git-annex/Types/Command.hs

{- git-annex command data types
 -
 - Copyright 2010-2011 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Types.Command where

import Data.Ord

import Types

{- A command runs in these stages.
 -
 - a. The check stage runs checks, that error out if
 -    anything prevents the command from running. -}
data CommandCheck = CommandCheck { idCheck :: Int, runCheck :: Annex () }
{- b. The seek stage takes the parameters passed to the command,
 -    looks through the repo to find the ones that are relevant
 -    to that command (ie, new files to add), and generates
 -    a list of start stage actions. -}
type CommandSeek = [String] -> Annex [CommandStart]
{- c. The start stage is run before anything is printed about the
  -   command, is passed some input, and can early abort it
  -   if the input does not make sense. It should run quickly and
  -   should not modify Annex state. -}
type CommandStart = Annex (Maybe CommandPerform)
{- d. The perform stage is run after a message is printed about the command
 -    being run, and it should be where the bulk of the work happens. -}
type CommandPerform = Annex (Maybe CommandCleanup)
{- e. The cleanup stage is run only if the perform stage succeeds, and it
 -    returns the overall success/fail of the command. -}
type CommandCleanup = Annex Bool

{- A command is defined by specifying these things. -}
data Command = Command
	{ cmdoptions :: [Option]     -- command-specific options
	, cmdnorepo :: Maybe (IO ()) -- an action to run when not in a repo
	, cmdcheck :: [CommandCheck] -- check stage
	, cmdoneshot :: Bool         -- don't save state after running
	, cmdname :: String
	, cmdparamdesc :: String     -- description of params for usage
	, cmdseek :: [CommandSeek]   -- seek stage
	, cmddesc :: String          -- description of command for usage
	}

{- CommandCheck functions can be compared using their unique id. -}
instance Eq CommandCheck where
	a == b = idCheck a == idCheck b

instance Eq Command where
	a == b = cmdname a == cmdname b

{- Order commands by name -}
instance Ord Command where
	compare = comparing cmdname