content: -----------------------------------------------------------------------------
  -- |
  -- Module      :  Distribution.Simple.Program.Types
  -- Copyright   :  Isaac Jones 2006, Duncan Coutts 2007-2009
  --
  -- Maintainer  :  cabal-devel@haskell.org
  -- Portability :  portable
  --
  -- This provides an abstraction which deals with configuring and running
  -- programs. A 'Program' is a static notion of a known program. A
  -- 'ConfiguredProgram' is a 'Program' that has been found on the current
  -- machine and is ready to be run (possibly with some user-supplied default
  -- args). Configuring a program involves finding its location and if necessary
  -- finding its version. There's reasonable default behavior for trying to find
  -- \"foo\" in PATH, being able to override its location, etc.
  --
  module Distribution.Simple.Program.Types (
      -- * Program and functions for constructing them
      Program(..),
      simpleProgram,
  
      -- * Configured program and related functions
      ConfiguredProgram(..),
      programPath,
      ProgArg,
      ProgramLocation(..),
      simpleConfiguredProgram,
    ) where
  
  import Distribution.Simple.Utils
           ( findProgramLocation )
  import Distribution.Version
           ( Version )
  import Distribution.Verbosity
           ( Verbosity )
  
  -- | Represents a program which can be configured.
  --
  -- Note: rather than constructing this directly, start with 'simpleProgram' and
  -- override any extra fields.
  --
  data Program = Program {
         -- | The simple name of the program, eg. ghc
         programName :: String,
  
         -- | A function to search for the program if it's location was not
         -- specified by the user. Usually this will just be a
         programFindLocation :: Verbosity -> IO (Maybe FilePath),
  
         -- | Try to find the version of the program. For many programs this is
         -- not possible or is not necessary so it's ok to return Nothing.
         programFindVersion :: Verbosity -> FilePath -> IO (Maybe Version),
  
         -- | A function to do any additional configuration after we have
         -- located the program (and perhaps identified its version). It is
         -- allowed to return additional flags that will be passed to the
         -- program on every invocation.
         programPostConf :: Verbosity -> ConfiguredProgram -> IO [ProgArg]
       }
  
  type ProgArg = String
  
  -- | Represents a program which has been configured and is thus ready to be run.
  --
  -- These are usually made by configuring a 'Program', but if you have to
  -- construct one directly then start with 'simpleConfiguredProgram' and
  -- override any extra fields.
  --
  data ConfiguredProgram = ConfiguredProgram {
         -- | Just the name again
         programId :: String,
  
         -- | The version of this program, if it is known.
         programVersion :: Maybe Version,
  
         -- | Default command-line args for this program.
         -- These flags will appear first on the command line, so they can be
         -- overridden by subsequent flags.
         programDefaultArgs :: [String],
  
         -- | Override command-line args for this program.
         -- These flags will appear last on the command line, so they override
         -- all earlier flags.
         programOverrideArgs :: [String],
  
         -- | Location of the program. eg. @\/usr\/bin\/ghc-6.4@
         programLocation :: ProgramLocation
       } deriving (Read, Show, Eq)
  
  -- | Where a program was found. Also tells us whether it's specifed by user or
  -- not.  This includes not just the path, but the program as well.
  data ProgramLocation
      = UserSpecified { locationPath :: FilePath }
        -- ^The user gave the path to this program,
        -- eg. --ghc-path=\/usr\/bin\/ghc-6.6
      | FoundOnSystem { locationPath :: FilePath }
        -- ^The program was found automatically.
        deriving (Read, Show, Eq)
  
  -- | The full path of a configured program.
  programPath :: ConfiguredProgram -> FilePath
  programPath = locationPath . programLocation
  
  -- | Make a simple named program.
  --
  -- By default we'll just search for it in the path and not try to find the
  -- version name. You can override these behaviours if necessary, eg:
  --
  -- > simpleProgram "foo" { programFindLocation = ... , programFindVersion ... }
  --
  simpleProgram :: String -> Program
  simpleProgram name = Program {
      programName         = name,
      programFindLocation = \v   -> findProgramLocation v name,
      programFindVersion  = \_ _ -> return Nothing,
      programPostConf     = \_ _ -> return []
    }
  
  -- | Make a simple 'ConfiguredProgram'.
  --
  -- > simpleConfiguredProgram "foo" (FoundOnSystem path)
  --
  simpleConfiguredProgram :: String -> ProgramLocation -> ConfiguredProgram
  simpleConfiguredProgram name loc = ConfiguredProgram {
       programId           = name,
       programVersion      = Nothing,
       programDefaultArgs  = [],
       programOverrideArgs = [],
       programLocation     = loc
    }
  