<?php
/**
 * Cache variation contract.
 *
 * @package WPAB
 */

namespace WPAB\Cache;

use WPAB\Runtime\Experiment_Context;
use WPAB\Support\Locations;
use WPAB\Support\Settings;

/**
 * Sends cache headers for participating requests and exposes an integration seam.
 *
 * WP Fastest Cache and LiteSpeed Cache each keep one copy per variant.
 * Other caches can hook `wpab_cache_vary_cookies` and `wpab_register_cache_integration`.
 */
final class Cache_Manager {
	/**
	 * Register hooks.
	 */
	public function register(): void {
		add_action( 'send_headers', array( $this, 'send_headers' ) );
		add_filter( 'wpab_cache_vary_cookies', array( $this, 'cookies' ) );
		( new Fastest_Cache() )->register();
		( new LiteSpeed_Cache() )->register();
		do_action( 'wpab_register_cache_integration', $this );
	}

	/**
	 * Cookie names integrations should vary on.
	 *
	 * @param string[] $cookies Cookies.
	 * @return string[]
	 */
	public function cookies( array $cookies ): array {
		$cookies[] = 'wpab_vid';
		$cookies[] = 'wpab_assignment_';
		$cookies[] = 'wpab_preview';
		return array_values( array_unique( $cookies ) );
	}

	/**
	 * Headers for a request that is rendering an experiment.
	 */
	public function send_headers(): void {
		$context = Experiment_Context::current();
		if ( ! $context instanceof Experiment_Context || $context->experiment_id() < 1 ) {
			return;
		}

		$mode = (string) Settings::all()['cache_mode'];
		if ( 'standard' === $mode ) {
			return;
		}

		header( 'Vary: Cookie', false );
		if ( 'private' === $mode ) {
			nocache_headers();
		}
	}

	/**
	 * Whether a full-page cache drop-in is present. Drop-ins load before this plugin.
	 *
	 * @return bool
	 */
	public function has_advanced_cache_dropin(): bool {
		$dir = Locations::content_dir();
		return '' !== $dir && is_file( $dir . '/advanced-cache.php' );
	}
}