    {-# LANGUAGE DeriveGeneric #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.Haddock
    -- Copyright   :  Isaac Jones 2003-2005
    -- License     :  BSD3
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This module deals with the @haddock@ and @hscolour@ commands.
    -- It uses information about installed packages (from @ghc-pkg@) to find the
    -- locations of documentation for dependent packages, so it can create links.
    --
    -- The @hscolour@ support allows generating HTML versions of the original
    -- source, with coloured syntax highlighting.

    module Distribution.Simple.Haddock (
      haddock, hscolour,

      haddockPackagePaths
      ) where

    import qualified Distribution.Simple.GHC   as GHC
    import qualified Distribution.Simple.GHCJS as GHCJS

    -- local
    import Distribution.Compat.Semigroup as Semi
    import Distribution.Package
    import qualified Distribution.ModuleName as ModuleName
    import Distribution.PackageDescription as PD hiding (Flag)
    import Distribution.Simple.Compiler hiding (Flag)
    import Distribution.Simple.Program.GHC
    import Distribution.Simple.Program
    import Distribution.Simple.PreProcess
    import Distribution.Simple.Setup
    import Distribution.Simple.Build
    import Distribution.Simple.InstallDirs
    import Distribution.Simple.LocalBuildInfo hiding (substPathTemplate)
    import Distribution.Simple.BuildPaths
    import qualified Distribution.Simple.PackageIndex as PackageIndex
    import qualified Distribution.InstalledPackageInfo as InstalledPackageInfo
    import Distribution.InstalledPackageInfo ( InstalledPackageInfo )
    import Distribution.Simple.Utils
    import Distribution.System
    import Distribution.Text
    import Distribution.Utils.NubList
    import Distribution.Version
    import Distribution.Verbosity
    import Language.Haskell.Extension

    import Control.Monad    ( when, forM_ )
    import Data.Char        ( isSpace )
    import Data.Either      ( rights )
    import Data.Foldable    ( traverse_, foldl' )
    import Data.Maybe       ( fromMaybe, listToMaybe )
    import GHC.Generics     ( Generic )

    import System.Directory (doesFileExist)
    import System.FilePath  ( (</>), (<.>)
                            , normalise, splitPath, joinPath, isAbsolute )
    import System.IO        (hClose, hPutStr, hPutStrLn, hSetEncoding, utf8)

    -- ------------------------------------------------------------------------------
    -- Types

    -- | A record that represents the arguments to the haddock executable, a product
    -- monoid.
    data HaddockArgs = HaddockArgs {
     argInterfaceFile :: Flag FilePath,
     -- ^ Path to the interface file, relative to argOutputDir, required.
     argPackageName :: Flag PackageIdentifier,
     -- ^ Package name, required.
     argHideModules :: (All,[ModuleName.ModuleName]),
     -- ^ (Hide modules ?, modules to hide)
     argIgnoreExports :: Any,
     -- ^ Ignore export lists in modules?
     argLinkSource :: Flag (Template,Template,Template),
     -- ^ (Template for modules, template for symbols, template for lines).
     argCssFile :: Flag FilePath,
     -- ^ Optional custom CSS file.
     argContents :: Flag String,
     -- ^ Optional URL to contents page.
     argVerbose :: Any,
     argOutput :: Flag [Output],
     -- ^ HTML or Hoogle doc or both? Required.
     argInterfaces :: [(FilePath, Maybe String)],
     -- ^ [(Interface file, URL to the HTML docs for links)].
     argOutputDir :: Directory,
     -- ^ Where to generate the documentation.
     argTitle :: Flag String,
     -- ^ Page title, required.
     argPrologue :: Flag String,
     -- ^ Prologue text, required.
     argGhcOptions :: Flag (GhcOptions, Version),
     -- ^ Additional flags to pass to GHC.
     argGhcLibDir :: Flag FilePath,
     -- ^ To find the correct GHC, required.
     argTargets :: [FilePath]
     -- ^ Modules to process.
    } deriving Generic

