-- Copyright (c) 2019 The DAML Authors. All rights reserved.
-- SPDX-License-Identifier: Apache-2.0

{-# LANGUAGE DuplicateRecordFields #-}

-- | Go to the definition of a variable.
module Development.IDE.LSP.CodeAction
    ( setHandlersCodeAction
    ) where

import           Language.Haskell.LSP.Types
import Development.IDE.GHC.Compat
import Development.IDE.Core.Rules
import Development.IDE.LSP.Server
import qualified Data.HashMap.Strict as Map
import qualified Data.HashSet as Set
import qualified Language.Haskell.LSP.Core as LSP
import Language.Haskell.LSP.VFS
import Language.Haskell.LSP.Messages
import qualified Data.Rope.UTF16 as Rope
import Data.Char
import Data.Maybe
import qualified Data.Text as T

-- | Generate code actions.
codeAction
    :: LSP.LspFuncs ()
    -> IdeState
    -> CodeActionParams
    -> IO (List CAResult)
codeAction lsp _ CodeActionParams{_textDocument=TextDocumentIdentifier uri,_context=CodeActionContext{_diagnostics=List xs}} = do
    -- disable logging as its quite verbose
    -- logInfo (ideLogger ide) $ T.pack $ "Code action req: " ++ show arg
    contents <- LSP.getVirtualFileFunc lsp $ toNormalizedUri uri
    let text = Rope.toText . (_text :: VirtualFile -> Rope.Rope) <$> contents
    pure $ List
        [ CACodeAction $ CodeAction title (Just CodeActionQuickFix) (Just $ List [x]) (Just edit) Nothing
        | x <- xs, (title, tedit) <- suggestAction text x
        , let edit = WorkspaceEdit (Just $ Map.singleton uri $ List tedit) Nothing
        ]


suggestAction :: Maybe T.Text -> Diagnostic -> [(T.Text, [TextEdit])]
suggestAction contents Diagnostic{_range=_range@Range{..},..}

-- File.hs:16:1: warning:
--     The import of `Data.List' is redundant
--       except perhaps to import instances from `Data.List'
--     To import instances alone, use: import Data.List()
    | "The import of " `T.isInfixOf` _message
    , " is redundant" `T.isInfixOf` _message
        = [("Remove import", [TextEdit (extendToWholeLineIfPossible contents _range) ""])]

-- File.hs:52:41: error:
--     * Variable not in scope:
--         suggestAcion :: Maybe T.Text -> Range -> Range
--     * Perhaps you meant ‘suggestAction’ (line 83)
-- File.hs:94:37: error:
--     Not in scope: ‘T.isPrfixOf’
--     Perhaps you meant one of these:
--       ‘T.isPrefixOf’ (imported from Data.Text),
--       ‘T.isInfixOf’ (imported from Data.Text),
--       ‘T.isSuffixOf’ (imported from Data.Text)
--     Module ‘Data.Text’ does not export ‘isPrfixOf’.
    | renameSuggestions@(_:_) <- extractRenamableTerms _message
        = [ ("Replace with ‘" <> name <> "’", [mkRenameEdit contents _range name]) | name <- renameSuggestions ]

-- Foo.hs:3:8: error:
--     * Found type wildcard `_' standing for `p -> p1 -> p'

    | "Found type wildcard" `T.isInfixOf` _message
    , " standing for " `T.isInfixOf` _message
    , typeSignature <- extractWildCardTypeSignature _message
        =  [("Use type signature: ‘" <> typeSignature <> "’", [TextEdit _range typeSignature])]

-- File.hs:22:8: error:
--     Illegal lambda-case (use -XLambdaCase)
-- File.hs:22:6: error:
--     Illegal view pattern:  x -> foo
--     Use ViewPatterns to enable view patterns
-- File.hs:26:8: error:
--     Illegal `..' in record pattern
--     Use RecordWildCards to permit this
-- File.hs:53:28: error:
--     Illegal tuple section: use TupleSections
-- File.hs:238:29: error:
--     * Can't make a derived instance of `Data FSATrace':
--         You need DeriveDataTypeable to derive an instance for this class
--     * In the data declaration for `FSATrace'
-- C:\Neil\shake\src\Development\Shake\Command.hs:515:31: error:
--     * Illegal equational constraint a ~ ()
--       (Use GADTs or TypeFamilies to permit this)
--     * In the context: a ~ ()
--       While checking an instance declaration
--       In the instance declaration for `Unit (m a)'
    | exts@(_:_) <- filter (`Set.member` ghcExtensions) $ T.split (not . isAlpha) $ T.replace "-X" "" _message
        = [("Add " <> x <> " extension", [TextEdit (Range (Position 0 0) (Position 0 0)) $ "{-# LANGUAGE " <> x <> " #-}\n"]) | x <- exts]

