-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.Simple.Build.Macros
-- Copyright   :  Simon Marlow 2008
--
-- Maintainer  :  cabal-devel@haskell.org
-- Portability :  portable
--
-- Generate cabal_macros.h - CPP macros for package version testing
--
-- When using CPP you get
--
-- > VERSION_<package>
-- > MIN_VERSION_<package>(A,B,C)
--
-- for each /package/ in @build-depends@, which is true if the version of
-- /package/ in use is @>= A.B.C@, using the normal ordering on version
-- numbers.
--
module Distribution.Simple.Build.Macros (
    generate,
    generatePackageVersionMacros,
  ) where

import Data.Maybe
         ( isJust )
import Distribution.Package
         ( PackageIdentifier(PackageIdentifier) )
import Distribution.Version
         ( Version(versionBranch) )
import Distribution.PackageDescription
         ( PackageDescription )
import Distribution.Simple.Compiler
         ( packageKeySupported )
import Distribution.Simple.LocalBuildInfo
         ( LocalBuildInfo(compiler, withPrograms), externalPackageDeps, localPackageKey )
import Distribution.Simple.Program.Db
         ( configuredPrograms )
import Distribution.Simple.Program.Types
         ( ConfiguredProgram(programId, programVersion) )
import Distribution.Text
         ( display )

-- ------------------------------------------------------------
-- * Generate cabal_macros.h
-- ------------------------------------------------------------

-- | The contents of the @cabal_macros.h@ for the given configured package.
--
generate :: PackageDescription -> LocalBuildInfo -> String
generate _pkg_descr lbi =
  "/* DO NOT EDIT: This file is automatically generated by Cabal */\n\n" ++
  generatePackageVersionMacros (map snd (externalPackageDeps lbi)) ++
  generateToolVersionMacros (configuredPrograms . withPrograms $ lbi) ++
  generatePackageKeyMacro lbi

-- | Helper function that generates just the @VERSION_pkg@ and @MIN_VERSION_pkg@
-- macros for a list of package ids (usually used with the specific deps of
-- a configured package).
--
generatePackageVersionMacros :: [PackageIdentifier] -> String
generatePackageVersionMacros pkgids = concat
  [ "/* package " ++ display pkgid ++ " */\n"
  ++ generateMacros "" pkgname version
  | pkgid@(PackageIdentifier name version) <- pkgids
  , let pkgname = map fixchar (display name)
  ]

-- | Helper function that generates just the @TOOL_VERSION_pkg@ and
-- @MIN_TOOL_VERSION_pkg@ macros for a list of configured programs.
--
generateToolVersionMacros :: [ConfiguredProgram] -> String
generateToolVersionMacros progs = concat
  [ "/* tool " ++ progid ++ " */\n"
  ++ generateMacros "TOOL_" progname version
  | prog <- progs
  , isJust . programVersion $ prog
  , let progid       = programId prog ++ "-" ++ display version
        progname     = map fixchar (programId prog)
        Just version = programVersion prog
  ]

-- | Common implementation of 'generatePackageVersionMacros' and
-- 'generateToolVersionMacros'.
--
generateMacros :: String -> String -> Version -> String
generateMacros prefix name version =
  concat
  ["#define ", prefix, "VERSION_",name," ",show (display version),"\n"
  ,"#define MIN_", prefix, "VERSION_",name,"(major1,major2,minor) (\\\n"
  ,"  (major1) <  ",major1," || \\\n"
  ,"  (major1) == ",major1," && (major2) <  ",major2," || \\\n"
  ,"  (major1) == ",major1," && (major2) == ",major2," && (minor) <= ",minor,")"
  ,"\n\n"
  ]
  where
    (major1:major2:minor:_) = map show (versionBranch version ++ repeat 0)

-- | Generate the @CURRENT_PACKAGE_KEY@ definition for the package key
--   of the current package, if supported by the compiler.
--   NB: this only makes sense for definite packages.
generatePackageKeyMacro :: LocalBuildInfo -> String
generatePackageKeyMacro lbi
  | packageKeySupported (compiler lbi) =
      "#define CURRENT_PACKAGE_KEY \"" ++ display (localPackageKey lbi) ++ "\"\n\n"
  | otherwise = ""

fixchar :: Char -> Char
fixchar '-' = '_'
fixchar c   = c
