module Tokenizer (
    tokenize,
) where

import qualified Data.Bifunctor as B
import Control.Monad.Except
import Utils

_tokenize :: [String] -> String -> String -> LContext [String]
_tokenize acc current src = case src of
    "" -> return $ reverse current : acc
    (x:xs)
        | x == ';' ->
            let commentDropped = dropWhile (\c -> c /= '\n') xs
             in _tokenize (reverse current : acc) "" commentDropped
        | x == '"' ->
            -- String length -1 signals an unbalanced error
            let inc k n = if n == -1 then -1 else n + k
                consume :: String -> (String, Int)
                consume str = case str of
                    ('\\':'"':rest) -> B.bimap ('\"' :) (inc 2) (consume rest)
                    ('\\':'n':rest) -> B.bimap ('\n' :) (inc 2) (consume rest)
                    ('\\':'t':rest) -> B.bimap ('\t' :) (inc 2) (consume rest)
                    ('"':_) -> ("", 1)
                    (c:rest) -> B.bimap (c :) (inc 1) (consume rest)
                    [] -> ("", -1)
                (string, stringLength) = consume xs
                stringDropped = drop (stringLength) xs
                withQuotes = "\"" ++ string ++ "\""
             in do
                when (stringLength == -1) $ throwL "unbalanced string literal"
                _tokenize (withQuotes : acc) "" stringDropped
        | x `elem` [' ', '\n', '\t', '\r'] ->
            _tokenize (reverse current : acc) "" xs
        | x `elem` ['(', ')', '[', ']', '{', '}', '\\'] ->
            _tokenize ([x] : reverse current : acc) "" xs
        | otherwise ->
            _tokenize acc (x : current) xs

tokenize :: String -> LContext [String]
tokenize src = do
    tokens <- _tokenize [] "" src
    return $ tokens
        $> reverse
        .> filter (\s -> length s > 0)