{-# OPTIONS_GHC -Wwarn #-}
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE ViewPatterns #-}
  -----------------------------------------------------------------------------
-- |
-- 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 Control.Arrow
import Control.Monad
import Data.Functor (($>))
import Data.List (maximumBy, (\\))
import Data.Ord
import Documentation.Haddock.Doc (metaDocConcat)
import GHC.Driver.Session (languageExtensions)
import qualified GHC.LanguageExtensions as LangExt
import GHC
import Haddock.Interface.ParseModuleHeader
import Haddock.Parser
import Haddock.Types
import GHC.Types.Name
import GHC.Types.Avail ( availName )
import GHC.Parser.PostProcess
import GHC.Driver.Ppr ( showPpr, showSDoc )
import GHC.Types.Name.Reader
import GHC.Data.EnumSet as EnumSet

processDocStrings :: DynFlags -> Maybe Package -> GlobalRdrEnv -> [HsDocString]
                  -> ErrMsgM (Maybe (MDoc Name))
processDocStrings dflags pkg gre strs = do
  mdoc <- metaDocConcat <$> traverse (processDocStringParas dflags pkg 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 Nothing Nothing, _doc = DocEmpty } -> pure Nothing
    x -> pure (Just x)

processDocStringParas :: DynFlags -> Maybe Package -> GlobalRdrEnv -> HsDocString -> ErrMsgM (MDoc Name)
processDocStringParas dflags pkg gre hds =
  overDocF (rename dflags gre) $ parseParas dflags pkg (unpackHDS hds)

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

processModuleHeader :: DynFlags -> Maybe Package -> GlobalRdrEnv -> SafeHaskellMode -> Maybe LHsDocString
                    -> ErrMsgM (HaddockModInfo Name, Maybe (MDoc Name))
processModuleHeader dflags pkgName gre safety mayStr = do
  (hmi, doc) <-
    case mayStr of
      Nothing -> return failure
      Just (L _ hds) -> do
        let str = unpackHDS hds
            (hmi, doc) = parseModuleHeader dflags pkgName 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 NsRdrName -> 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 i -> do
        let NsRdrName ns x = unwrap i
            occ = rdrNameOcc x
            isValueName = isDataOcc occ || isVarOcc occ

        let valueNsChoices | isValueName = [x]
                           | otherwise   = [] -- is this ever possible?
            typeNsChoices  | isValueName = [setRdrNameSpace x tcName]
                           | otherwise   = [x]

        -- Generate the choices for the possible kind of thing this
        -- is. We narrow down the possibilities with the namespace (if
        -- there is one).
        let choices = case ns of
                        Value -> valueNsChoices
                        Type  -> typeNsChoices
                        None  -> valueNsChoices ++ typeNsChoices

        -- Lookup any GlobalRdrElts that match the choices.
        case concatMap (\c -> lookupGRE_RdrName c gre) choices of
          -- We found no names in the env so we start guessing.
          [] ->
            case choices of
              -- The only way this can happen is if a value namespace was
              -- specified on something that cannot be a value.
              [] -> invalidValue dflags i

              -- 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:_ -> outOfScope dflags ns (i $> a)

          -- There is only one name in the environment that matches so
          -- use it.
          [a] -> pure $ DocIdentifier (i $> greMangledName a)

          -- There are multiple names available.
          gres -> ambiguous dflags i gres

      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 (Hyperlink u l) -> DocHyperlink . Hyperlink u <$> traverse rn l
      DocPic str -> pure (DocPic str)
      DocMathInline str -> pure (DocMathInline str)
      DocMathDisplay str -> pure (DocMathDisplay str)
      DocAName str -> pure (DocAName str)
      DocProperty p -> pure (DocProperty p)
      DocExamples e -> pure (DocExamples e)
      DocEmpty -> pure (DocEmpty)
      DocString str -> pure (DocString str)
      DocHeader (Header l t) -> DocHeader . Header l <$> rn t
      DocTable t -> DocTable <$> traverse 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 -> Namespace -> Wrap RdrName -> ErrMsgM (Doc a)
outOfScope dflags ns x =
  case unwrap x of
    Unqual occ -> warnAndMonospace (x $> occ)
    Qual mdl occ -> pure (DocIdentifierUnchecked (x $> (mdl, occ)))
    Orig _ occ -> warnAndMonospace (x $> occ)
    Exact name -> warnAndMonospace (x $> name)  -- Shouldn't happen since x is out of scope
  where
    prefix = case ns of
               Value -> "the value "
               Type -> "the type "
               None -> ""

    warnAndMonospace a = do
      let a' = showWrapped (showPpr dflags) a
      tell ["Warning: " ++ prefix ++ "'" ++ a' ++ "' is out of scope.\n" ++
            "    If you qualify the identifier, haddock can try to link it anyway."]
      pure (monospaced a')
    monospaced = DocMonospaced . DocString

-- | Handle ambiguous identifiers.
--
-- Prefers local names primarily and type constructors or class names secondarily.
--
-- Emits a warning if the 'GlobalRdrElts's don't belong to the same type or class.
ambiguous :: DynFlags
          -> Wrap NsRdrName
          -> [GlobalRdrElt] -- ^ More than one @gre@s sharing the same `RdrName` above.
          -> ErrMsgM (Doc Name)
ambiguous dflags x gres = do
  let noChildren = map availName (gresToAvailInfo gres)
      dflt = maximumBy (comparing (isLocalName &&& isTyConName)) noChildren
      msg = "Warning: " ++ showNsRdrName dflags x ++ " is ambiguous. It is defined\n" ++
            concatMap (\n -> "    * " ++ defnLoc n ++ "\n") (map greMangledName gres) ++
            "    You may be able to disambiguate the identifier by qualifying it or\n" ++
            "    by specifying the type/value namespace explicitly.\n" ++
            "    Defaulting to the one defined " ++ defnLoc dflt
  -- TODO: Once we have a syntax for namespace qualification (#667) we may also
  -- want to emit a warning when an identifier is a data constructor for a type
  -- of the same name, but not the only constructor.
  -- For example, for @data D = C | D@, someone may want to reference the @D@
  -- constructor.
  when (length noChildren > 1) $ tell [msg]
  pure (DocIdentifier (x $> dflt))
  where
    isLocalName (nameSrcLoc -> RealSrcLoc {}) = True
    isLocalName _ = False
    defnLoc = showSDoc dflags . pprNameDefnLoc

-- | Handle value-namespaced names that cannot be for values.
--
-- Emits a warning that the value-namespace is invalid on a non-value identifier.
invalidValue :: DynFlags -> Wrap NsRdrName -> ErrMsgM (Doc a)
invalidValue dflags x = do
  tell ["Warning: " ++ showNsRdrName dflags x ++ " cannot be value, yet it is\n" ++
            "    namespaced as such. Did you mean to specify a type namespace\n" ++
            "    instead?"]
  pure (DocMonospaced (DocString (showNsRdrName dflags x)))

-- | Printable representation of a wrapped and namespaced name
showNsRdrName :: DynFlags -> Wrap NsRdrName -> String
showNsRdrName dflags = (\p i -> p ++ "'" ++ i ++ "'") <$> prefix <*> ident
  where
    ident = showWrapped (showPpr dflags . rdrName)
    prefix = renderNs . namespace . unwrap