package logic

import (
	"context"
	"encoding/json"
	"time"

	"bj_power_mes/internal/svc"
)

// Service 业务逻辑服务（handler 薄层调用）
type Service struct {
	ctx *svc.ServiceContext
}

func New(s *svc.ServiceContext) *Service {
	return &Service{ctx: s}
}

// cached 看板缓存：TTL + 防击穿（SETNX 锁），同一 key 同时仅一个打到 DB
func (s *Service) cached(ctx context.Context, key string, ttl int, build func() (any, error)) (any, error) {
	if s.ctx.RedisClient == nil {
		return build()
	}
	if v, err := s.ctx.RedisClient.Get(key); err == nil && v != "" {
		var out any
		if json.Unmarshal([]byte(v), &out) == nil {
			return out, nil
		}
	}

	lockKey := key + ":lock"
	ok, _ := s.ctx.RedisClient.SetnxEx(lockKey, "1", 10)
	if !ok {
		// 有人正在重建缓存：短暂等待后重读
		for i := 0; i < 10; i++ {
			time.Sleep(100 * time.Millisecond)
			if v, err := s.ctx.RedisClient.Get(key); err == nil && v != "" {
				var out any
				if json.Unmarshal([]byte(v), &out) == nil {
					return out, nil
				}
			}
		}
		return build()
	}
	defer func() { _, _ = s.ctx.RedisClient.Del(lockKey) }()

	data, err := build()
	if err == nil {
		if b, e := json.Marshal(data); e == nil {
			_ = s.ctx.RedisClient.Setex(key, string(b), ttl)
		}
	}
	return data, err
}