    -- | The FilePath of a directory, it's a monoid under '(</>)'.
    newtype Directory = Dir { unDir' :: FilePath } deriving (Read,Show,Eq,Ord)

    unDir :: Directory -> FilePath
    unDir = joinPath . filter (\p -> p /="./" && p /= ".") . splitPath . unDir'

    type Template = String

    data Output = Html | Hoogle

    -- ------------------------------------------------------------------------------
    -- Haddock support

    haddock :: PackageDescription
            -> LocalBuildInfo
            -> [PPSuffixHandler]
            -> HaddockFlags
            -> IO ()
    haddock pkg_descr _ _ haddockFlags
      |    not (hasLibs pkg_descr)
        && not (fromFlag $ haddockExecutables haddockFlags)
        && not (fromFlag $ haddockTestSuites  haddockFlags)
        && not (fromFlag $ haddockBenchmarks  haddockFlags) =
          warn (fromFlag $ haddockVerbosity haddockFlags) $
               "No documentation was generated as this package does not contain "
            ++ "a library. Perhaps you want to use the --executables, --tests or"
            ++ " --benchmarks flags."

    haddock pkg_descr lbi suffixes flags' = do
        let verbosity     = flag haddockVerbosity
            comp          = compiler lbi
            platform      = hostPlatform lbi

            flags = case haddockTarget of
              ForDevelopment -> flags'
              ForHackage -> flags'
                { haddockHoogle       = Flag True
                , haddockHtml         = Flag True
                , haddockHtmlLocation = Flag (pkg_url ++ "/docs")
                , haddockContents     = Flag (toPathTemplate pkg_url)
                , haddockHscolour     = Flag True
                }
            pkg_url       = "/package/$pkg-$version"
            flag f        = fromFlag $ f flags

            tmpFileOpts   = defaultTempFileOptions
                           { optKeepTempFiles = flag haddockKeepTempFiles }
            htmlTemplate  = fmap toPathTemplate . flagToMaybe . haddockHtmlLocation
                            $ flags
            haddockTarget =
              haddockTargetFromFlag (haddockForHackage flags')

        setupMessage verbosity "Running Haddock for" (packageId pkg_descr)
        (confHaddock, version, _) <-
          requireProgramVersion verbosity haddockProgram
            (orLaterVersion (Version [2,0] [])) (withPrograms lbi)

        -- various sanity checks
        when ( flag haddockHoogle
               && version < Version [2,2] []) $
             die "haddock 2.0 and 2.1 do not support the --hoogle flag."

        haddockGhcVersionStr <- rawSystemProgramStdout verbosity confHaddock
                                  ["--ghc-version"]
        case (simpleParse haddockGhcVersionStr, compilerCompatVersion GHC comp) of
          (Nothing, _) -> die "Could not get GHC version from Haddock"
          (_, Nothing) -> die "Could not get GHC version from compiler"
          (Just haddockGhcVersion, Just ghcVersion)
            | haddockGhcVersion == ghcVersion -> return ()
            | otherwise -> die $
                   "Haddock's internal GHC version must match the configured "
                ++ "GHC version.\n"
                ++ "The GHC version is " ++ display ghcVersion ++ " but "
                ++ "haddock is using GHC version " ++ display haddockGhcVersion

        -- the tools match the requests, we can proceed

        initialBuildSteps (flag haddockDistPref) pkg_descr lbi verbosity

        when (flag haddockHscolour) $
          hscolour' (warn verbosity) haddockTarget pkg_descr lbi suffixes
          (defaultHscolourFlags `mappend` haddockToHscolour flags)

        libdirArgs <- getGhcLibDir  verbosity lbi
        let commonArgs = mconcat
                [ libdirArgs
                , fromFlags (haddockTemplateEnv lbi (packageId pkg_descr)) flags
                , fromPackageDescription haddockTarget pkg_descr ]

