<?php
declare(strict_types=1);

namespace WP_Rocket\Engine\Optimization\DelayJS;

use WP_Rocket\Admin\Options_Data;
use WP_Rocket\Event_Management\Subscriber_Interface;

class Subscriber implements Subscriber_Interface {

	/**
	 * HTML instance.
	 *
	 * @since 3.7
	 *
	 * @var HTML
	 */
	private $html;

	/**
	 * WP_Filesystem_Direct instance.
	 *
	 * @since 3.7
	 *
	 * @var \WP_Filesystem_Direct
	 */
	private $filesystem;

	/**
	 * Subscriber constructor.
	 *
	 * @param HTML                  $html HTML Instance.
	 * @param \WP_Filesystem_Direct $filesystem The Filesystem object.
	 */
	public function __construct( HTML $html, $filesystem ) {
		$this->html       = $html;
		$this->filesystem = $filesystem;
	}

	/**
	 * Return an array of events that this subscriber wants to listen to.
	 *
	 * @since 3.7
	 *
	 * @return array
	 */
	public static function get_subscribed_events() {
		return [
			'rocket_buffer'                               => [
				[ 'delay_js', 26 ],
				[ 'add_delay_js_script', 26 ],
			],
			'pre_get_rocket_option_minify_concatenate_js' => 'maybe_disable_option',
		];
	}

	/**
	 * Modifies scripts HTML to apply delay JS attribute
	 *
	 * @since 3.7
	 *
	 * @param string $buffer_html Html for the page.
	 *
	 * @return string
	 */
	public function delay_js( $buffer_html ) {
		return $this->html->delay_js( $buffer_html );
	}

	/**
	 * Displays the inline script to the head when the option is enabled.
	 *
	 * @since 3.9.4 Move meta charset to head.
	 * @since 3.9 Hooked on rocket_buffer, display the script right after <head>
	 * @since 3.7
	 *
	 * @param string $html HTML content.
	 *
	 * @return string
	 */
	public function add_delay_js_script( $html ): string {
		if ( ! $this->html->is_allowed() ) {
			return $html;
		}

		$pattern = '/<head[^>]*>/i';

		$lazyload_script = $this->filesystem->get_contents( rocket_get_constant( 'WP_ROCKET_PATH' ) . 'assets/js/lazyload-scripts.min.js' );

		$replaced_html = $html;

		if ( false !== $lazyload_script ) {
			$replaced_html = preg_replace( $pattern, "$0<script>{$lazyload_script}</script>", $replaced_html, 1 );

			if ( empty( $replaced_html ) ) {
				return $html;
			}
		}

		$replaced_html = preg_replace( $pattern, '$0<script>' . $this->html->get_ie_fallback() . '</script>', $replaced_html, 1 );

		if ( empty( $replaced_html ) ) {
			return $html;
		}

		return $this->html->move_meta_charset_to_head( $replaced_html );
	}

	/**
	 * Disables defer JS if delay JS is enabled
	 *
	 * @since 3.9
	 *
	 * @param null $value Original value. Should be always null.
	 *
	 * @return null|false
	 */
	public function maybe_disable_option( $value ) {
		if ( $this->html->is_allowed() ) {
			return false;
		}

		return $value;
	}
}
