StringParserVladFP

escape :: Parser String -- remove escapes before '/', as jq does
escape = do
        string "\\\\" <|> string "\\n" <|> string "\\t" <|> string "\\r" <|> string "\\f" <|> string "\\b" <|> (string "\\/" *> pure "/") <|> string "\\\""

parseHex :: Parser String
parseHex = do
    _ <- string "\\u" -- starts w/ "\" => needs to be escaped
    hex <- parseHexChar -- <|> parseOtherEscapeChar
    return [hex]


parseHexChar :: Parser Char
parseHexChar = do
    b3 <- parseHexDigit
    b2 <- parseHexDigit
    b1 <- parseHexDigit
    b0 <- parseHexDigit
    let
        decimalNumber = read ("0x" ++ [b3, b2, b1, b0]) :: Int
        decimalStr = show decimalNumber
        actualChar = fst $ head $ readLitChar ("\\" ++ decimalStr)
        in
            return actualChar

-- HELPER
parseHexDigit :: Parser Char -- [0..9] or [A..F]
parseHexDigit = do
        digit <|> sat (`elem` "abcdefABCDEF")

parseBasicChar :: Parser String
parseBasicChar = do
        ch <- sat isBasicChar
        return [ch]

isControlChar :: Char -> Bool
isControlChar ch = let codePoint = ord ch in codePoint >= 0x0000 && codePoint <= 0x001F

isBasicChar :: Char -> Bool
isBasicChar ch = ch `notElem` ['"', '\\'] && (not (isControlChar ch))

parseString :: Parser String
parseString = do
        char '\"'
        str <- many (parseBasicChar <|> parseHex <|> escape)
        char '\"'
        return (concat str)