<?php
/**
 * Notification module.
 *
 * @package FormPilot
 * @since   1.0.0
 */

declare( strict_types = 1 );

namespace FormPilot\Notifications;

use FormPilot\Contracts\Hookable;
use FormPilot\Contracts\NotificationQueue;
use FormPilot\Database\Repositories\FieldRepository;
use FormPilot\Database\Repositories\FormRepository;
use FormPilot\Models\Form;
use FormPilot\Settings\Settings;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Sends the emails a submission triggers.
 *
 * The module listens for a stored submission, asks the builder which mails it
 * should produce and hands them to the configured queue. It never calls the
 * mailer itself, which is what makes deferred delivery a one line change.
 *
 * @since 1.0.0
 */
final class Notifier implements Hookable {

	/**
	 * Resolved delivery queue.
	 *
	 * @var NotificationQueue|null
	 */
	private ?NotificationQueue $queue = null;

	/**
	 * Constructor.
	 *
	 * Both queues are injected rather than chosen here: which one is used is a
	 * runtime decision made once, on first delivery, by {@see Notifier::queue()}.
	 *
	 * @param FormRepository      $forms     Repository reading forms.
	 * @param FieldRepository     $fields    Repository reading fields.
	 * @param NotificationBuilder $builder   Builder producing the notifications.
	 * @param ImmediateQueue      $immediate Queue delivering inside the request.
	 * @param CronQueue           $cron      Queue deferring delivery to WP Cron.
	 */
	public function __construct(
		private FormRepository $forms,
		private FieldRepository $fields,
		private NotificationBuilder $builder,
		private ImmediateQueue $immediate,
		private CronQueue $cron
	) {}

	/**
	 * Registers the module hooks.
	 */
	public function register_hooks(): void {
		add_action( 'formpilot_submission_created', array( $this, 'on_submission_created' ), 10, 3 );
		add_action( CronQueue::HOOK, array( $this, 'process_queue' ) );
	}

	/**
	 * Sends the notifications of a stored submission.
	 *
	 * @param int                                                         $submission_id Stored submission ID.
	 * @param int                                                         $form_id       Form the submission belongs to.
	 * @param array<int, array{field_id: int, key: string, value: mixed}> $entries       Stored values.
	 */
	public function on_submission_created( int $submission_id, int $form_id, array $entries ): void {
		$form = $this->forms->find( $form_id );

		if ( ! $form instanceof Form ) {
			return;
		}

		$values = array();

		foreach ( $entries as $entry ) {
			$key = (string) ( $entry['key'] ?? '' );

			if ( '' === $key ) {
				continue;
			}

			$values[ $key ] = $entry['value'] ?? '';
		}

		$notifications = $this->builder->build( $form, $this->fields->for_form( $form_id ), $values, $submission_id );

		foreach ( $notifications as $notification ) {
			if ( ! $notification instanceof Notification ) {
				continue;
			}

			$this->queue()->push( $notification );
		}
	}

	/**
	 * Delivers the notifications waiting in the cron queue.
	 *
	 * Always the cron queue, whatever {@see Notifier::queue()} settled on: this
	 * runs to drain notifications that were *stored* earlier, and those are in
	 * the option whether or not the site still defers delivery.
	 *
	 * Hooked to {@see CronQueue::HOOK}.
	 */
	public function process_queue(): void {
		$this->cron->process();
	}

	/**
	 * Returns the queue notifications are handed to.
	 *
	 * Resolved once, on first use rather than at construction, so a site can
	 * still register the filter below on `init` or on a late `plugins_loaded`.
	 */
	public function queue(): NotificationQueue {
		if ( $this->queue instanceof NotificationQueue ) {
			return $this->queue;
		}

		$default = 'cron' === Settings::text( 'queue' ) ? $this->cron : $this->immediate;

		/**
		 * Filters the queue notifications are delivered through.
		 *
		 * Return a {@see CronQueue} to move delivery out of the submission
		 * request, or any other implementation of the interface to hand mail to
		 * Action Scheduler or an external worker.
		 *
		 * @since 1.0.0
		 *
		 * @param NotificationQueue $queue Delivery queue.
		 */
		$queue = apply_filters( 'formpilot_notification_queue', $default );

		$this->queue = $queue instanceof NotificationQueue ? $queue : $default;

		return $this->queue;
	}
}