    {-# LANGUAGE FlexibleContexts #-}
    {-# LANGUAGE RankNTypes #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.Build
    -- Copyright   :  Isaac Jones 2003-2005,
    --                Ross Paterson 2006,
    --                Duncan Coutts 2007-2008, 2012
    -- License     :  BSD3
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This is the entry point to actually building the modules in a package. It
    -- doesn't actually do much itself, most of the work is delegated to
    -- compiler-specific actions. It does do some non-compiler specific bits like
    -- running pre-processors.
    --

    module Distribution.Simple.Build (
        build, repl,
        startInterpreter,

        initialBuildSteps,
        componentInitialBuildSteps,
        writeAutogenFiles,
      ) where

    import Prelude ()
    import Distribution.Compat.Prelude

    import Distribution.Types.Dependency
    import Distribution.Types.LocalBuildInfo
    import Distribution.Types.TargetInfo
    import Distribution.Types.ComponentRequestedSpec
    import Distribution.Types.ForeignLib
    import Distribution.Types.MungedPackageId
    import Distribution.Types.MungedPackageName
    import Distribution.Types.UnqualComponentName
    import Distribution.Types.ComponentLocalBuildInfo
    import Distribution.Types.ExecutableScope

    import Distribution.Package
    import Distribution.Backpack
    import Distribution.Backpack.DescribeUnitId
    import qualified Distribution.Simple.GHC   as GHC
    import qualified Distribution.Simple.GHCJS as GHCJS
    import qualified Distribution.Simple.JHC   as JHC
    import qualified Distribution.Simple.LHC   as LHC
    import qualified Distribution.Simple.UHC   as UHC
    import qualified Distribution.Simple.HaskellSuite as HaskellSuite
    import qualified Distribution.Simple.PackageIndex as Index

    import qualified Distribution.Simple.Build.Macros      as Build.Macros
    import qualified Distribution.Simple.Build.PathsModule as Build.PathsModule
    import qualified Distribution.Simple.Program.HcPkg as HcPkg

    import Distribution.Simple.Compiler hiding (Flag)
    import Distribution.PackageDescription hiding (Flag)
    import qualified Distribution.InstalledPackageInfo as IPI
    import Distribution.InstalledPackageInfo (InstalledPackageInfo)
    import qualified Distribution.ModuleName as ModuleName

    import Distribution.Simple.Setup
    import Distribution.Simple.BuildTarget
    import Distribution.Simple.BuildToolDepends
    import Distribution.Simple.PreProcess
    import Distribution.Simple.LocalBuildInfo
    import Distribution.Simple.Program.Types
    import Distribution.Simple.Program.Db
    import Distribution.Simple.BuildPaths
    import Distribution.Simple.Configure
    import Distribution.Simple.Register
    import Distribution.Simple.Test.LibV09
    import Distribution.Simple.Utils

    import Distribution.System
    import Distribution.Text
    import Distribution.Verbosity

    import Distribution.Compat.Graph (IsNode(..))

    import Control.Monad
    import qualified Data.Set as Set
    import System.FilePath ( (</>), (<.>), takeDirectory )
    import System.Directory ( getCurrentDirectory )

    -- -----------------------------------------------------------------------------
    -- |Build the libraries and executables in this package.

    build    :: PackageDescription  -- ^ Mostly information from the .cabal file
             -> LocalBuildInfo      -- ^ Configuration information
             -> BuildFlags          -- ^ Flags that the user passed to build
             -> [ PPSuffixHandler ] -- ^ preprocessors to run before compiling
             -> IO ()
    build pkg_descr lbi flags suffixes = do
      targets <- readTargetInfos verbosity pkg_descr lbi (buildArgs flags)
      let componentsToBuild = neededTargetsInBuildOrder' pkg_descr lbi (map nodeKey targets)
      info verbosity $ "Component build order: "
                    ++ intercalate ", "
                        (map (showComponentName . componentLocalName . targetCLBI)
                            componentsToBuild)

