"""一次性任务 CRUD:列表状态 + 领奖。

领奖原子化:写 user_task(唯一约束防重复)+ 发金币,同一事务 commit。
"""
from __future__ import annotations

from dataclasses import dataclass

from sqlalchemy import select
from sqlalchemy.orm import Session

from app.core.rewards import TASK_REWARDS
from app.repositories import wallet as crud_wallet
from app.models.task import UserTask


class UnknownTaskError(Exception):
    """task_key 不在已知任务表里。"""


class AlreadyClaimedError(Exception):
    """该任务已经领过奖了。"""


@dataclass
class TaskState:
    task_key: str
    coin: int
    claimed: bool


def list_tasks(db: Session, user_id: int) -> list[TaskState]:
    """返回所有已知一次性任务及其领取状态。"""
    stmt = select(UserTask.task_key).where(UserTask.user_id == user_id)
    claimed_keys = set(db.execute(stmt).scalars().all())
    return [
        TaskState(task_key=key, coin=coin, claimed=key in claimed_keys)
        for key, coin in TASK_REWARDS.items()
    ]


def claim_task(db: Session, user_id: int, task_key: str) -> tuple[int, int]:
    """领取一次性任务奖励。返回 (发放金币, 领奖后余额)。

    未知任务抛 UnknownTaskError;重复领取抛 AlreadyClaimedError。
    """
    if task_key not in TASK_REWARDS:
        raise UnknownTaskError

    existing = db.execute(
        select(UserTask).where(
            UserTask.user_id == user_id, UserTask.task_key == task_key
        )
    ).scalar_one_or_none()
    if existing is not None:
        raise AlreadyClaimedError

    coin = TASK_REWARDS[task_key]
    db.add(
        UserTask(
            user_id=user_id,
            task_key=task_key,
            status="completed",
            coin_awarded=coin,
        )
    )
    acc, _ = crud_wallet.grant_coins(
        db, user_id, coin, biz_type=f"task_{task_key}", ref_id=task_key
    )
    db.commit()
    return coin, acc.coin_balance