from collections import deque
from typing import Iterable, Literal, Optional

from math_objects import Integer, Operator, Parenthesis, Token


def tokenize(string: str) -> Iterable[Token]:
    buffer: deque[str] = deque()
    prediction: Optional[Literal["number"]] = None

    def _take_buffer() -> str:
        string = "".join(buffer)
        buffer.clear()
        return string

    for c in string:
        if c.isdigit():
            if prediction != "number" and buffer:
                yield Integer.create_from_string(_take_buffer())
                prediction = "number"
            buffer.append(c)
        elif c in ["+", "-", "*", "/", "(", ")"]:
            if buffer:
                yield Integer.create_from_string(_take_buffer())
                prediction = None
            match c:
                case "+" | "-":
                    yield Operator(c, precedence=1)
                case "*" | "/":
                    yield Operator(c, precedence=2)
                case _:
                    yield Parenthesis(c) # type: ignore
            prediction = None
        elif c == " ":
            pass
        else:
            raise SyntaxError()
    if buffer:
        yield Integer.create_from_string(_take_buffer())