      when (null targets) $
        -- Only bother with this message if we're building the whole package
        setupMessage verbosity "Building" (packageId pkg_descr)

      internalPackageDB <- createInternalPackageDB verbosity lbi distPref

      (\f -> foldM_ f (installedPkgs lbi) componentsToBuild) $ \index target -> do
        let comp = targetComponent target
            clbi = targetCLBI target
        componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity
        let bi     = componentBuildInfo comp
            progs' = addInternalBuildTools pkg_descr lbi bi (withPrograms lbi)
            lbi'   = lbi {
                       withPrograms  = progs',
                       withPackageDB = withPackageDB lbi ++ [internalPackageDB],
                       installedPkgs = index
                     }
        mb_ipi <- buildComponent verbosity (buildNumJobs flags) pkg_descr
                       lbi' suffixes comp clbi distPref
        return (maybe index (Index.insert `flip` index) mb_ipi)
      return ()
     where
      distPref  = fromFlag (buildDistPref flags)
      verbosity = fromFlag (buildVerbosity flags)

    repl     :: PackageDescription  -- ^ Mostly information from the .cabal file
             -> LocalBuildInfo      -- ^ Configuration information
             -> ReplFlags           -- ^ Flags that the user passed to build
             -> [ PPSuffixHandler ] -- ^ preprocessors to run before compiling
             -> [String]
             -> IO ()
    repl pkg_descr lbi flags suffixes args = do
      let distPref  = fromFlag (replDistPref flags)
          verbosity = fromFlag (replVerbosity flags)

      target <- readTargetInfos verbosity pkg_descr lbi args >>= \r -> case r of
        -- This seems DEEPLY questionable.
        []       -> return (head (allTargetsInBuildOrder' pkg_descr lbi))
        [target] -> return target
        _        -> die' verbosity $ "The 'repl' command does not support multiple targets at once."
      let componentsToBuild = neededTargetsInBuildOrder' pkg_descr lbi [nodeKey target]
      debug verbosity $ "Component build order: "
                     ++ intercalate ", "
                          (map (showComponentName . componentLocalName . targetCLBI)
                               componentsToBuild)

      internalPackageDB <- createInternalPackageDB verbosity lbi distPref

      let lbiForComponent comp lbi' =
            lbi' {
              withPackageDB = withPackageDB lbi ++ [internalPackageDB],
              withPrograms  = addInternalBuildTools pkg_descr lbi'
                                (componentBuildInfo comp) (withPrograms lbi')
            }

      -- build any dependent components
      sequence_
        [ do let clbi = targetCLBI subtarget
                 comp = targetComponent subtarget
                 lbi' = lbiForComponent comp lbi
             componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity
             buildComponent verbosity NoFlag
                            pkg_descr lbi' suffixes comp clbi distPref
        | subtarget <- init componentsToBuild ]

      -- REPL for target components
      let clbi = targetCLBI target
          comp = targetComponent target
          lbi' = lbiForComponent comp lbi
      componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity
      replComponent verbosity pkg_descr lbi' suffixes comp clbi distPref

    -- | Start an interpreter without loading any package files.
    startInterpreter :: Verbosity -> ProgramDb -> Compiler -> Platform
                     -> PackageDBStack -> IO ()
    startInterpreter verbosity programDb comp platform packageDBs =
      case compilerFlavor comp of
        GHC   -> GHC.startInterpreter   verbosity programDb comp platform packageDBs
        GHCJS -> GHCJS.startInterpreter verbosity programDb comp platform packageDBs
        _     -> die' verbosity "A REPL is not supported with this compiler."

