/** src/lib/server/resend.ts
 * AUTHOR: Neil Clack
 * EMAIL: nclack@radiantwavetech.com
 * DATE: 07/06/2027
 *
 * A server side library and client for Resend
 * Includes the Resend client, as well as functions
 * for different email scenarios.
 *
 */
import { Resend } from 'resend';
import { env } from '$env/dynamic/private';

let _resend: Resend;

function getResend(): Resend {
	if (!_resend) {
		_resend = new Resend(env.RESEND_API_KEY);
	}
	return _resend;
}

/**
 * Send a transactional email using a Resend-hosted template.
 *
 * @example
 *   await sendMail({
 *     to: 'jane@example.com',
 *     templateId: 'tmpl_abc123',           // optional — defaults to RESEND_TEMPLATE_ID
 *     subject: 'Your license key is ready', // optional — defaults to 'Template Email'
 *     data: {                                // optional — template variables
 *       firstName: 'Jane',
 *       licenseKey: 'RWT-7X9K-2M4Q'
 *     }
 *   });
 *
 * @returns The Resend API response data on success.
 * @throws {Error} If the Resend API call fails.
 */
export async function sendMail(options: {
	to: string;
	subject?: string;
	templateId?: string;
	data?: Record<string, string | number>;
}) {
	const { to, subject, templateId, data } = options;

	const result = await getResend().emails.send({
		from: env.EMAIL_FROM,
		to: [to],
		subject: subject ?? 'Template Email',
		template: {
			id: templateId ?? env.RESEND_TEMPLATE_ID,
			variables: data ?? {}
		}
	});

	if (result.error) {
		throw new Error(result.error.message);
	}

	return result.data;
}