"""省钱 CRUD:演示数据 seeder + 累计/战绩聚合 + 明细分页。

设计:聚合逻辑都是"生产级"真实计算(SUM、按日分组、连续天数),只是数据本期来自
demo seeder。等比价真接入后停掉 seeder、改成上报写入,这些聚合无需改。

聚合在 Python 里算(每用户记录量很小),避免 SQLite 跨时区 date 比较的坑——
created_at 带时区,统一转成北京时间的 date 再分组。
"""
from __future__ import annotations

import random
from dataclasses import dataclass
from datetime import datetime, timedelta

from sqlalchemy import func, select
from sqlalchemy.orm import Session

from app.core.rewards import CN_TZ, cn_today
from app.models.savings import SavingsRecord

# 演示数据规模:最近 N 天每天 1 单(撑起"连续省钱"和"本周"),再补若干历史单
_DEMO_STREAK_DAYS = 9
_DEMO_EXTRA_ORDERS = 14

# 外卖订单演示模板:(平台, 店铺名, 菜品列表)。
# 平台只用有 logo 的三家(美团外卖/淘宝闪购/京东外卖),保证客户端 logo 命中;
# 菜品前 2 道直接展示,其余进「还有 N 道菜」展开。
_DEMO_ORDERS: list[tuple[str, str, list[str]]] = [
    ("美团外卖", "窑鸡王（王府井店）", ["招牌窑鸡(整只)", "凉拌黄瓜", "蒜蓉花甲", "紫菜蛋花汤"]),
    ("淘宝闪购", "海底捞外卖（2人餐）", ["川辣牛肉锅", "嫩牛肉", "海底捞自制饮料", "鸭血", "菌菇拼盘", "鲜虾滑", "麻辣牛百叶"]),
    ("京东外卖", "喜茶（国贸店）", ["多肉葡萄", "烤黑糖波波牛乳"]),
    ("美团外卖", "麦当劳（朝阳大悦城店）", ["巨无霸套餐", "麦麦脆汁鸡", "薯条(大)"]),
    ("淘宝闪购", "7-ELEVEn（建外SOHO店）", ["关东煮", "饭团", "北海道牛乳"]),
    ("美团外卖", "蜜雪冰城（三里屯店）", ["冰鲜柠檬水", "摩天脆脆筒"]),
    ("京东外卖", "西贝莜面村（凯德MALL店）", ["西贝莜面", "黄馍馍", "牛大骨", "沙棘汁"]),
    ("美团外卖", "瑞幸咖啡（CBD店）", ["生椰拿铁", "厚乳拿铁"]),
    ("淘宝闪购", "肯德基（西单店）", ["香辣鸡腿堡", "黄金鸡块", "可乐(中)"]),
    ("京东外卖", "星巴克（华贸店）", ["燕麦拿铁", "提拉米苏"]),
]


@dataclass
class SavingsSummary:
    total_saved_cents: int
    order_count: int
    avg_saved_cents: int  # 平均每单省(分)


@dataclass
class SavingsBattle:
    week_saved_cents: int  # 本周(周一起)已省
    beat_percent: int  # 超过百分之多少用户
    streak_days: int  # 连续省钱天数


def _local_date(dt: datetime):
    """把(可能带时区的)created_at 转成北京时间的 date。"""
    if dt.tzinfo is None:
        return dt.date()
    return dt.astimezone(CN_TZ).date()


def _all_records(db: Session, user_id: int) -> list[SavingsRecord]:
    stmt = select(SavingsRecord).where(SavingsRecord.user_id == user_id)
    return list(db.execute(stmt).scalars().all())


def ensure_seeded(db: Session, user_id: int) -> None:
    """该用户没有任何省钱记录时,幂等灌一批 demo 数据。"""
    exists = db.execute(
        select(SavingsRecord.id).where(SavingsRecord.user_id == user_id).limit(1)
    ).first()
    if exists is not None:
        return

    rng = random.Random(user_id)  # 按 user_id 播种,保证同一用户每次结果一致
    today = cn_today()
    records: list[SavingsRecord] = []

