package redisdao

import (
	"context"
	"fmt"
	"time"

	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/global"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/redismodel"
	"github.com/redis/go-redis/v9"
)

// notificationUnreadTTL 未读数 key 的过期时间，避免长期驻留与 MySQL 弱一致漂移。
const notificationUnreadTTL = 7 * 24 * time.Hour

// notificationUnreadIncrScript 首次自增时设置过期时间，保证 INCR 与 EXPIRE 原子执行。
var notificationUnreadIncrScript = redis.NewScript(`
local v = redis.call('INCR', KEYS[1])
if v == 1 then
  redis.call('EXPIRE', KEYS[1], ARGV[1])
end
return v
`)

// notificationUnreadDecrScript 未读数 -1，保证结果不低于 0
var notificationUnreadDecrScript = redis.NewScript(`
local v = redis.call('GET', KEYS[1])
if v and tonumber(v) > 0 then
  return redis.call('DECRBY', KEYS[1], 1)
end
return 0
`)

// NotificationUnreadIncr 用户未读消息数 +1，返回最新值
func NotificationUnreadIncr(ctx context.Context, userID int64) (int64, error) {
	ctx, span := global.Tracer.Start(ctx, "redisdao.NotificationUnreadIncr")
	defer span.End()

	key := fmt.Sprintf(redismodel.KeyNotificationUnread, userID)
	val, err := notificationUnreadIncrScript.Run(ctx, global.RedisEngine, []string{key}, int(notificationUnreadTTL.Seconds())).Int64()
	if err != nil {
		span.RecordError(err)
		return 0, err
	}
	return val, nil
}

// NotificationUnreadDecr 用户未读消息数 -1，返回扣减后的值（不低于 0）
func NotificationUnreadDecr(ctx context.Context, userID int64) (int64, error) {
	ctx, span := global.Tracer.Start(ctx, "redisdao.NotificationUnreadDecr")
	defer span.End()

	key := fmt.Sprintf(redismodel.KeyNotificationUnread, userID)
	val, err := notificationUnreadDecrScript.Run(ctx, global.RedisEngine, []string{key}).Int64()
	if err != nil {
		span.RecordError(err)
		return 0, err
	}
	return val, nil
}

// NotificationUnreadGet 获取用户未读消息数，不存在时返回 0
func NotificationUnreadGet(ctx context.Context, userID int64) (int64, error) {
	ctx, span := global.Tracer.Start(ctx, "redisdao.NotificationUnreadGet")
	defer span.End()

	key := fmt.Sprintf(redismodel.KeyNotificationUnread, userID)
	v, err := global.RedisEngine.Get(ctx, key).Int64()
	if err == redis.Nil {
		return 0, nil
	}
	if err != nil {
		span.RecordError(err)
	}
	return v, err
}

// NotificationUnreadSet 回填未读数缓存（DB 对账回源后使用），避免 key 过期导致后续扣减被吞。
func NotificationUnreadSet(ctx context.Context, userID int64, cnt int64) error {
	ctx, span := global.Tracer.Start(ctx, "redisdao.NotificationUnreadSet")
	defer span.End()

	key := fmt.Sprintf(redismodel.KeyNotificationUnread, userID)
	if err := global.RedisEngine.Set(ctx, key, cnt, notificationUnreadTTL).Err(); err != nil {
		span.RecordError(err)
		return err
	}
	return nil
}