{-# LANGUAGE DeriveGeneric #-}

{- |
Module      :  Neovim.Ghcid.Plugin
Description :  Ghcid quickfix integration plugin
Copyright   :  (c) Sebastian Witte
License     :  Apache-2.0

Maintainer  :  woozletoff@gmail.com
Stability   :  experimental
Portability :  GHC
-}
module Neovim.Ghcid.Plugin where

import Data.Yaml
import GHC.Generics
import Neovim
import Neovim.API.String
import Neovim.BuildTool
import Neovim.Quickfix as Q
import Neovim.User.Choice (yesOrNo)
import Neovim.User.Input

import Language.Haskell.Ghcid as Ghcid

import Control.Monad
import Control.Monad.IO.Class
import Control.Monad.Trans.Maybe
import qualified Control.Monad.Trans.Resource as Resource
import qualified Data.ByteString as BS
import Data.Either (rights)
import Data.List (groupBy, sort)
import Data.Map.Strict (Map)
import qualified Data.Map.Strict as Map
import Data.Maybe (mapMaybe)
import System.FilePath
import UnliftIO.Exception (SomeException (..), catch)
import UnliftIO.STM

-- | Simple data type containing a few information on how to start ghcid.
data ProjectSettings = ProjectSettings
    { -- | Project directory from which ghcid can be started successfully.
      rootDir :: FilePath
    , -- | Command to start a ghci session (usually @cabal repl@ or
      -- @stack ghci@).
      cmd :: String
    }
    deriving (Eq, Ord, Show, Generic)

instance ToJSON ProjectSettings

instance FromJSON ProjectSettings

data GhcidEnv = GhcidEnv
    { -- | A map from the root directory (see 'rootDir') to a 'Ghci' session and a
      -- release function which unregisters some autocmds and stops the ghci
      -- session.
      startedSessions :: TVar (Map FilePath (Ghci, Neovim GhcidEnv ()))
    , quickfixItems :: TVar [QuickfixListItem String]
    }

initGhcidEnv :: MonadIO m => m GhcidEnv
initGhcidEnv = GhcidEnv <$> newTVarIO mempty <*> newTVarIO mempty

modifyStartedSessions ::
    ( Map FilePath (Ghci, Neovim GhcidEnv ()) ->
      Map FilePath (Ghci, Neovim GhcidEnv ())
    ) ->
    Neovim GhcidEnv ()
modifyStartedSessions f = do
    atomically . flip modifyTVar' f =<< asks startedSessions

{- | Start or update a ghcid session.

 This will call 'determineProjectSettings' and ask you to confirm or overwrite
 its proposed settings. If you prepend a bang, it acts as if you have
 confirmed all settings.
-}
ghcidStart :: CommandArguments -> Neovim GhcidEnv ()
ghcidStart copts = do
    currentBufferPath <- fromObjectUnsafe <$> vim_call_function "expand" [ObjectBinary "%:p:h"]
    liftIO (determineProjectSettings' currentBufferPath) >>= \case
        Nothing ->
            void $
                yesOrNo "Could not determine project settings. This plugin needs a project with a .cabal file to work."
        Just s -> case bang copts of
            Just True ->
                startOrReload s
            _ -> do
                d <-
                    askForDirectory
                        "Specify directory from which ghcid should be started."
                        (Just (rootDir s))
                c <-
                    askForString
                        "Specify the command to execute (e.g. \"ghci\")."
                        (Just (cmd s))

                let s' = ProjectSettings d c
                whenM (yesOrNo "Save settings to file?")
                    . liftIO
                    . BS.writeFile (d </> "ghcid.yaml")
                    $ encode s'
                startOrReload s

{- | Start a new ghcid session or reload the modules to update the quickfix
 list.
-}
startOrReload :: ProjectSettings -> Neovim GhcidEnv ()
startOrReload s@(ProjectSettings d c) = do
    sessions <- atomically . readTVar =<< asks startedSessions
    case Map.lookup d sessions of
        Nothing -> do
            (g, ls) <-
                liftIO (startGhci c (Just d) (\_ _ -> return ()))
                    `catch` \(SomeException e) -> err . pretty $ "Failed to start ghcid session: " <> show e
            applyQuickfixActions $ loadToQuickfix ls
            void $ vim_command "cwindow"
            addAutocmd "BufWritePost" Sync def (startOrReload s) 

            modifyStartedSessions $ Map.insert d (g, liftIO (stopGhci g))
        Just (ghci, _) -> do
            applyQuickfixActions =<< loadToQuickfix <$> liftIO (reload ghci)
            void $ vim_command "cwindow"

