    {-# LANGUAGE CPP #-}
    {-# LANGUAGE DeriveGeneric #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.Setup
    -- Copyright   :  Isaac Jones 2003-2004
    --                Duncan Coutts 2007
    -- License     :  BSD3
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This is a big module, but not very complicated. The code is very regular
    -- and repetitive. It defines the command line interface for all the Cabal
    -- commands. For each command (like @configure@, @build@ etc) it defines a type
    -- that holds all the flags, the default set of flags and a 'CommandUI' that
    -- maps command line flags to and from the corresponding flags type.
    --
    -- All the flags types are instances of 'Monoid', see
    -- <http://www.haskell.org/pipermail/cabal-devel/2007-December/001509.html>
    -- for an explanation.
    --
    -- The types defined here get used in the front end and especially in
    -- @cabal-install@ which has to do quite a bit of manipulating sets of command
    -- line flags.
    --
    -- This is actually relatively nice, it works quite well. The main change it
    -- needs is to unify it with the code for managing sets of fields that can be
    -- read and written from files. This would allow us to save configure flags in
    -- config files.

    module Distribution.Simple.Setup (

      GlobalFlags(..),   emptyGlobalFlags,   defaultGlobalFlags,   globalCommand,
      ConfigFlags(..),   emptyConfigFlags,   defaultConfigFlags,   configureCommand,
      configPrograms,
      AllowNewer(..),    AllowNewerDep(..),  isAllowNewer,
      configAbsolutePaths, readPackageDbList, showPackageDbList,
      CopyFlags(..),     emptyCopyFlags,     defaultCopyFlags,     copyCommand,
      InstallFlags(..),  emptyInstallFlags,  defaultInstallFlags,  installCommand,
      HaddockTarget(..), haddockTargetFromFlag,
      HaddockFlags(..),  emptyHaddockFlags,  defaultHaddockFlags,  haddockCommand,
      HscolourFlags(..), emptyHscolourFlags, defaultHscolourFlags, hscolourCommand,
      BuildFlags(..),    emptyBuildFlags,    defaultBuildFlags,    buildCommand,
      buildVerbose,
      ReplFlags(..),                         defaultReplFlags,     replCommand,
      CleanFlags(..),    emptyCleanFlags,    defaultCleanFlags,    cleanCommand,
      RegisterFlags(..), emptyRegisterFlags, defaultRegisterFlags, registerCommand,
                                                                   unregisterCommand,
      SDistFlags(..),    emptySDistFlags,    defaultSDistFlags,    sdistCommand,
      TestFlags(..),     emptyTestFlags,     defaultTestFlags,     testCommand,
      TestShowDetails(..),
      BenchmarkFlags(..), emptyBenchmarkFlags,
      defaultBenchmarkFlags, benchmarkCommand,
      CopyDest(..),
      configureArgs, configureOptions, configureCCompiler, configureLinker,
      buildOptions, haddockOptions, installDirsOptions,
      programConfigurationOptions, programConfigurationPaths',
      splitArgs,

      defaultDistPref, optionDistPref,

      Flag(..),
      toFlag,
      fromFlag,
      fromFlagOrDefault,
      flagToMaybe,
      flagToList,
      boolOpt, boolOpt', trueArg, falseArg,
      optionVerbosity, optionNumJobs, readPToMaybe ) where

    import Distribution.Compiler
    import Distribution.ReadE
    import Distribution.Text
    import qualified Distribution.Compat.ReadP as Parse
    import qualified Text.PrettyPrint as Disp
    import Distribution.Package
    import Distribution.PackageDescription hiding (Flag)
    import Distribution.Simple.Command hiding (boolOpt, boolOpt')
    import qualified Distribution.Simple.Command as Command
    import Distribution.Simple.Compiler hiding (Flag)
    import Distribution.Simple.Utils
    import Distribution.Simple.Program
    import Distribution.Simple.InstallDirs
    import Distribution.Verbosity
    import Distribution.Utils.NubList
    import Distribution.Compat.Binary (Binary)
    import Distribution.Compat.Semigroup as Semi

    import Control.Applicative as A ( Applicative(..), (<*) )
    import Control.Monad            ( liftM )
    import Data.List                ( sort )
    import Data.Maybe               ( listToMaybe )
    import Data.Char                ( isSpace, isAlpha )
    import GHC.Generics             ( Generic )

    -- FIXME Not sure where this should live
    defaultDistPref :: FilePath
    defaultDistPref = "dist"

    -- ------------------------------------------------------------
    -- * Flag type
    -- ------------------------------------------------------------

    -- | All flags are monoids, they come in two flavours:
    --
    -- 1. list flags eg
    --
    -- > --ghc-option=foo --ghc-option=bar
    --
    -- gives us all the values ["foo", "bar"]
    --
    -- 2. singular value flags, eg:
    --
    -- > --enable-foo --disable-foo
    --
    -- gives us Just False
    -- So this Flag type is for the latter singular kind of flag.
    -- Its monoid instance gives us the behaviour where it starts out as
    -- 'NoFlag' and later flags override earlier ones.
    --
    data Flag a = Flag a | NoFlag deriving (Eq, Generic, Show, Read)

    instance Binary a => Binary (Flag a)

    instance Functor Flag where
      fmap f (Flag x) = Flag (f x)
      fmap _ NoFlag  = NoFlag

    instance Monoid (Flag a) where
      mempty = NoFlag
      mappend = (Semi.<>)

    instance Semigroup (Flag a) where
      _ <> f@(Flag _) = f
      f <> NoFlag     = f

    instance Bounded a => Bounded (Flag a) where
      minBound = toFlag minBound
      maxBound = toFlag maxBound

    instance Enum a => Enum (Flag a) where
      fromEnum = fromEnum . fromFlag
      toEnum   = toFlag   . toEnum
      enumFrom (Flag a) = map toFlag . enumFrom $ a
      enumFrom _        = []
      enumFromThen (Flag a) (Flag b) = toFlag `map` enumFromThen a b
      enumFromThen _        _        = []
      enumFromTo   (Flag a) (Flag b) = toFlag `map` enumFromTo a b
      enumFromTo   _        _        = []
      enumFromThenTo (Flag a) (Flag b) (Flag c) = toFlag `map` enumFromThenTo a b c
      enumFromThenTo _        _        _        = []

    toFlag :: a -> Flag a
    toFlag = Flag

    fromFlag :: Flag a -> a
    fromFlag (Flag x) = x
    fromFlag NoFlag   = error "fromFlag NoFlag. Use fromFlagOrDefault"

    fromFlagOrDefault :: a -> Flag a -> a
    fromFlagOrDefault _   (Flag x) = x
    fromFlagOrDefault def NoFlag   = def

    flagToMaybe :: Flag a -> Maybe a
    flagToMaybe (Flag x) = Just x
    flagToMaybe NoFlag   = Nothing

    flagToList :: Flag a -> [a]
    flagToList (Flag x) = [x]
    flagToList NoFlag   = []

    allFlags :: [Flag Bool] -> Flag Bool
    allFlags flags = if all (\f -> fromFlagOrDefault False f) flags
                     then Flag True
                     else NoFlag

    -- ------------------------------------------------------------
    -- * Global flags
    -- ------------------------------------------------------------

    -- In fact since individual flags types are monoids and these are just sets of
    -- flags then they are also monoids pointwise. This turns out to be really
    -- useful. The mempty is the set of empty flags and mappend allows us to
    -- override specific flags. For example we can start with default flags and
    -- override with the ones we get from a file or the command line, or both.

    -- | Flags that apply at the top level, not to any sub-command.
    data GlobalFlags = GlobalFlags {
        globalVersion        :: Flag Bool,
        globalNumericVersion :: Flag Bool
      } deriving (Generic)

    defaultGlobalFlags :: GlobalFlags
    defaultGlobalFlags  = GlobalFlags {
        globalVersion        = Flag False,
        globalNumericVersion = Flag False
      }

    globalCommand :: [Command action] -> CommandUI GlobalFlags
    globalCommand commands = CommandUI
      { commandName         = ""
      , commandSynopsis     = ""
      , commandUsage        = \pname ->
             "This Setup program uses the Haskell Cabal Infrastructure.\n"
          ++ "See http://www.haskell.org/cabal/ for more information.\n"
          ++ "\n"
          ++ "Usage: " ++ pname ++ " [GLOBAL FLAGS] [COMMAND [FLAGS]]\n"
      , commandDescription = Just $ \pname ->
          let
            commands' = commands ++ [commandAddAction helpCommandUI undefined]
            cmdDescs = getNormalCommandDescriptions commands'
            maxlen    = maximum $ [length name | (name, _) <- cmdDescs]
            align str = str ++ replicate (maxlen - length str) ' '
          in
             "Commands:\n"
          ++ unlines [ "  " ++ align name ++ "    " ++ descr
                     | (name, descr) <- cmdDescs ]
          ++ "\n"
          ++ "For more information about a command use\n"
          ++ "  " ++ pname ++ " COMMAND --help\n\n"
          ++ "Typical steps for installing Cabal packages:\n"
          ++ concat [ "  " ++ pname ++ " " ++ x ++ "\n"
                    | x <- ["configure", "build", "install"]]
      , commandNotes        = Nothing
      , commandDefaultFlags = defaultGlobalFlags
      , commandOptions      = \_ ->
          [option ['V'] ["version"]
             "Print version information"
             globalVersion (\v flags -> flags { globalVersion = v })
             trueArg
          ,option [] ["numeric-version"]
             "Print just the version number"
             globalNumericVersion (\v flags -> flags { globalNumericVersion = v })
             trueArg
          ]
      }

    emptyGlobalFlags :: GlobalFlags
    emptyGlobalFlags = mempty

    instance Monoid GlobalFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup GlobalFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * Config flags
    -- ------------------------------------------------------------

    -- | Policy for relaxing upper bounds in dependencies. For example, given
    -- 'build-depends: array >= 0.3 && < 0.5', are we allowed to relax the upper
    -- bound and choose a version of 'array' that is greater or equal to 0.5? By
    -- default the upper bounds are always strictly honored.
    data AllowNewer =

      -- | Default: honor the upper bounds in all dependencies, never choose
      -- versions newer than allowed.
      AllowNewerNone

      -- | Ignore upper bounds in dependencies on the given packages.
      | AllowNewerSome [AllowNewerDep]

      -- | Ignore upper bounds in dependencies on all packages.
      | AllowNewerAll
      deriving (Eq, Read, Show, Generic)

