<?php
/**
 * Keeping the lists fetched from Kordiam up to date.
 *
 * @package Kordiam
 */

declare( strict_types=1 );

namespace Kordiam\Import;

use Kordiam\Contracts\RequiresExclusiveSync;
use Kordiam\Export\ApiClient;
use Kordiam\Media\FormatRegistry;
use Kordiam\Support\Config;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Keeps every list the matching screens and the importer read reasonably fresh.
 *
 * Refreshes daily via cron, or immediately when a site has nothing cached. Exclusive with
 * an active Desk-Net plugin, which already fetches the same lists.
 */
final class RemoteListsServiceProvider implements RequiresExclusiveSync {

	/**
	 * Hook the refresh runs on.
	 *
	 * @var string
	 */
	public const REFRESH_ACTION = 'kordiam_refresh_remote_lists';

	/**
	 * Recurrence of the scheduled refresh.
	 *
	 * @var string
	 */
	private const SCHEDULE = 'daily';

	/**
	 * Transient throttling how often an immediate refresh may be asked for.
	 *
	 * @var string
	 */
	private const THROTTLE_KEY = 'kordiam_remote_lists_checked';

	/**
	 * Registering the refresh hooks.
	 */
	public function register(): void {
		// Not gated on is_admin(): cron requests are not admin requests.
		add_action( self::REFRESH_ACTION, array( $this, 'refresh' ) );

		if ( is_admin() ) {
			add_action( 'admin_init', array( $this, 'maybe_request_refresh' ) );
		}
	}

	/**
	 * Asking for a refresh when the site has nothing to show.
	 *
	 * Only schedules; the HTTP calls happen in the following cron request.
	 */
	public function maybe_request_refresh(): void {
		if ( false !== get_transient( self::THROTTLE_KEY ) ) {
			return;
		}

		set_transient( self::THROTTLE_KEY, '1', Config::REMOTE_LIST_TTL );

		if ( ! self::anything_missing() ) {
			return;
		}

		if ( ! ( new ApiClient() )->has_credentials() ) {
			// Saving credentials clears the throttle, so the refresh happens then.
			return;
		}

		if ( false === wp_next_scheduled( self::REFRESH_ACTION ) ) {
			wp_schedule_single_event( time(), self::REFRESH_ACTION );
		}
	}

	/**
	 * Refreshing every list fetched from Kordiam.
	 *
	 * @return int How many lists were updated.
	 */
	public function refresh(): int {
		$updated = 0;

		if ( ( new StatusRegistry() )->refresh() ) {
			++$updated;
		}

		if ( ( new CategoryRegistry() )->refresh() ) {
			++$updated;
		}

		if ( null !== ( new FormatRegistry( new ApiClient() ) )->refresh() ) {
			++$updated;
		}

		$custom_fields = new CustomFieldRegistry();

		foreach ( CustomFieldRegistry::scopes() as $scope ) {
			if ( $custom_fields->refresh( $scope ) ) {
				++$updated;
			}
		}

		return $updated;
	}

	/**
	 * Checking whether any list is still empty.
	 *
	 * @return bool Whether something is missing.
	 */
	public static function anything_missing(): bool {
		if ( ! StatusRegistry::is_populated() || ! CategoryRegistry::is_populated() ) {
			return true;
		}

		if ( array() === FormatRegistry::cached_formats() ) {
			return true;
		}

		foreach ( CustomFieldRegistry::scopes() as $scope ) {
			if ( ! CustomFieldRegistry::is_populated( $scope ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Allowing the next admin page load to ask for a refresh again.
	 *
	 * Called when the Kordiam credentials change.
	 */
	public static function forget_throttle(): void {
		delete_transient( self::THROTTLE_KEY );
	}

	/**
	 * Scheduling the recurring refresh on activation.
	 */
	public static function schedule(): void {
		if ( false === wp_next_scheduled( self::REFRESH_ACTION ) ) {
			wp_schedule_event( time() + MINUTE_IN_SECONDS, self::SCHEDULE, self::REFRESH_ACTION );
		}
	}

	/**
	 * Removing the recurring refresh on deactivation.
	 */
	public static function unschedule(): void {
		wp_clear_scheduled_hook( self::REFRESH_ACTION );

		self::forget_throttle();
	}
}