package distributed_lock

import (
	"errors"
	"fmt"
	"strings"
	"sync"
	"time"

	"modelRT/distributedlock/constant"
	luascript "modelRT/distributedlock/luascript"
	"modelRT/logger"

	"github.com/go-redis/redis"
	uuid "github.com/google/uuid"
	"go.uber.org/zap"
)

const (
	internalLockLeaseTime = uint64(30)
	unlockMessage         = 0
)

// RedissionLockConfig define redission lock config
type RedissionLockConfig struct {
	LockLeaseTime uint64
	Prefix        string
	ChanPrefix    string
	TimeoutPrefix string
	Key           string
}

type redissionLocker struct {
	lockLeaseTime uint64
	token         string
	key           string
	waitChanKey   string
	needRefresh   bool
	exit          chan struct{}
	client        *redis.Client
	once          *sync.Once
	logger        *zap.Logger
}

func (rl *redissionLocker) Lock(timeout ...time.Duration) error {
	if rl.exit == nil {
		rl.exit = make(chan struct{})
	}
	result := rl.tryLock().(*constant.RedisResult)
	if result.Code == constant.UnknownInternalError {
		rl.logger.Error(result.OutputResultMessage())
		return fmt.Errorf("get lock failed:%w", result)
	}

	if (result.Code == constant.LockSuccess) && rl.needRefresh {
		rl.once.Do(func() {
			// async refresh lock timeout unitl receive exit singal
			go rl.refreshLockTimeout()
		})
		return nil
	}

	subMsg := make(chan struct{}, 1)
	defer close(subMsg)
	sub := rl.client.Subscribe(rl.waitChanKey)
	defer sub.Close()
	go rl.subscribeLock(sub, subMsg)

	if len(timeout) > 0 && timeout[0] > 0 {
		acquireTimer := time.NewTimer(timeout[0])
		for {
			select {

			case _, ok := <-subMsg:
				if !ok {
					err := errors.New("failed to read the lock waiting for for the channel message")
					rl.logger.Error("failed to read the lock waiting for for the channel message")
					return err
				}

				resultErr := rl.tryLock().(*constant.RedisResult)
				if (resultErr.Code == constant.LockFailure) || (resultErr.Code == constant.UnknownInternalError) {
					rl.logger.Info(resultErr.OutputResultMessage())
					continue
				}

				if resultErr.Code == constant.LockSuccess {
					rl.logger.Info(resultErr.OutputResultMessage())
					return nil
				}
			case <-acquireTimer.C:
				err := errors.New("the waiting time for obtaining the lock operation has timed out")
				rl.logger.Info("the waiting time for obtaining the lock operation has timed out")
				return err
			}
		}
	}
	return fmt.Errorf("lock the redis lock failed:%w", result)
}

func (rl *redissionLocker) subscribeLock(sub *redis.PubSub, out chan struct{}) {
	if sub == nil || out == nil {
		return
	}
	rl.logger.Info("lock: enter sub routine", zap.String("token", rl.token))

	for {
		msg, err := sub.Receive()
		if err != nil {
			rl.logger.Info("sub receive message failed", zap.Error(err))
			continue
		}

		select {
		case <-rl.exit:
			break
		default:
			switch msg.(type) {
			case *redis.Subscription:
				// Ignore.
			case *redis.Pong:
				// Ignore.
			case *redis.Message:
				out <- struct{}{}
			default:
			}
		}
	}
}

/*
KEYS[1]:锁的键名（key）,通常是锁的唯一标识。
ARGV[1]:锁的过期时间（lockLeaseTime）,单位为秒。
ARGV[2]:当前客户端的唯一标识（token）,用于区分不同的客户端。
*/
func (rl *redissionLocker) refreshLockTimeout() {
	rl.logger.Info("lock refresh by key and token", zap.String("token", rl.token), zap.String("key", rl.key))

	lockTime := time.Duration(rl.lockLeaseTime/3) * time.Second
	timer := time.NewTimer(lockTime)
	defer timer.Stop()

