Second checkpoint

internal/messaging/rabbitmq/publisher.go

@@ -0,0 +1,37 @@
+package rabbitmq
+
+import (
+	"context"
+	"fmt"
+
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+// Publisher publishes messages to the connection's exchange.
+type Publisher struct {
+	conn *Connection
+}
+
+// NewPublisher returns a Publisher bound to the given connection.
+func NewPublisher(conn *Connection) *Publisher {
+	return &Publisher{conn: conn}
+}
+
+// Publish sends a JSON-encoded body to the exchange using the given routing key.
+func (p *Publisher) Publish(ctx context.Context, routingKey string, body []byte) error {
+	err := p.conn.publishChannel().PublishWithContext(ctx,
+		p.conn.Exchange(),
+		routingKey,
+		false, // mandatory
+		false, // immediate
+		amqp.Publishing{
+			ContentType:  "application/json",
+			DeliveryMode: amqp.Persistent,
+			Body:         body,
+		},
+	)
+	if err != nil {
+		return fmt.Errorf("publish to %q: %w", routingKey, err)
+	}
+	return nil
+}