{-# LANGUAGE DataKinds           #-}
{-# LANGUAGE DeriveAnyClass      #-}
{-# LANGUAGE DeriveGeneric       #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE ScopedTypeVariables #-}

{-# LANGUAGE TypeOperators       #-}

module Server where

import           Config
import           Parse
import           ToodlesApi
import           Types

import qualified Control.Exception      as E
import           Control.Monad
import           Control.Monad.IO.Class
import           Data.Aeson             (FromJSON)
import           Data.Aeson.Types
import           Data.Either
import           Data.IORef
import           Data.List              (find, nub)
import           Data.Maybe
import           Data.String.Utils
import           Data.Text              (Text)
import qualified Data.Text              as T
import qualified Data.Yaml              as Y
import           Servant
import           System.Directory
import           System.IO.HVFS
import qualified System.IO.Strict       as SIO
import           System.Path
import           System.Path.NameManip
import           Text.Blaze.Html5       (Html)
import qualified Text.Blaze.Html5       as BZ
import           Text.Printf
import           Text.Regex.Posix

data ToodlesConfig = ToodlesConfig
  { ignore :: [FilePath]
  , flags  :: [UserFlag]
  } deriving (Show)

instance FromJSON ToodlesConfig where
  parseJSON (Object o) = do
    parsedIgnore <- o .:? "ignore"  .!= []
    parsedFlags <- o .:? "flags"  .!= []
    return $ ToodlesConfig parsedIgnore parsedFlags
  parseJSON invalid    = typeMismatch "Invalid config" invalid

app :: ToodlesState -> Application
app s = serve toodlesAPI server

    where
    server :: Server ToodlesAPI
    server = liftIO . getFullSearchResults s
        :<|> deleteTodos s
        :<|> editTodos s
        :<|> serveDirectoryFileServer (dataPath s)
        :<|> showRawFile s
        :<|> root s

root :: ToodlesState -> [Text] -> Handler Html
root (ToodlesState _ dPath) path =
    if null path then
        liftIO $ BZ.preEscapedToHtml <$> readFile (dPath ++ "/html/index.html")
    else throwError $ err404 { errBody = "Not found" }

showRawFile :: ToodlesState -> Integer -> Handler Html
showRawFile (ToodlesState ref _) eId = do
    (TodoListResult r _) <- liftIO $ readIORef ref
    let entry = find (\t -> entryId t == eId) r
    liftIO $
        maybe
        (return "Not found")
        (\e -> addAnchors <$> readFile (sourceFile e))
        entry

    where
    addAnchors :: String -> Html
    addAnchors s =
        let codeLines = zip [1::Int ..] $ lines s
        in BZ.preEscapedToHtml $
            (unlines $
            map
                (\(i, l) -> printf "<pre><a name=\"line-%s\">%s</a></pre>" (show i) l)
                codeLines)

editTodos :: ToodlesState -> EditTodoRequest -> Handler Text
editTodos (ToodlesState ref _) req = do
    (TodoListResult r _) <- liftIO $ readIORef ref
    let editedList = map
            (\t ->
                if willEditTodo req t
                then editTodo req t
                else t)
            r
        editedFilteredList = filter (willEditTodo req) editedList
    _ <- mapM_ recordUpdates editedFilteredList
    return "{}"
    where
    willEditTodo :: EditTodoRequest -> TodoEntry -> Bool
    willEditTodo editRequest entry = entryId entry `elem` editIds editRequest

    editTodo :: EditTodoRequest -> TodoEntry -> TodoEntry
    editTodo editRequest entry =
        let newAssignee = if isJust (setAssignee editRequest) && (not . T.null . fromJust $ setAssignee editRequest)
            then setAssignee editRequest
            else assignee entry
            newPriority = if isJust (setPriority editRequest) then setPriority editRequest else priority entry in

        entry {assignee = newAssignee,
                tags = tags entry ++ addTags editRequest,
                priority = newPriority,
                customAttributes = nub $ customAttributes entry ++ addKeyVals editRequest}

