module Language.Core.Encoding where
import Data.Char
import Numeric
type UserString = String
type EncodedString = String
zEncodeString :: UserString -> EncodedString
zEncodeString cs = case maybe_tuple cs of
Just n -> n
Nothing -> go cs
where
go [] = []
go (c:cs) = encode_ch c ++ go cs
unencodedChar :: Char -> Bool
unencodedChar 'Z' = False
unencodedChar 'z' = False
unencodedChar c = c >= 'a' && c <= 'z'
|| c >= 'A' && c <= 'Z'
|| c >= '0' && c <= '9'
encode_ch :: Char -> EncodedString
encode_ch c | unencodedChar c = [c]
encode_ch '(' = "ZL"
encode_ch ')' = "ZR"
encode_ch '[' = "ZM"
encode_ch ']' = "ZN"
encode_ch ':' = "ZC"
encode_ch 'Z' = "ZZ"
encode_ch 'z' = "zz"
encode_ch '&' = "za"
encode_ch '|' = "zb"
encode_ch '^' = "zc"
encode_ch '$' = "zd"
encode_ch '=' = "ze"
encode_ch '>' = "zg"
encode_ch '#' = "zh"
encode_ch '.' = "zi"
encode_ch '<' = "zl"
encode_ch '-' = "zm"
encode_ch '!' = "zn"
encode_ch '+' = "zp"
encode_ch '\'' = "zq"
encode_ch '\\' = "zr"
encode_ch '/' = "zs"
encode_ch '*' = "zt"
encode_ch '_' = "zu"
encode_ch '%' = "zv"
encode_ch c = 'z' : if isDigit (head hex_str) then hex_str
else '0':hex_str
where hex_str = showHex (ord c) "U"
showHex = showIntAtBase 16 intToDigit
zDecodeString :: EncodedString -> UserString
zDecodeString [] = []
zDecodeString ('Z' : d : rest)
| isDigit d = decode_tuple d rest
| otherwise = decode_upper d : zDecodeString rest
zDecodeString ('z' : d : rest)
| isDigit d = decode_num_esc d rest
| otherwise = decode_lower d : zDecodeString rest
zDecodeString (c : rest) = c : zDecodeString rest
decode_upper, decode_lower :: Char -> Char
decode_upper 'L' = '('
decode_upper 'R' = ')'
decode_upper 'M' = '['
decode_upper 'N' = ']'
decode_upper 'C' = ':'
decode_upper 'Z' = 'Z'
decode_upper ch = ch
decode_lower 'z' = 'z'
decode_lower 'a' = '&'
decode_lower 'b' = '|'
decode_lower 'c' = '^'
decode_lower 'd' = '$'
decode_lower 'e' = '='
decode_lower 'g' = '>'
decode_lower 'h' = '#'
decode_lower 'i' = '.'
decode_lower 'l' = '<'
decode_lower 'm' = '-'
decode_lower 'n' = '!'
decode_lower 'p' = '+'
decode_lower 'q' = '\''
decode_lower 'r' = '\\'
decode_lower 's' = '/'
decode_lower 't' = '*'
decode_lower 'u' = '_'
decode_lower 'v' = '%'
decode_lower ch = ch
decode_num_esc :: Char -> EncodedString -> UserString
decode_num_esc d rest
= go (digitToInt d) rest
where
go n (c : rest) | isHexDigit c = go (16*n + digitToInt c) rest
go n ('U' : rest) = chr n : zDecodeString rest
go n other = error ("decode_num_esc: " ++ show n ++ ' ':other)
decode_tuple :: Char -> EncodedString -> UserString
decode_tuple d rest
= go (digitToInt d) rest
where
go n (c : rest) | isDigit c = go (10*n + digitToInt c) rest
go 0 ('T':rest) = "()" ++ zDecodeString rest
go n ('T':rest) = '(' : replicate (n1) ',' ++ ")" ++ zDecodeString rest
go 1 ('H':rest) = "(# #)" ++ zDecodeString rest
go n ('H':rest) = '(' : '#' : replicate (n1) ',' ++ "#)" ++ zDecodeString rest
go n other = error ("decode_tuple: " ++ show n ++ ' ':other)
maybe_tuple :: UserString -> Maybe EncodedString
maybe_tuple "(# #)" = Just("Z1H")
maybe_tuple ('(' : '#' : cs) = case count_commas (0::Int) cs of
(n, '#' : ')' : _) -> Just ('Z' : shows (n+1) "H")
_ -> Nothing
maybe_tuple "()" = Just("Z0T")
maybe_tuple ('(' : cs) = case count_commas (0::Int) cs of
(n, ')' : _) -> Just ('Z' : shows (n+1) "T")
_ -> Nothing
maybe_tuple _ = Nothing
count_commas :: Int -> String -> (Int, String)
count_commas n (',' : cs) = count_commas (n+1) cs
count_commas n cs = (n,cs)