        let pre c = preprocessComponent pkg_descr c lbi False verbosity suffixes
        withAllComponentsInBuildOrder pkg_descr lbi $ \component clbi -> do
          pre component
          let
            doExe com = case (compToExe com) of
              Just exe -> do
                withTempDirectoryEx verbosity tmpFileOpts (buildDir lbi) "tmp" $
                  \tmp -> do
                    exeArgs <- fromExecutable verbosity tmp lbi exe clbi htmlTemplate
                               version
                    let exeArgs' = commonArgs `mappend` exeArgs
                    runHaddock verbosity tmpFileOpts comp platform
                      confHaddock exeArgs'
              Nothing -> do
               warn (fromFlag $ haddockVerbosity flags)
                 "Unsupported component, skipping..."
               return ()
          case component of
            CLib lib -> do
              withTempDirectoryEx verbosity tmpFileOpts (buildDir lbi) "tmp" $
                \tmp -> do
                  libArgs <- fromLibrary verbosity tmp lbi lib clbi htmlTemplate
                             version
                  let libArgs' = commonArgs `mappend` libArgs
                  runHaddock verbosity tmpFileOpts comp platform confHaddock libArgs'
            CExe   _ -> when (flag haddockExecutables) $ doExe component
            CTest  _ -> when (flag haddockTestSuites)  $ doExe component
            CBench _ -> when (flag haddockBenchmarks)  $ doExe component

        forM_ (extraDocFiles pkg_descr) $ \ fpath -> do
          files <- matchFileGlob fpath
          forM_ files $ copyFileTo verbosity (unDir $ argOutputDir commonArgs)

    -- ------------------------------------------------------------------------------
    -- Contributions to HaddockArgs.

    fromFlags :: PathTemplateEnv -> HaddockFlags -> HaddockArgs
    fromFlags env flags =
        mempty {
          argHideModules = (maybe mempty (All . not)
                            $ flagToMaybe (haddockInternal flags), mempty),
          argLinkSource = if fromFlag (haddockHscolour flags)
                                   then Flag ("src/%{MODULE/./-}.html"
                                             ,"src/%{MODULE/./-}.html#%{NAME}"
                                             ,"src/%{MODULE/./-}.html#line-%{LINE}")
                                   else NoFlag,
          argCssFile = haddockCss flags,
          argContents = fmap (fromPathTemplate . substPathTemplate env)
                        (haddockContents flags),
          argVerbose = maybe mempty (Any . (>= deafening))
                       . flagToMaybe $ haddockVerbosity flags,
          argOutput =
              Flag $ case [ Html | Flag True <- [haddockHtml flags] ] ++
                          [ Hoogle | Flag True <- [haddockHoogle flags] ]
                     of [] -> [ Html ]
                        os -> os,
          argOutputDir = maybe mempty Dir . flagToMaybe $ haddockDistPref flags
        }

    fromPackageDescription :: HaddockTarget -> PackageDescription -> HaddockArgs
    fromPackageDescription haddockTarget pkg_descr =
          mempty { argInterfaceFile = Flag $ haddockName pkg_descr,
                   argPackageName = Flag $ packageId $ pkg_descr,
                   argOutputDir = Dir $
                       "doc" </> "html" </> haddockDirName haddockTarget pkg_descr,
                   argPrologue = Flag $ if null desc then synopsis pkg_descr
                                        else desc,
                   argTitle = Flag $ showPkg ++ subtitle
                 }
          where
            desc = PD.description pkg_descr
            showPkg = display (packageId pkg_descr)
            subtitle | null (synopsis pkg_descr) = ""
                     | otherwise                 = ": " ++ synopsis pkg_descr

    componentGhcOptions :: Verbosity -> LocalBuildInfo
                     -> BuildInfo -> ComponentLocalBuildInfo -> FilePath
                     -> GhcOptions
    componentGhcOptions verbosity lbi bi clbi odir =
      let f = case compilerFlavor (compiler lbi) of
                GHC   -> GHC.componentGhcOptions
                GHCJS -> GHCJS.componentGhcOptions
                _     -> error $
                           "Distribution.Simple.Haddock.componentGhcOptions:" ++
                           "haddock only supports GHC and GHCJS"
      in f verbosity lbi bi clbi odir