    buildComponent :: Verbosity
                   -> Flag (Maybe Int)
                   -> PackageDescription
                   -> LocalBuildInfo
                   -> [PPSuffixHandler]
                   -> Component
                   -> ComponentLocalBuildInfo
                   -> FilePath
                   -> IO (Maybe InstalledPackageInfo)
    buildComponent verbosity numJobs pkg_descr lbi suffixes
                   comp@(CLib lib) clbi distPref = do
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        setupMessage' verbosity "Building" (packageId pkg_descr)
          (componentLocalName clbi) (maybeComponentInstantiatedWith clbi)
        let libbi = libBuildInfo lib
            lib' = lib { libBuildInfo = addExtraCxxSources (addExtraCSources libbi extras) extras }
        buildLib verbosity numJobs pkg_descr lbi lib' clbi

        let oneComponentRequested (OneComponentRequestedSpec _) = True
            oneComponentRequested _ = False
        -- Don't register inplace if we're only building a single component;
        -- it's not necessary because there won't be any subsequent builds
        -- that need to tag us
        if (not (oneComponentRequested (componentEnabledSpec lbi)))
          then do
            -- Register the library in-place, so exes can depend
            -- on internally defined libraries.
            pwd <- getCurrentDirectory
            let -- The in place registration uses the "-inplace" suffix, not an ABI hash
                installedPkgInfo = inplaceInstalledPackageInfo pwd distPref pkg_descr
                                        -- NB: Use a fake ABI hash to avoid
                                        -- needing to recompute it every build.
                                        (mkAbiHash "inplace") lib' lbi clbi

            debug verbosity $ "Registering inplace:\n" ++ (IPI.showInstalledPackageInfo installedPkgInfo)
            registerPackage verbosity (compiler lbi) (withPrograms lbi)
                            (withPackageDB lbi) installedPkgInfo
                            HcPkg.defaultRegisterOptions {
                              HcPkg.registerMultiInstance = True
                            }
            return (Just installedPkgInfo)
          else return Nothing

    buildComponent verbosity numJobs pkg_descr lbi suffixes
                   comp@(CFLib flib) clbi _distPref = do
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        setupMessage' verbosity "Building" (packageId pkg_descr)
          (componentLocalName clbi) (maybeComponentInstantiatedWith clbi)
        buildFLib verbosity numJobs pkg_descr lbi flib clbi
        return Nothing

    buildComponent verbosity numJobs pkg_descr lbi suffixes
                   comp@(CExe exe) clbi _ = do
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        setupMessage' verbosity "Building" (packageId pkg_descr)
          (componentLocalName clbi) (maybeComponentInstantiatedWith clbi)
        let ebi = buildInfo exe
            exe' = exe { buildInfo = addExtraCSources ebi extras }
        buildExe verbosity numJobs pkg_descr lbi exe' clbi
        return Nothing

    buildComponent verbosity numJobs pkg_descr lbi suffixes
                   comp@(CTest test@TestSuite { testInterface = TestSuiteExeV10{} })
                   clbi _distPref = do
        let exe = testSuiteExeV10AsExe test
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        setupMessage' verbosity "Building" (packageId pkg_descr)
          (componentLocalName clbi) (maybeComponentInstantiatedWith clbi)
        let ebi = buildInfo exe
            exe' = exe { buildInfo = addExtraCSources ebi extras }
        buildExe verbosity numJobs pkg_descr lbi exe' clbi
        return Nothing

    buildComponent verbosity numJobs pkg_descr lbi0 suffixes
                   comp@(CTest
                     test@TestSuite { testInterface = TestSuiteLibV09{} })
                   clbi -- This ComponentLocalBuildInfo corresponds to a detailed
                        -- test suite and not a real component. It should not
                        -- be used, except to construct the CLBIs for the
                        -- library and stub executable that will actually be
                        -- built.
                   distPref = do
        pwd <- getCurrentDirectory
        let (pkg, lib, libClbi, lbi, ipi, exe, exeClbi) =
              testSuiteLibV09AsLibAndExe pkg_descr test clbi lbi0 distPref pwd
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        setupMessage' verbosity "Building" (packageId pkg_descr)
          (componentLocalName clbi) (maybeComponentInstantiatedWith clbi)
        buildLib verbosity numJobs pkg lbi lib libClbi
        -- NB: need to enable multiple instances here, because on 7.10+
        -- the package name is the same as the library, and we still
        -- want the registration to go through.
        registerPackage verbosity (compiler lbi) (withPrograms lbi)
                        (withPackageDB lbi) ipi
                        HcPkg.defaultRegisterOptions {
                          HcPkg.registerMultiInstance = True
                        }
        let ebi = buildInfo exe
            -- NB: The stub executable is linked against the test-library
            --     which already contains all `other-modules`, so we need
            --     to remove those from the stub-exe's build-info
            exe' = exe { buildInfo = (addExtraCSources ebi extras) { otherModules = [] } }
        buildExe verbosity numJobs pkg_descr lbi exe' exeClbi
        return Nothing -- Can't depend on test suite