    -- | Dependencies can be relaxed either for all packages in the install plan, or
    -- only for some packages.
    data AllowNewerDep = AllowNewerDep PackageName
                       | AllowNewerDepScoped PackageName PackageName
                       deriving (Eq, Read, Show, Generic)

    instance Text AllowNewerDep where
      disp (AllowNewerDep p0)          = disp p0
      disp (AllowNewerDepScoped p0 p1) = disp p0 Disp.<> Disp.colon Disp.<> disp p1

      parse = scopedP Parse.<++ normalP
        where
          scopedP = AllowNewerDepScoped `fmap` parse A.<* Parse.char ':' A.<*> parse
          normalP = AllowNewerDep       `fmap` parse

    instance Binary AllowNewer
    instance Binary AllowNewerDep

    instance Semigroup AllowNewer where
      AllowNewerNone       <> r                    = r
      l@AllowNewerAll      <> _                    = l
      l@(AllowNewerSome _) <> AllowNewerNone       = l
      (AllowNewerSome   _) <> r@AllowNewerAll      = r
      (AllowNewerSome   a) <> (AllowNewerSome b)   = AllowNewerSome (a ++ b)

    instance Monoid AllowNewer where
      mempty  = AllowNewerNone
      mappend = (Semi.<>)

    -- | Convert 'AllowNewer' to a boolean.
    isAllowNewer :: AllowNewer -> Bool
    isAllowNewer AllowNewerNone     = False
    isAllowNewer (AllowNewerSome _) = True
    isAllowNewer AllowNewerAll      = True

    allowNewerParser :: Parse.ReadP r (Maybe AllowNewer)
    allowNewerParser =
      (Just . AllowNewerSome) `fmap` Parse.sepBy1 parse (Parse.char ',')

    allowNewerPrinter :: (Maybe AllowNewer) -> [Maybe String]
    allowNewerPrinter Nothing                      = []
    allowNewerPrinter (Just AllowNewerNone)        = []
    allowNewerPrinter (Just AllowNewerAll)         = [Nothing]
    allowNewerPrinter (Just (AllowNewerSome pkgs)) = map (Just . display) $ pkgs

    -- | Flags to @configure@ command.
    --
    -- IMPORTANT: every time a new flag is added, 'D.C.Setup.filterConfigureFlags'
    -- should be updated.
    data ConfigFlags = ConfigFlags {
        --FIXME: the configPrograms is only here to pass info through to configure
        -- because the type of configure is constrained by the UserHooks.
        -- when we change UserHooks next we should pass the initial
        -- ProgramConfiguration directly and not via ConfigFlags
        configPrograms_     :: Last' ProgramConfiguration, -- ^All programs that
                                                           -- @cabal@ may run

        configProgramPaths  :: [(String, FilePath)], -- ^user specified programs paths
        configProgramArgs   :: [(String, [String])], -- ^user specified programs args
        configProgramPathExtra :: NubList FilePath,  -- ^Extend the $PATH
        configHcFlavor      :: Flag CompilerFlavor, -- ^The \"flavor\" of the
                                                    -- compiler, such as GHC or
                                                    -- JHC.
        configHcPath        :: Flag FilePath, -- ^given compiler location
        configHcPkg         :: Flag FilePath, -- ^given hc-pkg location
        configVanillaLib    :: Flag Bool,     -- ^Enable vanilla library
        configProfLib       :: Flag Bool,     -- ^Enable profiling in the library
        configSharedLib     :: Flag Bool,     -- ^Build shared library
        configDynExe        :: Flag Bool,     -- ^Enable dynamic linking of the
                                              -- executables.
        configProfExe       :: Flag Bool,     -- ^Enable profiling in the
                                              -- executables.
        configProf          :: Flag Bool,     -- ^Enable profiling in the library
                                              -- and executables.
        configProfDetail    :: Flag ProfDetailLevel, -- ^Profiling detail level
                                              --  in the library and executables.
        configProfLibDetail :: Flag ProfDetailLevel, -- ^Profiling  detail level
                                                     -- in the library
        configConfigureArgs :: [String],      -- ^Extra arguments to @configure@
        configOptimization  :: Flag OptimisationLevel,  -- ^Enable optimization.
        configProgPrefix    :: Flag PathTemplate, -- ^Installed executable prefix.
        configProgSuffix    :: Flag PathTemplate, -- ^Installed executable suffix.
        configInstallDirs   :: InstallDirs (Flag PathTemplate), -- ^Installation
                                                                -- paths
        configScratchDir    :: Flag FilePath,
        configExtraLibDirs  :: [FilePath],   -- ^ path to search for extra libraries
        configExtraFrameworkDirs :: [FilePath],   -- ^ path to search for extra
                                                  -- frameworks (OS X only)
        configExtraIncludeDirs :: [FilePath],   -- ^ path to search for header files
        configIPID          :: Flag String, -- ^ explicit IPID to be used

        configDistPref :: Flag FilePath, -- ^"dist" prefix
        configVerbosity :: Flag Verbosity, -- ^verbosity level
        configUserInstall :: Flag Bool,    -- ^The --user\/--global flag
        configPackageDBs :: [Maybe PackageDB], -- ^Which package DBs to use
        configGHCiLib   :: Flag Bool,      -- ^Enable compiling library for GHCi
        configSplitObjs :: Flag Bool,      -- ^Enable -split-objs with GHC
        configStripExes :: Flag Bool,      -- ^Enable executable stripping
        configStripLibs :: Flag Bool,      -- ^Enable library stripping
        configConstraints :: [Dependency], -- ^Additional constraints for
                                           -- dependencies.
        configDependencies :: [(PackageName, UnitId)],
          -- ^The packages depended on.
        configConfigurationsFlags :: FlagAssignment,
        configTests               :: Flag Bool, -- ^Enable test suite compilation
        configBenchmarks          :: Flag Bool, -- ^Enable benchmark compilation
        configCoverage :: Flag Bool, -- ^Enable program coverage
        configLibCoverage :: Flag Bool, -- ^Enable program coverage (deprecated)
        configExactConfiguration  :: Flag Bool,
          -- ^All direct dependencies and flags are provided on the command line by
          -- the user via the '--dependency' and '--flags' options.
        configFlagError :: Flag String,
          -- ^Halt and show an error message indicating an error in flag assignment
        configRelocatable :: Flag Bool, -- ^ Enable relocatable package built
        configDebugInfo :: Flag DebugInfoLevel,  -- ^ Emit debug info.
        configAllowNewer :: Maybe AllowNewer
        -- ^ Ignore upper bounds on all or some dependencies. Wrapped in 'Maybe' to
        -- distinguish between "default" and "explicitly disabled".
      }
      deriving (Generic, Read, Show)

    instance Binary ConfigFlags

    -- | More convenient version of 'configPrograms'. Results in an
    -- 'error' if internal invariant is violated.
    configPrograms :: ConfigFlags -> ProgramConfiguration
    configPrograms = maybe (error "FIXME: remove configPrograms") id . getLast' . configPrograms_

    configAbsolutePaths :: ConfigFlags -> IO ConfigFlags
    configAbsolutePaths f =
      (\v -> f { configPackageDBs = v })
      `liftM` mapM (maybe (return Nothing) (liftM Just . absolutePackageDBPath))
      (configPackageDBs f)

    defaultConfigFlags :: ProgramConfiguration -> ConfigFlags
    defaultConfigFlags progConf = emptyConfigFlags {
        configPrograms_    = pure progConf,
        configHcFlavor     = maybe NoFlag Flag defaultCompilerFlavor,
        configVanillaLib   = Flag True,
        configProfLib      = NoFlag,
        configSharedLib    = NoFlag,
        configDynExe       = Flag False,
        configProfExe      = NoFlag,
        configProf         = NoFlag,
        configProfDetail   = NoFlag,
        configProfLibDetail= NoFlag,
        configOptimization = Flag NormalOptimisation,
        configProgPrefix   = Flag (toPathTemplate ""),
        configProgSuffix   = Flag (toPathTemplate ""),
        configDistPref     = NoFlag,
        configVerbosity    = Flag normal,
        configUserInstall  = Flag False,           --TODO: reverse this
    #if defined(mingw32_HOST_OS)
        -- See #1589.
        configGHCiLib      = Flag True,
    #else
        configGHCiLib      = NoFlag,
    #endif
        configSplitObjs    = Flag False, -- takes longer, so turn off by default
        configStripExes    = Flag True,
        configStripLibs    = Flag True,
        configTests        = Flag False,
        configBenchmarks   = Flag False,
        configCoverage     = Flag False,
        configLibCoverage  = NoFlag,
        configExactConfiguration = Flag False,
        configFlagError    = NoFlag,
        configRelocatable  = Flag False,
        configDebugInfo    = Flag NoDebugInfo,
        configAllowNewer   = Nothing
      }

    configureCommand :: ProgramConfiguration -> CommandUI ConfigFlags
    configureCommand progConf = CommandUI
      { commandName         = "configure"
      , commandSynopsis     = "Prepare to build the package."
      , commandDescription  = Just $ \_ -> wrapText $
             "Configure how the package is built by setting "
          ++ "package (and other) flags.\n"
          ++ "\n"
          ++ "The configuration affects several other commands, "
          ++ "including build, test, bench, run, repl.\n"
      , commandNotes        = Just $ \_pname -> programFlagsDescription progConf
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " configure [FLAGS]\n"
      , commandDefaultFlags = defaultConfigFlags progConf
      , commandOptions      = \showOrParseArgs ->
             configureOptions showOrParseArgs
          ++ programConfigurationPaths   progConf showOrParseArgs
               configProgramPaths (\v fs -> fs { configProgramPaths = v })
          ++ programConfigurationOption progConf showOrParseArgs
               configProgramArgs (\v fs -> fs { configProgramArgs = v })
          ++ programConfigurationOptions progConf showOrParseArgs
               configProgramArgs (\v fs -> fs { configProgramArgs = v })
      }

    configureOptions :: ShowOrParseArgs -> [OptionField ConfigFlags]
    configureOptions showOrParseArgs =
          [optionVerbosity configVerbosity
           (\v flags -> flags { configVerbosity = v })
          ,optionDistPref
             configDistPref (\d flags -> flags { configDistPref = d })
             showOrParseArgs

          ,option [] ["compiler"] "compiler"
             configHcFlavor (\v flags -> flags { configHcFlavor = v })
             (choiceOpt [ (Flag GHC,   ("g", ["ghc"]),   "compile with GHC")
                        , (Flag GHCJS, ([] , ["ghcjs"]), "compile with GHCJS")
                        , (Flag JHC,   ([] , ["jhc"]),   "compile with JHC")
                        , (Flag LHC,   ([] , ["lhc"]),   "compile with LHC")
                        , (Flag UHC,   ([] , ["uhc"]),   "compile with UHC")
                        -- "haskell-suite" compiler id string will be replaced
                        -- by a more specific one during the configure stage
                        , (Flag (HaskellSuite "haskell-suite"), ([] , ["haskell-suite"]),
                            "compile with a haskell-suite compiler")])

