{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE LambdaCase #-}

-- | A formatter for Haskell source code.
module Ormolu
  ( ormolu,
    ormoluFile,
    ormoluStdin,
    Config (..),
    ColorMode (..),
    RegionIndices (..),
    defaultConfig,
    DynOption (..),
    OrmoluException (..),
    withPrettyOrmoluExceptions,
  )
where

import Control.Exception
import Control.Monad
import Control.Monad.IO.Class (MonadIO (..))
import Data.Text (Text)
import qualified Data.Text as T
import Debug.Trace
import qualified GHC.Driver.CmdLine as GHC
import qualified GHC.Types.SrcLoc as GHC
import Ormolu.Config
import Ormolu.Diff.ParseResult
import Ormolu.Diff.Text
import Ormolu.Exception
import Ormolu.Parser
import Ormolu.Parser.Result
import Ormolu.Printer
import Ormolu.Utils (showOutputable)
import Ormolu.Utils.IO

-- | Format a 'String', return formatted version as 'Text'.
--
-- The function
--
--     * Takes 'String' because that's what GHC parser accepts.
--     * Needs 'IO' because some functions from GHC that are necessary to
--       setup parsing context require 'IO'. There should be no visible
--       side-effects though.
--     * Takes file name just to use it in parse error messages.
--     * Throws 'OrmoluException'.
ormolu ::
  MonadIO m =>
  -- | Ormolu configuration
  Config RegionIndices ->
  -- | Location of source file
  FilePath ->
  -- | Input to format
  String ->
  m Text
ormolu cfgWithIndices path str = do
  let totalLines = length (lines str)
      cfg = regionIndicesToDeltas totalLines <$> cfgWithIndices
  (warnings, result0) <-
    parseModule' cfg OrmoluParsingFailed path str
  when (cfgDebug cfg) $ do
    traceM "warnings:\n"
    traceM (concatMap showWarn warnings)
  -- We're forcing 'txt' here because otherwise errors (such as messages
  -- about not-yet-supported functionality) will be thrown later when we try
  -- to parse the rendered code back, inside of GHC monad wrapper which will
  -- lead to error messages presenting the exceptions as GHC bugs.
  let !txt = printModule result0
  when (not (cfgUnsafe cfg) || cfgCheckIdempotence cfg) $ do
    -- Parse the result of pretty-printing again and make sure that AST
    -- is the same as AST of original snippet module span positions.
    (_, result1) <-
      parseModule'
        cfg
        OrmoluOutputParsingFailed
        path
        (T.unpack txt)
    unless (cfgUnsafe cfg) $ do
      when (length result0 /= length result1) $
        liftIO $ throwIO (OrmoluASTDiffers path [])
      forM_ (result0 `zip` result1) $ \case
        (ParsedSnippet s, ParsedSnippet s') -> case diffParseResult s s' of
          Same -> return ()
          Different ss -> liftIO $ throwIO (OrmoluASTDiffers path ss)
        (RawSnippet {}, RawSnippet {}) -> pure ()
        _ -> liftIO $ throwIO (OrmoluASTDiffers path [])
    -- Try re-formatting the formatted result to check if we get exactly
    -- the same output.
    when (cfgCheckIdempotence cfg) $
      let txt2 = printModule result1
       in case diffText txt txt2 path of
            Nothing -> return ()
            Just diff ->
              liftIO $
                throwIO (OrmoluNonIdempotentOutput diff)
  return txt

-- | Load a file and format it. The file stays intact and the rendered
-- version is returned as 'Text'.
--
-- > ormoluFile cfg path =
-- >   liftIO (readFile path) >>= ormolu cfg path
ormoluFile ::
  MonadIO m =>
  -- | Ormolu configuration
  Config RegionIndices ->
  -- | Location of source file
  FilePath ->
  -- | Resulting rendition
  m Text
ormoluFile cfg path =
  readFileUtf8 path >>= ormolu cfg path . T.unpack

-- | Read input from stdin and format it.
--
-- > ormoluStdin cfg =
-- >   liftIO (hGetContents stdin) >>= ormolu cfg "<stdin>"
ormoluStdin ::
  MonadIO m =>
  -- | Ormolu configuration
  Config RegionIndices ->
  -- | Resulting rendition
  m Text
ormoluStdin cfg =
  liftIO getContents >>= ormolu cfg "<stdin>"

----------------------------------------------------------------------------
-- Helpers

-- | A wrapper around 'parseModule'.
parseModule' ::
  MonadIO m =>
  -- | Ormolu configuration
  Config RegionDeltas ->
  -- | How to obtain 'OrmoluException' to throw when parsing fails
  (GHC.SrcSpan -> String -> OrmoluException) ->
  -- | File name to use in errors
  FilePath ->
  -- | Actual input for the parser
  String ->
  m ([GHC.Warn], [SourceSnippet])
parseModule' cfg mkException path str = do
  (warnings, r) <- parseModule cfg path str
  case r of
    Left (spn, err) -> liftIO $ throwIO (mkException spn err)
    Right x -> return (warnings, x)

-- | Pretty-print a 'GHC.Warn'.
showWarn :: GHC.Warn -> String
showWarn (GHC.Warn reason l) =
  unlines
    [ showOutputable reason,
      showOutputable l
    ]