    buildComponent verbosity _ _ _ _
                   (CTest TestSuite { testInterface = TestSuiteUnsupported tt })
                   _ _ =
        die' verbosity $ "No support for building test suite type " ++ display tt

    buildComponent verbosity numJobs pkg_descr lbi suffixes
                   comp@(CBench bm@Benchmark { benchmarkInterface = BenchmarkExeV10 {} })
                   clbi _ = do
        let (exe, exeClbi) = benchmarkExeV10asExe bm clbi
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        setupMessage' verbosity "Building" (packageId pkg_descr)
          (componentLocalName clbi) (maybeComponentInstantiatedWith clbi)
        let ebi = buildInfo exe
            exe' = exe { buildInfo = addExtraCSources ebi extras }
        buildExe verbosity numJobs pkg_descr lbi exe' exeClbi
        return Nothing

    buildComponent verbosity _ _ _ _
                   (CBench Benchmark { benchmarkInterface = BenchmarkUnsupported tt })
                   _ _ =
        die' verbosity $ "No support for building benchmark type " ++ display tt

    -- | Add extra C sources generated by preprocessing to build
    -- information.
    addExtraCSources :: BuildInfo -> [FilePath] -> BuildInfo
    addExtraCSources bi extras = bi { cSources = new }
      where new = Set.toList $ old `Set.union` exs
            old = Set.fromList $ cSources bi
            exs = Set.fromList extras

    -- | Add extra C++ sources generated by preprocessing to build
    -- information.
    addExtraCxxSources :: BuildInfo -> [FilePath] -> BuildInfo
    addExtraCxxSources bi extras = bi { cxxSources = new }
      where new = Set.toList $ old `Set.union` exs
            old = Set.fromList $ cxxSources bi
            exs = Set.fromList extras

    replComponent :: Verbosity
                  -> PackageDescription
                  -> LocalBuildInfo
                  -> [PPSuffixHandler]
                  -> Component
                  -> ComponentLocalBuildInfo
                  -> FilePath
                  -> IO ()
    replComponent verbosity pkg_descr lbi suffixes
                   comp@(CLib lib) clbi _ = do
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        let libbi = libBuildInfo lib
            lib' = lib { libBuildInfo = libbi { cSources = cSources libbi ++ extras } }
        replLib verbosity pkg_descr lbi lib' clbi

    replComponent verbosity pkg_descr lbi suffixes
                   comp@(CFLib flib) clbi _ = do
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        replFLib verbosity pkg_descr lbi flib clbi

    replComponent verbosity pkg_descr lbi suffixes
                   comp@(CExe exe) clbi _ = do
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        let ebi = buildInfo exe
            exe' = exe { buildInfo = ebi { cSources = cSources ebi ++ extras } }
        replExe verbosity pkg_descr lbi exe' clbi

    replComponent verbosity pkg_descr lbi suffixes
                   comp@(CTest test@TestSuite { testInterface = TestSuiteExeV10{} })
                   clbi _distPref = do
        let exe = testSuiteExeV10AsExe test
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        let ebi = buildInfo exe
            exe' = exe { buildInfo = ebi { cSources = cSources ebi ++ extras } }
        replExe verbosity pkg_descr lbi exe' clbi

