package goredislock

import (
	"context"
	"errors"
	"fmt"
	"github.com/redis/go-redis/v9"
	"sync/atomic"
	"time"
)

const RedisLockPrefix = "goredislock"

var ErrorLockByOthers = errors.New("lock by other")

type RedisLock struct {
	opts   *Options
	client *redis.Client
	key    string
	token  string

	running int32
	celFu   context.CancelFunc
}

func NewRedisLock(client *redis.Client, key string, opts ...Option) *RedisLock {
	redisLock := &RedisLock{
		client: client,
		key:    key,
		opts:   &Options{},
		token:  fmt.Sprintf("%d", time.Now().UnixNano()),
	}

	for _, opt := range opts {
		opt(redisLock.opts)
	}

	redisLock.opts.repair()

	return redisLock
}

func (r *RedisLock) getRedisLockKey(key string) string {
	return fmt.Sprintf("%s_%s", RedisLockPrefix, key)
}

func (r *RedisLock) isMyLock(ctx context.Context) bool {
	s, err := r.client.Get(ctx, r.getRedisLockKey(r.key)).Result()
	if err != nil {
		return false
	}

	if s == r.getRedisLockKey(r.key) {
		return true
	}

	return false
}

func (r *RedisLock) tryLock(ctx context.Context) error {
	result, err := r.client.SetNX(ctx, r.getRedisLockKey(r.key), r.token,
		time.Duration(r.opts.expireTime)*time.Second).Result()

	if err != nil {
		return err
	}

	if !result {
		return ErrorLockByOthers
	}

	return nil
}

func (r *RedisLock) watchDog(ctx context.Context) {
	ticker := time.NewTicker(3 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			// 执行续期
			_ = r.renewal(ctx)
		}
	}
}

func (r *RedisLock) renewal(ctx context.Context) error {
	result, err := r.client.Eval(ctx, LuaRenewal,
		[]string{r.getRedisLockKey(r.key)}, r.token,
		r.opts.expireTime).Result()

	fmt.Println(result, err)

	if err != nil {
		return err
	}

	if res, ok := result.(int64); ok && res == 1 {
		return nil
	}

	return ErrorLockByOthers
}

func (r *RedisLock) unlock(ctx context.Context) error {
	result, err := r.client.Eval(ctx, LuaUnlock,
		[]string{r.getRedisLockKey(r.key)}, r.token).Result()

	if err != nil {
		return err
	}

	if res, ok := result.(int64); ok && res == 1 {
		return nil
	}

	return ErrorLockByOthers
}

func (r *RedisLock) watch(ctx context.Context) {
	// 如果用户指定过期时间则不进行续期
	if !r.opts.reNewLock {
		return
	}

	for !atomic.CompareAndSwapInt32(&r.running, 0, 1) {
	}

	var nctx context.Context
	nctx, r.celFu = context.WithCancel(ctx)

	go func() {
		defer func() {
			atomic.StoreInt32(&r.running, 0)
		}()
		r.watchDog(nctx)
	}()
}

func (r *RedisLock) block(ctx context.Context) error {
	var after <-chan time.Time
	if r.opts.waitTime > 0 {
		after = time.After(time.Duration(r.opts.waitTime) * time.Second)
	}

	ticker := time.NewTicker(200 * time.Millisecond)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-after:
			return errors.New("timeout")
		case <-ticker.C:
			err := r.tryLock(ctx)

			if err == nil {
				return nil
			}

			if !errors.Is(err, ErrorLockByOthers) {
				return err
			}
		}
	}
}

func (r *RedisLock) Lock(ctx context.Context) (err error) {
	defer func() {
		// 如果正常情况需要考虑是否启动续期
		if err == nil {
			r.watch(ctx)
		}
	}()

	if r.isMyLock(ctx) {
		return nil
	}

	err = r.tryLock(ctx)

	// 正常得到锁则返回即可
	if err == nil {
		return nil
	}

	// 如果不是被占用错误,或者是非阻塞模式 则需要返回
	if !errors.Is(err, ErrorLockByOthers) || !r.opts.block {
		return err
	}

	// 进入阻塞模式不停尝试获取锁
	return r.block(ctx)
}

func (r *RedisLock) Unlock(ctx context.Context) (err error) {
	err = r.unlock(ctx)

	if r.celFu != nil {
		r.celFu()
	}

	return err
}