from __future__ import annotations

import secrets
from dataclasses import dataclass
from datetime import UTC, datetime, timedelta

from argon2 import PasswordHasher


@dataclass(slots=True)
class SessionData:
    session_id: str
    csrf_token: str
    expires_at: datetime
    role: str
    username: str


class AuthService:
    def __init__(self) -> None:
        self._hasher = PasswordHasher()
        self._sessions: dict[str, SessionData] = {}

    def hash_password(self, password: str) -> str:
        return self._hasher.hash(password)

    def verify_password(self, password: str, password_hash: str) -> bool:
        try:
            return self._hasher.verify(password_hash, password)
        except Exception:
            return False

    def create_session(self, username: str, role: str) -> SessionData:
        session_id = secrets.token_hex(24)
        csrf_token = secrets.token_hex(16)
        expires_at = datetime.now(UTC) + timedelta(hours=12)
        session = SessionData(
            session_id=session_id,
            csrf_token=csrf_token,
            expires_at=expires_at,
            role=role,
            username=username,
        )
        self._sessions[session_id] = session
        return session

    def get_session(self, session_id: str | None) -> SessionData | None:
        if session_id is None:
            return None
        session = self._sessions.get(session_id)
        if session is None:
            return None
        if session.expires_at < datetime.now(UTC):
            self._sessions.pop(session_id, None)
            return None
        return session