// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2023 mysubarumq
// SPDX-FileContributor: alex-savin

package workers

import (
	"context"
	"fmt"
	"log/slog"
	"sync"
	"sync/atomic"
	"time"

	"git.savin.nyc/alex/mysubaru-mq/bus"
	"git.savin.nyc/alex/mysubaru-mq/config"
	mqtt "github.com/eclipse/paho.mqtt.golang"
)

const (
	ServiceAvailable   = `{"value":"online"}`
	ServiceUnavailable = `{"value":"offline"}`
)

// UPSClient is a client that connects to the APCUPSd server by establishing tcp connection
type MQTTClient struct {
	sync.RWMutex
	id           string             // the internal id of the listener
	bus          *bus.Bus           // the internal bus for the interapp communication
	config       *config.Config     // configuration values for the listener
	mqtt         mqtt.Client        //
	cancel       context.CancelFunc //
	end          uint32             // ensure the close methods are only called once
	log          *slog.Logger       // server logger
	mqttHandlers mqttHandlers       //
}

type mqttHandlers struct {
	publish      mqtt.MessageHandler        //
	connected    mqtt.OnConnectHandler      //
	disconnected mqtt.ConnectionLostHandler //
}

// NewUPSClient initialises and returns a UPS client
func NewMQTTClient(id string, bus *bus.Bus, config *config.Config) *MQTTClient {
	if config == nil {
		slog.Error("")
	}

	return &MQTTClient{
		id:     id,
		bus:    bus,
		config: config,
	}
}

// ID returns the id of the listener.
func (w *MQTTClient) ID() string {
	return w.id
}

// ID returns the id of the listener.
func (w *MQTTClient) Type() string {
	return "mqtt-client"
}

// Init .
func (w *MQTTClient) Init(log *slog.Logger) error {
	w.log = log

	opts := mqtt.NewClientOptions()
	opts.AddBroker(fmt.Sprintf("tcp://%s:%d", w.config.MQTT.Host, w.config.MQTT.Port))
	opts.SetUsername(w.config.MQTT.Username)
	opts.SetPassword(w.config.MQTT.Password)
	opts.SetClientID(w.config.MQTT.ClientId)
	opts.SetWill(w.config.MQTT.Topic+"/status", ServiceUnavailable, 0, true)
	opts.OnConnect = func(m mqtt.Client) {
		w.log.Debug("mqtt client is connected to a mqtt server")
		m.Publish(w.config.MQTT.Topic+"/status", 0, w.config.MQTT.Retained, ServiceAvailable)
	}

	w.mqtt = mqtt.NewClient(opts)
	token := w.mqtt.Connect()
	for !token.WaitTimeout(1 * time.Second) {
	}
	if err := token.Error(); err != nil {
		w.log.Error("couldn't connect to a mqtt server", "error", err.Error())

		return err
	}

	w.mqttHandlers.publish = func(client mqtt.Client, msg mqtt.Message) {
		var messages []*bus.Message

		w.log.Debug("received mqtt message", "topic", msg.Topic(), "payload", msg.Payload())
		switch msg.Topic() {
		case w.config.Hassio.Topics.Status:
			// Subscribing for the topic to resend auto discovery topics after Home Assistant restarted and got a status "online"
			messages = append(messages, &bus.Message{
				Topic:   msg.Topic(),
				Payload: string(msg.Payload()),
			})
			w.bus.Publish("hassio:status", messages)
		case "mysubarumq/4S4BTGPD0P3199198/lock/set":
			messages = append(messages, &bus.Message{
				Topic:   msg.Topic(),
				Payload: string(msg.Payload()),
			})
			w.bus.Publish("mysubarumq:4S4BTGPD0P3199198:lock", messages)
		case "mysubarumq/4S4BTGPD0P3199198/ignition/set":
			messages = append(messages, &bus.Message{
				Topic:   msg.Topic(),
				Payload: string(msg.Payload()),
			})
			w.bus.Publish("mysubarumq:4S4BTGPD0P3199198:ignition", messages)
		}
	}

	w.mqttHandlers.connected = func(client mqtt.Client) {
		w.log.Debug("mqtt client is connected")
	}

	w.mqttHandlers.disconnected = func(client mqtt.Client, err error) {
		w.log.Debug("mqtt lost connection", "error", err)
	}

	return nil
}

// OneTime .
func (w *MQTTClient) OneTime() error {
	return nil
}

// Serve starts waiting for new TCP connections, and calls the establish
// connection callback for any received.
func (w *MQTTClient) Serve() {
	if atomic.LoadUint32(&w.end) == 1 {
		return
	}

	chMQTTSubscribeCommand, err := w.bus.Subscribe("mqtt:subscribe", "command", w.config.SubscriptionSize["mqtt:subscribe"])
	if err != nil {
		w.log.Error("couldn't subscribe to a channel", "channel", "mqtt:subscribe", "error", err.Error())
	}

	chMQTTPublishStatus, err := w.bus.Subscribe("mqtt:publish", "status", w.config.SubscriptionSize["mqtt:publish"])
	if err != nil {
		w.log.Error("couldn't subscribe to a channel", "channel", "mqtt:subscribe", "error", err.Error())
	}

	// ctx is used only by tests.
	// ctx, ctxCancel := context.WithCancel(context.Background())
	ctx, cancel := context.WithCancel(context.Background())

	w.cancel = cancel

	go w.eventLoop(ctx, chMQTTPublishStatus, chMQTTSubscribeCommand)

	if atomic.LoadUint32(&w.end) == 0 {
		go func() {
			if !w.mqtt.IsConnected() {
				w.bus.Publish("app:connected", &bus.ConnectionStatus{WorkerID: w.ID(), WorkerType: w.Type(), IsConnected: false})
				w.log.Warn("mqtt client is disconnected")
			}
		}()
	}
}

// Close closes the listener and any client connections.
func (w *MQTTClient) Close() {
	w.Lock()
	defer w.Unlock()

	if atomic.CompareAndSwapUint32(&w.end, 0, 1) {
		w.cancel()
		w.bus.Unsubscribe("mqtt:publish", "status")
		w.mqtt.Publish(w.config.MQTT.Topic+"/status", 0, true, ServiceUnavailable)
		w.mqtt.Disconnect(250)
		w.log.Info("disconnected from mqtt server")
	}
}

// eventLoop loops forever
func (w *MQTTClient) eventLoop(ctx context.Context, chMQTTPublishStatus, chMQTTSubscribeCommand chan bus.Event) {
	w.log.Debug("mqtt communication event loop started")
	defer w.log.Debug("mqtt communication event loop halted")

	for {
		select {
		case event := <-chMQTTPublishStatus:
			for _, message := range event.Data.([]*bus.Message) {
				w.log.Debug("publishing mqtt message", "topic", message.Topic, "qos", message.QOS, "retained", message.Retained, "payload", message.Payload)
				w.mqtt.Publish(message.Topic, message.QOS, message.Retained, message.Payload)
			}
		case event := <-chMQTTSubscribeCommand:
			for _, message := range event.Data.([]*bus.Message) {
				w.log.Debug("subscribing to a topic", "topic", message.Topic, "qos", message.QOS)
				// w.mqtt.SubscribeMultiple()
				w.mqtt.Subscribe(message.Topic, message.QOS, w.mqttHandlers.publish)
			}
		case <-ctx.Done():
			w.log.Info("stopping mqtt communication event loop")
			return
		}
	}
}