    recordUpdates :: MonadIO m => TodoEntry -> m ()
    recordUpdates t = void $ updateTodoLinesInFile renderTodo t

renderTodo :: TodoEntry -> [Text]
renderTodo t =
  let comment =
        fromJust $ lookup ("." <> getExtension (sourceFile t)) fileTypeToComment
      detail =
        renderFlag (flag t) <> " (" <>
        (T.pack $
         Data.String.Utils.join
           "|"
           (map T.unpack $ [fromMaybe "" $ assignee t] ++
            listIfNotNull (fmap (T.pack . maybe "" ((\n -> "p=" ++ n) . show)) priority t) ++
            tags t ++
            map (\a -> fst a <> "=" <> snd a) (customAttributes t))) <>
        ") "
      fullNoComments = mapHead (\l -> detail <> "- " <> l) $ body t
      commented = map (\l -> comment <> " " <> l) fullNoComments in
      mapHead (\l -> leadingText t <> l) $
        mapInit (\l -> foldl (<>) "" [" " | _ <- [1..(T.length $ leadingText t)]] <> l) commented

  where
    mapHead :: (a -> a) -> [a] -> [a]
    mapHead f (x:xs) = f x : xs
    mapHead _ xs     = xs

    mapInit :: (a -> a) -> [a] -> [a]
    mapInit f (x:xs) = [x] ++ map f xs
    mapInit _ x      = x

    listIfNotNull :: Text -> [Text]
    listIfNotNull "" = []
    listIfNotNull s  = [s]

    renderFlag :: Flag -> Text
    renderFlag TODO              = "TODO"
    renderFlag FIXME             = "FIXME"
    renderFlag XXX               = "XXX"
    renderFlag (UF (UserFlag x)) = x

-- | Given a function to emit new lines for a given todo, write that update in
-- place of the current todo lines
updateTodoLinesInFile :: MonadIO m => (TodoEntry -> [Text]) -> TodoEntry -> m ()
updateTodoLinesInFile f todo = do
  let startIndex = lineNumber todo - 1
      newLines = map T.unpack $ f todo
  fileLines <- liftIO $ lines <$> SIO.readFile (sourceFile todo)
  let updatedLines =
        slice 0 (fromIntegral $ startIndex - 1) fileLines ++ newLines ++
        (slice
           (fromIntegral startIndex + length (body todo))
           (length fileLines - 1)
           fileLines)
  liftIO $ writeFile (sourceFile todo) $ unlines updatedLines

    where
    slice :: Int -> Int -> [a] -> [a]
    slice a b xs = take (b - a + 1) (drop a xs)

deleteTodos :: ToodlesState -> DeleteTodoRequest -> Handler Text
deleteTodos (ToodlesState ref _) req = do
    refVal@(TodoListResult r _) <- liftIO $ readIORef ref
    let toDelete = filter (\t -> entryId t `elem` ids req) r
    liftIO $ doUntilNull removeAndAdjust toDelete
    let remainingResults = filter (\t -> entryId t `notElem` map entryId toDelete) r
    updatedResults <- return $ foldl (flip adjustLinesAfterDeletionOf) remainingResults toDelete
    let remainingResultsRef = refVal { todos = updatedResults }
    _ <- liftIO $ atomicModifyIORef' ref (const (remainingResultsRef, remainingResultsRef))
    return "{}"

    where

    doUntilNull :: ([a] -> IO [a]) -> [a] -> IO ()
    doUntilNull f xs = do
        result <- f xs
        if null result
            then return ()
            else doUntilNull f result

