module Darcs.Patch.Format
    ( PatchListFormat(..), ListFormat(..)
    , FileNameFormat(..) )
    where

#include "gadts.h"

-- |Showing and reading lists of patches This class allows us to control how
-- lists of patches are formatted on disk. For legacy reasons V1 patches
-- have their own special treatment (see 'ListFormat'). Other patch types
-- use the default format which just puts them in a sequence without separators
-- or any prelude/epilogue.
--
-- This means that 'FL (FL p)' etc would be ambiguous, so there are
-- no instances for 'FL p' or other list types.
class PatchListFormat p where
  patchListFormat :: ListFormat p
  patchListFormat = ListFormatDefault

-- | This type is used to tweak the way that lists of 'p' are shown for a
-- given 'Patch' type 'p'. It is needed to maintain backwards compatibility
-- for V1 and V2 patches.
data ListFormat (p :: PATCHKIND)
  = ListFormatDefault -- ^Show and read lists without braces.
  | ListFormatV1      -- ^Show lists with a single layer of braces around the outside,
                      -- except for singletons which have no braces.
                      -- Read with arbitrary nested braces and parens and flatten them out.
  | ListFormatV2      -- ^Show lists without braces
                      -- Read with arbitrary nested parens and flatten them out.

data FileNameFormat = OldFormat | NewFormat