{-# LANGUAGE MultiWayIf #-}
{-#LANGUAGE RecordWildCards #-}

module State.Editing where

import           Prelude ()
import           Prelude.Compat

import           Brick.Widgets.Edit (Editor, handleEditorEvent, getEditContents, editContentsL)
import           Brick.Widgets.Edit (applyEdit)
import qualified Codec.Binary.UTF8.Generic as UTF8
import           Control.Arrow
import qualified Control.Concurrent.STM as STM
import           Control.Monad (when)
import           Control.Monad.IO.Class (liftIO)
import qualified Data.ByteString as BS
import           Data.Monoid ((<>))
import qualified Data.Set as S
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
import qualified Data.Text.Zipper as Z
import qualified Data.Text.Zipper.Generic.Words as Z
import           Data.Time (getCurrentTime)
import           Graphics.Vty (Event(..), Key(..), Modifier(..))
import           Lens.Micro.Platform
import qualified System.Environment as Sys
import qualified System.Exit as Sys
import qualified System.IO as Sys
import qualified System.IO.Temp as Sys
import qualified System.Process as Sys
import           Text.Aspell (AspellResponse(..), mistakeWord, askAspell)

import           Config
import           Types
import           Events.Keybindings

import           State.Common

import           Network.Mattermost.Types (Post(..))

startMultilineEditing :: MH ()
startMultilineEditing = csEditState.cedMultiline .= True

toggleMultilineEditing :: MH ()
toggleMultilineEditing = csEditState.cedMultiline %= not

invokeExternalEditor :: MH ()
invokeExternalEditor = do
    -- If EDITOR is in the environment, write the current message to a
    -- temp file, invoke EDITOR on it, read the result, remove the temp
    -- file, and update the program state.
    --
    -- If EDITOR is not present, fall back to 'vi'.
    mEnv <- liftIO $ Sys.lookupEnv "EDITOR"
    let editorProgram = maybe "vi" id mEnv

    mhSuspendAndResume $ \ st -> do
      Sys.withSystemTempFile "matterhorn_editor.tmp" $ \tmpFileName tmpFileHandle -> do
        -- Write the current message to the temp file
        Sys.hPutStr tmpFileHandle $ T.unpack $ T.intercalate "\n" $
            getEditContents $ st^.csEditState.cedEditor
        Sys.hClose tmpFileHandle

        -- Run the editor
        status <- Sys.system (editorProgram <> " " <> tmpFileName)

        -- On editor exit, if exited with zero status, read temp file.
        -- If non-zero status, skip temp file read.
        case status of
            Sys.ExitSuccess -> do
                tmpBytes <- BS.readFile tmpFileName
                case T.decodeUtf8' tmpBytes of
                    Left _ -> do
                        postErrorMessageIO "Failed to decode file contents as UTF-8" st
                    Right t -> do
                        let tmpLines = T.lines t
                        return $ st & csEditState.cedEditor.editContentsL .~ (Z.textZipper tmpLines Nothing)
                                    & csEditState.cedMultiline .~ (length tmpLines > 1)
            Sys.ExitFailure _ -> return st

toggleMessagePreview :: MH ()
toggleMessagePreview = csShowMessagePreview %= not

handlePaste :: BS.ByteString -> MH ()
handlePaste bytes = do
  let pasteStr = T.pack (UTF8.toString bytes)
  csEditState.cedEditor %= applyEdit (Z.insertMany pasteStr)
  contents <- use (csEditState.cedEditor.to getEditContents)
  case length contents > 1 of
      True -> startMultilineEditing
      False -> return ()

editingPermitted :: ChatState -> Bool
editingPermitted st =
    (length (getEditContents $ st^.csEditState.cedEditor) == 1) ||
    st^.csEditState.cedMultiline

