package mqtt

import (
	"context"
	"time"

	paho "github.com/eclipse/paho.mqtt.golang"
)

// copy the paho lib Message interface
// so no need for deps to import paho lib
type Message interface {
	Duplicate() bool
	Qos() byte
	Retained() bool
	Topic() string
	MessageID() uint16
	Payload() []byte
	Ack()
}

type PubMessage interface {
	Topic() string
	Payload() []byte
	Qos() byte
	Retained() bool
}

type message struct {
	qos      int
	retained bool
	topic    string
	payload  []byte
}

func (m *message) Qos() byte {
	return byte(m.qos)
}

func (m *message) Retained() bool {
	return m.retained
}

func (m *message) Topic() string {
	return m.topic
}

func (m *message) Payload() []byte {
	return m.payload
}

func NewPubMessage(topic string, payload []byte, qos int, retained bool) *message {
	return &message{
		topic:    topic,
		payload:  payload,
		qos:      qos,
		retained: retained,
	}
}

type Config struct {
	Host          string
	Port          string
	Username      string
	Password      string
	ClientID      string
	CleanSession  bool
	AutoReconnect bool
	Retained      bool
	KeepAlive     time.Duration
	MsgChanDept   uint
	WillMessage   PubMessage
}

type Client struct {
	Config     Config
	pahoClient paho.Client
}

func New(conf Config) *Client {
	opts := paho.NewClientOptions()

	broker := conf.Host + ":" + conf.Port

	opts.AddBroker(broker)
	opts.SetClientID(conf.ClientID)
	opts.SetUsername(conf.Username)
	opts.SetPassword(conf.Password)
	opts.SetCleanSession(conf.CleanSession)
	opts.SetAutoReconnect(conf.AutoReconnect)
	opts.SetKeepAlive(conf.KeepAlive)
	opts.SetMessageChannelDepth(conf.MsgChanDept)

	if conf.WillMessage != nil {
		m := conf.WillMessage
		opts.SetBinaryWill(m.Topic(), m.Payload(), m.Qos(), m.Retained())
	}
	if conf.AutoReconnect {
		opts.SetResumeSubs(true)
	}

	client := paho.NewClient(opts)

	return &Client{
		Config:     conf,
		pahoClient: client,
	}
}

func (c *Client) Connect(ctx context.Context) error {
	if token := c.pahoClient.Connect(); token.Wait() && token.Error() != nil {
		return token.Error()
	}

	go func(ctx context.Context) {
		//TODO remove the select, only wait on signal chanel
		for {
			select {
			case <-ctx.Done():
				c.pahoClient.Disconnect(1000)
				return
			}
		}
	}(ctx)

	return nil
}

type Subscriber struct {
	OnMessage chan Message
	OnError   chan error
}

func (c *Client) Subscribe(ctx context.Context, topic string, qos int) *Subscriber {
	sub := &Subscriber{
		OnMessage: make(chan Message),
		OnError:   make(chan error),
	}

	go func(ctx context.Context, sub *Subscriber) {
		defer func() {
			close(sub.OnMessage)
			close(sub.OnError)
		}()

		if token := c.pahoClient.Subscribe(topic, byte(qos), func(mqttClient paho.Client, message paho.Message) {
			sub.OnMessage <- message
		}); token.Wait() && token.Error() != nil {
			sub.OnError <- token.Error()
		}

		<-ctx.Done()
	}(ctx, sub)

	return sub
}

type frame struct {
	topic   string
	qos     int
	payload []byte
	retain  bool
}

type Publisher struct {
	OnError chan error
	publish chan *frame
}

// Publisher will create MQTT publisher and private listener for messages to be published.
// All messages to be published are sent through private publish channel.
// Errors will be sent to OnError channel.
func (c *Client) Publisher(ctx context.Context) *Publisher {
	pub := &Publisher{
		OnError: make(chan error),
		publish: make(chan *frame),
	}

	go func(ctx context.Context, pub *Publisher) {
		defer close(pub.OnError)

		for {
			select {
			case fr := <-pub.publish:
				if token := c.pahoClient.
					Publish(fr.topic,
						byte(fr.qos),
						fr.retain,
						fr.payload); token.Wait() && token.Error() != nil {
					pub.OnError <- token.Error()
				}
			case <-ctx.Done():
				return
			}
		}
	}(ctx, pub)

	return pub
}

// Publish message to topic through private pub.publish channel.
// Thread-safe.
func (pub *Publisher) Publish(topic string, qos int, message []byte, retain bool) {
	pub.publish <- &frame{
		topic:   topic,
		qos:     qos,
		payload: message,
		retain:  retain,
	}
}