"""Lexer module placeholder for SLS.

Provide a Lexer class that will later be expanded to match the C implementation.
"""

from dataclasses import dataclass
from typing import Iterator, NamedTuple


class Token(NamedTuple):
    type: str
    value: str
    lineno: int
    col: int


@dataclass
class Lexer:
    source: str

    def tokenize(self) -> Iterator[Token]:
        """Yield tokens from `source`. Currently yields a single EOF token.
        Replace with full logic when porting the C lexer.
        """
        yield Token("EOF", "", 1, 0)