<?php
/**
 * Environment compatibility checks.
 *
 * @package WPAB
 */

namespace WPAB\Compatibility;

use WPAB\Support\Local_File;
use WPAB\Support\Locations;

/**
 * Reports likely conflicts. A plugin may declare itself compatible.
 */
final class Compatibility_Checker {
	/**
	 * Third-party callbacks keyed by plugin file.
	 *
	 * @var array<string, callable>
	 */
	private array $callbacks = array();

	/**
	 * Known sensitive plugins and a short reason.
	 *
	 * @var array<string, string>
	 */
	private const WATCHLIST = array(
		'woocommerce/woocommerce.php'              => 'WooCommerce carts and sessions can diverge when plugins or themes change per visitor.',
		'elementor/elementor.php'                  => 'Elementor output is tied to theme locations and may not follow a per-request theme change.',
		'js_composer/js_composer.php'              => 'WPBakery stores layout in content that may assume the original theme.',
		'divi-builder/divi-builder.php'            => 'Divi layouts can depend on the Divi theme being the active theme.',
		'wordpress-seo/wp-seo.php'                 => 'SEO plugins should keep seeing one canonical URL. Confirm crawlers are excluded.',
		'seo-by-rank-math/rank-math.php'           => 'Confirm the SEO plugin does not emit a variant-specific canonical.',
		'wp-rocket/wp-rocket.php'                  => 'Page cache must vary on WPAB cookies or bypass experiment URLs.',
		'litespeed-cache/litespeed-cache.php'      => 'LiteSpeed Cache keeps a separate public copy for each variant, using the assignment cookie. The first visit and previews are not cached.',
		'wp-fastest-cache/wpFastestCache.php'      => 'Logged-out visitors receive a separate WP Fastest Cache file for each variant. Logged-in visitors are not served from that cache.',
		'w3-total-cache/w3-total-cache.php'        => 'Page cache must vary on the assignment cookie.',
		'sitepress-multilingual-cms/sitepress.php' => 'Language plugins may resolve content before the experiment context exists.',
		'polylang/polylang.php'                    => 'Language negotiation can run before the variant is known.',
		'wordfence/wordfence.php'                  => 'Security plugins may treat variant traffic or missing plugins as suspicious.',
	);

	/**
	 * Register a compatibility callback.
	 *
	 * @param string   $plugin_file Plugin file.
	 * @param callable $callback    Callback receiving the environment array.
	 */
	public function register( string $plugin_file, callable $callback ): void {
		$this->callbacks[ $plugin_file ] = $callback;
	}

	/**
	 * Let other plugins register during wpab_register_compatibility.
	 */
	public function boot(): void {
		do_action( 'wpab_register_compatibility', $this );
	}

	/**
	 * Check one theme.
	 *
	 * @param string $stylesheet Stylesheet slug.
	 * @return array<int, array<string, string>>
	 */
	public function check_theme( string $stylesheet ): array {
		$notes = array();
		if ( '' === $stylesheet ) {
			return $notes;
		}
		$path = get_theme_root() . '/' . $stylesheet . '/style.css';
		if ( ! is_readable( $path ) ) {
			$notes[] = array(
				'level'   => 'error',
				'message' => sprintf( 'Theme "%s" is not available.', $stylesheet ),
			);
			return $notes;
		}
		$contents = Local_File::read( $path );
		if ( str_contains( $contents, 'WPAB-compatible' ) || str_contains( $contents, 'WPAB-Compatible' ) ) {
			$notes[] = array(
				'level'   => 'info',
				'message' => sprintf( 'Theme "%s" declares WPAB-compatible.', $stylesheet ),
			);
		}
		return $notes;
	}

	/**
	 * Check one plugin file.
	 *
	 * @param string $plugin_file Plugin file.
	 * @return array<int, array<string, string>>
	 */
	public function check_plugin( string $plugin_file ): array {
		if ( isset( self::WATCHLIST[ $plugin_file ] ) ) {
			$handled = in_array(
				$plugin_file,
				array(
					'wp-fastest-cache/wpFastestCache.php',
					'litespeed-cache/litespeed-cache.php',
				),
				true
			);
			$level   = $handled || $this->declares_compatible( $plugin_file ) ? 'info' : 'warning';
			return array(
				array(
					'level'   => $level,
					'message' => self::WATCHLIST[ $plugin_file ],
				),
			);
		}
		if ( $this->declares_compatible( $plugin_file ) ) {
			return array(
				array(
					'level'   => 'info',
					'message' => sprintf( '%s declares WPAB-compatible.', $plugin_file ),
				),
			);
		}
		return array();
	}

	/**
	 * Check a whole experiment environment.
	 *
	 * @param array<string, mixed> $environment Environment: theme, disabled_plugins, and active plugin files.
	 * @return array<int, array<string, string>>
	 */
	public function check_experiment_environment( array $environment ): array {
		$notes    = $this->check_theme( (string) ( $environment['theme'] ?? '' ) );
		$active   = isset( $environment['active_plugins'] ) && is_array( $environment['active_plugins'] ) ? $environment['active_plugins'] : array();
		$disabled = isset( $environment['disabled_plugins'] ) && is_array( $environment['disabled_plugins'] ) ? $environment['disabled_plugins'] : array();

		foreach ( $active as $file ) {
			$file = (string) $file;
			if ( in_array( $file, $disabled, true ) ) {
				continue;
			}
			$notes = array_merge( $notes, $this->check_plugin( $file ) );
			if ( isset( $this->callbacks[ $file ] ) ) {
				$result = call_user_func( $this->callbacks[ $file ], $environment );
				if ( is_array( $result ) ) {
					$notes = array_merge( $notes, $result );
				}
			}
		}

		return $notes;
	}

	/**
	 * Whether the plugin header declares compatibility.
	 *
	 * @param string $plugin_file Plugin file.
	 * @return bool
	 */
	private function declares_compatible( string $plugin_file ): bool {
		$path = Locations::plugin_file( $plugin_file );
		if ( '' === $path || ! is_readable( $path ) ) {
			return false;
		}
		$contents = Local_File::read( $path, 8192 );
		return str_contains( $contents, 'WPAB-Compatible:' ) || str_contains( $contents, 'WPAB-compatible:' );
	}
}