# -*- coding: utf-8 -*-
"""下载次数增减与格式化。

（自 auth_system.py 拆出，行为与原实现一致。）
"""

import time

from .db import (
    _DB_LOCK,
    _x,
    get_conn,
)
from .users import (
    get_user_by_id,
    get_user_by_name,
)

# ============ 使用次数（按次计费：一首歌 = 1 次） ============


def refund_credits(uid: int, count: int) -> int:
    """退回下载次数（批量打包失败部分自动退费）。返回剩余次数（-1 表示不限）"""
    user = get_user_by_id(uid)
    if user and (user['duration_seconds'] or 0) == -1:
        return -1  # 不限次数用户无需退费
    count = max(0, int(count))
    if count <= 0:
        return (user['duration_seconds'] or 0) if user else 0
    _x('UPDATE users SET duration_seconds = COALESCE(duration_seconds, 0) + ? WHERE id = ?',
       (count, uid))
    user = get_user_by_id(uid)
    return (user['duration_seconds'] or 0) if user else 0


def charge_credits(uid: int, count: int = 1) -> int:
    """按次扣减使用次数（管理员与不限次数(-1)用户不扣减，返回 -1）。返回剩余次数

    扣减在 _DB_LOCK 内"读取-判断-写入"一次完成，防止并发双击导致超扣/双花"""
    user = get_user_by_id(uid)
    if not user:
        return 0
    if user['role'] == 'admin' or (user['duration_seconds'] or 0) == -1:
        _x('UPDATE users SET last_active = ? WHERE id = ?', (int(time.time()), uid))
        return -1
    count = max(1, int(count))
    with _DB_LOCK:
        conn = get_conn()
        try:
            row = conn.execute('SELECT duration_seconds FROM users WHERE id = ?', (uid,)).fetchone()
            cur = int(row['duration_seconds'] or 0) if row else 0
            if cur == -1:
                conn.execute('UPDATE users SET last_active = ? WHERE id = ?', (int(time.time()), uid))
                conn.commit()
                return -1
            newval = max(0, cur - count)
            conn.execute('UPDATE users SET duration_seconds = ?, last_active = ? WHERE id = ?',
                         (newval, int(time.time()), uid))
            conn.commit()
            return newval
        finally:
            conn.close()


def reserve_credits(uid: int, count: int = 1):
    """原子预扣下载次数（下载类接口在路由执行前调用，防止并发双击双花）。

    足额：扣减并返回剩余次数；不限次数(-1)/管理员：不扣减返回 -1；
    不足：返回 None（调用方应拒绝请求）"""
    count = max(1, int(count))
    with _DB_LOCK:
        conn = get_conn()
        try:
            row = conn.execute('SELECT role, duration_seconds FROM users WHERE id = ?', (uid,)).fetchone()
            if not row:
                return None
            if row['role'] == 'admin':
                conn.execute('UPDATE users SET last_active = ? WHERE id = ?', (int(time.time()), uid))
                conn.commit()
                return -1
            cur = int(row['duration_seconds'] or 0)
            if cur == -1:
                conn.execute('UPDATE users SET last_active = ? WHERE id = ?', (int(time.time()), uid))
                conn.commit()
                return -1
            if cur < count:
                return None
            conn.execute('UPDATE users SET duration_seconds = ?, last_active = ? WHERE id = ?',
                         (cur - count, int(time.time()), uid))
            conn.commit()
            return cur - count
        finally:
            conn.close()


def add_credits(username: str, count: int) -> int:
    """增加次数（卡密充值/试用领取），返回新剩余次数；不限次数(-1)用户保持不限

    累加用 SQL 原生自增（原子），避免并发充值互相覆盖"""
    user = get_user_by_name(username)
    if not user:
        return 0
    if user['role'] == 'admin' or (user['duration_seconds'] or 0) == -1:
        return -1
    _x('UPDATE users SET duration_seconds = COALESCE(duration_seconds, 0) + ? WHERE id = ?',
       (max(0, int(count)), user['id']))
    user = get_user_by_name(username)
    return (user['duration_seconds'] or 0) if user else 0


def format_credits(count: int) -> str:
    if count < 0:
        return '不限次数'
    if count <= 0:
        return '已用完'
    return f'{count} 次'