suggestAction _ _ = []

mkRenameEdit :: Maybe T.Text -> Range -> T.Text -> TextEdit
mkRenameEdit contents range name =
    if fromMaybe False maybeIsInfixFunction
      then TextEdit range ("`" <> name <> "`")
      else TextEdit range name
  where
    maybeIsInfixFunction = do
      curr <- textInRange range <$> contents
      pure $ "`" `T.isPrefixOf` curr && "`" `T.isSuffixOf` curr

extractWildCardTypeSignature :: T.Text -> T.Text
extractWildCardTypeSignature =
  -- inferring when parens are actually needed around the type signature would
  -- require understanding both the precedence of the context of the _ and of
  -- the signature itself. Inserting them unconditionally is ugly but safe.
  ("(" `T.append`) . (`T.append` ")") .
  T.takeWhile (/='’') . T.dropWhile (=='‘') . T.dropWhile (/='‘') .
  snd . T.breakOnEnd "standing for "

extractRenamableTerms :: T.Text -> [T.Text]
extractRenamableTerms msg
  -- Account for both "Variable not in scope" and "Not in scope"
  | "ot in scope:" `T.isInfixOf` msg = extractSuggestions msg
  | otherwise = []
  where
    extractSuggestions = map getEnclosed
                       . concatMap singleSuggestions
                       . filter isKnownSymbol
                       . T.lines
    singleSuggestions = T.splitOn "), " -- Each suggestion is comma delimited
    isKnownSymbol t = " (imported from" `T.isInfixOf` t || " (line " `T.isInfixOf` t
    getEnclosed = T.dropWhile (== '‘')
                . T.dropWhileEnd (== '’')
                . T.dropAround (\c -> c /= '‘' && c /= '’')

-- | If a range takes up a whole line (it begins at the start of the line and there's only whitespace
-- between the end of the range and the next newline), extend the range to take up the whole line.
extendToWholeLineIfPossible :: Maybe T.Text -> Range -> Range
extendToWholeLineIfPossible contents range@Range{..} =
    let newlineAfter = maybe False (T.isPrefixOf "\n" . T.dropWhile (\x -> isSpace x && x /= '\n') . snd . splitTextAtPosition _end) contents
        extend = newlineAfter && _character _start == 0 -- takes up an entire line, so remove the whole line
    in if extend then Range _start (Position (_line _end + 1) 0) else range

-- | All the GHC extensions
ghcExtensions :: Set.HashSet T.Text
ghcExtensions = Set.fromList $ map (T.pack . show) ghcEnumerateExtensions

splitTextAtPosition :: Position -> T.Text -> (T.Text, T.Text)
splitTextAtPosition (Position row col) x
    | (preRow, mid:postRow) <- splitAt row $ T.splitOn "\n" x
    , (preCol, postCol) <- T.splitAt col mid
        = (T.intercalate "\n" $ preRow ++ [preCol], T.intercalate "\n" $ postCol : postRow)
    | otherwise = (x, T.empty)

textInRange :: Range -> T.Text -> T.Text
textInRange (Range (Position startRow startCol) (Position endRow endCol)) text =
    case compare startRow endRow of
      LT ->
        let (linesInRangeBeforeEndLine, endLineAndFurtherLines) = splitAt (endRow - startRow) linesBeginningWithStartLine
            (textInRangeInFirstLine, linesBetween) = case linesInRangeBeforeEndLine of
              [] -> ("", [])
              firstLine:linesInBetween -> (T.drop startCol firstLine, linesInBetween)
            maybeTextInRangeInEndLine = T.take endCol <$> listToMaybe endLineAndFurtherLines
        in T.intercalate "\n" (textInRangeInFirstLine : linesBetween ++ maybeToList maybeTextInRangeInEndLine)
      EQ ->
        let line = fromMaybe "" (listToMaybe linesBeginningWithStartLine)
        in T.take (endCol - startCol) (T.drop startCol line)
      GT -> ""
    where
      linesBeginningWithStartLine = drop startRow (T.splitOn "\n" text)

setHandlersCodeAction :: PartialHandlers
setHandlersCodeAction = PartialHandlers $ \WithMessage{..} x -> return x{
    LSP.codeActionHandler = withResponse RspCodeAction codeAction
    }