    fromLibrary :: Verbosity
                -> FilePath
                -> LocalBuildInfo -> Library -> ComponentLocalBuildInfo
                -> Maybe PathTemplate -- ^ template for HTML location
                -> Version
                -> IO HaddockArgs
    fromLibrary verbosity tmp lbi lib clbi htmlTemplate haddockVersion = do
        inFiles <- map snd `fmap` getLibSourceFiles lbi lib
        ifaceArgs <- getInterfaces verbosity lbi clbi htmlTemplate
        let vanillaOpts = (componentGhcOptions normal lbi bi clbi (buildDir lbi)) {
                              -- Noooooooooo!!!!!111
                              -- haddock stomps on our precious .hi
                              -- and .o files. Workaround by telling
                              -- haddock to write them elsewhere.
                              ghcOptObjDir     = toFlag tmp,
                              ghcOptHiDir      = toFlag tmp,
                              ghcOptStubDir    = toFlag tmp
                          } `mappend` getGhcCppOpts haddockVersion bi
            sharedOpts = vanillaOpts {
                             ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                             ghcOptFPic        = toFlag True,
                             ghcOptHiSuffix    = toFlag "dyn_hi",
                             ghcOptObjSuffix   = toFlag "dyn_o",
                             ghcOptExtra       =
                               toNubListR $ hcSharedOptions GHC bi

                         }
        opts <- if withVanillaLib lbi
                then return vanillaOpts
                else if withSharedLib lbi
                then return sharedOpts
                else die $ "Must have vanilla or shared libraries "
                           ++ "enabled in order to run haddock"
        ghcVersion <- maybe (die "Compiler has no GHC version")
                            return
                            (compilerCompatVersion GHC (compiler lbi))

        return ifaceArgs {
          argHideModules = (mempty,otherModules $ bi),
          argGhcOptions  = toFlag (opts, ghcVersion),
          argTargets     = inFiles
        }
      where
        bi = libBuildInfo lib

    fromExecutable :: Verbosity
                   -> FilePath
                   -> LocalBuildInfo -> Executable -> ComponentLocalBuildInfo
                   -> Maybe PathTemplate -- ^ template for HTML location
                   -> Version
                   -> IO HaddockArgs
    fromExecutable verbosity tmp lbi exe clbi htmlTemplate haddockVersion = do
        inFiles <- map snd `fmap` getExeSourceFiles lbi exe
        ifaceArgs <- getInterfaces verbosity lbi clbi htmlTemplate
        let vanillaOpts = (componentGhcOptions normal lbi bi clbi (buildDir lbi)) {
                              -- Noooooooooo!!!!!111
                              -- haddock stomps on our precious .hi
                              -- and .o files. Workaround by telling
                              -- haddock to write them elsewhere.
                              ghcOptObjDir  = toFlag tmp,
                              ghcOptHiDir   = toFlag tmp,
                              ghcOptStubDir = toFlag tmp
                          } `mappend` getGhcCppOpts haddockVersion bi
            sharedOpts = vanillaOpts {
                             ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                             ghcOptFPic        = toFlag True,
                             ghcOptHiSuffix    = toFlag "dyn_hi",
                             ghcOptObjSuffix   = toFlag "dyn_o",
                             ghcOptExtra       =
                               toNubListR $ hcSharedOptions GHC bi
                         }
        opts <- if withVanillaLib lbi
                then return vanillaOpts
                else if withSharedLib lbi
                then return sharedOpts
                else die $ "Must have vanilla or shared libraries "
                           ++ "enabled in order to run haddock"
        ghcVersion <- maybe (die "Compiler has no GHC version")
                            return
                            (compilerCompatVersion GHC (compiler lbi))

        return ifaceArgs {
          argGhcOptions = toFlag (opts, ghcVersion),
          argOutputDir  = Dir (exeName exe),
          argTitle      = Flag (exeName exe),
          argTargets    = inFiles
        }
      where
        bi = buildInfo exe

    compToExe :: Component -> Maybe Executable
    compToExe comp =
      case comp of
        CTest test@TestSuite { testInterface = TestSuiteExeV10 _ f } ->
          Just Executable {
            exeName    = testName test,
            modulePath = f,
            buildInfo  = testBuildInfo test
          }
        CBench bench@Benchmark { benchmarkInterface = BenchmarkExeV10 _ f } ->
          Just Executable {
            exeName    = benchmarkName bench,
            modulePath = f,
            buildInfo  = benchmarkBuildInfo bench
          }
        CExe exe -> Just exe
        _ -> Nothing

    getInterfaces :: Verbosity
                  -> LocalBuildInfo
                  -> ComponentLocalBuildInfo
                  -> Maybe PathTemplate -- ^ template for HTML location
                  -> IO HaddockArgs
    getInterfaces verbosity lbi clbi htmlTemplate = do
        (packageFlags, warnings) <- haddockPackageFlags lbi clbi htmlTemplate
        traverse_ (warn verbosity) warnings
        return $ mempty {
                     argInterfaces = packageFlags
                   }

