module Darcs.Patch.Witnesses.Show
    ( ShowDict(..)
    , showD
    , showListD
    , showsPrecD
    , Show1(..)
    , Show2(..)
    , show1
    , showsPrec1
    , show2
    , showsPrec2
    , showOp2
    , appPrec
    ) where

import Prelude ()
import Darcs.Prelude

import Darcs.Util.Show ( appPrec )

data ShowDict a where
    ShowDictClass :: Show a => ShowDict a
    ShowDictRecord :: (Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> ShowDict a

showsPrecD :: ShowDict a -> Int -> a -> ShowS
showsPrecD ShowDictClass       = showsPrec
showsPrecD (ShowDictRecord showsPrecR _ _) = showsPrecR

showD :: ShowDict a -> a -> String
showD ShowDictClass       = show
showD (ShowDictRecord _ showR _) = showR

showListD :: ShowDict a -> [a] -> ShowS
showListD ShowDictClass       = showList
showListD (ShowDictRecord _ _ showListR) = showListR

class Show1 a where
    showDict1 :: ShowDict (a wX)

showsPrec1 :: Show1 a => Int -> a wX -> ShowS
showsPrec1 = showsPrecD showDict1

show1 :: Show1 a => a wX -> String
show1 = showD showDict1

class Show2 a where
    showDict2 :: ShowDict (a wX wY)

showsPrec2 :: Show2 a => Int -> a wX wY -> ShowS
showsPrec2 = showsPrecD showDict2

show2 :: Show2 a => a wX wY -> String
show2 = showD showDict2

showOp2 :: (Show2 a, Show2 b) => Int -> String -> Int -> a wW wX -> b wY wZ -> String -> String
showOp2 prec opstr d x y = showParen (d > prec) $ showsPrec2 (prec + 1) x .
                          showString opstr . showsPrec2 (prec + 1) y