    --
    -- (c) The University of Glasgow, 2004
    --

    -- | Package configuration information: essentially the interface to Cabal, with some utilities
    module PackageConfig (
        -- $package_naming

    	-- * PackageId
    	mkPackageId, packageConfigId,

    	-- * The PackageConfig type: information about a package
    	PackageConfig,
    	InstalledPackageInfo_(..), display,
    	Version(..),
    	PackageIdentifier(..),
    	defaultPackageConfig,
            packageConfigToInstalledPackageInfo,
            installedPackageInfoToPackageConfig,
      ) where

    #include "HsVersions.h"

    import Maybes
    import Module
    import Distribution.InstalledPackageInfo
    import Distribution.ModuleName
    import Distribution.Package hiding (PackageId)
    import Distribution.Text
    import Distribution.Version

    -- -----------------------------------------------------------------------------
    -- Our PackageConfig type is just InstalledPackageInfo from Cabal.  Later we
    -- might need to extend it with some GHC-specific stuff, but for now it's fine.

    type PackageConfig = InstalledPackageInfo_ Module.ModuleName
    defaultPackageConfig :: PackageConfig
    defaultPackageConfig = emptyInstalledPackageInfo

    -- -----------------------------------------------------------------------------
    -- PackageId (package names with versions)

    -- $package_naming
    -- #package_naming#
    -- Mostly the compiler deals in terms of 'PackageName's, which don't
    -- have the version suffix.  This is so that we don't need to know the
    -- version for the @-package-name@ flag, or know the versions of
    -- wired-in packages like @base@ & @rts@.  Versions are confined to the
    -- package sub-system.
    --
    -- This means that in theory you could have multiple base packages installed
    -- (for example), and switch between them using @-package@\/@-hide-package@.
    --
    -- A 'PackageId' is a string of the form @<pkg>-<version>@.

    -- | Turn a Cabal 'PackageIdentifier' into a GHC 'PackageId'
    mkPackageId :: PackageIdentifier -> PackageId
    mkPackageId = stringToPackageId . display

    -- | Get the GHC 'PackageId' right out of a Cabalish 'PackageConfig'
    packageConfigId :: PackageConfig -> PackageId
    packageConfigId = mkPackageId . sourcePackageId

    -- | Turn a 'PackageConfig', which contains GHC 'Module.ModuleName's into a Cabal specific
    -- 'InstalledPackageInfo' which contains Cabal 'Distribution.ModuleName.ModuleName's
    packageConfigToInstalledPackageInfo :: PackageConfig -> InstalledPackageInfo
    packageConfigToInstalledPackageInfo
        (pkgconf@(InstalledPackageInfo { exposedModules = e,
                                         hiddenModules = h })) =
            pkgconf{ exposedModules = map convert e,
                     hiddenModules  = map convert h }
        where convert :: Module.ModuleName -> Distribution.ModuleName.ModuleName
              convert = (expectJust "packageConfigToInstalledPackageInfo") . simpleParse . moduleNameString

    -- | Turn an 'InstalledPackageInfo', which contains Cabal 'Distribution.ModuleName.ModuleName's
    -- into a GHC specific 'PackageConfig' which contains GHC 'Module.ModuleName's
    installedPackageInfoToPackageConfig :: InstalledPackageInfo_ String -> PackageConfig
    installedPackageInfoToPackageConfig
        (pkgconf@(InstalledPackageInfo { exposedModules = e,
                                         hiddenModules = h })) =
            pkgconf{ exposedModules = map mkModuleName e,
                     hiddenModules  = map mkModuleName h }