applyQuickfixActions :: [QuickfixListItem String] -> Neovim GhcidEnv ()
applyQuickfixActions qs = do
    qfItems <- asks quickfixItems
    fqs <- (nub' . rights . map bufOrFile) <$> atomically (readTVar qfItems)
    atomically $ modifyTVar' qfItems (const qs)
    forM_ fqs $ \f -> void $ vim_command $ "sign unplace * file=" <> f
    setqflist qs Replace
    placeSigns qs
  where
    nub' = map head . groupBy (==) . sort

placeSigns :: [QuickfixListItem String] -> Neovim env ()
placeSigns qs = forM_ (zip [(1 :: Integer) ..] qs) $ \(i, q) -> case (lnumOrPattern q, bufOrFile q) of
    (Right _, _) ->
        -- Patterns not handled as they are not produced
        return ()
    (_, Left _) ->
        -- Buffer type not handled because i don't know how to pass that here
        -- and it is not produced.
        return ()
    (Left lnum, Right f) -> do
        let signType = case errorType q of
                Q.Error -> "GhcidErr"
                Q.Warning -> "GhcidWarn"

        -- TODO What if the file name contains spaces?
        void $
            vim_command $
                unwords
                    [ "sign place"
                    , show i
                    , "line=" <> show lnum
                    , "name=" <> signType
                    , "file=" <> f
                    ]

-- | Stop a ghcid session associated to the currently active buffer.
ghcidStop :: CommandArguments -> Neovim GhcidEnv ()
ghcidStop _ = do
    d <- fromObjectUnsafe <$> vim_call_function "expand" [ObjectBinary "%:p:h"]
    sessions <- atomically . readTVar =<< asks startedSessions
    case Map.lookupLE d sessions of
        Nothing ->
            return ()
        Just (p, (_, releaseAction)) -> do
            modifyStartedSessions $ Map.delete p
            releaseAction

-- | Same as @:GhcidStop@ followed by @:GhcidStart!@. Note the bang!
ghcidRestart :: CommandArguments -> Neovim GhcidEnv ()
ghcidRestart _ = do
    ghcidStop def
    ghcidStart def{bang = Just True}

loadToQuickfix :: [Load] -> [QuickfixListItem String]
loadToQuickfix = dropWarningsIfErrorsArePresent . mapMaybe f
  where
    f m@Message{} =
        Just $
            ( quickfixListItem
                ((Right . loadFile) m)
                ((Left . fst . loadFilePos) m)
            )
                { col = VisualColumn . snd $ loadFilePos m
                , Q.text = (unlines . loadMessage) m
                , errorType = case loadSeverity m of
                    Ghcid.Warning -> Q.Warning
                    _ -> Q.Error
                }
    f _ = Nothing

    dropWarningsIfErrorsArePresent xs =
        case filter ((== Q.Error) . errorType) xs of
            [] -> xs
            xs' -> xs'

maybePluginConfig :: MonadIO io => Directory -> io (Maybe BuildTool)
maybePluginConfig d =
    fmap (const Custom)
        <$> mkFile (Just d) "ghcid.yaml"

{- | Determine project settings for a directory.

 This will traverse through all parent directories and search for a hint on
 how to start the ghcid background process. The following configurations will
 be tried in this order:

 * A @ghcid.yaml@ file which can be created with the @GhcidStart@ command
 * A @stack.yaml@ file
 * A @cabal.sandbox.config@ file
 * A @\*.cabal@ file

 Note that 'ghcidStart' prompts for confirmation unless you prepend a bang.
 So, if you want to use your preferred settings, simply save them to the
 @ghcid.yaml@ file and you're done.
-}
determineProjectSettings' :: FilePath -> IO (Maybe ProjectSettings)
determineProjectSettings' dir = runMaybeT $ do
    ds <- MaybeT $ fmap thisAndParentDirectories <$> mkDirectory dir
    buildTool <- MaybeT $ determineProjectSettings (maybePluginConfig : defaultProjectIdentifiers) ds
    case buildTool of
        (Stack, d) -> return $ ProjectSettings (getDirectory d) "stack ghci"
        (Cabal _, d) -> return $ ProjectSettings (getDirectory d) "cabal repl"
        (Custom, d) -> do
            f <- MaybeT $ mkFile (Just d) "ghcid.yaml"
            MaybeT $ decodeThrow <$> BS.readFile (getFile f)
        _ -> MaybeT $ return Nothing