package cache

import (
	"context"
	"fmt"
	"time"

	"github.com/redis/go-redis/v9"
)

const (
	curveLockTTL = 10 * time.Second
	curveLockRetryDelay = 100 * time.Millisecond
	curveLockMaxRetries = 50
)

// CurveCache 曲线数据缓存（Redis Hash）
type CurveCache struct {
	rdb *redis.Client
}

func NewCurveCache(rdb *redis.Client) *CurveCache {
	return &CurveCache{rdb: rdb}
}

// Get 从 Redis Hash 中获取曲线缓存
func (c *CurveCache) Get(ctx context.Context, brand, name, target string) (string, error) {
	key := brand + " " + name
	val, err := c.rdb.HGet(ctx, key, target).Result()
	if err == redis.Nil {
		return "", nil
	}
	if err != nil {
		return "", fmt.Errorf("hget curve cache: %w", err)
	}
	return val, nil
}

// Set 将曲线数据存入 Redis Hash
func (c *CurveCache) Set(ctx context.Context, brand, name, target, data string) error {
	key := brand + " " + name
	return c.rdb.HSet(ctx, key, target, data).Err()
}

// AcquireLock 获取分布式锁（SETNX），防止并发请求同一个曲线数据
func (c *CurveCache) AcquireLock(ctx context.Context, brand, name, target string) (bool, error) {
	lockKey := brand + " " + name + ":" + target + ":lock"
	return c.rdb.SetNX(ctx, lockKey, "locked", curveLockTTL).Result()
}

// ReleaseLock 释放分布式锁
func (c *CurveCache) ReleaseLock(ctx context.Context, brand, name, target string) error {
	lockKey := brand + " " + name + ":" + target + ":lock"
	return c.rdb.Del(ctx, lockKey).Err()
}

// GetWithLock 获取缓存数据，缓存不存在时尝试加锁后重新获取
// 返回值: (data, acquired, error)
//   - data: 缓存数据（空字符串表示无数据）
//   - acquired: 是否成功获取锁（缓存不存在时需要加锁）
func (c *CurveCache) GetWithLock(ctx context.Context, brand, name, target string) (data string, acquired bool, err error) {
	// 先查缓存
	data, err = c.Get(ctx, brand, name, target)
	if err != nil {
		return "", false, err
	}
	if data != "" {
		return data, false, nil // 缓存命中
	}

	// 缓存不存在，尝试加锁
	acquired, err = c.AcquireLock(ctx, brand, name, target)
	if err != nil {
		return "", false, fmt.Errorf("acquire curve lock: %w", err)
	}

	if acquired {
		// 加锁成功，再次检查缓存（双重检查）
		data, err = c.Get(ctx, brand, name, target)
		if err != nil {
			return "", true, err
		}
		return data, true, nil
	}

	// 未获取锁，等待后重试
	return "", false, nil
}