{-# OPTIONS_GHC -Wwarn #-}
{-# LANGUAGE BangPatterns #-}
  -----------------------------------------------------------------------------
-- |
-- Module      :  Haddock.Interface.LexParseRn
-- Copyright   :  (c) Isaac Dupree 2009,
--                    Mateusz Kowalczyk 2013
-- License     :  BSD-like
--
-- Maintainer  :  haddock@projects.haskell.org
-- Stability   :  experimental
-- Portability :  portable
-----------------------------------------------------------------------------
module Haddock.Interface.LexParseRn
  ( processDocString
  , processDocStringParas
  , processDocStrings
  , processModuleHeader
  ) where

import Data.IntSet (toList)
import Data.List
import Documentation.Haddock.Doc (metaDocConcat)
import DynFlags (languageExtensions)
import qualified GHC.LanguageExtensions as LangExt
import FastString
import GHC
import Haddock.Interface.ParseModuleHeader
import Haddock.Parser
import Haddock.Types
import Name
import Outputable ( showPpr )
import RdrName
import EnumSet
import RnEnv (dataTcOccs)

processDocStrings :: DynFlags -> GlobalRdrEnv -> [HsDocString]
                  -> ErrMsgM (Maybe (MDoc Name))
processDocStrings dflags gre strs = do
  mdoc <- metaDocConcat <$> traverse (processDocStringParas dflags gre) strs
  case mdoc of
    -- We check that we don't have any version info to render instead
    -- of just checking if there is no comment: there may not be a
    -- comment but we still want to pass through any meta data.
    MetaDoc { _meta = Meta { _version = Nothing }, _doc = DocEmpty } -> pure Nothing
    x -> pure (Just x)

processDocStringParas :: DynFlags -> GlobalRdrEnv -> HsDocString -> ErrMsgM (MDoc Name)
processDocStringParas dflags gre (HsDocString fs) =
  overDocF (rename dflags gre) $ parseParas dflags (unpackFS fs)

processDocString :: DynFlags -> GlobalRdrEnv -> HsDocString -> ErrMsgM (Doc Name)
processDocString dflags gre (HsDocString fs) =
  rename dflags gre $ parseString dflags (unpackFS fs)

processModuleHeader :: DynFlags -> GlobalRdrEnv -> SafeHaskellMode -> Maybe LHsDocString
                    -> ErrMsgM (HaddockModInfo Name, Maybe (MDoc Name))
processModuleHeader dflags gre safety mayStr = do
  (hmi, doc) <-
    case mayStr of
      Nothing -> return failure
      Just (L _ (HsDocString fs)) -> do
        let str = unpackFS fs
            (hmi, doc) = parseModuleHeader dflags str
        !descr <- case hmi_description hmi of
                    Just hmi_descr -> Just <$> rename dflags gre hmi_descr
                    Nothing        -> pure Nothing
        let hmi' = hmi { hmi_description = descr }
        doc'  <- overDocF (rename dflags gre) doc
        return (hmi', Just doc')

  let flags :: [LangExt.Extension]
      -- We remove the flags implied by the language setting and we display the language instead
      flags = EnumSet.toList (extensionFlags dflags) \\ languageExtensions (language dflags)
  return (hmi { hmi_safety = Just $ showPpr dflags safety
              , hmi_language = language dflags
              , hmi_extensions = flags
              } , doc)
  where
    failure = (emptyHaddockModInfo, Nothing)

-- | Takes a 'GlobalRdrEnv' which (hopefully) contains all the
-- definitions and a parsed comment and we attempt to make sense of
-- where the identifiers in the comment point to. We're in effect
-- trying to convert 'RdrName's to 'Name's, with some guesswork and
-- fallbacks in case we can't locate the identifiers.
--
-- See the comments in the source for implementation commentary.
rename :: DynFlags -> GlobalRdrEnv -> Doc RdrName -> ErrMsgM (Doc Name)
rename dflags gre = rn
  where
    rn d = case d of
      DocAppend a b -> DocAppend <$> rn a <*> rn b
      DocParagraph doc -> DocParagraph <$> rn doc
      DocIdentifier x -> do
        -- Generate the choices for the possible kind of thing this
        -- is.
        let choices = dataTcOccs x
        -- Try to look up all the names in the GlobalRdrEnv that match
        -- the names.
        let names = concatMap (\c -> map gre_name (lookupGRE_RdrName c gre)) choices

        case names of
          -- We found no names in the env so we start guessing.
          [] ->
            case choices of
              [] -> pure (DocMonospaced (DocString (showPpr dflags x)))
              -- There was nothing in the environment so we need to
              -- pick some default from what's available to us. We
              -- diverge here from the old way where we would default
              -- to type constructors as we're much more likely to
              -- actually want anchors to regular definitions than
              -- type constructor names (such as in #253). So now we
              -- only get type constructor links if they are actually
              -- in scope.
              a:_ -> pure (outOfScope dflags a)

          -- There is only one name in the environment that matches so
          -- use it.
          [a] -> pure (DocIdentifier a)
          -- But when there are multiple names available, default to
          -- type constructors: somewhat awfully GHC returns the
          -- values in the list positionally.
          a:b:_ | isTyConName a -> pure (DocIdentifier a)
                | otherwise -> pure (DocIdentifier b)

      DocWarning doc -> DocWarning <$> rn doc
      DocEmphasis doc -> DocEmphasis <$> rn doc
      DocBold doc -> DocBold <$> rn doc
      DocMonospaced doc -> DocMonospaced <$> rn doc
      DocUnorderedList docs -> DocUnorderedList <$> traverse rn docs
      DocOrderedList docs -> DocOrderedList <$> traverse rn docs
      DocDefList list -> DocDefList <$> traverse (\(a, b) -> (,) <$> rn a <*> rn b) list
      DocCodeBlock doc -> DocCodeBlock <$> rn doc
      DocIdentifierUnchecked x -> pure (DocIdentifierUnchecked x)
      DocModule str -> pure (DocModule str)
      DocHyperlink l -> pure (DocHyperlink l)
      DocPic str -> pure (DocPic str)
      DocMathInline str -> pure (DocMathInline str)
      DocMathDisplay str -> pure (DocMathDisplay str)
      DocAName str -> pure (DocAName str)
      DocProperty p -> pure (DocProperty p)
      DocExamples e -> pure (DocExamples e)
      DocEmpty -> pure (DocEmpty)
      DocString str -> pure (DocString str)
      DocHeader (Header l t) -> DocHeader . Header l <$> rn t

-- | Wrap an identifier that's out of scope (i.e. wasn't found in
-- 'GlobalReaderEnv' during 'rename') in an appropriate doc. Currently
-- we simply monospace the identifier in most cases except when the
-- identifier is qualified: if the identifier is qualified then we can
-- still try to guess and generate anchors accross modules but the
-- users shouldn't rely on this doing the right thing. See tickets
-- #253 and #375 on the confusion this causes depending on which
-- default we pick in 'rename'.
outOfScope :: DynFlags -> RdrName -> Doc a
outOfScope dflags x =
  case x of
    Unqual occ -> monospaced occ
    Qual mdl occ -> DocIdentifierUnchecked (mdl, occ)
    Orig _ occ -> monospaced occ
    Exact name -> monospaced name  -- Shouldn't happen since x is out of scope
  where
    monospaced a = DocMonospaced (DocString (showPpr dflags a))