package service

import (
	"math/rand"
	"time"

	"nl-game-api-gin/internal/database"
	"nl-game-api-gin/internal/model"
)

// VipPeriodStart 计算当前周免周期的起点：最近一个已经到来的周五 12:00（服务器本地时区）
// 周免批次以该时间戳作随机种子，整周稳定，每周五中午自动轮换
func VipPeriodStart(now time.Time) time.Time {
	t := time.Date(now.Year(), now.Month(), now.Day(), 12, 0, 0, 0, now.Location())
	for t.Weekday() != time.Friday {
		t = t.AddDate(0, 0, -1)
	}
	// 今天恰好是周五但还没到中午 12 点：仍属于上一周期
	if t.After(now) {
		t = t.AddDate(0, 0, -7)
	}
	return t
}

// VipNextRefresh 下一次周免刷新时间（当前周期起点 + 7 天）
func VipNextRefresh(now time.Time) time.Time {
	return VipPeriodStart(now).AddDate(0, 0, 7)
}

// VipWeeklyPool 本周期的周免候选池：全部上架付费游戏按种子洗牌后的固定顺序
// 各等级按配额取前 N 款，等级越高批次越大（高等级天然包含低等级的周免）
func VipWeeklyPool(now time.Time) []model.Game {
	var paid []model.Game
	database.DB.Where("status = 1 AND price > 0").Order("id").Find(&paid)
	seed := VipPeriodStart(now).Unix()
	rng := rand.New(rand.NewSource(seed))
	rng.Shuffle(len(paid), func(i, j int) { paid[i], paid[j] = paid[j], paid[i] })
	return paid
}

// VipWeeklyBatch 指定等级本周的周免游戏列表（等级≤0 返回空）
func VipWeeklyBatch(pool []model.Game, levels []model.VipLevel, level int) []model.Game {
	if level <= 0 {
		return nil
	}
	quota := 0
	for _, l := range levels {
		if l.Level == level {
			quota = l.WeeklyFreeQuota
			break
		}
	}
	if quota > len(pool) {
		quota = len(pool)
	}
	return pool[:quota]
}

// UserVipLevel 用户当前生效的 VIP 等级（已过期视为 0）
func UserVipLevel(u *model.User, now time.Time) int {
	if u.VipLevel > 0 && u.VipExpire > now.Unix() {
		return u.VipLevel
	}
	return 0
}

// VipWeeklyFreeSet 用户本周可白嫖的付费游戏ID集合（非VIP返回空集合）
func VipWeeklyFreeSet(u *model.User, now time.Time) map[int]bool {
	set := map[int]bool{}
	level := UserVipLevel(u, now)
	if level <= 0 {
		return set
	}
	var levels []model.VipLevel
	database.DB.Order("level").Find(&levels)
	pool := VipWeeklyPool(now)
	for _, g := range VipWeeklyBatch(pool, levels, level) {
		set[g.ID] = true
	}
	return set
}