// Package mq provides read or write access to message queue services
package mq

import (
	"context"
	"encoding/json"
	"time"

	"modelRT/constants"
	"modelRT/logger"
	"modelRT/mq/event"

	amqp "github.com/rabbitmq/amqp091-go"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/propagation"
)

// amqpHeaderCarrier adapts amqp.Table to propagation.TextMapCarrier for trace context injection.
type amqpHeaderCarrier amqp.Table

func (c amqpHeaderCarrier) Get(key string) string {
	val, ok := amqp.Table(c)[key]
	if !ok {
		return ""
	}
	str, _ := val.(string)
	return str
}

func (c amqpHeaderCarrier) Set(key, value string) {
	amqp.Table(c)[key] = value
}

func (c amqpHeaderCarrier) Keys() []string {
	keys := make([]string, 0, len(c))
	for k := range c {
		keys = append(keys, k)
	}
	return keys
}

var _ propagation.TextMapCarrier = amqpHeaderCarrier{}

// EventMessage wraps an EventRecord with the trace context of the computation cycle that produced it.
type EventMessage struct {
	Record       *event.EventRecord
	TraceCarrier map[string]string
}

// MsgChan define variable of channel to store messages that need to be sent to rabbitMQ
var MsgChan chan *EventMessage

func init() {
	MsgChan = make(chan *EventMessage, 10000)
}

func initUpDownLimitEventChannel(ctx context.Context) (*amqp.Channel, error) {
	var channel *amqp.Channel
	var err error

	channel, err = GetConn().Channel()
	if err != nil {
		logger.Error(ctx, "open rabbitMQ server channel failed", "error", err)
		return nil, err
	}

	err = channel.ExchangeDeclare(constants.EventDeadExchangeName, "topic", true, false, false, false, nil)
	if err != nil {
		logger.Error(ctx, "declare event dead letter exchange failed", "error", err)
		return nil, err
	}

	_, err = channel.QueueDeclare(constants.EventUpDownDeadQueueName, true, false, false, false, nil)
	if err != nil {
		logger.Error(ctx, "declare event dead letter queue failed", "error", err)
		return nil, err
	}

	err = channel.QueueBind(constants.EventUpDownDeadQueueName, "#", constants.EventDeadExchangeName, false, nil)
	if err != nil {
		logger.Error(ctx, "bind event dead letter queue with routing key and exchange failed", "error", err)
		return nil, err
	}

	err = channel.ExchangeDeclare(constants.EventExchangeName, "topic", true, false, false, false, nil)
	if err != nil {
		logger.Error(ctx, "declare event exchange failed", "error", err)
		return nil, err
	}

	args := amqp.Table{
		"x-max-length":              int32(50),
		"x-dead-letter-exchange":    constants.EventDeadExchangeName,
		"x-dead-letter-routing-key": constants.EventUpDownDeadRoutingKey,
	}
	_, err = channel.QueueDeclare(constants.EventUpDownQueueName, true, false, false, false, args)
	if err != nil {
		logger.Error(ctx, "declare event queue failed", "error", err)
		return nil, err
	}

	err = channel.QueueBind(constants.EventUpDownQueueName, constants.EventUpDownRoutingKey, constants.EventExchangeName, false, nil)
	if err != nil {
		logger.Error(ctx, "bind event queue with routing key and exchange failed", "error", err)
		return nil, err
	}

	if err := channel.Confirm(false); err != nil {
		logger.Error(ctx, "channel could not be put into confirm mode", "error", err)
		return nil, err
	}
	return channel, nil
}

// PushUpDownLimitEventToRabbitMQ define func to push up and down limit event message to rabbitMQ
func PushUpDownLimitEventToRabbitMQ(ctx context.Context, msgChan chan *EventMessage) {
	channel, err := initUpDownLimitEventChannel(ctx)
	if err != nil {
		logger.Error(ctx, "initializing rabbitMQ channel failed", "error", err)
		return
	}
	// TODO 使用配置修改确认模式通道参数
	confirms := channel.NotifyPublish(make(chan amqp.Confirmation, 100))

	go func() {
		for {
			select {
			case confirm, ok := <-confirms:
				if !ok {
					return
				}
				if !confirm.Ack {
					logger.Error(ctx, "publish message failed (rejected by rabbitMQ)", "tag", confirm.DeliveryTag)
				}
			case <-ctx.Done():
				return
			}
		}
	}()

	for {
		select {
		case <-ctx.Done():
			logger.Info(ctx, "push event alarm message to rabbitMQ stopped by context cancel")
			channel.Close()
			return
		case msg, ok := <-msgChan:
			if !ok {
				logger.Info(ctx, "push event alarm message to rabbitMQ stopped by msgChan closed, exiting push loop")
				channel.Close()
				return
			}

			eventRecord := msg.Record

			// TODO 将消息的序列化移动到发送之前，以便使用eventRecord的category来作为routing key
			recordBytes, err := json.Marshal(eventRecord)
			if err != nil {
				logger.Error(ctx, "marshal event record failed", "event_uuid", eventRecord.EventUUID, "error", err)
				continue
			}

			// restore computation cycle trace context so the AMQP message carries the correct parent span
			msgCtx := otel.GetTextMapPropagator().Extract(ctx, propagation.MapCarrier(msg.TraceCarrier))
			headers := amqp.Table{}
			otel.GetTextMapPropagator().Inject(msgCtx, amqpHeaderCarrier(headers))

			// send event alarm message to rabbitMQ queue
			routingKey := eventRecord.Category
			pubCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
			err = channel.PublishWithContext(pubCtx,
				constants.EventExchangeName, // exchange
				routingKey,                  // routing key
				false,                       // mandatory
				false,                       // immediate
				amqp.Publishing{
					ContentType: "text/plain",
					Body:        recordBytes,
					Headers:     headers,
				})
			cancel()

			if err != nil {
				logger.Error(ctx, "publish message to rabbitMQ queue failed", "message", recordBytes, "error", err)
			}
		}
	}
}