          ,option "w" ["with-compiler"]
             "give the path to a particular compiler"
             configHcPath (\v flags -> flags { configHcPath = v })
             (reqArgFlag "PATH")

          ,option "" ["with-hc-pkg"]
             "give the path to the package tool"
             configHcPkg (\v flags -> flags { configHcPkg = v })
             (reqArgFlag "PATH")
          ]
       ++ map liftInstallDirs installDirsOptions
       ++ [option "" ["program-prefix"]
              "prefix to be applied to installed executables"
              configProgPrefix
              (\v flags -> flags { configProgPrefix = v })
              (reqPathTemplateArgFlag "PREFIX")

          ,option "" ["program-suffix"]
              "suffix to be applied to installed executables"
              configProgSuffix (\v flags -> flags { configProgSuffix = v } )
              (reqPathTemplateArgFlag "SUFFIX")

          ,option "" ["library-vanilla"]
             "Vanilla libraries"
             configVanillaLib (\v flags -> flags { configVanillaLib = v })
             (boolOpt [] [])

          ,option "p" ["library-profiling"]
             "Library profiling"
             configProfLib (\v flags -> flags { configProfLib = v })
             (boolOpt "p" [])

          ,option "" ["shared"]
             "Shared library"
             configSharedLib (\v flags -> flags { configSharedLib = v })
             (boolOpt [] [])

          ,option "" ["executable-dynamic"]
             "Executable dynamic linking"
             configDynExe (\v flags -> flags { configDynExe = v })
             (boolOpt [] [])

          ,option "" ["profiling"]
             "Executable and library profiling"
             configProf (\v flags -> flags { configProf = v })
             (boolOpt [] [])

          ,option "" ["executable-profiling"]
             "Executable profiling (DEPRECATED)"
             configProfExe (\v flags -> flags { configProfExe = v })
             (boolOpt [] [])

          ,option "" ["profiling-detail"]
             ("Profiling detail level for executable and library (default, " ++
              "none, exported-functions, toplevel-functions,  all-functions).")
             configProfDetail (\v flags -> flags { configProfDetail = v })
             (reqArg' "level" (Flag . flagToProfDetailLevel)
                              showProfDetailLevelFlag)

          ,option "" ["library-profiling-detail"]
             "Profiling detail level for libraries only."
             configProfLibDetail (\v flags -> flags { configProfLibDetail = v })
             (reqArg' "level" (Flag . flagToProfDetailLevel)
                              showProfDetailLevelFlag)

          ,multiOption "optimization"
             configOptimization (\v flags -> flags { configOptimization = v })
             [optArg' "n" (Flag . flagToOptimisationLevel)
                         (\f -> case f of
                                  Flag NoOptimisation      -> []
                                  Flag NormalOptimisation  -> [Nothing]
                                  Flag MaximumOptimisation -> [Just "2"]
                                  _                        -> [])
                     "O" ["enable-optimization","enable-optimisation"]
                     "Build with optimization (n is 0--2, default is 1)",
              noArg (Flag NoOptimisation) []
                    ["disable-optimization","disable-optimisation"]
                    "Build without optimization"
             ]

          ,multiOption "debug-info"
             configDebugInfo (\v flags -> flags { configDebugInfo = v })
             [optArg' "n" (Flag . flagToDebugInfoLevel)
                         (\f -> case f of
                                  Flag NoDebugInfo      -> []
                                  Flag MinimalDebugInfo -> [Just "1"]
                                  Flag NormalDebugInfo  -> [Nothing]
                                  Flag MaximalDebugInfo -> [Just "3"]
                                  _                     -> [])
                     "" ["enable-debug-info"]
                     "Emit debug info (n is 0--3, default is 0)",
              noArg (Flag NoDebugInfo) []
                    ["disable-debug-info"]
                    "Don't emit debug info"
             ]

          ,option "" ["library-for-ghci"]
             "compile library for use with GHCi"
             configGHCiLib (\v flags -> flags { configGHCiLib = v })
             (boolOpt [] [])

          ,option "" ["split-objs"]
             "split library into smaller objects to reduce binary sizes (GHC 6.6+)"
             configSplitObjs (\v flags -> flags { configSplitObjs = v })
             (boolOpt [] [])

          ,option "" ["executable-stripping"]
             "strip executables upon installation to reduce binary sizes"
             configStripExes (\v flags -> flags { configStripExes = v })
             (boolOpt [] [])

          ,option "" ["library-stripping"]
             "strip libraries upon installation to reduce binary sizes"
             configStripLibs (\v flags -> flags { configStripLibs = v })
             (boolOpt [] [])

          ,option "" ["configure-option"]
             "Extra option for configure"
             configConfigureArgs (\v flags -> flags { configConfigureArgs = v })
             (reqArg' "OPT" (\x -> [x]) id)

          ,option "" ["user-install"]
             "doing a per-user installation"
             configUserInstall (\v flags -> flags { configUserInstall = v })
             (boolOpt' ([],["user"]) ([], ["global"]))

          ,option "" ["package-db"]
             (   "Append the given package database to the list of package"
              ++ " databases used (to satisfy dependencies and register into)."
              ++ " May be a specific file, 'global' or 'user'. The initial list"
              ++ " is ['global'], ['global', 'user'], or ['global', $sandbox],"
              ++ " depending on context. Use 'clear' to reset the list to empty."
              ++ " See the user guide for details.")
             configPackageDBs (\v flags -> flags { configPackageDBs = v })
             (reqArg' "DB" readPackageDbList showPackageDbList)

          ,option "f" ["flags"]
             "Force values for the given flags in Cabal conditionals in the .cabal file.  E.g., --flags=\"debug -usebytestrings\" forces the flag \"debug\" to true and \"usebytestrings\" to false."
             configConfigurationsFlags (\v flags -> flags { configConfigurationsFlags = v })
             (reqArg' "FLAGS" readFlagList showFlagList)

          ,option "" ["extra-include-dirs"]
             "A list of directories to search for header files"
             configExtraIncludeDirs (\v flags -> flags {configExtraIncludeDirs = v})
             (reqArg' "PATH" (\x -> [x]) id)

          ,option "" ["ipid"]
             "Installed package ID to compile this package as"
             configIPID (\v flags -> flags {configIPID = v})
             (reqArgFlag "IPID")

          ,option "" ["extra-lib-dirs"]
             "A list of directories to search for external libraries"
             configExtraLibDirs (\v flags -> flags {configExtraLibDirs = v})
             (reqArg' "PATH" (\x -> [x]) id)

          ,option "" ["extra-framework-dirs"]
             "A list of directories to search for external frameworks (OS X only)"
             configExtraFrameworkDirs
             (\v flags -> flags {configExtraFrameworkDirs = v})
             (reqArg' "PATH" (\x -> [x]) id)

          ,option "" ["extra-prog-path"]
             "A list of directories to search for required programs (in addition to the normal search locations)"
             configProgramPathExtra (\v flags -> flags {configProgramPathExtra = v})
             (reqArg' "PATH" (\x -> toNubList [x]) fromNubList)

          ,option "" ["constraint"]
             "A list of additional constraints on the dependencies."
             configConstraints (\v flags -> flags { configConstraints = v})
             (reqArg "DEPENDENCY"
                     (readP_to_E (const "dependency expected") ((\x -> [x]) `fmap` parse))
                     (map (\x -> display x)))

          ,option "" ["dependency"]
             "A list of exact dependencies. E.g., --dependency=\"void=void-0.5.8-177d5cdf20962d0581fe2e4932a6c309\""
             configDependencies (\v flags -> flags { configDependencies = v})
             (reqArg "NAME=ID"
                     (readP_to_E (const "dependency expected") ((\x -> [x]) `fmap` parseDependency))
                     (map (\x -> display (fst x) ++ "=" ++ display (snd x))))

          ,option "" ["tests"]
             "dependency checking and compilation for test suites listed in the package description file."
             configTests (\v flags -> flags { configTests = v })
             (boolOpt [] [])

          ,option "" ["coverage"]
             "build package with Haskell Program Coverage. (GHC only)"
             configCoverage (\v flags -> flags { configCoverage = v })
             (boolOpt [] [])

          ,option "" ["library-coverage"]
             "build package with Haskell Program Coverage. (GHC only) (DEPRECATED)"
             configLibCoverage (\v flags -> flags { configLibCoverage = v })
             (boolOpt [] [])

          ,option [] ["allow-newer"]
           ("Ignore upper bounds in all dependencies or DEPS")
           configAllowNewer (\v flags -> flags { configAllowNewer = v})
           (optArg "DEPS"
            (readP_to_E ("Cannot parse the list of packages: " ++) allowNewerParser)
            (Just AllowNewerAll) allowNewerPrinter)

          ,option "" ["exact-configuration"]
             "All direct dependencies and flags are provided on the command line."
             configExactConfiguration
             (\v flags -> flags { configExactConfiguration = v })
             trueArg

          ,option "" ["benchmarks"]
             "dependency checking and compilation for benchmarks listed in the package description file."
             configBenchmarks (\v flags -> flags { configBenchmarks = v })
             (boolOpt [] [])

          ,option "" ["relocatable"]
             "building a package that is relocatable. (GHC only)"
             configRelocatable (\v flags -> flags { configRelocatable = v})
             (boolOpt [] [])
          ]
      where
        readFlagList :: String -> FlagAssignment
        readFlagList = map tagWithValue . words
          where tagWithValue ('-':fname) = (FlagName (lowercase fname), False)
                tagWithValue fname       = (FlagName (lowercase fname), True)

        showFlagList :: FlagAssignment -> [String]
        showFlagList fs = [ if not set then '-':fname else fname
                          | (FlagName fname, set) <- fs]

        liftInstallDirs =
          liftOption configInstallDirs (\v flags -> flags { configInstallDirs = v })

        reqPathTemplateArgFlag title _sf _lf d get set =
          reqArgFlag title _sf _lf d
            (fmap fromPathTemplate . get) (set . fmap toPathTemplate)

    readPackageDbList :: String -> [Maybe PackageDB]
    readPackageDbList "clear"  = [Nothing]
    readPackageDbList "global" = [Just GlobalPackageDB]
    readPackageDbList "user"   = [Just UserPackageDB]
    readPackageDbList other    = [Just (SpecificPackageDB other)]

    showPackageDbList :: [Maybe PackageDB] -> [String]
    showPackageDbList = map showPackageDb
      where
        showPackageDb Nothing                       = "clear"
        showPackageDb (Just GlobalPackageDB)        = "global"
        showPackageDb (Just UserPackageDB)          = "user"
        showPackageDb (Just (SpecificPackageDB db)) = db

    showProfDetailLevelFlag :: Flag ProfDetailLevel -> [String]
    showProfDetailLevelFlag NoFlag    = []
    showProfDetailLevelFlag (Flag dl) = [showProfDetailLevel dl]

    parseDependency :: Parse.ReadP r (PackageName, UnitId)
    parseDependency = do
      x <- parse
      _ <- Parse.char '='
      y <- parse
      return (x, y)

    installDirsOptions :: [OptionField (InstallDirs (Flag PathTemplate))]
    installDirsOptions =
      [ option "" ["prefix"]
          "bake this prefix in preparation of installation"
          prefix (\v flags -> flags { prefix = v })
          installDirArg