    replComponent verbosity pkg_descr lbi0 suffixes
                   comp@(CTest
                     test@TestSuite { testInterface = TestSuiteLibV09{} })
                   clbi distPref = do
        pwd <- getCurrentDirectory
        let (pkg, lib, libClbi, lbi, _, _, _) =
              testSuiteLibV09AsLibAndExe pkg_descr test clbi lbi0 distPref pwd
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        let libbi = libBuildInfo lib
            lib' = lib { libBuildInfo = libbi { cSources = cSources libbi ++ extras } }
        replLib verbosity pkg lbi lib' libClbi

    replComponent verbosity _ _ _
                  (CTest TestSuite { testInterface = TestSuiteUnsupported tt })
                  _ _ =
        die' verbosity $ "No support for building test suite type " ++ display tt

    replComponent verbosity pkg_descr lbi suffixes
                   comp@(CBench bm@Benchmark { benchmarkInterface = BenchmarkExeV10 {} })
                   clbi _ = do
        let (exe, exeClbi) = benchmarkExeV10asExe bm clbi
        preprocessComponent pkg_descr comp lbi clbi False verbosity suffixes
        extras <- preprocessExtras verbosity comp lbi
        let ebi = buildInfo exe
            exe' = exe { buildInfo = ebi { cSources = cSources ebi ++ extras } }
        replExe verbosity pkg_descr lbi exe' exeClbi

    replComponent verbosity _ _ _
                  (CBench Benchmark { benchmarkInterface = BenchmarkUnsupported tt })
                  _ _ =
        die' verbosity $ "No support for building benchmark type " ++ display tt

    ----------------------------------------------------
    -- Shared code for buildComponent and replComponent
    --

    -- | Translate a exe-style 'TestSuite' component into an exe for building
    testSuiteExeV10AsExe :: TestSuite -> Executable
    testSuiteExeV10AsExe test@TestSuite { testInterface = TestSuiteExeV10 _ mainFile } =
        Executable {
          exeName    = testName test,
          modulePath = mainFile,
          exeScope   = ExecutablePublic,
          buildInfo  = testBuildInfo test
        }
    testSuiteExeV10AsExe TestSuite{} = error "testSuiteExeV10AsExe: wrong kind"

