from __future__ import annotations

from dataclasses import dataclass
import re


@dataclass(frozen=True)
class Token:
    kind: str
    value: str
    line: int
    column: int


_RE = re.compile(r"(?P<ws>\s+)|(?P<comment>//[^\n]*|/\*.*?\*/)|(?P<string>\"(?:\\.|[^\"\\])*\"|'(?:\\.|[^'\\])*')|(?P<number>[+-]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?)|(?P<ident>[A-Za-z_][A-Za-z0-9_.]*)|(?P<op>==|!=|<=|>=|=>|[{}\[\]():,;=+*/-])", re.S)


def lex(source: str) -> list[Token]:
    out: list[Token] = []
    pos = 0; line = 1; column = 1
    while pos < len(source):
        match = _RE.match(source, pos)
        if not match:
            raise SyntaxError(f"unexpected character at {line}:{column}: {source[pos]!r}")
        kind, value = match.lastgroup or "", match.group(0)
        if kind not in {"ws", "comment"}:
            out.append(Token(kind, value, line, column))
        nl = value.count("\n")
        if nl: line, column = line + nl, len(value.rsplit("\n", 1)[-1]) + 1
        else: column += len(value)
        pos = match.end()
    out.append(Token("eof", "", line, column))
    return out