<?php
/**
 * Conflicting SEO plugin detection.
 *
 * @package ElevenRank
 * @since   1.0.0
 */

namespace ElevenRank;

defined( 'ABSPATH' ) || exit;

/**
 * Finds other active SEO plugins that print the same head tags.
 *
 * Detection looks for the version constant each plugin defines when it loads, so it works
 * from `plugins_loaded` on and needs no database access.
 *
 * @since 1.0.0
 */
final class Conflicts {

	/**
	 * Known plugins: id => display name and version constant.
	 *
	 * @since 1.0.0
	 *
	 * @var array<string, array{name: string, constant: string}>
	 */
	const KNOWN = array(
		'yoast'     => array(
			'name'     => 'Yoast SEO',
			'constant' => 'WPSEO_VERSION',
		),
		'rank_math' => array(
			'name'     => 'Rank Math SEO',
			'constant' => 'RANK_MATH_VERSION',
		),
		'aioseo'    => array(
			'name'     => 'All in One SEO',
			'constant' => 'AIOSEO_VERSION',
		),
		'seopress'  => array(
			'name'     => 'SEOPress',
			'constant' => 'SEOPRESS_VERSION',
		),
	);

	/**
	 * Callable that tells whether a constant is defined. Replaceable for tests.
	 *
	 * @since 1.0.0
	 *
	 * @var callable
	 */
	private $is_defined;

	/**
	 * Constructor.
	 *
	 * @since 1.0.0
	 *
	 * @param callable|null $is_defined Optional replacement for `defined()`.
	 */
	public function __construct( ?callable $is_defined = null ) {
		$this->is_defined = null !== $is_defined ? $is_defined : 'defined';
	}

	/**
	 * The conflicting plugins that are active.
	 *
	 * @since 1.0.0
	 *
	 * @return array<string, string> Plugin id => display name.
	 */
	public function detect(): array {
		$found = array();

		foreach ( self::KNOWN as $id => $plugin ) {
			if ( call_user_func( $this->is_defined, $plugin['constant'] ) ) {
				$found[ $id ] = $plugin['name'];
			}
		}

		/**
		 * Filters the detected conflicting SEO plugins.
		 *
		 * @since 1.0.0
		 *
		 * @param array<string, string> $found Plugin id => display name.
		 */
		return apply_filters( 'elevenrank_detected_seo_plugins', $found );
	}
}