	for {
		select {
		case <-timer.C:
			// extend key lease time
			res := rl.client.Eval(luascript.RefreshLockScript, []string{rl.key}, rl.lockLeaseTime, rl.token)
			val, err := res.Int()
			if err != redis.Nil && err != nil {
				rl.logger.Info("lock refresh failed", zap.String("token", rl.token), zap.String("key", rl.key), zap.Error(err))
				return
			}

			if constant.RedisCode(val) == constant.RefreshLockFailure {
				rl.logger.Error("lock refreash failed,can not find the lock by key and token", zap.String("token", rl.token), zap.String("key", rl.key))
				break
			}

			if constant.RedisCode(val) == constant.RefreshLockSuccess {
				rl.logger.Info("lock refresh success by key and token", zap.String("token", rl.token), zap.String("key", rl.key))
			}
			timer.Reset(lockTime)
		case <-rl.exit:
			break
		}
	}
}

func (rl *redissionLocker) cancelRefreshLockTime() {
	if rl.exit != nil {
		close(rl.exit)
		rl.once = &sync.Once{}
	}
}

/*
KEYS[1]:锁的键名（key）,通常是锁的唯一标识。
ARGV[1]:锁的过期时间（lockLeaseTime）,单位为秒。
ARGV[2]:当前客户端的唯一标识（token）,用于区分不同的客户端。
*/
func (rl *redissionLocker) tryLock() error {
	lockType := constant.LockType
	res := rl.client.Eval(luascript.LockScript, []string{rl.key}, rl.lockLeaseTime, rl.token)
	val, err := res.Int()
	if err != redis.Nil && err != nil {
		return constant.NewRedisResult(constant.UnknownInternalError, lockType, err.Error())
	}
	return constant.NewRedisResult(constant.RedisCode(val), lockType, "")
}

/*
KEYS[1]:锁的键名（key）,通常是锁的唯一标识。
KEYS[2]:锁的释放通知频道（chankey）,用于通知其他客户端锁已释放。
ARGV[1]:解锁消息（unlockMessage）,用于通知其他客户端锁已释放。
ARGV[2]:当前客户端的唯一标识（token）,用于区分不同的客户端。
*/
func (rl *redissionLocker) UnLock() error {
	res := rl.client.Eval(luascript.UnLockScript, []string{rl.key, rl.waitChanKey}, unlockMessage, rl.token)
	val, err := res.Int()
	if err != redis.Nil && err != nil {
		rl.logger.Info("unlock lock failed", zap.String("token", rl.token), zap.String("key", rl.key), zap.Error(err))
		return fmt.Errorf("unlock lock failed:%w", constant.NewRedisResult(constant.UnknownInternalError, constant.UnLockType, err.Error()))
	}

	if constant.RedisCode(val) == constant.UnLockSuccess {
		if rl.needRefresh {
			rl.cancelRefreshLockTime()
		}

		rl.logger.Info("unlock lock success", zap.String("token", rl.token), zap.String("key", rl.key))
		return nil
	}

	if constant.RedisCode(val) == constant.UnLocakFailureWithLockOccupancy {
		rl.logger.Info("unlock lock failed", zap.String("token", rl.token), zap.String("key", rl.key))
		return fmt.Errorf("unlock lock failed:%w", constant.NewRedisResult(constant.UnLocakFailureWithLockOccupancy, constant.UnLockType, ""))
	}
	return nil
}

func GetLocker(client *redis.Client, ops *RedissionLockConfig) *redissionLocker {
	r := &redissionLocker{
		token:       uuid.New().String(),
		needRefresh: true,
		client:      client,
		exit:        make(chan struct{}),
		logger:      logger.GetLoggerInstance(),
	}

	if len(ops.Prefix) <= 0 {
		ops.Prefix = "redission-lock"
	}

	if len(ops.ChanPrefix) <= 0 {
		ops.ChanPrefix = "redission-lock-channel"
	}

	if ops.LockLeaseTime == 0 {
		r.lockLeaseTime = internalLockLeaseTime
	}
	r.key = strings.Join([]string{ops.Prefix, ops.Key}, ":")
	r.waitChanKey = strings.Join([]string{ops.ChanPrefix, ops.Key, "wait"}, ":")
	return r
}