// Package event define real time data evnet operation functions
package event

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

	"eventRT/constants"
	"eventRT/logger"
	"eventRT/mq"

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

// initUIEventChannel declares the fanout exchange and queue used by UI consumers,
// then returns a channel ready for publishing.
func initUIEventChannel(ctx context.Context) (*amqp.Channel, error) {
	ch, err := mq.GetConn().Channel()
	if err != nil {
		logger.Error(ctx, "open rabbitMQ channel for UI event publish failed", "error", err)
		return nil, err
	}

	err = ch.ExchangeDeclare(constants.EventUIExchangeName, "fanout", true, false, false, false, nil)
	if err != nil {
		logger.Error(ctx, "declare UI event exchange failed", "error", err)
		return nil, err
	}

	_, err = ch.QueueDeclare(constants.EventUIQueueName, true, false, false, false, nil)
	if err != nil {
		logger.Error(ctx, "declare UI event queue failed", "error", err)
		return nil, err
	}

	// fanout exchange routes to all bound queues regardless of routing key
	err = ch.QueueBind(constants.EventUIQueueName, "", constants.EventUIExchangeName, false, nil)
	if err != nil {
		logger.Error(ctx, "bind UI event queue to exchange failed", "error", err)
		return nil, err
	}

	return ch, nil
}

// PublishEventToUI sets the event status to Reported and publishes the record
// to the UI-facing fanout exchange. Intended to be called after the event has
// been successfully persisted to the database.
func PublishEventToUI(ctx context.Context, ch *amqp.Channel, record *EventRecord) error {
	body, err := json.Marshal(record)
	if err != nil {
		logger.Error(ctx, "marshal event record for UI publish failed", "event_uuid", record.EventUUID, "error", err)
		return err
	}

	headers := amqp.Table{}
	otel.GetTextMapPropagator().Inject(ctx, amqpHeaderCarrier(headers))

	pubCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

	err = ch.PublishWithContext(pubCtx,
		constants.EventUIExchangeName,
		"",    // fanout exchange ignores routing key
		false, // mandatory
		false, // immediate
		amqp.Publishing{
			ContentType: "application/json",
			Body:        body,
			Headers:     headers,
		})
	if err != nil {
		logger.Error(ctx, "publish event to UI exchange failed", "event_uuid", record.EventUUID, "error", err)
		return err
	}

	logger.Info(ctx, "event published to UI exchange", "event_uuid", record.EventUUID, "status", record.Status)
	return nil
}