    -- | Translate a lib-style 'TestSuite' component into a lib + exe for building
    testSuiteLibV09AsLibAndExe :: PackageDescription
                               -> TestSuite
                               -> ComponentLocalBuildInfo
                               -> LocalBuildInfo
                               -> FilePath
                               -> FilePath
                               -> (PackageDescription,
                                   Library, ComponentLocalBuildInfo,
                                   LocalBuildInfo,
                                   IPI.InstalledPackageInfo,
                                   Executable, ComponentLocalBuildInfo)
    testSuiteLibV09AsLibAndExe pkg_descr
                         test@TestSuite { testInterface = TestSuiteLibV09 _ m }
                         clbi lbi distPref pwd =
        (pkg, lib, libClbi, lbi, ipi, exe, exeClbi)
      where
        bi  = testBuildInfo test
        lib = Library {
                libName = Nothing,
                exposedModules = [ m ],
                reexportedModules = [],
                signatures = [],
                libExposed     = True,
                libBuildInfo   = bi
              }
        -- This is, like, the one place where we use a CTestName for a library.
        -- Should NOT use library name, since that could conflict!
        PackageIdentifier pkg_name pkg_ver = package pkg_descr
        compat_name = computeCompatPackageName pkg_name (Just (testName test))
        compat_key = computeCompatPackageKey (compiler lbi) compat_name pkg_ver (componentUnitId clbi)
        libClbi = LibComponentLocalBuildInfo
                    { componentPackageDeps = componentPackageDeps clbi
                    , componentInternalDeps = componentInternalDeps clbi
                    , componentIsIndefinite_ = False
                    , componentExeDeps = componentExeDeps clbi
                    , componentLocalName = CSubLibName (testName test)
                    , componentIsPublic = False
                    , componentIncludes = componentIncludes clbi
                    , componentUnitId = componentUnitId clbi
                    , componentComponentId = componentComponentId clbi
                    , componentInstantiatedWith = []
                    , componentCompatPackageName = compat_name
                    , componentCompatPackageKey = compat_key
                    , componentExposedModules = [IPI.ExposedModule m Nothing]
                    }
        pkg = pkg_descr {
                package      = (package pkg_descr) { pkgName = mkPackageName $ unMungedPackageName compat_name }
              , buildDepends = targetBuildDepends $ testBuildInfo test
              , executables  = []
              , testSuites   = []
              , subLibraries = [lib]
              }
        ipi    = inplaceInstalledPackageInfo pwd distPref pkg (mkAbiHash "") lib lbi libClbi
        testDir = buildDir lbi </> stubName test
              </> stubName test ++ "-tmp"
        testLibDep = thisPackageVersion $ package pkg
        exe = Executable {
                exeName    = mkUnqualComponentName $ stubName test,
                modulePath = stubFilePath test,
                exeScope   = ExecutablePublic,
                buildInfo  = (testBuildInfo test) {
                               hsSourceDirs       = [ testDir ],
                               targetBuildDepends = testLibDep
                                 : (targetBuildDepends $ testBuildInfo test)
                             }
              }
        -- | The stub executable needs a new 'ComponentLocalBuildInfo'
        -- that exposes the relevant test suite library.
        deps = (IPI.installedUnitId ipi, mungedId ipi)
             : (filter (\(_, x) -> let name = unMungedPackageName $ mungedName x
                                   in name == "Cabal" || name == "base")
                       (componentPackageDeps clbi))
        exeClbi = ExeComponentLocalBuildInfo {
                    -- TODO: this is a hack, but as long as this is unique
                    -- (doesn't clobber something) we won't run into trouble
                    componentUnitId = mkUnitId (stubName test),
                    componentComponentId = mkComponentId (stubName test),
                    componentInternalDeps = [componentUnitId clbi],
                    componentExeDeps = [],
                    componentLocalName = CExeName $ mkUnqualComponentName $ stubName test,
                    componentPackageDeps = deps,
                    -- Assert DefUnitId invariant!
                    -- Executable can't be indefinite, so dependencies must
                    -- be definite packages.
                    componentIncludes = zip (map (DefiniteUnitId . unsafeMkDefUnitId . fst) deps)
                                            (repeat defaultRenaming)
                  }
    testSuiteLibV09AsLibAndExe _ TestSuite{} _ _ _ _ = error "testSuiteLibV09AsLibAndExe: wrong kind"

    -- | Translate a exe-style 'Benchmark' component into an exe for building
    benchmarkExeV10asExe :: Benchmark -> ComponentLocalBuildInfo
                         -> (Executable, ComponentLocalBuildInfo)
    benchmarkExeV10asExe bm@Benchmark { benchmarkInterface = BenchmarkExeV10 _ f }
                         clbi =
        (exe, exeClbi)
      where
        exe = Executable {
                exeName    = benchmarkName bm,
                modulePath = f,
                exeScope   = ExecutablePublic,
                buildInfo  = benchmarkBuildInfo bm
              }
        exeClbi = ExeComponentLocalBuildInfo {
                    componentUnitId = componentUnitId clbi,
                    componentComponentId = componentComponentId clbi,
                    componentLocalName = CExeName (benchmarkName bm),
                    componentInternalDeps = componentInternalDeps clbi,
                    componentExeDeps = componentExeDeps clbi,
                    componentPackageDeps = componentPackageDeps clbi,
                    componentIncludes = componentIncludes clbi
                  }
    benchmarkExeV10asExe Benchmark{} _ = error "benchmarkExeV10asExe: wrong kind"