    getGhcCppOpts :: Version
                  -> BuildInfo
                  -> GhcOptions
    getGhcCppOpts haddockVersion bi =
        mempty {
            ghcOptExtensions   = toNubListR [EnableExtension CPP | needsCpp],
            ghcOptCppOptions   = toNubListR defines
        }
      where
        needsCpp             = EnableExtension CPP `elem` usedExtensions bi
        defines              = [haddockVersionMacro]
        haddockVersionMacro  = "-D__HADDOCK_VERSION__="
                               ++ show (v1 * 1000 + v2 * 10 + v3)
          where
            [v1, v2, v3] = take 3 $ versionBranch haddockVersion ++ [0,0]

    getGhcLibDir :: Verbosity -> LocalBuildInfo
                 -> IO HaddockArgs
    getGhcLibDir verbosity lbi = do
        l <- case compilerFlavor (compiler lbi) of
                GHC   -> GHC.getLibDir   verbosity lbi
                GHCJS -> GHCJS.getLibDir verbosity lbi
                _     -> error "haddock only supports GHC and GHCJS"
        return $ mempty { argGhcLibDir = Flag l }

    -- ------------------------------------------------------------------------------
    -- | Call haddock with the specified arguments.
    runHaddock :: Verbosity
                  -> TempFileOptions
                  -> Compiler
                  -> Platform
                  -> ConfiguredProgram
                  -> HaddockArgs
                  -> IO ()
    runHaddock verbosity tmpFileOpts comp platform confHaddock args = do
      let haddockVersion = fromMaybe (error "unable to determine haddock version")
                           (programVersion confHaddock)
      renderArgs verbosity tmpFileOpts haddockVersion comp platform args $
        \(flags,result)-> do

          rawSystemProgram verbosity confHaddock flags

          notice verbosity $ "Documentation created: " ++ result

    renderArgs :: Verbosity
                  -> TempFileOptions
                  -> Version
                  -> Compiler
                  -> Platform
                  -> HaddockArgs
                  -> (([String], FilePath) -> IO a)
                  -> IO a
    renderArgs verbosity tmpFileOpts version comp platform args k = do
      let haddockSupportsUTF8          = version >= Version [2,14,4] []
          haddockSupportsResponseFiles = version >  Version [2,16,2] []
      createDirectoryIfMissingVerbose verbosity True outputDir
      withTempFileEx tmpFileOpts outputDir "haddock-prologue.txt" $
        \prologueFileName h -> do
              do
                 when haddockSupportsUTF8 (hSetEncoding h utf8)
                 hPutStrLn h $ fromFlag $ argPrologue args
                 hClose h
                 let pflag = "--prologue=" ++ prologueFileName
                     renderedArgs = pflag : renderPureArgs version comp platform args
                 if haddockSupportsResponseFiles
                   then
                     withTempFileEx tmpFileOpts outputDir "haddock-response.txt" $
                        \responseFileName hf -> do
                             when haddockSupportsUTF8 (hSetEncoding hf utf8)
                             let responseContents =
                                     unlines $ map escapeArg renderedArgs
                             hPutStr hf responseContents
                             hClose hf
                             info verbosity $ responseFileName ++ " contents: <<<"
                             info verbosity responseContents
                             info verbosity $ ">>> " ++ responseFileName
                             let respFile = "@" ++ responseFileName
                             k ([respFile], result)
                   else
                     k (renderedArgs, result)
        where
          outputDir = (unDir $ argOutputDir args)
          result = intercalate ", "
                 . map (\o -> outputDir </>
                                case o of
                                  Html -> "index.html"
                                  Hoogle -> pkgstr <.> "txt")
                 $ arg argOutput
                where
                  pkgstr = display $ packageName pkgid
                  pkgid = arg argPackageName
          arg f = fromFlag $ f args
          -- Support a gcc-like response file syntax.  Each separate
          -- argument and its possible parameter(s), will be separated in the
          -- response file by an actual newline; all other whitespace,
          -- single quotes, double quotes, and the character used for escaping
          -- (backslash) are escaped.  The called program will need to do a similar
          -- inverse operation to de-escape and re-constitute the argument list.
          escape cs c
            |    isSpace c
              || '\\' == c
              || '\'' == c
              || '"'  == c = c:'\\':cs -- n.b., our caller must reverse the result
            | otherwise    = c:cs
          escapeArg = reverse . foldl' escape []

    renderPureArgs :: Version -> Compiler -> Platform -> HaddockArgs -> [String]
    renderPureArgs version comp platform args = concat
        [ (:[]) . (\f -> "--dump-interface="++ unDir (argOutputDir args) </> f)
          . fromFlag . argInterfaceFile $ args