    def _mk(day) -> SavingsRecord:
        hour = rng.randint(8, 21)
        minute = rng.randint(0, 59)
        ts = datetime(day.year, day.month, day.day, hour, minute, tzinfo=CN_TZ)
        platform, shop, dishes = rng.choice(_DEMO_ORDERS)
        # 三成订单设为"未省"(saved=0),对齐原型里有省/没省两种卡
        saved = 0 if rng.random() < 0.3 else rng.randint(300, 4000)  # 0 或 3~40 元
        return SavingsRecord(
            user_id=user_id,
            order_amount_cents=rng.randint(1500, 12000),  # 15~120 元(到手价)
            saved_amount_cents=saved,
            platform=platform,
            title=shop,
            shop_name=shop,
            dishes=dishes,
            source="demo",
            created_at=ts,
        )

    # 最近 N 天每天 1 单 → 连续省钱 N 天
    for d in range(_DEMO_STREAK_DAYS):
        records.append(_mk(today - timedelta(days=d)))
    # 历史散单(第 10~40 天)
    for _ in range(_DEMO_EXTRA_ORDERS):
        records.append(_mk(today - timedelta(days=rng.randint(10, 40))))

    db.add_all(records)
    db.commit()


def get_summary(db: Session, user_id: int) -> SavingsSummary:
    ensure_seeded(db, user_id)
    records = _all_records(db, user_id)
    total = sum(r.saved_amount_cents for r in records)
    count = len(records)
    avg = total // count if count else 0
    return SavingsSummary(total_saved_cents=total, order_count=count, avg_saved_cents=avg)


def _streak_days(dates: set) -> int:
    """从最近活跃日往前数连续有省钱记录的天数。"""
    if not dates:
        return 0
    cur = max(dates)
    streak = 0
    while cur in dates:
        streak += 1
        cur = cur - timedelta(days=1)
    return streak


def get_battle(db: Session, user_id: int) -> SavingsBattle:
    ensure_seeded(db, user_id)
    records = _all_records(db, user_id)

    today = cn_today()
    week_start = today - timedelta(days=today.weekday())  # 本周一
    week_saved = sum(
        r.saved_amount_cents for r in records if _local_date(r.created_at) >= week_start
    )

    dates = {_local_date(r.created_at) for r in records}
    streak = _streak_days(dates)

    beat_percent = _compute_beat_percent(db, user_id)

    return SavingsBattle(
        week_saved_cents=week_saved, beat_percent=beat_percent, streak_days=streak
    )


def _compute_beat_percent(db: Session, user_id: int) -> int:
    """超过百分之多少用户:按"累计省下金额"在所有有省钱记录的用户中做真实分位。

    = 严格少于我的其他用户数 / 其他用户总数 * 100。
    全部省得比我少 → 100;只有自己一个用户 → 0(无可比)。
    """
    rows = db.execute(
        select(SavingsRecord.user_id, func.sum(SavingsRecord.saved_amount_cents))
        .group_by(SavingsRecord.user_id)
    ).all()
    totals = {uid: (total or 0) for uid, total in rows}
    others = {uid: t for uid, t in totals.items() if uid != user_id}
    if not others:
        return 0
    my_total = totals.get(user_id, 0)
    beaten = sum(1 for t in others.values() if t < my_total)
    return round(100 * beaten / len(others))


def list_records(
    db: Session,
    user_id: int,
    *,
    limit: int = 20,
    cursor: int | None = None,
) -> tuple[list[SavingsRecord], int | None]:
    """省钱明细分页(按 id 倒序,游标式)。"""
    ensure_seeded(db, user_id)
    stmt = select(SavingsRecord).where(SavingsRecord.user_id == user_id)
    if cursor is not None:
        stmt = stmt.where(SavingsRecord.id < cursor)
    stmt = stmt.order_by(SavingsRecord.id.desc()).limit(limit)

    items = list(db.execute(stmt).scalars().all())
    next_cursor = items[-1].id if len(items) == limit else None
    return items, next_cursor