    -- | Initialize a new package db file for libraries defined
    -- internally to the package.
    createInternalPackageDB :: Verbosity -> LocalBuildInfo -> FilePath
                            -> IO PackageDB
    createInternalPackageDB verbosity lbi distPref = do
        existsAlready <- doesPackageDBExist dbPath
        when existsAlready $ deletePackageDB dbPath
        createPackageDB verbosity (compiler lbi) (withPrograms lbi) False dbPath
        return (SpecificPackageDB dbPath)
      where
        dbPath = internalPackageDBPath lbi distPref

    addInternalBuildTools :: PackageDescription -> LocalBuildInfo -> BuildInfo
                          -> ProgramDb -> ProgramDb
    addInternalBuildTools pkg lbi bi progs =
        foldr updateProgram progs internalBuildTools
      where
        internalBuildTools =
          [ simpleConfiguredProgram toolName' (FoundOnSystem toolLocation)
          | toolName <- getAllInternalToolDependencies pkg bi
          , let toolName' = unUnqualComponentName toolName
          , let toolLocation = buildDir lbi </> toolName' </> toolName' <.> exeExtension ]

    -- TODO: build separate libs in separate dirs so that we can build
    -- multiple libs, e.g. for 'LibTest' library-style test suites
    buildLib :: Verbosity -> Flag (Maybe Int)
                          -> PackageDescription -> LocalBuildInfo
                          -> Library            -> ComponentLocalBuildInfo -> IO ()
    buildLib verbosity numJobs pkg_descr lbi lib clbi =
      case compilerFlavor (compiler lbi) of
        GHC   -> GHC.buildLib   verbosity numJobs pkg_descr lbi lib clbi
        GHCJS -> GHCJS.buildLib verbosity numJobs pkg_descr lbi lib clbi
        JHC   -> JHC.buildLib   verbosity         pkg_descr lbi lib clbi
        LHC   -> LHC.buildLib   verbosity         pkg_descr lbi lib clbi
        UHC   -> UHC.buildLib   verbosity         pkg_descr lbi lib clbi
        HaskellSuite {} -> HaskellSuite.buildLib verbosity pkg_descr lbi lib clbi
        _    -> die' verbosity "Building is not supported with this compiler."

    -- | Build a foreign library
    --
    -- NOTE: We assume that we already checked that we can actually build the
    -- foreign library in configure.
    buildFLib :: Verbosity -> Flag (Maybe Int)
                           -> PackageDescription -> LocalBuildInfo
                           -> ForeignLib         -> ComponentLocalBuildInfo -> IO ()
    buildFLib verbosity numJobs pkg_descr lbi flib clbi =
        case compilerFlavor (compiler lbi) of
          GHC -> GHC.buildFLib verbosity numJobs pkg_descr lbi flib clbi
          _   -> die' verbosity "Building is not supported with this compiler."

    buildExe :: Verbosity -> Flag (Maybe Int)
                          -> PackageDescription -> LocalBuildInfo
                          -> Executable         -> ComponentLocalBuildInfo -> IO ()
    buildExe verbosity numJobs pkg_descr lbi exe clbi =
      case compilerFlavor (compiler lbi) of
        GHC   -> GHC.buildExe   verbosity numJobs pkg_descr lbi exe clbi
        GHCJS -> GHCJS.buildExe verbosity numJobs pkg_descr lbi exe clbi
        JHC   -> JHC.buildExe   verbosity         pkg_descr lbi exe clbi
        LHC   -> LHC.buildExe   verbosity         pkg_descr lbi exe clbi
        UHC   -> UHC.buildExe   verbosity         pkg_descr lbi exe clbi
        _     -> die' verbosity "Building is not supported with this compiler."

    replLib :: Verbosity -> PackageDescription -> LocalBuildInfo
                         -> Library            -> ComponentLocalBuildInfo -> IO ()
    replLib verbosity pkg_descr lbi lib clbi =
      case compilerFlavor (compiler lbi) of
        -- 'cabal repl' doesn't need to support 'ghc --make -j', so we just pass
        -- NoFlag as the numJobs parameter.
        GHC   -> GHC.replLib   verbosity NoFlag pkg_descr lbi lib clbi
        GHCJS -> GHCJS.replLib verbosity NoFlag pkg_descr lbi lib clbi
        _     -> die' verbosity "A REPL is not supported for this compiler."