        , if isVersion 2 16
            then (\pkg -> [ "--package-name=" ++ display (pkgName pkg)
                          , "--package-version="++display (pkgVersion pkg)
                          ])
                 . fromFlag . argPackageName $ args
            else []

        , (\(All b,xs) -> bool (map (("--hide=" ++). display) xs) [] b)
                         . argHideModules $ args

        , bool ["--ignore-all-exports"] [] . getAny . argIgnoreExports $ args

        , maybe [] (\(m,e,l) ->
                     ["--source-module=" ++ m
                     ,"--source-entity=" ++ e]
                     ++ if isVersion 2 14 then ["--source-entity-line=" ++ l]
                        else []
                   ) . flagToMaybe . argLinkSource $ args

        , maybe [] ((:[]) . ("--css="++)) . flagToMaybe . argCssFile $ args

        , maybe [] ((:[]) . ("--use-contents="++)) . flagToMaybe . argContents $ args

        , bool [] [verbosityFlag] . getAny . argVerbose $ args

        , map (\o -> case o of Hoogle -> "--hoogle"; Html -> "--html")
          . fromFlag . argOutput $ args

        , renderInterfaces . argInterfaces $ args

        , (:[]) . ("--odir="++) . unDir . argOutputDir $ args

        , (:[]) . ("--title="++)
          . (bool (++" (internal documentation)")
             id (getAny $ argIgnoreExports args))
          . fromFlag . argTitle $ args

        , [ "--optghc=" ++ opt | (opts, _ghcVer) <- flagToList (argGhcOptions args)
                               , opt <- renderGhcOptions comp platform opts ]

        , maybe [] (\l -> ["-B"++l]) $
          flagToMaybe (argGhcLibDir args) -- error if Nothing?

        , argTargets $ args
        ]
        where
          renderInterfaces =
            map (\(i,mh) -> "--read-interface=" ++
              maybe "" (++",") mh ++ i)
          bool a b c = if c then a else b
          isVersion major minor  = version >= Version [major,minor]  []
          verbosityFlag
           | isVersion 2 5 = "--verbosity=1"
           | otherwise     = "--verbose"

    ---------------------------------------------------------------------------------

    -- | Given a list of 'InstalledPackageInfo's, return a list of interfaces and
    -- HTML paths, and an optional warning for packages with missing documentation.
    haddockPackagePaths :: [InstalledPackageInfo]
                        -> Maybe (InstalledPackageInfo -> FilePath)
                        -> IO ([(FilePath, Maybe FilePath)], Maybe String)
    haddockPackagePaths ipkgs mkHtmlPath = do
      interfaces <- sequence
        [ case interfaceAndHtmlPath ipkg of
            Nothing -> return (Left (packageId ipkg))
            Just (interface, html) -> do
              exists <- doesFileExist interface
              if exists
                then return (Right (interface, html))
                else return (Left pkgid)
        | ipkg <- ipkgs, let pkgid = packageId ipkg
        , pkgName pkgid `notElem` noHaddockWhitelist
        ]

      let missing = [ pkgid | Left pkgid <- interfaces ]
          warning = "The documentation for the following packages are not "
                 ++ "installed. No links will be generated to these packages: "
                 ++ intercalate ", " (map display missing)
          flags = rights interfaces

      return (flags, if null missing then Nothing else Just warning)

      where
        -- Don't warn about missing documentation for these packages. See #1231.
        noHaddockWhitelist = map PackageName [ "rts" ]

