package utils

import (
	"context"
	"fmt"
	"git.hlsq.asia/alex/service-common/db/redis"
	"git.hlsq.asia/alex/service-common/net/http/httpresp"
	"google.golang.org/grpc/metadata"
	"time"
)

const (
	replayTTL = 2 * time.Minute  // 防重放缓存有效期
	lockTTL   = 10 * time.Second // 分布式锁有效期
)

// WrapPreventReplay 防止重放请求
func WrapPreventReplay[T any](ctx context.Context, usn int64, fun func() (T, error)) (T, error) {
	var zero T
	key := ""
	if md, ok := metadata.FromIncomingContext(ctx); ok {
		ridArr := md.Get("Request-Id")
		if len(ridArr) == 0 || ridArr[0] == "" {
			return fun()
		}
		key = fmt.Sprintf("cache:replay:%v:%v", usn, ridArr[0])
	} else {
		return fun()
	}

	// 先查缓存，命中直接返回
	if val := getReplayCache[T](ctx, key); val != nil {
		return *val, nil
	}

	// 尝试抢分布式锁，抢到就执行，没抢到报错
	lockKey := fmt.Sprintf("%s:lock", key)
	locked, err := redis.GetClient().SetNX(ctx, lockKey, "1", lockTTL).Result()
	if err == nil && locked {
		defer redis.GetClient().Del(ctx, lockKey)
		result, err := fun()
		// 这里报错了是没有缓存的
		if err != nil {
			return zero, err
		}
		redis.GetCacheClient().Set(ctx, key, result, replayTTL)
		return result, nil
	}
	return zero, httpresp.RequestTooFast
}

// getReplayCache 从 Redis 读取重放缓存
func getReplayCache[T any](ctx context.Context, key string) *T {
	var dst T
	if redis.GetCacheClient().Get(ctx, key, &dst) {
		return &dst
	}
	return nil
}