    replExe :: Verbosity -> PackageDescription -> LocalBuildInfo
                         -> Executable         -> ComponentLocalBuildInfo -> IO ()
    replExe verbosity pkg_descr lbi exe clbi =
      case compilerFlavor (compiler lbi) of
        GHC   -> GHC.replExe   verbosity NoFlag pkg_descr lbi exe clbi
        GHCJS -> GHCJS.replExe verbosity NoFlag pkg_descr lbi exe clbi
        _     -> die' verbosity "A REPL is not supported for this compiler."

    replFLib :: Verbosity -> PackageDescription -> LocalBuildInfo
                          -> ForeignLib         -> ComponentLocalBuildInfo -> IO ()
    replFLib verbosity pkg_descr lbi exe clbi =
      case compilerFlavor (compiler lbi) of
        GHC -> GHC.replFLib verbosity NoFlag pkg_descr lbi exe clbi
        _   -> die' verbosity "A REPL is not supported for this compiler."

    -- | Runs 'componentInitialBuildSteps' on every configured component.
    initialBuildSteps :: FilePath -- ^"dist" prefix
                      -> PackageDescription  -- ^mostly information from the .cabal file
                      -> LocalBuildInfo -- ^Configuration information
                      -> Verbosity -- ^The verbosity to use
                      -> IO ()
    initialBuildSteps distPref pkg_descr lbi verbosity =
        withAllComponentsInBuildOrder pkg_descr lbi $ \_comp clbi ->
            componentInitialBuildSteps distPref pkg_descr lbi clbi verbosity

    -- | Creates the autogenerated files for a particular configured component.
    componentInitialBuildSteps :: FilePath -- ^"dist" prefix
                      -> PackageDescription  -- ^mostly information from the .cabal file
                      -> LocalBuildInfo -- ^Configuration information
                      -> ComponentLocalBuildInfo
                      -> Verbosity -- ^The verbosity to use
                      -> IO ()
    componentInitialBuildSteps _distPref pkg_descr lbi clbi verbosity = do
      createDirectoryIfMissingVerbose verbosity True (componentBuildDir lbi clbi)

      writeAutogenFiles verbosity pkg_descr lbi clbi

    -- | Generate and write out the Paths_<pkg>.hs and cabal_macros.h files
    --
    writeAutogenFiles :: Verbosity
                      -> PackageDescription
                      -> LocalBuildInfo
                      -> ComponentLocalBuildInfo
                      -> IO ()
    writeAutogenFiles verbosity pkg lbi clbi = do
      createDirectoryIfMissingVerbose verbosity True (autogenComponentModulesDir lbi clbi)

      let pathsModulePath = autogenComponentModulesDir lbi clbi
                     </> ModuleName.toFilePath (autogenPathsModuleName pkg) <.> "hs"
          pathsModuleDir = takeDirectory pathsModulePath
      -- Ensure that the directory exists!
      createDirectoryIfMissingVerbose verbosity True pathsModuleDir
      rewriteFileEx verbosity pathsModulePath (Build.PathsModule.generate pkg lbi clbi)

      --TODO: document what we're doing here, and move it to its own function
      case clbi of
        LibComponentLocalBuildInfo { componentInstantiatedWith = insts } ->
            -- Write out empty hsig files for all requirements, so that GHC
            -- has a source file to look at it when it needs to typecheck
            -- a signature.  It's harmless to write these out even when
            -- there is a real hsig file written by the user, since
            -- include path ordering ensures that the real hsig file
            -- will always be picked up before the autogenerated one.
            for_ (map fst insts) $ \mod_name -> do
                let sigPath = autogenComponentModulesDir lbi clbi
                          </> ModuleName.toFilePath mod_name <.> "hsig"
                createDirectoryIfMissingVerbose verbosity True (takeDirectory sigPath)
                rewriteFileEx verbosity sigPath $
                    "{-# LANGUAGE NoImplicitPrelude #-}\n" ++
                    "signature " ++ display mod_name ++ " where"
        _ -> return ()

      let cppHeaderPath = autogenComponentModulesDir lbi clbi </> cppHeaderName
      rewriteFileEx verbosity cppHeaderPath (Build.Macros.generate pkg lbi clbi)