        -- Actually extract interface and HTML paths from an 'InstalledPackageInfo'.
        interfaceAndHtmlPath :: InstalledPackageInfo
                             -> Maybe (FilePath, Maybe FilePath)
        interfaceAndHtmlPath pkg = do
          interface <- listToMaybe (InstalledPackageInfo.haddockInterfaces pkg)
          html <- case mkHtmlPath of
            Nothing -> fmap fixFileUrl
                            (listToMaybe (InstalledPackageInfo.haddockHTMLs pkg))
            Just mkPath -> Just (mkPath pkg)
          return (interface, if null html then Nothing else Just html)
          where
            -- The 'haddock-html' field in the hc-pkg output is often set as a
            -- native path, but we need it as a URL. See #1064.
            fixFileUrl f | isAbsolute f = "file://" ++ f
                         | otherwise    = f

    haddockPackageFlags :: LocalBuildInfo
                        -> ComponentLocalBuildInfo
                        -> Maybe PathTemplate
                        -> IO ([(FilePath, Maybe FilePath)], Maybe String)
    haddockPackageFlags lbi clbi htmlTemplate = do
      let allPkgs = installedPkgs lbi
          directDeps = map fst (componentPackageDeps clbi)
      transitiveDeps <- case PackageIndex.dependencyClosure allPkgs directDeps of
        Left x    -> return x
        Right inf -> die $ "internal error when calculating transitive "
                        ++ "package dependencies.\nDebug info: " ++ show inf
      haddockPackagePaths (PackageIndex.allPackages transitiveDeps) mkHtmlPath
        where
          mkHtmlPath                  = fmap expandTemplateVars htmlTemplate
          expandTemplateVars tmpl pkg =
            fromPathTemplate . substPathTemplate (env pkg) $ tmpl
          env pkg                     = haddockTemplateEnv lbi (packageId pkg)

    haddockTemplateEnv :: LocalBuildInfo -> PackageIdentifier -> PathTemplateEnv
    haddockTemplateEnv lbi pkg_id =
      (PrefixVar, prefix (installDirTemplates lbi))
      -- We want the legacy unit ID here, because it gives us nice paths
      -- (Haddock people don't care about the dependencies)
      : initialPathTemplateEnv pkg_id (mkLegacyUnitId pkg_id) (compilerInfo (compiler lbi))
      (hostPlatform lbi)

    -- ------------------------------------------------------------------------------
    -- hscolour support.

    hscolour :: PackageDescription
             -> LocalBuildInfo
             -> [PPSuffixHandler]
             -> HscolourFlags
             -> IO ()
    hscolour pkg_descr lbi suffixes flags = do
      -- we preprocess even if hscolour won't be found on the machine
      -- will this upset someone?
      initialBuildSteps distPref pkg_descr lbi verbosity
      hscolour' die ForDevelopment pkg_descr lbi suffixes flags
     where
       verbosity  = fromFlag (hscolourVerbosity flags)
       distPref = fromFlag $ hscolourDistPref flags

    hscolour' :: (String -> IO ()) -- ^ Called when the 'hscolour' exe is not found.
              -> HaddockTarget
              -> PackageDescription
              -> LocalBuildInfo
              -> [PPSuffixHandler]
              -> HscolourFlags
              -> IO ()
    hscolour' onNoHsColour haddockTarget pkg_descr lbi suffixes flags =
        either onNoHsColour (\(hscolourProg, _, _) -> go hscolourProg) =<<
          lookupProgramVersion verbosity hscolourProgram
          (orLaterVersion (Version [1,8] [])) (withPrograms lbi)
      where
        go :: ConfiguredProgram -> IO ()
        go hscolourProg = do
          setupMessage verbosity "Running hscolour for" (packageId pkg_descr)
          createDirectoryIfMissingVerbose verbosity True $
            hscolourPref' haddockTarget distPref pkg_descr

          let pre c = preprocessComponent pkg_descr c lbi False verbosity suffixes
          withAllComponentsInBuildOrder pkg_descr lbi $ \comp _ -> do
            pre comp
            let
              doExe com = case (compToExe com) of
                Just exe -> do
                  let outputDir = hscolourPref' haddockTarget distPref pkg_descr
                                  </> exeName exe </> "src"
                  runHsColour hscolourProg outputDir =<< getExeSourceFiles lbi exe
                Nothing -> do
                  warn (fromFlag $ hscolourVerbosity flags)
                    "Unsupported component, skipping..."
                  return ()
            case comp of
              CLib lib -> do
                let outputDir = hscolourPref' haddockTarget distPref pkg_descr </> "src"
                runHsColour hscolourProg outputDir =<< getLibSourceFiles lbi lib
              CExe   _ -> when (fromFlag (hscolourExecutables flags)) $ doExe comp
              CTest  _ -> when (fromFlag (hscolourTestSuites  flags)) $ doExe comp
              CBench _ -> when (fromFlag (hscolourBenchmarks  flags)) $ doExe comp