      , option "" ["bindir"]
          "installation directory for executables"
          bindir (\v flags -> flags { bindir = v })
          installDirArg

      , option "" ["libdir"]
          "installation directory for libraries"
          libdir (\v flags -> flags { libdir = v })
          installDirArg

      , option "" ["libsubdir"]
          "subdirectory of libdir in which libs are installed"
          libsubdir (\v flags -> flags { libsubdir = v })
          installDirArg

      , option "" ["dynlibdir"]
          "installation directory for dynamic libraries"
          dynlibdir (\v flags -> flags { dynlibdir = v })
          installDirArg

      , option "" ["libexecdir"]
          "installation directory for program executables"
          libexecdir (\v flags -> flags { libexecdir = v })
          installDirArg

      , option "" ["datadir"]
          "installation directory for read-only data"
          datadir (\v flags -> flags { datadir = v })
          installDirArg

      , option "" ["datasubdir"]
          "subdirectory of datadir in which data files are installed"
          datasubdir (\v flags -> flags { datasubdir = v })
          installDirArg

      , option "" ["docdir"]
          "installation directory for documentation"
          docdir (\v flags -> flags { docdir = v })
          installDirArg

      , option "" ["htmldir"]
          "installation directory for HTML documentation"
          htmldir (\v flags -> flags { htmldir = v })
          installDirArg

      , option "" ["haddockdir"]
          "installation directory for haddock interfaces"
          haddockdir (\v flags -> flags { haddockdir = v })
          installDirArg

      , option "" ["sysconfdir"]
          "installation directory for configuration files"
          sysconfdir (\v flags -> flags { sysconfdir = v })
          installDirArg
      ]
      where
        installDirArg _sf _lf d get set =
          reqArgFlag "DIR" _sf _lf d
            (fmap fromPathTemplate . get) (set . fmap toPathTemplate)

    emptyConfigFlags :: ConfigFlags
    emptyConfigFlags = mempty

    instance Monoid ConfigFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup ConfigFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * Copy flags
    -- ------------------------------------------------------------

    -- | Flags to @copy@: (destdir, copy-prefix (backwards compat), verbosity)
    data CopyFlags = CopyFlags {
        copyDest      :: Flag CopyDest,
        copyDistPref  :: Flag FilePath,
        copyVerbosity :: Flag Verbosity
      }
      deriving (Show, Generic)

    defaultCopyFlags :: CopyFlags
    defaultCopyFlags  = CopyFlags {
        copyDest      = Flag NoCopyDest,
        copyDistPref  = NoFlag,
        copyVerbosity = Flag normal
      }

    copyCommand :: CommandUI CopyFlags
    copyCommand = CommandUI
      { commandName         = "copy"
      , commandSynopsis     = "Copy the files into the install locations."
      , commandDescription  = Just $ \_ -> wrapText $
              "Does not call register, and allows a prefix at install time. "
           ++ "Without the --destdir flag, configure determines location.\n"
      , commandNotes        = Nothing
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " copy [FLAGS]\n"
      , commandDefaultFlags = defaultCopyFlags
      , commandOptions      = \showOrParseArgs ->
          [optionVerbosity copyVerbosity (\v flags -> flags { copyVerbosity = v })

          ,optionDistPref
             copyDistPref (\d flags -> flags { copyDistPref = d })
             showOrParseArgs

          ,option "" ["destdir"]
             "directory to copy files to, prepended to installation directories"
             copyDest (\v flags -> flags { copyDest = v })
             (reqArg "DIR" (succeedReadE (Flag . CopyTo))
                           (\f -> case f of Flag (CopyTo p) -> [p]; _ -> []))
          ]
      }

    emptyCopyFlags :: CopyFlags
    emptyCopyFlags = mempty

    instance Monoid CopyFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup CopyFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * Install flags
    -- ------------------------------------------------------------

    -- | Flags to @install@: (package db, verbosity)
    data InstallFlags = InstallFlags {
        installPackageDB :: Flag PackageDB,
        installDistPref  :: Flag FilePath,
        installUseWrapper :: Flag Bool,
        installInPlace    :: Flag Bool,
        installVerbosity :: Flag Verbosity
      }
      deriving (Show, Generic)

    defaultInstallFlags :: InstallFlags
    defaultInstallFlags  = InstallFlags {
        installPackageDB = NoFlag,
        installDistPref  = NoFlag,
        installUseWrapper = Flag False,
        installInPlace    = Flag False,
        installVerbosity = Flag normal
      }

    installCommand :: CommandUI InstallFlags
    installCommand = CommandUI
      { commandName         = "install"
      , commandSynopsis     =
          "Copy the files into the install locations. Run register."
      , commandDescription  = Just $ \_ -> wrapText $
             "Unlike the copy command, install calls the register command."
          ++ "If you want to install into a location that is not what was"
          ++ "specified in the configure step, use the copy command.\n"
      , commandNotes        = Nothing
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " install [FLAGS]\n"
      , commandDefaultFlags = defaultInstallFlags
      , commandOptions      = \showOrParseArgs ->
          [optionVerbosity installVerbosity (\v flags -> flags { installVerbosity = v })
          ,optionDistPref
             installDistPref (\d flags -> flags { installDistPref = d })
             showOrParseArgs

          ,option "" ["inplace"]
             "install the package in the install subdirectory of the dist prefix, so it can be used without being installed"
             installInPlace (\v flags -> flags { installInPlace = v })
             trueArg

          ,option "" ["shell-wrappers"]
             "using shell script wrappers around executables"
             installUseWrapper (\v flags -> flags { installUseWrapper = v })
             (boolOpt [] [])

          ,option "" ["package-db"] ""
             installPackageDB (\v flags -> flags { installPackageDB = v })
             (choiceOpt [ (Flag UserPackageDB, ([],["user"]),
                          "upon configuration register this package in the user's local package database")
                        , (Flag GlobalPackageDB, ([],["global"]),
                          "(default) upon configuration register this package in the system-wide package database")])
          ]
      }

    emptyInstallFlags :: InstallFlags
    emptyInstallFlags = mempty

    instance Monoid InstallFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup InstallFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * SDist flags
    -- ------------------------------------------------------------

    -- | Flags to @sdist@: (snapshot, verbosity)
    data SDistFlags = SDistFlags {
        sDistSnapshot    :: Flag Bool,
        sDistDirectory   :: Flag FilePath,
        sDistDistPref    :: Flag FilePath,
        sDistListSources :: Flag FilePath,
        sDistVerbosity   :: Flag Verbosity
      }
      deriving (Show, Generic)

    defaultSDistFlags :: SDistFlags
    defaultSDistFlags = SDistFlags {
        sDistSnapshot    = Flag False,
        sDistDirectory   = mempty,
        sDistDistPref    = NoFlag,
        sDistListSources = mempty,
        sDistVerbosity   = Flag normal
      }

    sdistCommand :: CommandUI SDistFlags
    sdistCommand = CommandUI
      { commandName         = "sdist"
      , commandSynopsis     =
          "Generate a source distribution file (.tar.gz)."
      , commandDescription  = Nothing
      , commandNotes        = Nothing
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " sdist [FLAGS]\n"
      , commandDefaultFlags = defaultSDistFlags
      , commandOptions      = \showOrParseArgs ->
          [optionVerbosity sDistVerbosity (\v flags -> flags { sDistVerbosity = v })
          ,optionDistPref
             sDistDistPref (\d flags -> flags { sDistDistPref = d })
             showOrParseArgs

          ,option "" ["list-sources"]
             "Just write a list of the package's sources to a file"
             sDistListSources (\v flags -> flags { sDistListSources = v })
             (reqArgFlag "FILE")

          ,option "" ["snapshot"]
             "Produce a snapshot source distribution"
             sDistSnapshot (\v flags -> flags { sDistSnapshot = v })
             trueArg

          ,option "" ["output-directory"]
           ("Generate a source distribution in the given directory, "
            ++ "without creating a tarball")
             sDistDirectory (\v flags -> flags { sDistDirectory = v })
             (reqArgFlag "DIR")
          ]
      }

    emptySDistFlags :: SDistFlags
    emptySDistFlags = mempty

    instance Monoid SDistFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup SDistFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * Register flags
    -- ------------------------------------------------------------

    -- | Flags to @register@ and @unregister@: (user package, gen-script,
    -- in-place, verbosity)
    data RegisterFlags = RegisterFlags {
        regPackageDB   :: Flag PackageDB,
        regGenScript   :: Flag Bool,
        regGenPkgConf  :: Flag (Maybe FilePath),
        regInPlace     :: Flag Bool,
        regDistPref    :: Flag FilePath,
        regPrintId     :: Flag Bool,
        regVerbosity   :: Flag Verbosity
      }
      deriving (Show, Generic)

    defaultRegisterFlags :: RegisterFlags
    defaultRegisterFlags = RegisterFlags {
        regPackageDB   = NoFlag,
        regGenScript   = Flag False,
        regGenPkgConf  = NoFlag,
        regInPlace     = Flag False,
        regDistPref    = NoFlag,
        regPrintId     = Flag False,
        regVerbosity   = Flag normal
      }

    registerCommand :: CommandUI RegisterFlags
    registerCommand = CommandUI
      { commandName         = "register"
      , commandSynopsis     =
          "Register this package with the compiler."
      , commandDescription  = Nothing
      , commandNotes        = Nothing
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " register [FLAGS]\n"
      , commandDefaultFlags = defaultRegisterFlags
      , commandOptions      = \showOrParseArgs ->
          [optionVerbosity regVerbosity (\v flags -> flags { regVerbosity = v })
          ,optionDistPref
             regDistPref (\d flags -> flags { regDistPref = d })
             showOrParseArgs

