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

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

	"modelRT/constants"
	"modelRT/logger"

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

// MessageMsgChan buffers message records to be published to the message exchange asynchronously
var MessageMsgChan chan *EventMessage

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

func initMessageChannel(ctx context.Context) (*amqp.Channel, 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.MessageDeadExchangeName, "topic", true, false, false, false, nil)
	if err != nil {
		logger.Error(ctx, "declare message dead letter exchange failed", "error", err)
		return nil, err
	}

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

	err = channel.QueueBind(constants.MessageDeadQueueName, constants.MessageDeadRoutingKey, constants.MessageDeadExchangeName, false, nil)
	if err != nil {
		logger.Error(ctx, "bind message dead letter queue failed", "error", err)
		return nil, err
	}

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

	args := amqp.Table{
		"x-dead-letter-exchange":    constants.MessageDeadExchangeName,
		"x-dead-letter-routing-key": constants.MessageDeadRoutingKey,
	}
	_, err = channel.QueueDeclare(constants.MessageQueueName, true, false, false, false, args)
	if err != nil {
		logger.Error(ctx, "declare message queue failed", "error", err)
		return nil, err
	}

	err = channel.QueueBind(constants.MessageQueueName, constants.MessageRoutingKey, constants.MessageExchangeName, false, nil)
	if err != nil {
		logger.Error(ctx, "bind message queue 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
}

// PushMessageToRabbitMQ publishes message records from msgChan to the message exchange.
// The category of each record is used as the routing key so consumers can bind selectively.
func PushMessageToRabbitMQ(ctx context.Context, msgChan chan *EventMessage) {
	channel, err := initMessageChannel(ctx)
	if err != nil {
		logger.Error(ctx, "initializing message rabbitMQ channel failed", "error", err)
		return
	}

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

			record := msg.Record

			recordBytes, err := json.Marshal(record)
			if err != nil {
				logger.Error(ctx, "marshal message record failed", "event_uuid", record.EventUUID, "error", err)
				continue
			}

			msgCtx := otel.GetTextMapPropagator().Extract(ctx, propagation.MapCarrier(msg.TraceCarrier))
			headers := amqp.Table{}
			otel.GetTextMapPropagator().Inject(msgCtx, amqpHeaderCarrier(headers))

			routingKey := record.Category
			pubCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
			err = channel.PublishWithContext(pubCtx,
				constants.MessageExchangeName,
				routingKey,
				false,
				false,
				amqp.Publishing{
					ContentType: "text/plain",
					Body:        recordBytes,
					Headers:     headers,
				})
			cancel()

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