{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleContexts #-}
{-# OPTIONS_HADDOCK show-extensions #-}

-- |
-- Module      :  Yi.Eval
-- License     :  GPL-2
-- Maintainer  :  yi-devel@googlegroups.com
-- Stability   :  experimental
-- Portability :  portable
--
-- Evaluator for actions ('Action', 'YiAction'). Uses a @GHCi@ session
-- under the hood.

module Yi.Eval (
        -- * Main (generic) evaluation interface
        execEditorAction,
        getAllNamesInScope,
        describeNamedAction,
        Evaluator(..),
        evaluator,
        -- ** Standard evaluators
        ghciEvaluator,
        publishedActionsEvaluator,
        publishedActions,
        publishAction,
        -- * Eval/Interpretation
        jumpToErrorE,
        jumpToE,
        consoleKeymap
) where

import           Control.Applicative ((<$>), (<*>))
import           Control.Concurrent
import           Control.Monad.Catch (try)
import           Control.Lens hiding (Action)
import           Control.Monad hiding (mapM_)
import           Control.Monad.Base
import           Control.Monad.Trans (lift)
import           Data.Array
import           Data.Binary
import           Data.Default
import           Data.Foldable (mapM_)
import qualified Data.HashMap.Strict as M
import           Data.List
import           Data.Monoid
import           Data.Typeable
import qualified Language.Haskell.Interpreter as LHI
import           Prelude hiding (error, mapM_)
import           System.Directory (doesFileExist)
import           Text.Read (readMaybe)
import           Yi.Boot.Internal (reload)
import           Yi.Buffer
import           Yi.Config.Simple.Types
import           Yi.Core (errorEditor, runAction)
import           Yi.Types (YiVariable,YiConfigVariable)
import           Yi.Editor
import           Yi.File
import           Yi.Hooks
import           Yi.Keymap
import           Yi.Keymap.Keys
import qualified Yi.Paths (getEvaluatorContextFilename)
import           Yi.Regex
import qualified Yi.Rope as R
import           Yi.String
import           Yi.Utils

-- TODO: should we be sticking Text here?

-- | Runs the action, as written by the user.
--
-- The behaviour of this function can be customised by modifying the
-- 'Evaluator' variable.
execEditorAction :: String -> YiM ()
execEditorAction = runHook execEditorActionImpl

-- | Lists the action names in scope, for use by 'execEditorAction',
-- and 'help' index.
--
-- The behaviour of this function can be customised by modifying the
-- 'Evaluator' variable.
getAllNamesInScope :: YiM [String]
getAllNamesInScope = runHook getAllNamesInScopeImpl

-- | Describes the named action in scope, for use by 'help'.
--
-- The behaviour of this function can be customised by modifying the
-- 'Evaluator' variable.
describeNamedAction :: String -> YiM String
describeNamedAction = runHook describeNamedActionImpl

-- | Config variable for customising the behaviour of
-- 'execEditorAction' and 'getAllNamesInScope'.
--
-- Set this variable using 'evaluator'. See 'ghciEvaluator' and
-- 'finiteListEvaluator' for two implementation.
data Evaluator = Evaluator
  { execEditorActionImpl :: String -> YiM ()
    -- ^ implementation of 'execEditorAction'
  , getAllNamesInScopeImpl :: YiM [String]
    -- ^ implementation of 'getAllNamesInScope'
  , describeNamedActionImpl :: String -> YiM String
    -- ^ describe named action (or at least its type.), simplest implementation is at least @return@.
  } deriving (Typeable)

-- | The evaluator to use for 'execEditorAction' and
-- 'getAllNamesInScope'.
evaluator :: Field Evaluator
evaluator = customVariable

instance Default Evaluator where def = ghciEvaluator
instance YiConfigVariable Evaluator

-- * Evaluator based on GHCi
-- | Cached variable for getAllNamesInScopeImpl
newtype NamesCache = NamesCache [String] deriving (Typeable, Binary)

instance Default NamesCache where
    def = NamesCache []
instance YiVariable NamesCache