          ,option "" ["packageDB"] ""
             regPackageDB (\v flags -> flags { regPackageDB = v })
             (choiceOpt [ (Flag UserPackageDB, ([],["user"]),
                                    "upon registration, register this package in the user's local package database")
                        , (Flag GlobalPackageDB, ([],["global"]),
                                    "(default)upon registration, register this package in the system-wide package database")])

          ,option "" ["inplace"]
             "register the package in the build location, so it can be used without being installed"
             regInPlace (\v flags -> flags { regInPlace = v })
             trueArg

          ,option "" ["gen-script"]
             "instead of registering, generate a script to register later"
             regGenScript (\v flags -> flags { regGenScript = v })
             trueArg

          ,option "" ["gen-pkg-config"]
             "instead of registering, generate a package registration file"
             regGenPkgConf (\v flags -> flags { regGenPkgConf  = v })
             (optArg' "PKG" Flag flagToList)

          ,option "" ["print-ipid"]
             "print the installed package ID calculated for this package"
             regPrintId (\v flags -> flags { regPrintId = v })
             trueArg
          ]
      }

    unregisterCommand :: CommandUI RegisterFlags
    unregisterCommand = CommandUI
      { commandName         = "unregister"
      , commandSynopsis     =
          "Unregister this package with the compiler."
      , commandDescription  = Nothing
      , commandNotes        = Nothing
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " unregister [FLAGS]\n"
      , commandDefaultFlags = defaultRegisterFlags
      , commandOptions      = \showOrParseArgs ->
          [optionVerbosity regVerbosity (\v flags -> flags { regVerbosity = v })
          ,optionDistPref
             regDistPref (\d flags -> flags { regDistPref = d })
              showOrParseArgs

          ,option "" ["user"] ""
             regPackageDB (\v flags -> flags { regPackageDB = v })
             (choiceOpt [ (Flag UserPackageDB, ([],["user"]),
                                  "unregister this package in the user's local package database")
                        , (Flag GlobalPackageDB, ([],["global"]),
                                  "(default) unregister this package in the  system-wide package database")])

          ,option "" ["gen-script"]
             "Instead of performing the unregister command, generate a script to unregister later"
             regGenScript (\v flags -> flags { regGenScript = v })
             trueArg
          ]
      }

    emptyRegisterFlags :: RegisterFlags
    emptyRegisterFlags = mempty

    instance Monoid RegisterFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup RegisterFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * HsColour flags
    -- ------------------------------------------------------------

    data HscolourFlags = HscolourFlags {
        hscolourCSS         :: Flag FilePath,
        hscolourExecutables :: Flag Bool,
        hscolourTestSuites  :: Flag Bool,
        hscolourBenchmarks  :: Flag Bool,
        hscolourDistPref    :: Flag FilePath,
        hscolourVerbosity   :: Flag Verbosity
      }
      deriving (Show, Generic)

    emptyHscolourFlags :: HscolourFlags
    emptyHscolourFlags = mempty

    defaultHscolourFlags :: HscolourFlags
    defaultHscolourFlags = HscolourFlags {
        hscolourCSS         = NoFlag,
        hscolourExecutables = Flag False,
        hscolourTestSuites  = Flag False,
        hscolourBenchmarks  = Flag False,
        hscolourDistPref    = NoFlag,
        hscolourVerbosity   = Flag normal
      }

    instance Monoid HscolourFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup HscolourFlags where
      (<>) = gmappend

    hscolourCommand :: CommandUI HscolourFlags
    hscolourCommand = CommandUI
      { commandName         = "hscolour"
      , commandSynopsis     =
          "Generate HsColour colourised code, in HTML format."
      , commandDescription  = Just (\_ -> "Requires the hscolour program.\n")
      , commandNotes        = Nothing
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " hscolour [FLAGS]\n"
      , commandDefaultFlags = defaultHscolourFlags
      , commandOptions      = \showOrParseArgs ->
          [optionVerbosity hscolourVerbosity
           (\v flags -> flags { hscolourVerbosity = v })
          ,optionDistPref
             hscolourDistPref (\d flags -> flags { hscolourDistPref = d })
             showOrParseArgs

          ,option "" ["executables"]
             "Run hscolour for Executables targets"
             hscolourExecutables (\v flags -> flags { hscolourExecutables = v })
             trueArg

          ,option "" ["tests"]
             "Run hscolour for Test Suite targets"
             hscolourTestSuites (\v flags -> flags { hscolourTestSuites = v })
             trueArg

          ,option "" ["benchmarks"]
             "Run hscolour for Benchmark targets"
             hscolourBenchmarks (\v flags -> flags { hscolourBenchmarks = v })
             trueArg

          ,option "" ["all"]
             "Run hscolour for all targets"
             (\f -> allFlags [ hscolourExecutables f
                             , hscolourTestSuites  f
                             , hscolourBenchmarks  f])
             (\v flags -> flags { hscolourExecutables = v
                                , hscolourTestSuites  = v
                                , hscolourBenchmarks  = v })
             trueArg

          ,option "" ["css"]
             "Use a cascading style sheet"
             hscolourCSS (\v flags -> flags { hscolourCSS = v })
             (reqArgFlag "PATH")
          ]
      }

    -- ------------------------------------------------------------
    -- * Haddock flags
    -- ------------------------------------------------------------

    -- | When we build haddock documentation, there are two cases:
    --
    -- 1. We build haddocks only for the current development version,
    --    intended for local use and not for distribution. In this case,
    --    we store the generated documentation in @<dist>/doc/html/<package name>@.
    --
    -- 2. We build haddocks for intended for uploading them to hackage.
    --    In this case, we need to follow the layout that hackage expects
    --    from documentation tarballs, and we might also want to use different
    --    flags than for development builds, so in this case we store the generated
    --    documentation in @<dist>/doc/html/<package id>-docs@.
    data HaddockTarget = ForHackage | ForDevelopment deriving (Eq, Show, Generic)

    -- | Convert '--for-hackage' to 'HaddockTarget'.
    haddockTargetFromFlag :: Flag Bool -> HaddockTarget
    haddockTargetFromFlag NoFlag       = ForDevelopment
    haddockTargetFromFlag (Flag False) = ForDevelopment
    haddockTargetFromFlag (Flag True)  = ForHackage

    data HaddockFlags = HaddockFlags {
        haddockProgramPaths :: [(String, FilePath)],
        haddockProgramArgs  :: [(String, [String])],
        haddockHoogle       :: Flag Bool,
        haddockHtml         :: Flag Bool,
        haddockHtmlLocation :: Flag String,
        haddockForHackage   :: Flag Bool,
        haddockExecutables  :: Flag Bool,
        haddockTestSuites   :: Flag Bool,
        haddockBenchmarks   :: Flag Bool,
        haddockInternal     :: Flag Bool,
        haddockCss          :: Flag FilePath,
        haddockHscolour     :: Flag Bool,
        haddockHscolourCss  :: Flag FilePath,
        haddockContents     :: Flag PathTemplate,
        haddockDistPref     :: Flag FilePath,
        haddockKeepTempFiles:: Flag Bool,
        haddockVerbosity    :: Flag Verbosity
      }
      deriving (Show, Generic)

    defaultHaddockFlags :: HaddockFlags
    defaultHaddockFlags  = HaddockFlags {
        haddockProgramPaths = mempty,
        haddockProgramArgs  = [],
        haddockHoogle       = Flag False,
        haddockHtml         = Flag False,
        haddockHtmlLocation = NoFlag,
        haddockForHackage   = Flag False,
        haddockExecutables  = Flag False,
        haddockTestSuites   = Flag False,
        haddockBenchmarks   = Flag False,
        haddockInternal     = Flag False,
        haddockCss          = NoFlag,
        haddockHscolour     = Flag False,
        haddockHscolourCss  = NoFlag,
        haddockContents     = NoFlag,
        haddockDistPref     = NoFlag,
        haddockKeepTempFiles= Flag False,
        haddockVerbosity    = Flag normal
      }

    haddockCommand :: CommandUI HaddockFlags
    haddockCommand = CommandUI
      { commandName         = "haddock"
      , commandSynopsis     = "Generate Haddock HTML documentation."
      , commandDescription  = Just $ \_ ->
          "Requires the program haddock, version 2.x.\n"
      , commandNotes        = Nothing
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " haddock [FLAGS]\n"
      , commandDefaultFlags = defaultHaddockFlags
      , commandOptions      = \showOrParseArgs ->
             haddockOptions showOrParseArgs
          ++ programConfigurationPaths   progConf ParseArgs
                 haddockProgramPaths (\v flags -> flags { haddockProgramPaths = v})
          ++ programConfigurationOption  progConf showOrParseArgs
                 haddockProgramArgs (\v fs -> fs { haddockProgramArgs = v })
          ++ programConfigurationOptions progConf ParseArgs
                 haddockProgramArgs  (\v flags -> flags { haddockProgramArgs = v})
      }
      where
        progConf = addKnownProgram haddockProgram
                 $ addKnownProgram ghcProgram
                 $ emptyProgramConfiguration

    haddockOptions :: ShowOrParseArgs -> [OptionField HaddockFlags]
    haddockOptions showOrParseArgs =
      [optionVerbosity haddockVerbosity
       (\v flags -> flags { haddockVerbosity = v })
      ,optionDistPref
       haddockDistPref (\d flags -> flags { haddockDistPref = d })
       showOrParseArgs

      ,option "" ["keep-temp-files"]
       "Keep temporary files"
       haddockKeepTempFiles (\b flags -> flags { haddockKeepTempFiles = b })
       trueArg

      ,option "" ["hoogle"]
       "Generate a hoogle database"
       haddockHoogle (\v flags -> flags { haddockHoogle = v })
       trueArg

      ,option "" ["html"]
       "Generate HTML documentation (the default)"
       haddockHtml (\v flags -> flags { haddockHtml = v })
       trueArg

      ,option "" ["html-location"]
       "Location of HTML documentation for pre-requisite packages"
       haddockHtmlLocation (\v flags -> flags { haddockHtmlLocation = v })
       (reqArgFlag "URL")

      ,option "" ["for-hackage"]
       "Collection of flags to generate documentation suitable for upload to hackage"
       haddockForHackage (\v flags -> flags { haddockForHackage = v })
       trueArg

      ,option "" ["executables"]
       "Run haddock for Executables targets"
       haddockExecutables (\v flags -> flags { haddockExecutables = v })
       trueArg

      ,option "" ["tests"]
       "Run haddock for Test Suite targets"
       haddockTestSuites (\v flags -> flags { haddockTestSuites = v })
       trueArg