editingKeybindings :: [Keybinding]
editingKeybindings =
  let kb desc ev mote = KB desc ev mote Nothing in
  map withUserTypingAction
  [ kb "Transpose the final two characters"
    (EvKey (KChar 't') [MCtrl]) $ do
    csEditState.cedEditor %= applyEdit Z.transposeChars
    csEditState.cedCompleter .= Nothing
  , kb "Go to the start of the current line"
    (EvKey (KChar 'a') [MCtrl]) $ do
    csEditState.cedEditor %= applyEdit Z.gotoBOL
  , kb "Go to the end of the current line"
    (EvKey (KChar 'e') [MCtrl]) $ do
    csEditState.cedEditor %= applyEdit Z.gotoEOL
  , kb "Delete the character at the cursor"
    (EvKey (KChar 'd') [MCtrl]) $ do
    csEditState.cedEditor %= applyEdit Z.deleteChar
    csEditState.cedCompleter .= Nothing
  , kb "Delete from the cursor to the start of the current line"
    (EvKey (KChar 'u') [MCtrl]) $ do
    csEditState.cedEditor %= applyEdit Z.killToBOL
    csEditState.cedCompleter .= Nothing
  , kb "Move one character to the right"
    (EvKey (KChar 'f') [MCtrl]) $ do
    csEditState.cedEditor %= applyEdit Z.moveRight
    csEditState.cedCompleter .= Nothing
  , kb "Move one character to the left"
    (EvKey (KChar 'b') [MCtrl]) $ do
    csEditState.cedEditor %= applyEdit Z.moveLeft
    csEditState.cedCompleter .= Nothing
  , kb "Move one word to the right"
    (EvKey (KChar 'f') [MMeta]) $ do
    csEditState.cedEditor %= applyEdit Z.moveWordRight
    csEditState.cedCompleter .= Nothing
  , kb "Move one word to the left"
    (EvKey (KChar 'b') [MMeta]) $ do
    csEditState.cedEditor %= applyEdit Z.moveWordLeft
    csEditState.cedCompleter .= Nothing
  , kb "Delete the word to the left of the cursor"
    (EvKey KBS [MMeta]) $ do
    csEditState.cedEditor %= applyEdit Z.deletePrevWord
    csEditState.cedCompleter .= Nothing
  , kb "Delete the word to the left of the cursor"
    (EvKey (KChar 'w') [MCtrl]) $ do
    csEditState.cedEditor %= applyEdit Z.deletePrevWord
    csEditState.cedCompleter .= Nothing
  , kb "Delete the word to the right of the cursor"
    (EvKey (KChar 'd') [MMeta]) $ do
    csEditState.cedEditor %= applyEdit Z.deleteWord
    csEditState.cedCompleter .= Nothing
  , kb "Move the cursor to the beginning of the input"
    (EvKey KHome []) $ do
    csEditState.cedEditor %= applyEdit gotoHome
  , kb "Move the cursor to the end of the input"
    (EvKey KEnd []) $ do
    csEditState.cedEditor %= applyEdit gotoEnd
  , kb "Kill the line to the right of the current position and copy it"
    (EvKey (KChar 'k') [MCtrl]) $ do
      z <- use (csEditState.cedEditor.editContentsL)
      let restOfLine = Z.currentLine (Z.killToBOL z)
      csEditState.cedYankBuffer .= restOfLine
      csEditState.cedEditor %= applyEdit Z.killToEOL
      csEditState.cedCompleter .= Nothing
  , kb "Paste the current buffer contents at the cursor"
    (EvKey (KChar 'y') [MCtrl]) $ do
      buf <- use (csEditState.cedYankBuffer)
      csEditState.cedEditor %= applyEdit (Z.insertMany buf)
      csEditState.cedCompleter .= Nothing
  ]
  where
    withUserTypingAction (KB {..}) =
      KB kbDescription kbEvent
         (kbAction >> sendUserTypingAction)
         kbBindingInfo

handleEditingInput :: Event -> MH ()
handleEditingInput e = do
    -- Only handle input events to the editor if we permit editing:
    -- if multiline mode is off, or if there is only one line of text
    -- in the editor. This means we skip input this catch-all handler
    -- if we're *not* in multiline mode *and* there are multiple lines,
    -- i.e., we are showing the user the status message about the
    -- current editor state and editing is not permitted.

    smartBacktick <- use (csResources.crConfiguration.to configSmartBacktick)
    let smartChars = "*`_"
    st <- use id
    case lookupKeybinding e editingKeybindings of
      Just kb | editingPermitted st -> kbAction kb
      _ -> do
        case e of
          -- Not editing; backspace here means cancel multi-line message
          -- composition
          EvKey KBS [] | (not $ editingPermitted st) ->
            csEditState.cedEditor %= applyEdit Z.clearZipper

          -- Backspace in editing mode with smart pair insertion means
          -- smart pair removal when possible
          EvKey KBS [] | editingPermitted st && smartBacktick ->
              let backspace = csEditState.cedEditor %= applyEdit Z.deletePrevChar
              in case cursorAtOneOf smartChars (st^.csEditState.cedEditor) of
                  Nothing -> backspace
                  Just ch ->
                      -- Smart char removal:
                      if | (cursorAtChar ch $ applyEdit Z.moveLeft $ st^.csEditState.cedEditor) &&
                           (cursorIsAtEnd $ applyEdit Z.moveRight $ st^.csEditState.cedEditor) ->
                             csEditState.cedEditor %= applyEdit (Z.deleteChar >>> Z.deletePrevChar)
                         | otherwise -> backspace

