{-# LANGUAGE GADTs #-}
{-# LANGUAGE OverloadedStrings #-}
module Command where

import Prelude ()
import Prelude.Compat

import           Control.Applicative ((<|>))
import qualified Control.Exception as Exn
import           Control.Monad.IO.Class (liftIO)
import           Control.Monad (void)
import           Data.Monoid ((<>))
import qualified Data.Text as T
import           Lens.Micro.Platform
import qualified Network.Mattermost as MM
import qualified Network.Mattermost.Lenses as MM
import qualified Network.Mattermost.Exceptions as MM

import State
import State.Common
import State.Editing
import State.PostListOverlay
import Types
import HelpTopics
import Scripts

printArgSpec :: CmdArgs a -> T.Text
printArgSpec NoArg = ""
printArgSpec (LineArg ts) = "[" <> ts <> "]"
printArgSpec (TokenArg t NoArg) = "[" <> t <> "]"
printArgSpec (TokenArg t rs) = "[" <> t <> "] " <> printArgSpec rs

matchArgs :: CmdArgs a -> [T.Text] -> Either T.Text a
matchArgs NoArg []  = return ()
matchArgs NoArg [t] = Left ("unexpected argument '" <> t <> "'")
matchArgs NoArg ts  = Left ("unexpected arguments '" <> T.unwords ts <> "'")
matchArgs (LineArg _) ts = return (T.unwords ts)
matchArgs rs@(TokenArg _ NoArg) [] = Left ("missing argument: " <> printArgSpec rs)
matchArgs rs@(TokenArg _ _) [] = Left ("missing arguments: " <> printArgSpec rs)
matchArgs (TokenArg _ rs) (t:ts) = (,) <$> pure t <*> matchArgs rs ts

commandList :: [Cmd]
commandList =
  [ Cmd "quit" "Exit Matterhorn" NoArg $ \ () -> requestQuit
  , Cmd "right" "Focus on the next channel" NoArg $ \ () ->
      nextChannel
  , Cmd "left" "Focus on the previous channel" NoArg $ \ () ->
      prevChannel
  , Cmd "create-channel" "Create a new channel"
    (LineArg "channel name") $ \ name ->
      createOrdinaryChannel name
  , Cmd "delete-channel" "Delete the current channel"
    NoArg $ \ () ->
      beginCurrentChannelDeleteConfirm
  , Cmd "members" "Show the current channel's members"
    NoArg $ \ () ->
      fetchCurrentChannelMembers
  , Cmd "leave" "Leave the current channel" NoArg $ \ () ->
      startLeaveCurrentChannel
  , Cmd "join" "Join a channel" NoArg $ \ () ->
      startJoinChannel
  , Cmd "theme" "List the available themes" NoArg $ \ () ->
      listThemes
  , Cmd "theme" "Set the color theme"
    (TokenArg "theme" NoArg) $ \ (themeName, ()) ->
      setTheme themeName
  , Cmd "topic" "Set the current channel's topic"
    (LineArg "topic") $ \ p ->
      if not (T.null p) then setChannelTopic p else return ()
  , Cmd "add-user" "Add a user to the current channel"
    (TokenArg "username" NoArg) $ \ (uname, ()) ->
        addUserToCurrentChannel uname
  , Cmd "focus" "Focus on a named channel"
    (TokenArg "channel" NoArg) $ \ (name, ()) ->
        changeChannel name
  , Cmd "help" "Show this help screen" NoArg $ \ _ ->
        showHelpScreen mainHelpTopic
  , Cmd "help" "Show help about a particular topic"
      (TokenArg "topic" NoArg) $ \ (topicName, ()) ->
          case lookupHelpTopic topicName of
              Nothing -> do
                  let msg = ("Unknown help topic: `" <> topicName <> "`. " <>
                            (T.unlines $ "Available topics are:" : knownTopics))
                      knownTopics = ("  - " <>) <$> helpTopicName <$> helpTopics
                  postErrorMessage msg
              Just topic -> showHelpScreen topic
  , Cmd "sh" "List the available shell scripts" NoArg $ \ () ->
      listScripts
  , Cmd "sh" "Run a prewritten shell script"
    (TokenArg "script" (LineArg "message")) $ \ (script, text) ->
      findAndRunScript script text
  , Cmd "me" "Send an emote message"
    (LineArg "message") $
    \msg -> execMMCommand "me" msg

  , Cmd "shrug" "Send a message followed by a shrug emoticon"
    (LineArg "message") $
    \msg -> execMMCommand "shrug" msg

  , Cmd "flags" "Open up a pane of flagged posts"  NoArg $ \ () ->
      enterFlaggedPostListMode
  ]

execMMCommand :: T.Text -> T.Text -> MH ()
execMMCommand name rest = do
  cId      <- use csCurrentChannelId
  session  <- use (csResources.crSession)
  myTeamId <- use (csMyTeam.(MM.teamIdL))
  em       <- use (csEditState.cedEditMode)
  let mc = MM.MinCommand
             { MM.minComChannelId = cId
             , MM.minComCommand   = "/" <> name <> " " <> rest
             , MM.minComParentId  = case em of
                 Replying _ p -> Just $ MM.getId p
                 Editing p    -> MM.postParentId p
                 _            -> Nothing
             , MM.minComRootId  = case em of
                 Replying _ p -> MM.postRootId p <|> (Just $ MM.postId p)
                 Editing p    -> MM.postRootId p
                 _            -> Nothing
             }
      runCmd = liftIO $ do
        void $ MM.mmExecute session myTeamId mc
      handleHTTP (MM.HTTPResponseException err) =
        return (Just (T.pack err))
        -- XXX: this might be a bit brittle in the future, because it
        -- assumes the shape of an error message. We might want to
        -- think about a better way of discovering this error and
        -- reporting it accordingly?
      handleCmdErr (MM.MattermostServerError err) =
        let (_, msg) = T.breakOn ": " err in
          return (Just (T.drop 2 msg))
  errMsg <- liftIO $ (runCmd >> return Nothing) `Exn.catch` handleHTTP
                                                `Exn.catch` handleCmdErr
  case errMsg of
    Nothing -> return ()
    Just err ->
      postErrorMessage ("Error running command: " <> err)

dispatchCommand :: T.Text -> MH ()
dispatchCommand cmd =
  case T.words cmd of
    (x:xs) | matchingCmds <- [ c | c@(Cmd name _ _ _) <- commandList
                             , name == x
                             ] -> go [] matchingCmds
      where go [] [] = do
              execMMCommand x (T.unwords xs)
            go errs [] = do
              let msg = ("error running command /" <> x <> ":\n" <>
                         mconcat [ "    " <> e | e <- errs ])
              postErrorMessage msg
            go errs (Cmd _ _ spec exe : cs) =
              case matchArgs spec xs of
                Left e -> go (e:errs) cs
                Right args -> exe args
    _ -> return ()