      ,option "" ["benchmarks"]
       "Run haddock for Benchmark targets"
       haddockBenchmarks (\v flags -> flags { haddockBenchmarks = v })
       trueArg

      ,option "" ["all"]
       "Run haddock for all targets"
       (\f -> allFlags [ haddockExecutables f
                       , haddockTestSuites  f
                       , haddockBenchmarks  f])
             (\v flags -> flags { haddockExecutables = v
                                , haddockTestSuites  = v
                                , haddockBenchmarks  = v })
             trueArg

      ,option "" ["internal"]
       "Run haddock for internal modules and include all symbols"
       haddockInternal (\v flags -> flags { haddockInternal = v })
       trueArg

      ,option "" ["css"]
       "Use PATH as the haddock stylesheet"
       haddockCss (\v flags -> flags { haddockCss = v })
       (reqArgFlag "PATH")

      ,option "" ["hyperlink-source","hyperlink-sources"]
       "Hyperlink the documentation to the source code (using HsColour)"
       haddockHscolour (\v flags -> flags { haddockHscolour = v })
       trueArg

      ,option "" ["hscolour-css"]
       "Use PATH as the HsColour stylesheet"
       haddockHscolourCss (\v flags -> flags { haddockHscolourCss = v })
       (reqArgFlag "PATH")

      ,option "" ["contents-location"]
       "Bake URL in as the location for the contents page"
       haddockContents (\v flags -> flags { haddockContents = v })
       (reqArg' "URL"
        (toFlag . toPathTemplate)
        (flagToList . fmap fromPathTemplate))
      ]

    emptyHaddockFlags :: HaddockFlags
    emptyHaddockFlags = mempty

    instance Monoid HaddockFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup HaddockFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * Clean flags
    -- ------------------------------------------------------------

    data CleanFlags = CleanFlags {
        cleanSaveConf  :: Flag Bool,
        cleanDistPref  :: Flag FilePath,
        cleanVerbosity :: Flag Verbosity
      }
      deriving (Show, Generic)

    defaultCleanFlags :: CleanFlags
    defaultCleanFlags  = CleanFlags {
        cleanSaveConf  = Flag False,
        cleanDistPref  = NoFlag,
        cleanVerbosity = Flag normal
      }

    cleanCommand :: CommandUI CleanFlags
    cleanCommand = CommandUI
      { commandName         = "clean"
      , commandSynopsis     = "Clean up after a build."
      , commandDescription  = Just $ \_ ->
          "Removes .hi, .o, preprocessed sources, etc.\n"
      , commandNotes        = Nothing
      , commandUsage        = \pname ->
          "Usage: " ++ pname ++ " clean [FLAGS]\n"
      , commandDefaultFlags = defaultCleanFlags
      , commandOptions      = \showOrParseArgs ->
          [optionVerbosity cleanVerbosity (\v flags -> flags { cleanVerbosity = v })
          ,optionDistPref
             cleanDistPref (\d flags -> flags { cleanDistPref = d })
             showOrParseArgs

          ,option "s" ["save-configure"]
             "Do not remove the configuration file (dist/setup-config) during cleaning.  Saves need to reconfigure."
             cleanSaveConf (\v flags -> flags { cleanSaveConf = v })
             trueArg
          ]
      }

    emptyCleanFlags :: CleanFlags
    emptyCleanFlags = mempty

    instance Monoid CleanFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup CleanFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * Build flags
    -- ------------------------------------------------------------

    data BuildFlags = BuildFlags {
        buildProgramPaths :: [(String, FilePath)],
        buildProgramArgs :: [(String, [String])],
        buildDistPref    :: Flag FilePath,
        buildVerbosity   :: Flag Verbosity,
        buildNumJobs     :: Flag (Maybe Int),
        -- TODO: this one should not be here, it's just that the silly
        -- UserHooks stop us from passing extra info in other ways
        buildArgs :: [String]
      }
      deriving (Show, Generic)

    {-# DEPRECATED buildVerbose "Use buildVerbosity instead" #-}
    buildVerbose :: BuildFlags -> Verbosity
    buildVerbose = fromFlagOrDefault normal . buildVerbosity

    defaultBuildFlags :: BuildFlags
    defaultBuildFlags  = BuildFlags {
        buildProgramPaths = mempty,
        buildProgramArgs = [],
        buildDistPref    = mempty,
        buildVerbosity   = Flag normal,
        buildNumJobs     = mempty,
        buildArgs        = []
      }

    buildCommand :: ProgramConfiguration -> CommandUI BuildFlags
    buildCommand progConf = CommandUI
      { commandName         = "build"
      , commandSynopsis     = "Compile all/specific components."
      , commandDescription  = Just $ \_ -> wrapText $
             "Components encompass executables, tests, and benchmarks.\n"
          ++ "\n"
          ++ "Affected by configuration options, see `configure`.\n"
      , commandNotes        = Just $ \pname ->
           "Examples:\n"
            ++ "  " ++ pname ++ " build           "
            ++ "    All the components in the package\n"
            ++ "  " ++ pname ++ " build foo       "
            ++ "    A component (i.e. lib, exe, test suite)\n\n"
            ++ programFlagsDescription progConf
    --TODO: re-enable once we have support for module/file targets
    --        ++ "  " ++ pname ++ " build Foo.Bar   "
    --        ++ "    A module\n"
    --        ++ "  " ++ pname ++ " build Foo/Bar.hs"
    --        ++ "    A file\n\n"
    --        ++ "If a target is ambiguous it can be qualified with the component "
    --        ++ "name, e.g.\n"
    --        ++ "  " ++ pname ++ " build foo:Foo.Bar\n"
    --        ++ "  " ++ pname ++ " build testsuite1:Foo/Bar.hs\n"
      , commandUsage        = usageAlternatives "build" $
          [ "[FLAGS]"
          , "COMPONENTS [FLAGS]"
          ]
      , commandDefaultFlags = defaultBuildFlags
      , commandOptions      = \showOrParseArgs ->
          [ optionVerbosity
            buildVerbosity (\v flags -> flags { buildVerbosity = v })

          , optionDistPref
            buildDistPref (\d flags -> flags { buildDistPref = d }) showOrParseArgs
          ]
          ++ buildOptions progConf showOrParseArgs
      }

    buildOptions :: ProgramConfiguration -> ShowOrParseArgs
                    -> [OptionField BuildFlags]
    buildOptions progConf showOrParseArgs =
      [ optionNumJobs
          buildNumJobs (\v flags -> flags { buildNumJobs = v })
      ]

      ++ programConfigurationPaths progConf showOrParseArgs
           buildProgramPaths (\v flags -> flags { buildProgramPaths = v})

      ++ programConfigurationOption progConf showOrParseArgs
           buildProgramArgs (\v fs -> fs { buildProgramArgs = v })

      ++ programConfigurationOptions progConf showOrParseArgs
           buildProgramArgs (\v flags -> flags { buildProgramArgs = v})

    emptyBuildFlags :: BuildFlags
    emptyBuildFlags = mempty

    instance Monoid BuildFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup BuildFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * REPL Flags
    -- ------------------------------------------------------------

    data ReplFlags = ReplFlags {
        replProgramPaths :: [(String, FilePath)],
        replProgramArgs :: [(String, [String])],
        replDistPref    :: Flag FilePath,
        replVerbosity   :: Flag Verbosity,
        replReload      :: Flag Bool
      }
      deriving (Show, Generic)

    defaultReplFlags :: ReplFlags
    defaultReplFlags  = ReplFlags {
        replProgramPaths = mempty,
        replProgramArgs = [],
        replDistPref    = NoFlag,
        replVerbosity   = Flag normal,
        replReload      = Flag False
      }

    instance Monoid ReplFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup ReplFlags where
      (<>) = gmappend

    replCommand :: ProgramConfiguration -> CommandUI ReplFlags
    replCommand progConf = CommandUI
      { commandName         = "repl"
      , commandSynopsis     =
          "Open an interpreter session for the given component."
      , commandDescription  = Just $ \pname -> wrapText $
             "If the current directory contains no package, ignores COMPONENT "
          ++ "parameters and opens an interactive interpreter session; if a "
          ++ "sandbox is present, its package database will be used.\n"
          ++ "\n"
          ++ "Otherwise, (re)configures with the given or default flags, and "
          ++ "loads the interpreter with the relevant modules. For executables, "
          ++ "tests and benchmarks, loads the main module (and its "
          ++ "dependencies); for libraries all exposed/other modules.\n"
          ++ "\n"
          ++ "The default component is the library itself, or the executable "
          ++ "if that is the only component.\n"
          ++ "\n"
          ++ "Support for loading specific modules is planned but not "
          ++ "implemented yet. For certain scenarios, `" ++ pname
          ++ " exec -- ghci :l Foo` may be used instead. Note that `exec` will "
          ++ "not (re)configure and you will have to specify the location of "
          ++ "other modules, if required.\n"

      , commandNotes        = Just $ \pname ->
             "Examples:\n"
          ++ "  " ++ pname ++ " repl           "
          ++ "    The first component in the package\n"
          ++ "  " ++ pname ++ " repl foo       "
          ++ "    A named component (i.e. lib, exe, test suite)\n"
          ++ "  " ++ pname ++ " repl --ghc-options=\"-lstdc++\""
          ++ "  Specifying flags for interpreter\n"
    --TODO: re-enable once we have support for module/file targets
    --        ++ "  " ++ pname ++ " repl Foo.Bar   "
    --        ++ "    A module\n"
    --        ++ "  " ++ pname ++ " repl Foo/Bar.hs"
    --        ++ "    A file\n\n"
    --        ++ "If a target is ambiguous it can be qualified with the component "
    --        ++ "name, e.g.\n"
    --        ++ "  " ++ pname ++ " repl foo:Foo.Bar\n"
    --        ++ "  " ++ pname ++ " repl testsuite1:Foo/Bar.hs\n"
      , commandUsage =  \pname -> "Usage: " ++ pname ++ " repl [COMPONENT] [FLAGS]\n"
      , commandDefaultFlags = defaultReplFlags
      , commandOptions = \showOrParseArgs ->
          optionVerbosity replVerbosity (\v flags -> flags { replVerbosity = v })
          : optionDistPref
              replDistPref (\d flags -> flags { replDistPref = d })
              showOrParseArgs

          : programConfigurationPaths   progConf showOrParseArgs
              replProgramPaths (\v flags -> flags { replProgramPaths = v})

         ++ programConfigurationOption progConf showOrParseArgs
              replProgramArgs (\v flags -> flags { replProgramArgs = v})

         ++ programConfigurationOptions progConf showOrParseArgs
              replProgramArgs (\v flags -> flags { replProgramArgs = v})