          EvKey (KChar ch) [] | editingPermitted st && smartBacktick && ch `elem` smartChars ->
              -- Smart char insertion:
              let doInsertChar = do
                    csEditState.cedEditor %= applyEdit (Z.insertChar ch)
                    sendUserTypingAction
              in if | (editorEmpty $ st^.csEditState.cedEditor) ||
                         ((cursorAtChar ' ' (applyEdit Z.moveLeft $ st^.csEditState.cedEditor)) &&
                          (cursorIsAtEnd $ st^.csEditState.cedEditor)) ->
                        csEditState.cedEditor %= applyEdit (Z.insertMany (T.pack $ ch:ch:[]) >>> Z.moveLeft)
                    | (cursorAtChar ch $ st^.csEditState.cedEditor) &&
                      (cursorIsAtEnd $ applyEdit Z.moveRight $ st^.csEditState.cedEditor) ->
                        csEditState.cedEditor %= applyEdit Z.moveRight
                    | otherwise -> doInsertChar

          _ | editingPermitted st -> do
              mhHandleEventLensed (csEditState.cedEditor) handleEditorEvent e
              sendUserTypingAction
            | otherwise -> return ()

        csEditState.cedCompleter .= Nothing

    liftIO $ resetSpellCheckTimer $ st^.csEditState

-- | Send the user_typing action to the server asynchronously, over the connected websocket.
-- | If the websocket is not connected, drop the action silently.
sendUserTypingAction :: MH ()
sendUserTypingAction = do
  st <- use id
  when (configShowTypingIndicator (st^.csResources.crConfiguration)) $
    case st^.csConnectionStatus of
      Connected -> do
        let pId = case st^.csEditState.cedEditMode of
                    Replying _ post -> Just $ postId post
                    _               -> Nothing
        liftIO $ do
          now <- getCurrentTime
          let action = UserTyping now (st^.csCurrentChannelId) pId
          STM.atomically $ STM.writeTChan (st^.csResources.crWebsocketActionChan) action
      Disconnected -> return ()

-- Kick off an async request to the spell checker for the current editor
-- contents.
requestSpellCheck :: MH ()
requestSpellCheck = do
    st <- use id
    case st^.csEditState.cedSpellChecker of
        Nothing -> return ()
        Just (checker, _) -> do
            -- Get the editor contents.
            contents <- getEditContents <$> use (csEditState.cedEditor)
            doAsyncWith Preempt $ do
                -- For each line in the editor, submit an aspell request.
                let query = concat <$> mapM (askAspell checker) contents
                    postMistakes :: [AspellResponse] -> MH ()
                    postMistakes responses = do
                        let getMistakes AllCorrect = []
                            getMistakes (Mistakes ms) = mistakeWord <$> ms
                            allMistakes = S.fromList $ concat $ getMistakes <$> responses
                        csEditState.cedMisspellings .= allMistakes

                tryMM query (return . postMistakes)

editorEmpty :: Editor T.Text a -> Bool
editorEmpty e = cursorIsAtEnd e &&
                cursorIsAtBeginning e

cursorIsAtEnd :: Editor T.Text a -> Bool
cursorIsAtEnd e =
    let col = snd $ Z.cursorPosition z
        curLine = Z.currentLine z
        z = e^.editContentsL
    in col == T.length curLine

cursorIsAtBeginning :: Editor T.Text a -> Bool
cursorIsAtBeginning e =
    let col = snd $ Z.cursorPosition z
        z = e^.editContentsL
    in col == 0

cursorAtOneOf :: [Char] -> Editor T.Text a -> Maybe Char
cursorAtOneOf [] _ = Nothing
cursorAtOneOf (c:cs) e =
    if cursorAtChar c e
    then Just c
    else cursorAtOneOf cs e

cursorAtChar :: Char -> Editor T.Text a -> Bool
cursorAtChar ch e =
    let col = snd $ Z.cursorPosition z
        curLine = Z.currentLine z
        z = e^.editContentsL
    in (T.singleton ch) `T.isPrefixOf` T.drop col curLine

gotoHome :: Z.TextZipper T.Text -> Z.TextZipper T.Text
gotoHome = Z.moveCursor (0, 0)

gotoEnd :: Z.TextZipper T.Text -> Z.TextZipper T.Text
gotoEnd z =
    let zLines = Z.getText z
        numLines = length zLines
        lastLineLength = T.length $ last zLines
    in if numLines > 0
       then Z.moveCursor (numLines - 1, lastLineLength) z
       else z