package helper

import (
	"context"
	"errors"
	"fmt"
	"go-admin/pkg/utility"
	"math/rand"
	"strconv"
	"sync"
	"sync/atomic"
	"time"

	log "github.com/go-admin-team/go-admin-core/logger"
	"github.com/go-redis/redis/v8"
	"go.uber.org/zap"
)

const (
	tolerance       = 500 // milliseconds
	millisPerSecond = 1000
	lockCommand     = `if redis.call("GET", KEYS[1]) == ARGV[1] then
    redis.call("SET", KEYS[1], ARGV[1], "PX", ARGV[2])
    return "OK"
else
    return redis.call("SET", KEYS[1], ARGV[1], "NX", "PX", ARGV[2])
end`
	delCommand = `if redis.call("GET", KEYS[1]) == ARGV[1] then
    return redis.call("DEL", KEYS[1])
else
    return 0
end`
	touchCommand = `if redis.call("GET", KEYS[1]) == ARGV[1] then
    return redis.call("PEXPIRE", KEYS[1], ARGV[2])
else
    return 0
end`
)

var (
	clientRedisLock *redis.Client
	onece           sync.Once
	ErrFailed       = errors.New("redsync: failed to acquire lock")
)

// InitLockRedisConn 初始化 Redis 连接
func InitLockRedisConn(host, password, dbIndex string) {
	onece.Do(func() {
		dbIndexInt, err := strconv.Atoi(dbIndex)
		if err != nil {
			dbIndexInt = 0
		}
		clientRedisLock = redis.NewClient(&redis.Options{
			Addr:     host,
			Password: password,
			DB:       dbIndexInt,
		})

		// 测试连接
		if _, err := clientRedisLock.Ping(context.Background()).Result(); err != nil {
			log.Error("Failed to connect to Redis", zap.Error(err))
			panic(err)
		}

		fmt.Println("redis lock初始化完毕")
	})
}

// RedisLock 分布式锁结构
type RedisLock struct {
	redisClient   *redis.Client
	key           string
	id            string
	expiry        time.Duration
	retryCount    int           // 重试次数
	retryInterval time.Duration // 重试间隔时间
	seconds       uint32
}

// NewRedisLock 创建一个新的 Redis 锁
func NewRedisLock(key string, timeout uint32, retryCount int, retryInterval time.Duration) *RedisLock {
	return &RedisLock{
		redisClient:   clientRedisLock,
		key:           key,
		id:            utility.GetXid(),
		expiry:        time.Duration(timeout) * time.Second,
		retryCount:    retryCount,
		retryInterval: retryInterval,
		seconds:       timeout,
	}
}

// Acquire 获取锁
func (rl *RedisLock) Acquire() (bool, error) {
	return rl.acquireCtx(context.Background())
}

// AcquireWait 获取锁，支持重试和超时
func (rl *RedisLock) AcquireWait(ctx context.Context) (bool, error) {
	if ctx == nil {
		ctx = context.Background()
	}

	for i := 0; i < rl.retryCount; i++ {
		if i > 0 {
			// 指数退避
			baseInterval := time.Duration(int64(rl.retryInterval) * (1 << i)) // 指数增长
			if baseInterval > time.Second {
				baseInterval = time.Second
			}

			if baseInterval <= 0 {
				baseInterval = time.Millisecond * 100 // 至少 100ms
			}
			// 随机退避
			retryInterval := time.Duration(rand.Int63n(int64(baseInterval))) // 随机退避
			if retryInterval < time.Millisecond*100 {
				retryInterval = time.Millisecond * 100 // 至少 100ms
			}
			select {
			case <-ctx.Done():
				return false, ctx.Err()
			case <-time.After(retryInterval):
			}
		}

		ok, err := rl.acquireCtx(ctx)
		if ok {
			return true, nil
		}
		if err != nil {
			log.Error("Failed to acquire lock", zap.String("key", rl.key), zap.Error(err))
		}
	}
	return false, ErrFailed
}

func safeRandomDuration(max time.Duration) time.Duration {
	if max <= 0 {
		return 100 * time.Millisecond // fallback default
	}
	return time.Duration(rand.Int63n(int64(max)))
}

// Release 释放锁
func (rl *RedisLock) Release() (bool, error) {
	return rl.releaseCtx(context.Background())
}

// Touch 续期锁
func (rl *RedisLock) Touch() (bool, error) {
	return rl.touchCtx(context.Background())
}

// acquireCtx 获取锁的核心逻辑
func (rl *RedisLock) acquireCtx(ctx context.Context) (bool, error) {
	resp, err := rl.redisClient.Eval(ctx, lockCommand, []string{rl.key}, []string{
		rl.id, strconv.Itoa(int(rl.seconds)*millisPerSecond + tolerance),
	}).Result()
	if err == redis.Nil {
		return false, nil
	} else if err != nil {
		log.Error("Error acquiring lock", zap.String("key", rl.key), zap.Error(err))
		return false, err
	}

	reply, ok := resp.(string)
	return ok && reply == "OK", nil
}

// releaseCtx 释放锁的核心逻辑
func (rl *RedisLock) releaseCtx(ctx context.Context) (bool, error) {
	resp, err := rl.redisClient.Eval(ctx, delCommand, []string{rl.key}, []string{rl.id}).Result()
	if err != nil {
		log.Error("Error releasing lock", zap.String("key", rl.key), zap.Error(err))
		return false, err
	}

	reply, ok := resp.(int64)
	return ok && reply == 1, nil
}

// touchCtx 续期锁的核心逻辑
func (rl *RedisLock) touchCtx(ctx context.Context) (bool, error) {
	seconds := atomic.LoadUint32(&rl.seconds)
	resp, err := rl.redisClient.Eval(ctx, touchCommand, []string{rl.key}, []string{
		rl.id, strconv.Itoa(int(seconds)*millisPerSecond + tolerance),
	}).Result()
	if err != nil {
		log.Error("Error touching lock", zap.String("key", rl.key), zap.Error(err))
		return false, err
	}

	reply, ok := resp.(int64)
	return ok && reply == 1, nil
}