         ++ case showOrParseArgs of
              ParseArgs ->
                [ option "" ["reload"]
                  "Used from within an interpreter to update files."
                  replReload (\v flags -> flags { replReload = v })
                  trueArg
                ]
              _ -> []
      }

    -- ------------------------------------------------------------
    -- * Test flags
    -- ------------------------------------------------------------

    data TestShowDetails = Never | Failures | Always | Streaming | Direct
        deriving (Eq, Ord, Enum, Bounded, Show)

    knownTestShowDetails :: [TestShowDetails]
    knownTestShowDetails = [minBound..maxBound]

    instance Text TestShowDetails where
        disp  = Disp.text . lowercase . show

        parse = maybe Parse.pfail return . classify =<< ident
          where
            ident        = Parse.munch1 (\c -> isAlpha c || c == '_' || c == '-')
            classify str = lookup (lowercase str) enumMap
            enumMap     :: [(String, TestShowDetails)]
            enumMap      = [ (display x, x)
                           | x <- knownTestShowDetails ]

    --TODO: do we need this instance?
    instance Monoid TestShowDetails where
        mempty = Never
        mappend = (Semi.<>)

    instance Semigroup TestShowDetails where
        a <> b = if a < b then b else a

    data TestFlags = TestFlags {
        testDistPref    :: Flag FilePath,
        testVerbosity   :: Flag Verbosity,
        testHumanLog    :: Flag PathTemplate,
        testMachineLog  :: Flag PathTemplate,
        testShowDetails :: Flag TestShowDetails,
        testKeepTix     :: Flag Bool,
        -- TODO: think about if/how options are passed to test exes
        testOptions     :: [PathTemplate]
      } deriving (Generic)

    defaultTestFlags :: TestFlags
    defaultTestFlags  = TestFlags {
        testDistPref    = NoFlag,
        testVerbosity   = Flag normal,
        testHumanLog    = toFlag $ toPathTemplate $ "$pkgid-$test-suite.log",
        testMachineLog  = toFlag $ toPathTemplate $ "$pkgid.log",
        testShowDetails = toFlag Failures,
        testKeepTix     = toFlag False,
        testOptions     = []
      }

    testCommand :: CommandUI TestFlags
    testCommand = CommandUI
      { commandName         = "test"
      , commandSynopsis     =
          "Run all/specific tests in the test suite."
      , commandDescription  = Just $ \pname -> wrapText $
             "If necessary (re)configures with `--enable-tests` flag and builds"
          ++ " the test suite.\n"
          ++ "\n"
          ++ "Remember that the tests' dependencies must be installed if there"
          ++ " are additional ones; e.g. with `" ++ pname
          ++ " install --only-dependencies --enable-tests`.\n"
          ++ "\n"
          ++ "By defining UserHooks in a custom Setup.hs, the package can"
          ++ " define actions to be executed before and after running tests.\n"
      , commandNotes        = Nothing
      , commandUsage        = usageAlternatives "test"
          [ "[FLAGS]"
          , "TESTCOMPONENTS [FLAGS]"
          ]
      , commandDefaultFlags = defaultTestFlags
      , commandOptions = \showOrParseArgs ->
          [ optionVerbosity testVerbosity (\v flags -> flags { testVerbosity = v })
          , optionDistPref
                testDistPref (\d flags -> flags { testDistPref = d })
                showOrParseArgs
          , option [] ["log"]
                ("Log all test suite results to file (name template can use "
                ++ "$pkgid, $compiler, $os, $arch, $test-suite, $result)")
                testHumanLog (\v flags -> flags { testHumanLog = v })
                (reqArg' "TEMPLATE"
                    (toFlag . toPathTemplate)
                    (flagToList . fmap fromPathTemplate))
          , option [] ["machine-log"]
                ("Produce a machine-readable log file (name template can use "
                ++ "$pkgid, $compiler, $os, $arch, $result)")
                testMachineLog (\v flags -> flags { testMachineLog = v })
                (reqArg' "TEMPLATE"
                    (toFlag . toPathTemplate)
                    (flagToList . fmap fromPathTemplate))
          , option [] ["show-details"]
                ("'always': always show results of individual test cases. "
                 ++ "'never': never show results of individual test cases. "
                 ++ "'failures': show results of failing test cases. "
                 ++ "'streaming': show results of test cases in real time."
                 ++ "'direct': send results of test cases in real time; no log file.")
                testShowDetails (\v flags -> flags { testShowDetails = v })
                (reqArg "FILTER"
                    (readP_to_E (\_ -> "--show-details flag expects one of "
                                  ++ intercalate ", "
                                       (map display knownTestShowDetails))
                                (fmap toFlag parse))
                    (flagToList . fmap display))
          , option [] ["keep-tix-files"]
                "keep .tix files for HPC between test runs"
                testKeepTix (\v flags -> flags { testKeepTix = v})
                trueArg
          , option [] ["test-options"]
                ("give extra options to test executables "
                 ++ "(name templates can use $pkgid, $compiler, "
                 ++ "$os, $arch, $test-suite)")
                testOptions (\v flags -> flags { testOptions = v })
                (reqArg' "TEMPLATES" (map toPathTemplate . splitArgs)
                    (const []))
          , option [] ["test-option"]
                ("give extra option to test executables "
                 ++ "(no need to quote options containing spaces, "
                 ++ "name template can use $pkgid, $compiler, "
                 ++ "$os, $arch, $test-suite)")
                testOptions (\v flags -> flags { testOptions = v })
                (reqArg' "TEMPLATE" (\x -> [toPathTemplate x])
                    (map fromPathTemplate))
          ]
      }

    emptyTestFlags :: TestFlags
    emptyTestFlags  = mempty

    instance Monoid TestFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup TestFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * Benchmark flags
    -- ------------------------------------------------------------

    data BenchmarkFlags = BenchmarkFlags {
        benchmarkDistPref  :: Flag FilePath,
        benchmarkVerbosity :: Flag Verbosity,
        benchmarkOptions   :: [PathTemplate]
      } deriving (Generic)

    defaultBenchmarkFlags :: BenchmarkFlags
    defaultBenchmarkFlags  = BenchmarkFlags {
        benchmarkDistPref  = NoFlag,
        benchmarkVerbosity = Flag normal,
        benchmarkOptions   = []
      }

    benchmarkCommand :: CommandUI BenchmarkFlags
    benchmarkCommand = CommandUI
      { commandName         = "bench"
      , commandSynopsis     =
          "Run all/specific benchmarks."
      , commandDescription  = Just $ \pname -> wrapText $
             "If necessary (re)configures with `--enable-benchmarks` flag and"
          ++ " builds the benchmarks.\n"
          ++ "\n"
          ++ "Remember that the benchmarks' dependencies must be installed if"
          ++ " there are additional ones; e.g. with `" ++ pname
          ++ " install --only-dependencies --enable-benchmarks`.\n"
          ++ "\n"
          ++ "By defining UserHooks in a custom Setup.hs, the package can"
          ++ " define actions to be executed before and after running"
          ++ " benchmarks.\n"
      , commandNotes        = Nothing
      , commandUsage        = usageAlternatives "bench"
          [ "[FLAGS]"
          , "BENCHCOMPONENTS [FLAGS]"
          ]
      , commandDefaultFlags = defaultBenchmarkFlags
      , commandOptions = \showOrParseArgs ->
          [ optionVerbosity benchmarkVerbosity
            (\v flags -> flags { benchmarkVerbosity = v })
          , optionDistPref
                benchmarkDistPref (\d flags -> flags { benchmarkDistPref = d })
                showOrParseArgs
          , option [] ["benchmark-options"]
                ("give extra options to benchmark executables "
                 ++ "(name templates can use $pkgid, $compiler, "
                 ++ "$os, $arch, $benchmark)")
                benchmarkOptions (\v flags -> flags { benchmarkOptions = v })
                (reqArg' "TEMPLATES" (map toPathTemplate . splitArgs)
                    (const []))
          , option [] ["benchmark-option"]
                ("give extra option to benchmark executables "
                 ++ "(no need to quote options containing spaces, "
                 ++ "name template can use $pkgid, $compiler, "
                 ++ "$os, $arch, $benchmark)")
                benchmarkOptions (\v flags -> flags { benchmarkOptions = v })
                (reqArg' "TEMPLATE" (\x -> [toPathTemplate x])
                    (map fromPathTemplate))
          ]
      }

    emptyBenchmarkFlags :: BenchmarkFlags
    emptyBenchmarkFlags = mempty

    instance Monoid BenchmarkFlags where
      mempty = gmempty
      mappend = (Semi.<>)

    instance Semigroup BenchmarkFlags where
      (<>) = gmappend

    -- ------------------------------------------------------------
    -- * Shared options utils
    -- ------------------------------------------------------------

    programFlagsDescription :: ProgramConfiguration -> String
    programFlagsDescription progConf =
         "The flags --with-PROG and --PROG-option(s) can be used with"
      ++ " the following programs:"
      ++ (concatMap (\line -> "\n  " ++ unwords line) . wrapLine 77 . sort)
         [ programName prog | (prog, _) <- knownPrograms progConf ]
      ++ "\n"

    -- | For each known program @PROG@ in 'progConf', produce a @with-PROG@
    -- 'OptionField'.
    programConfigurationPaths
      :: ProgramConfiguration
      -> ShowOrParseArgs
      -> (flags -> [(String, FilePath)])
      -> ([(String, FilePath)] -> (flags -> flags))
      -> [OptionField flags]
    programConfigurationPaths progConf showOrParseArgs get set =
      programConfigurationPaths' ("with-" ++) progConf showOrParseArgs get set

    -- | Like 'programConfigurationPaths', but allows to customise the option name.
    programConfigurationPaths'
      :: (String -> String)
      -> ProgramConfiguration
      -> ShowOrParseArgs
      -> (flags -> [(String, FilePath)])
      -> ([(String, FilePath)] -> (flags -> flags))
      -> [OptionField flags]
    programConfigurationPaths' mkName progConf showOrParseArgs get set =
      case showOrParseArgs of
        -- we don't want a verbose help text list so we just show a generic one:
        ShowArgs  -> [withProgramPath "PROG"]
        ParseArgs -> map (withProgramPath . programName . fst)
                     (knownPrograms progConf)
      where
        withProgramPath prog =
          option "" [mkName prog]
            ("give the path to " ++ prog)
            get set
            (reqArg' "PATH" (\path -> [(prog, path)])
              (\progPaths -> [ path | (prog', path) <- progPaths, prog==prog' ]))

