package redis

import (
	"encoding/json"
	"fmt"
	"sync"

	logging "git.loafle.net/commons/logging-go"
	"git.loafle.net/overflow/gateway/subscribe"
	"github.com/gomodule/redigo/redis"
)

type Subscribers struct {
	Conn          redis.Conn
	pubSubConn    *redis.PubSubConn
	subscriptions map[string]chan *subscribe.Message

	stopChan chan struct{}
	stopWg   sync.WaitGroup
}

func (s *Subscribers) Start() error {
	if s.stopChan != nil {
		return fmt.Errorf("Subscriber: already running. Stop it before starting it again")
	}

	if nil == s.Conn {
		return fmt.Errorf("Subscriber: Conn is nil")
	}

	if nil == s.subscriptions {
		s.subscriptions = make(map[string]chan *subscribe.Message)
	}

	s.pubSubConn = &redis.PubSubConn{Conn: s.Conn}

	s.stopChan = make(chan struct{})

	s.stopWg.Add(1)
	go s.handleSubscriber()

	return nil
}

func (s *Subscribers) Stop() error {
	if s.stopChan == nil {
		return fmt.Errorf("Subscriber: must be started before stopping it")
	}
	close(s.stopChan)
	s.stopWg.Wait()
	s.stopChan = nil
	return nil
}

func (s *Subscribers) Subscribe(channel string) (<-chan *subscribe.Message, error) {
	if _, ok := s.subscriptions[channel]; ok {
		return nil, subscribe.ChannelExistError{Channel: channel}
	}

	if err := s.pubSubConn.Subscribe(channel); nil != err {
		return nil, err
	}

	msgChan := make(chan *subscribe.Message)
	s.subscriptions[channel] = msgChan

	return msgChan, nil
}

func (s *Subscribers) Unsubscribe(channel string) error {
	msgChan, ok := s.subscriptions[channel]
	if !ok {
		return subscribe.ChannelIsNotExistError{Channel: channel}
	}
	delete(s.subscriptions, channel)
	close(msgChan)

	return s.pubSubConn.Unsubscribe(channel)
}

func (s *Subscribers) handleSubscriber() {
	var (
		receive interface{}
	)
	defer func() {
		if nil != s.subscriptions {
			for _, msgChan := range s.subscriptions {
				close(msgChan)
			}
		}

		if nil != s.pubSubConn {
			s.pubSubConn.Close()
		}

		s.stopWg.Done()
	}()

	receiveChan := make(chan interface{})

	for {
		go func() {
			receive = s.pubSubConn.Receive()
			receiveChan <- receive
		}()

		select {
		case msg := <-receiveChan:
			switch v := msg.(type) {
			case redis.Message:
				msgChan, ok := s.subscriptions[v.Channel]
				if !ok {
					logging.Logger().Warnf("Subscriber: Channel[%s] is not exist", v.Channel)
					break
				}
				message := &subscribe.Message{}
				if err := json.Unmarshal(v.Data, message); nil != err {
					logging.Logger().Errorf("Subscriber: Cannot unmarshal data[%s] of Channel[%s] %v", string(v.Data), v.Channel, err)
					break
				}
				if nil == message.Message {
					logging.Logger().Errorf("Subscriber: Message is not valid data[%s] of Channel[%s]", string(v.Data), v.Channel)
					break
				}
				msgChan <- message
			case redis.Subscription:
			case error:
			}
		case <-s.stopChan:
			return
		}
	}
}