-- | Cached dictioary for describeNameImpl
newtype HelpCache = HelpCache (M.HashMap String String) deriving (Typeable, Binary)

instance Default HelpCache where
    def = HelpCache M.empty
instance YiVariable HelpCache

type HintRequest = (String, MVar (Either LHI.InterpreterError Action))
newtype HintThreadVar = HintThreadVar (Maybe (MVar HintRequest))
  deriving (Typeable, Default)

instance Binary HintThreadVar where
  put _ = return ()
  get = return def
instance YiVariable HintThreadVar

getHintThread :: (MonadEditor m, MonadBase IO m) => m (MVar HintRequest)
getHintThread = do
  HintThreadVar x <- getEditorDyn
  case x of
    Just t -> return t
    Nothing -> do
      req <- io newEmptyMVar
      contextFile <- Yi.Paths.getEvaluatorContextFilename
      void . io . forkIO $ hintEvaluatorThread req contextFile
      putEditorDyn . HintThreadVar $ Just req
      return req

hintEvaluatorThread :: MVar HintRequest -> FilePath -> IO ()
hintEvaluatorThread request contextFile = do
  haveUserContext <- doesFileExist contextFile
  void $ LHI.runInterpreter $ do
    LHI.set [LHI.searchPath LHI.:= []]

    -- We no longer have Yi.Prelude, perhaps we should remove
    -- NoImplicitPrelude?
    LHI.set [LHI.languageExtensions LHI.:= [ LHI.OverloadedStrings
                                           , LHI.NoImplicitPrelude
                                           ]]
    when haveUserContext $ do
      LHI.loadModules [contextFile]
      LHI.setTopLevelModules ["Env"]

    -- Yi.Keymap: Action lives there
    LHI.setImportsQ [("Yi", Nothing), ("Yi.Keymap",Just "Yi.Keymap")]
    forever $ do
      (s,response) <- lift $ takeMVar request
      res <- try $ LHI.interpret ("Yi.makeAction (" ++ s ++ ")") (LHI.as :: Action)
      lift $ putMVar response res

-- Evaluator implemented by calling GHCi. This evaluator can run
-- arbitrary expressions in the class 'YiAction'.
--
-- The following two imports are always present:
--
-- > import Yi
-- > import qualified Yi.Keymap as Yi.Keymap
--
-- Also, if the file
--
-- > $HOME/.config/yi/local/Env.hs
--
-- exists, it is imported unqualified.
ghciEvaluator :: Evaluator
ghciEvaluator = Evaluator { execEditorActionImpl = execAction
                          , getAllNamesInScopeImpl = getNames
                          , describeNamedActionImpl = describeName -- TODO: use haddock to add docs
                          }
  where
    execAction :: String -> YiM ()
    execAction "reload" = reload
    execAction s = do
      request <- getHintThread
      res <- io $ do
        response <- newEmptyMVar
        putMVar request (s,response)
        takeMVar response
      case res of
        Left err -> errorEditor (showT err)
        Right action -> runAction action

    getNames :: YiM [String]
    getNames = do
      NamesCache cache <- getEditorDyn
      result <- if null cache
                then do
                  res <- io $ LHI.runInterpreter $ do
                    LHI.set [LHI.searchPath LHI.:= []]
                    LHI.getModuleExports "Yi"
                  return $ case res of
                    Left err ->[show err]
                    Right exports -> flattenExports exports
                else return $ sort cache
      putEditorDyn $ NamesCache result
      return result

    flattenExports :: [LHI.ModuleElem] -> [String]
    flattenExports = concatMap flattenExport

    flattenExport :: LHI.ModuleElem -> [String]
    flattenExport (LHI.Fun x) = [x]
    flattenExport (LHI.Class _ xs) = xs
    flattenExport (LHI.Data _ xs) = xs
      
    describeName :: String -> YiM String
    describeName name = do
      HelpCache cache <- getEditorDyn
      description <- case name `M.lookup` cache of
                       Nothing -> do
                         result <- io $ LHI.runInterpreter $ do
                           LHI.set [LHI.searchPath LHI.:= []]
                           -- when haveUserContext $ do
                           --   LHI.loadModules [contextFile]
                           --   LHI.setTopLevelModules ["Env"]
                           LHI.setImportsQ [("Yi", Nothing), ("Yi.Keymap",Just "Yi.Keymap")]
                           LHI.typeOf name
                         let newDescription = either show id result
                         putEditorDyn $ HelpCache $ M.insert name newDescription cache
                         return newDescription
                       Just description -> return description
      return $ name ++ " :: " ++ description