    -- | For each known program @PROG@ in 'progConf', produce a @PROG-option@
    -- 'OptionField'.
    programConfigurationOption
      :: ProgramConfiguration
      -> ShowOrParseArgs
      -> (flags -> [(String, [String])])
      -> ([(String, [String])] -> (flags -> flags))
      -> [OptionField flags]
    programConfigurationOption progConf showOrParseArgs get set =
      case showOrParseArgs of
        -- we don't want a verbose help text list so we just show a generic one:
        ShowArgs  -> [programOption "PROG"]
        ParseArgs -> map (programOption  . programName . fst)
                     (knownPrograms progConf)
      where
        programOption prog =
          option "" [prog ++ "-option"]
            ("give an extra option to " ++ prog ++
             " (no need to quote options containing spaces)")
            get set
            (reqArg' "OPT" (\arg -> [(prog, [arg])])
               (\progArgs -> concat [ args
                                    | (prog', args) <- progArgs, prog==prog' ]))

    -- | For each known program @PROG@ in 'progConf', produce a @PROG-options@
    -- 'OptionField'.
    programConfigurationOptions
      :: ProgramConfiguration
      -> ShowOrParseArgs
      -> (flags -> [(String, [String])])
      -> ([(String, [String])] -> (flags -> flags))
      -> [OptionField flags]
    programConfigurationOptions progConf showOrParseArgs get set =
      case showOrParseArgs of
        -- we don't want a verbose help text list so we just show a generic one:
        ShowArgs  -> [programOptions  "PROG"]
        ParseArgs -> map (programOptions . programName . fst)
                     (knownPrograms progConf)
      where
        programOptions prog =
          option "" [prog ++ "-options"]
            ("give extra options to " ++ prog)
            get set
            (reqArg' "OPTS" (\args -> [(prog, splitArgs args)]) (const []))

    -- ------------------------------------------------------------
    -- * GetOpt Utils
    -- ------------------------------------------------------------

    boolOpt :: SFlags -> SFlags
               -> MkOptDescr (a -> Flag Bool) (Flag Bool -> a -> a) a
    boolOpt  = Command.boolOpt  flagToMaybe Flag

    boolOpt' :: OptFlags -> OptFlags
                -> MkOptDescr (a -> Flag Bool) (Flag Bool -> a -> a) a
    boolOpt' = Command.boolOpt' flagToMaybe Flag

    trueArg, falseArg :: MkOptDescr (a -> Flag Bool) (Flag Bool -> a -> a) a
    trueArg  sfT lfT = boolOpt' (sfT, lfT) ([], [])   sfT lfT
    falseArg sfF lfF = boolOpt' ([],  [])  (sfF, lfF) sfF lfF

    reqArgFlag :: ArgPlaceHolder -> SFlags -> LFlags -> Description ->
                  (b -> Flag String) -> (Flag String -> b -> b) -> OptDescr b
    reqArgFlag ad = reqArg ad (succeedReadE Flag) flagToList

    optionDistPref :: (flags -> Flag FilePath)
                   -> (Flag FilePath -> flags -> flags)
                   -> ShowOrParseArgs
                   -> OptionField flags
    optionDistPref get set = \showOrParseArgs ->
      option "" (distPrefFlagName showOrParseArgs)
        (   "The directory where Cabal puts generated build files "
         ++ "(default " ++ defaultDistPref ++ ")")
        get set
        (reqArgFlag "DIR")
      where
        distPrefFlagName ShowArgs  = ["builddir"]
        distPrefFlagName ParseArgs = ["builddir", "distdir", "distpref"]

    optionVerbosity :: (flags -> Flag Verbosity)
                    -> (Flag Verbosity -> flags -> flags)
                    -> OptionField flags
    optionVerbosity get set =
      option "v" ["verbose"]
        "Control verbosity (n is 0--3, default verbosity level is 1)"
        get set
        (optArg "n" (fmap Flag flagToVerbosity)
                    (Flag verbose) -- default Value if no n is given
                    (fmap (Just . showForCabal) . flagToList))

    optionNumJobs :: (flags -> Flag (Maybe Int))
                  -> (Flag (Maybe Int) -> flags -> flags)
                  -> OptionField flags
    optionNumJobs get set =
      option "j" ["jobs"]
        "Run NUM jobs simultaneously (or '$ncpus' if no NUM is given)."
        get set
        (optArg "NUM" (fmap Flag numJobsParser)
                      (Flag Nothing)
                      (map (Just . maybe "$ncpus" show) . flagToList))
      where
        numJobsParser :: ReadE (Maybe Int)
        numJobsParser = ReadE $ \s ->
          case s of
            "$ncpus" -> Right Nothing
            _        -> case reads s of
              [(n, "")]
                | n < 1     -> Left "The number of jobs should be 1 or more."
                | otherwise -> Right (Just n)
              _             -> Left "The jobs value should be a number or '$ncpus'"

    -- ------------------------------------------------------------
    -- * Other Utils
    -- ------------------------------------------------------------

    readPToMaybe :: Parse.ReadP a a -> String -> Maybe a
    readPToMaybe p str = listToMaybe [ r | (r,s) <- Parse.readP_to_S p str
                                         , all isSpace s ]

    -- | Arguments to pass to a @configure@ script, e.g. generated by
    -- @autoconf@.
    configureArgs :: Bool -> ConfigFlags -> [String]
    configureArgs bcHack flags
      = hc_flag
     ++ optFlag  "with-hc-pkg" configHcPkg
     ++ optFlag' "prefix"      prefix
     ++ optFlag' "bindir"      bindir
     ++ optFlag' "libdir"      libdir
     ++ optFlag' "libexecdir"  libexecdir
     ++ optFlag' "datadir"     datadir
     ++ optFlag' "sysconfdir"  sysconfdir
     ++ configConfigureArgs flags
      where
            hc_flag = case (configHcFlavor flags, configHcPath flags) of
                            (_, Flag hc_path) -> [hc_flag_name ++ hc_path]
                            (Flag hc, NoFlag) -> [hc_flag_name ++ display hc]
                            (NoFlag,NoFlag)   -> []
            hc_flag_name
                --TODO kill off thic bc hack when defaultUserHooks is removed.
                | bcHack    = "--with-hc="
                | otherwise = "--with-compiler="
            optFlag name config_field = case config_field flags of
                            Flag p -> ["--" ++ name ++ "=" ++ p]
                            NoFlag -> []
            optFlag' name config_field = optFlag name (fmap fromPathTemplate
                                                     . config_field
                                                     . configInstallDirs)

    configureCCompiler :: Verbosity -> ProgramConfiguration
                          -> IO (FilePath, [String])
    configureCCompiler verbosity lbi = configureProg verbosity lbi gccProgram

    configureLinker :: Verbosity -> ProgramConfiguration -> IO (FilePath, [String])
    configureLinker verbosity lbi = configureProg verbosity lbi ldProgram

    configureProg :: Verbosity -> ProgramConfiguration -> Program
                     -> IO (FilePath, [String])
    configureProg verbosity programConfig prog = do
        (p, _) <- requireProgram verbosity prog programConfig
        let pInv = programInvocation p []
        return (progInvokePath pInv, progInvokeArgs pInv)

    -- | Helper function to split a string into a list of arguments.
    -- It's supposed to handle quoted things sensibly, eg:
    --
    -- > splitArgs "--foo=\"C:\Program Files\Bar\" --baz"
    -- >   = ["--foo=C:\Program Files\Bar", "--baz"]
    --
    splitArgs :: String -> [String]
    splitArgs  = space []
      where
        space :: String -> String -> [String]
        space w []      = word w []
        space w ( c :s)
            | isSpace c = word w (space [] s)
        space w ('"':s) = string w s
        space w s       = nonstring w s

        string :: String -> String -> [String]
        string w []      = word w []
        string w ('"':s) = space w s
        string w ( c :s) = string (c:w) s

        nonstring :: String -> String -> [String]
        nonstring w  []      = word w []
        nonstring w  ('"':s) = string w s
        nonstring w  ( c :s) = space (c:w) s

        word [] s = s
        word w  s = reverse w : s

    -- The test cases kinda have to be rewritten from the ground up... :/
    --hunitTests :: [Test]
    --hunitTests =
    --    let m = [("ghc", GHC), ("nhc98", NHC), ("hugs", Hugs)]
    --        (flags, commands', unkFlags, ers)
    --               = getOpt Permute options ["configure", "foobar", "--prefix=/foo", "--ghc", "--nhc98", "--hugs", "--with-compiler=/comp", "--unknown1", "--unknown2", "--install-prefix=/foo", "--user", "--global"]
    --       in  [TestLabel "very basic option parsing" $ TestList [
    --                 "getOpt flags" ~: "failed" ~:
    --                 [Prefix "/foo", GhcFlag, NhcFlag, HugsFlag,
    --                  WithCompiler "/comp", InstPrefix "/foo", UserFlag, GlobalFlag]
    --                 ~=? flags,
    --                 "getOpt commands" ~: "failed" ~: ["configure", "foobar"] ~=? commands',
    --                 "getOpt unknown opts" ~: "failed" ~:
    --                      ["--unknown1", "--unknown2"] ~=? unkFlags,
    --                 "getOpt errors" ~: "failed" ~: [] ~=? ers],
    --
    --               TestLabel "test location of various compilers" $ TestList
    --               ["configure parsing for prefix and compiler flag" ~: "failed" ~:
    --                    (Right (ConfigCmd (Just comp, Nothing, Just "/usr/local"), []))
    --                   ~=? (parseArgs ["--prefix=/usr/local", "--"++name, "configure"])
    --                   | (name, comp) <- m],
    --
    --               TestLabel "find the package tool" $ TestList
    --               ["configure parsing for prefix comp flag, withcompiler" ~: "failed" ~:
    --                    (Right (ConfigCmd (Just comp, Just "/foo/comp", Just "/usr/local"), []))
    --                   ~=? (parseArgs ["--prefix=/usr/local", "--"++name,
    --                                   "--with-compiler=/foo/comp", "configure"])
    --                   | (name, comp) <- m],
    --
    --               TestLabel "simpler commands" $ TestList
    --               [flag ~: "failed" ~: (Right (flagCmd, [])) ~=? (parseArgs [flag])
    --                   | (flag, flagCmd) <- [("build", BuildCmd),
    --                                         ("install", InstallCmd Nothing False),
    --                                         ("sdist", SDistCmd),
    --                                         ("register", RegisterCmd False)]
    --                  ]
    --               ]

    {- Testing ideas:
       * IO to look for hugs and hugs-pkg (which hugs, etc)
       * quickCheck to test permutations of arguments
       * what other options can we over-ride with a command-line flag?
    -}