    -- If we delete an entry, we need to decrement the line-numbers for the
    -- other entries that come later in the file
    adjustLinesAfterDeletionOf :: TodoEntry -> [TodoEntry] -> [TodoEntry]
    adjustLinesAfterDeletionOf deleted =
      map (\remaining ->
          if (sourceFile remaining == sourceFile deleted) && (lineNumber remaining > lineNumber deleted)
              then remaining { lineNumber = lineNumber remaining - (fromIntegral . length $ body deleted)}
              else remaining)

    removeAndAdjust :: MonadIO m => [TodoEntry] -> m [TodoEntry]
    removeAndAdjust [] = return []
    removeAndAdjust (x:xs) = do
        removeTodoFromCode x
        return $ adjustLinesAfterDeletionOf x xs

        where
        removeTodoFromCode :: MonadIO m => TodoEntry -> m ()
        removeTodoFromCode = updateTodoLinesInFile (const [])

setAbsolutePath :: ToodlesArgs -> IO ToodlesArgs
setAbsolutePath args = do
    let pathOrDefault = if T.null . T.pack $ directory args
                            then "."
                            else directory args
    absolute <- normalise_path <$> absolute_path pathOrDefault
    return $ args {directory = absolute}

getFullSearchResults :: ToodlesState -> Bool -> IO TodoListResult
getFullSearchResults (ToodlesState ref _) recompute =
  if recompute
    then do
      putStrLn "refreshing todo's"
      userArgs <- toodlesArgs >>= setAbsolutePath
      sResults <- runFullSearch userArgs
      atomicModifyIORef' ref (const (sResults, sResults))
    else putStrLn "cached read" >> readIORef ref

runFullSearch :: ToodlesArgs -> IO TodoListResult
runFullSearch userArgs = do
    let projectRoot = directory userArgs
    configExists <- doesFileExist $ projectRoot ++ "/.toodles.yaml"
    config <- if configExists
        then Y.decodeFileEither (projectRoot ++ "/.toodles.yaml")
        else return . Right $ ToodlesConfig [] []
    when (isLeft config)
        $ putStrLn $ "[WARNING] Invalid .toodles.yaml: " ++ show config
    let config' = fromRight (ToodlesConfig [] []) config
    allFiles <- getAllFiles config' projectRoot
    let parsedTodos = concatMap (runTodoParser $ userFlag userArgs ++ flags config') allFiles
        filteredTodos = filter (filterSearch (assignee_search userArgs)) parsedTodos
        resultList = limitSearch filteredTodos $ limit_results userArgs
        indexedResults = map (\(i, r) -> r {entryId = i}) $ zip [1 ..] resultList
    return $ TodoListResult indexedResults ""

    where
    filterSearch :: Maybe SearchFilter -> TodoEntry -> Bool
    filterSearch                                             Nothing     _ = True
    filterSearch (Just (AssigneeFilter (AssigneeFilterRegex query))) entry = fromMaybe "" (assignee entry) == query

    limitSearch :: [TodoEntry] -> Int -> [TodoEntry]
    limitSearch todoList 0 = todoList
    limitSearch todoList n = take n todoList

getAllFiles :: ToodlesConfig -> FilePath -> IO [SourceFile]
getAllFiles (ToodlesConfig ignoredPaths _) basePath =
  E.catch
    (do putStrLn $ printf "Running toodles for path: %s" basePath
        files <- recurseDir SystemFS basePath
        let validFiles = filter isValidFile files
        mapM
          (\f ->
             SourceFile f . (map T.pack . lines) <$>
             E.catch
               (SIO.readFile f)
               (\(e :: E.IOException) -> print e >> return ""))
          validFiles)
    (\(e :: E.IOException) ->
       putStrLn ("Error reading " ++ basePath ++ ": " ++ show e) >> return [])

    where

    isValidFile :: FilePath -> Bool
    isValidFile path = fileHasValidExtension && not ignoreFile

        where

        fileHasValidExtension :: Bool
        fileHasValidExtension = any (\ext -> ext `T.isSuffixOf` T.pack path) (map fst fileTypeToComment)

        ignoreFile :: Bool
        ignoreFile =
            let p = T.pack path
            in T.isInfixOf "node_modules" p || T.isSuffixOf "pb.go" p ||
                T.isSuffixOf "_pb2.py" p ||
                any (\r -> path =~ r :: Bool) ignoredPaths