JSM () -> WebView -> IO ()
runInWebView f webView = do
    (processResults, start) <- runJavaScript (\batch -> postGUIAsync $
        webViewRunJavascript webView (decodeUtf8 . toStrict $ "runJSaddleBatch(" <> encode batch <> ");") noCancellable Nothing)
        f

    addJSaddleHandler webView processResults
    webViewRunJavascript webView (decodeUtf8 $ toStrict jsaddleJs) noCancellable . Just $
        \_obj _asyncResult ->
            void $ forkIO start

onUserContentManagerScriptMessageReceived :: (GObject a, MonadIO m) => a -> UserContentManagerScriptMessageReceivedCallback -> m SignalHandlerId
onUserContentManagerScriptMessageReceived obj cb = liftIO $ connectUserContentManagerScriptMessageReceived obj cb SignalConnectBefore

connectUserContentManagerScriptMessageReceived :: (GObject a, MonadIO m) =>
                                                  a -> UserContentManagerScriptMessageReceivedCallback -> SignalConnectMode -> m SignalHandlerId
connectUserContentManagerScriptMessageReceived obj cb after = liftIO $ do
    let cb' = wrap_UserContentManagerScriptMessageReceivedCallback cb
    cb'' <- mk_UserContentManagerScriptMessageReceivedCallback cb'
    connectSignalFunPtr obj "script-message-received::jsaddle" cb'' after

addJSaddleHandler :: WebView -> (Results -> IO ()) -> IO ()
addJSaddleHandler webView processResult = do
    manager <- webViewGetUserContentManager webView
    _ <- onUserContentManagerScriptMessageReceived manager $ \result -> do
        ctx <- javascriptResultGetGlobalContext result
        arg <- javascriptResultGetValue result
        bs <- withJSContextRef ctx $ \ctxRef ->
            withJSValueRef arg $ \argRef ->
                encodeUtf8 <$> valueToText ctxRef argRef
        mapM_ processResult (decode (fromStrict bs))
    void $ userContentManagerRegisterScriptMessageHandler manager "jsaddle"

jsaddleJs :: LB.ByteString
jsaddleJs = ghcjsHelpers <> "\
    \runJSaddleBatch = (function() {\n\
    \ " <> initState <> "\n\
    \ return function(batch) {\n\
    \ " <> runBatch (\a -> "window.webkit.messageHandlers.jsaddle.postMessage(JSON.stringify(" <> a <> "));") <> "\
    \ };\n\
    \})()\n\
    \"