        stylesheet = flagToMaybe (hscolourCSS flags)

        verbosity  = fromFlag (hscolourVerbosity flags)
        distPref   = fromFlag (hscolourDistPref flags)

        runHsColour prog outputDir moduleFiles = do
             createDirectoryIfMissingVerbose verbosity True outputDir

             case stylesheet of -- copy the CSS file
               Nothing | programVersion prog >= Just (Version [1,9] []) ->
                           rawSystemProgram verbosity prog
                              ["-print-css", "-o" ++ outputDir </> "hscolour.css"]
                       | otherwise -> return ()
               Just s -> copyFileVerbose verbosity s (outputDir </> "hscolour.css")

             forM_ moduleFiles $ \(m, inFile) ->
                 rawSystemProgram verbosity prog
                        ["-css", "-anchor", "-o" ++ outFile m, inFile]
            where
              outFile m = outputDir </>
                          intercalate "-" (ModuleName.components m) <.> "html"

    haddockToHscolour :: HaddockFlags -> HscolourFlags
    haddockToHscolour flags =
        HscolourFlags {
          hscolourCSS         = haddockHscolourCss flags,
          hscolourExecutables = haddockExecutables flags,
          hscolourTestSuites  = haddockTestSuites  flags,
          hscolourBenchmarks  = haddockBenchmarks  flags,
          hscolourVerbosity   = haddockVerbosity   flags,
          hscolourDistPref    = haddockDistPref    flags
        }
    ---------------------------------------------------------------------------------
    -- TODO these should be moved elsewhere.

    getLibSourceFiles :: LocalBuildInfo
                         -> Library
                         -> IO [(ModuleName.ModuleName, FilePath)]
    getLibSourceFiles lbi lib = getSourceFiles searchpaths modules
      where
        bi               = libBuildInfo lib
        modules          = PD.exposedModules lib ++ otherModules bi
        searchpaths      = autogenModulesDir lbi : buildDir lbi : hsSourceDirs bi

    getExeSourceFiles :: LocalBuildInfo
                         -> Executable
                         -> IO [(ModuleName.ModuleName, FilePath)]
    getExeSourceFiles lbi exe = do
        moduleFiles <- getSourceFiles searchpaths modules
        srcMainPath <- findFile (hsSourceDirs bi) (modulePath exe)
        return ((ModuleName.main, srcMainPath) : moduleFiles)
      where
        bi          = buildInfo exe
        modules     = otherModules bi
        searchpaths = autogenModulesDir lbi : exeBuildDir lbi exe : hsSourceDirs bi

    getSourceFiles :: [FilePath]
                      -> [ModuleName.ModuleName]
                      -> IO [(ModuleName.ModuleName, FilePath)]
    getSourceFiles dirs modules = flip mapM modules $ \m -> fmap ((,) m) $
        findFileWithExtension ["hs", "lhs"] dirs (ModuleName.toFilePath m)
          >>= maybe (notFound m) (return . normalise)
      where
        notFound module_ = die $ "can't find source for module " ++ display module_

    -- | The directory where we put build results for an executable
    exeBuildDir :: LocalBuildInfo -> Executable -> FilePath
    exeBuildDir lbi exe = buildDir lbi </> exeName exe </> exeName exe ++ "-tmp"

    -- ------------------------------------------------------------------------------
    -- Boilerplate Monoid instance.
    instance Monoid HaddockArgs where
        mempty = gmempty
        mappend = (Semi.<>)

    instance Semigroup HaddockArgs where
        (<>) = gmappend

    instance Monoid Directory where
        mempty = Dir "."
        mappend = (Semi.<>)

    instance Semigroup Directory where
        Dir m <> Dir n = Dir $ m </> n