module Data.Encoding.KOI8R
	(KOI8R(..)) where

import Control.Exception (throwDyn)
import Data.Array.Unboxed
import Data.Char (ord,chr)
import qualified Data.ByteString.Lazy as Lazy
import Data.Map hiding (map,(!))
import Data.Word
import Prelude hiding (lookup)

import Data.Encoding.Base

data KOI8R = KOI8R deriving Show

koi8rArr :: UArray Word8 Char
koi8rArr = listArray (128,255) koi8rList

koi8rMap :: Map Char Word8
koi8rMap = fromList (zip koi8rList [0..])

koi8rList :: [Char]
koi8rList =
	['\x2500','\x2502','\x250c','\x2510','\x2514','\x2518','\x251c','\x2524'
	,'\x252c','\x2534','\x253c','\x2580','\x2584','\x2588','\x258c','\x2590'
	,'\x2591','\x2592','\x2593','\x2320','\x25a0','\x2219','\x221a','\x2248'
	,'\x2264','\x2265','\x00a0','\x2321','\x00b0','\x00b2','\x00b7','\x00f7'
	,'\x2550','\x2551','\x2552','\x0451','\x2553','\x2554','\x2555','\x2556'
	,'\x2557','\x2558','\x2559','\x255a','\x255b','\x255c','\x255d','\x255e'
	,'\x255f','\x2560','\x2561','\x0401','\x2562','\x2563','\x2564','\x2565'
	,'\x2566','\x2567','\x2568','\x2569','\x256a','\x256b','\x256c','\x00a9'
	,'\x044e','\x0430','\x0431','\x0446','\x0434','\x0435','\x0444','\x0433'
	,'\x0445','\x0438','\x0439','\x043a','\x043b','\x043c','\x043d','\x043e'
	,'\x043f','\x044f','\x0440','\x0441','\x0442','\x0443','\x0436','\x0432'
	,'\x044c','\x044b','\x0437','\x0448','\x044d','\x0449','\x0447','\x044a'
	,'\x042e','\x0410','\x0411','\x0426','\x0414','\x0415','\x0424','\x0413'
	,'\x0425','\x0418','\x0419','\x041a','\x041b','\x041c','\x041d','\x041e'
	,'\x041f','\x042f','\x0420','\x0421','\x0422','\x0423','\x0416','\x0412'
	,'\x042c','\x042b','\x0417','\x0428','\x042d','\x0429','\x0427','\x042a']

koi8rDecode :: Word8 -> Char
koi8rDecode ch
	| ch < 128 = chr $ fromIntegral ch
	| otherwise = koi8rArr!ch

koi8rEncode :: Char -> Word8
koi8rEncode ch
	| ch < '\128' = fromIntegral $ ord ch
	| otherwise   = case lookup ch koi8rMap of
		Just w -> w
		Nothing -> throwDyn (HasNoRepresentation ch)

instance Encoding KOI8R where
	encode _ = encodeSinglebyte koi8rEncode
	encodeLazy _ = encodeSinglebyteLazy koi8rEncode
	encodable _ c = (c < '\128') || (member c koi8rMap)
	decode _ = decodeSinglebyte koi8rDecode
	decodeLazy _ str = concatMap (decodeSinglebyte koi8rDecode) (Lazy.toChunks str)
	decodable _ = const True