-- * 'PublishedActions' evaluator

newtype PublishedActions = PublishedActions {
    _publishedActions :: M.HashMap String Action
  } deriving(Typeable, Monoid)

instance Default PublishedActions where def = mempty

makeLensesWithSuffix "A" ''PublishedActions
instance YiConfigVariable PublishedActions

-- | Accessor for the published actions. Consider using
-- 'publishAction'.
publishedActions :: Field (M.HashMap String Action)
publishedActions = customVariable . _publishedActionsA

-- | Publish the given action, by the given name. This will overwrite
-- any existing actions by the same name.
publishAction :: (YiAction a x, Show x) => String -> a -> ConfigM ()
publishAction s a = publishedActions %= M.insert s (makeAction a)

-- | Evaluator based on a fixed list of published actions. Has a few
-- differences from 'ghciEvaluator':
--
-- * expressions can't be evaluated
--
-- * all suggested actions are actually valued
--
-- * (related to the above) doesn't contain junk actions from Prelude
--
-- * doesn't require GHCi backend, so uses less memory
publishedActionsEvaluator :: Evaluator
publishedActionsEvaluator = Evaluator
  { getAllNamesInScopeImpl = askCfg <&> M.keys . (^. publishedActions)
  , execEditorActionImpl = \s ->
      askCfg <&> M.lookup s . (^. publishedActions) >>= mapM_ runAction
  , describeNamedActionImpl = return -- TODO: try to show types using TemplateHaskell!
  }

-- * Miscellaneous interpreter

-- | Jumps to specified position in a given file.
jumpToE :: FilePath -- ^ Filename to make the jump in.
        -> Int -- ^ Line to jump to.
        -> Int -- ^ Column to jump to.
        -> YiM ()
jumpToE filename line column =
  openingNewFile filename $ gotoLn line >> moveXorEol column

-- | Regex parsing the error message format.
errorRegex :: Regex
errorRegex = makeRegex ("^(.+):([0-9]+):([0-9]+):.*$" :: String)

-- | Parses an error message. Fails if it can't parse out the needed
-- information, namely filename, line number and column number.
parseErrorMessage :: R.YiString -> Maybe (String, Int, Int)
parseErrorMessage ln = do
  (_ ,result, _) <- matchOnceText errorRegex (R.toString ln)
  case take 3 $ map fst $ elems result of
    [_, fname, l, c] -> (,,) <$> return fname <*> readMaybe l <*> readMaybe c
    _                        -> Nothing

-- | Tries to parse an error message at current line using
-- 'parseErrorMessage'.
parseErrorMessageB :: BufferM (Maybe (String, Int, Int))
parseErrorMessageB = parseErrorMessage <$> readLnB

-- | Tries to jump to error at the current line. See
-- 'parseErrorMessageB'.
jumpToErrorE :: YiM ()
jumpToErrorE = withCurrentBuffer parseErrorMessageB >>= \case
  Nothing -> printMsg "Couldn't parse out an error message."
  Just (f, l, c) -> jumpToE f l c

prompt :: R.YiString
prompt = "Yi> "

-- | Tries to strip the 'prompt' from the front of the given 'String'.
-- If the prompt is not found, returns the input command as-is.
takeCommand :: R.YiString -> R.YiString
takeCommand t = case R.splitAt (R.length prompt) t of
  (f, s) -> if f == prompt then s else t

consoleKeymap :: Keymap
consoleKeymap = do
  _ <- event (Event KEnter [])
  write $ withCurrentBuffer readLnB >>= \x -> case parseErrorMessage x of
    Just (f,l,c) -> jumpToE f l c
    Nothing -> do
      withCurrentBuffer $ do
        p <- pointB
        botB
        p' <- pointB
        when (p /= p') $ insertN ("\n" <> prompt <> takeCommand x)
        insertN "\n"
        pt <- pointB
        insertN prompt
        bm <- getBookmarkB "errorInsert"
        markPointA bm .= pt
      execEditorAction . R.toString $ takeCommand x