<?php
/**
 * Discover known form placements before the page head is printed.
 *
 * Rendering still enqueues assets as a fallback for custom page builders and
 * PHP templates. Discovery must never render content: doing so could execute
 * shortcodes twice, change instance IDs or run unrelated plugins' callbacks.
 *
 * @package AccessibleForms
 */
namespace AccessibleForms;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

class FrontendAssets {
	/** Bound work for deeply nested or cyclic reusable content. */
	const MAX_DEPTH      = 32;
	const MAX_BLOCKS     = 2000;
	const MAX_REFERENCES = 100;
	const MAX_BYTES      = 1048576;

	/**
	 * Keep accessibility-critical styles intact when Boost rewrites CDN links.
	 *
	 * Older Boost versions can replace double-quoted link attributes as well as
	 * media. Its supported opt-out preserves our URLs, integrity and media while
	 * leaving all other stylesheets under the site's chosen loading policy.
	 *
	 * @param string|bool $method Requested stylesheet loading method.
	 * @param string      $handle Registered stylesheet handle.
	 * @return string|bool
	 */
	public static function stylesheet_loading( $method, $handle ) {
		return in_array( $handle, array( 'accessible-forms', 'accessible-forms-check' ), true ) ? false : $method;
	}

	/** Queue CSS only for content that can actually contain a form. */
	public static function enqueue() {
		global $wp_query, $_wp_current_template_content;
		$state = array( 'blocks' => 0, 'bytes' => 0, 'references' => array() );

		foreach ( (array) ( $wp_query->posts ?? array() ) as $post ) {
			if ( $post instanceof \WP_Post && self::content_contains_form( $post->post_content, $state, 0 ) ) {
				wp_enqueue_style( 'accessible-forms' );
				return;
			}
		}

		// Block themes resolve their selected template before calling wp_head().
		// Inspect only that template, not every template or sidebar on the site.
		if ( is_string( $_wp_current_template_content ) && self::content_contains_form( $_wp_current_template_content, $state, 0 ) ) {
			wp_enqueue_style( 'accessible-forms' );
		}
	}

	/**
	 * Detect direct embeds and the reusable content WordPress resolves for them.
	 *
	 * @param string $content Post, pattern or template content.
	 * @return bool Whether a form or its unavailable notice can be rendered.
	 */
	public static function contains_form( $content ) {
		$state = array( 'blocks' => 0, 'bytes' => 0, 'references' => array() );
		return self::content_contains_form( (string) $content, $state, 0 );
	}

	/** Inspect content without executing any shortcodes or render callbacks. */
	private static function content_contains_form( $content, array &$state, $depth ) {
		$state['bytes'] += strlen( $content );
		if ( $depth > self::MAX_DEPTH || $state['bytes'] > self::MAX_BYTES || $state['blocks'] >= self::MAX_BLOCKS ) {
			return false;
		}
		if ( false !== strpos( $content, '[accessible_form' ) && preg_match_all( '/' . get_shortcode_regex( array( 'accessible_form' ) ) . '/s', $content, $matches, PREG_SET_ORDER ) ) {
			foreach ( $matches as $match ) {
				if ( '[' !== $match[1] || ']' !== $match[6] ) {
					return true;
				}
			}
		}
		return false !== strpos( $content, '<!-- wp:' ) && self::blocks_contain_form( parse_blocks( $content ), $state, $depth );
	}

	/** Follow only the references used by the selected content. */
	private static function blocks_contain_form( array $blocks, array &$state, $depth ) {
		if ( $depth > self::MAX_DEPTH ) {
			return false;
		}
		foreach ( $blocks as $block ) {
			if ( ++$state['blocks'] > self::MAX_BLOCKS ) {
				return false;
			}
			$name = $block['blockName'] ?? '';
			$attrs = $block['attrs'] ?? array();
			if ( 'accessible-forms/form' === $name && ( ! empty( $attrs['formId'] ) || ! empty( $attrs['formKey'] ) ) ) {
				return true;
			}

			$key = '';
			if ( 'core/block' === $name && ! empty( $attrs['ref'] ) ) {
				$key = 'block:' . absint( $attrs['ref'] );
			} elseif ( 'core/template-part' === $name && ! empty( $attrs['slug'] ) && get_stylesheet() === ( $attrs['theme'] ?? get_stylesheet() ) ) {
				$key = 'part:' . ( $attrs['theme'] ?? get_stylesheet() ) . '//' . $attrs['slug'];
			} elseif ( 'core/pattern' === $name && ! empty( $attrs['slug'] ) ) {
				$key = 'pattern:' . $attrs['slug'];
			}
			if ( $key && ! isset( $state['references'][ $key ] ) && count( $state['references'] ) < self::MAX_REFERENCES ) {
				$state['references'][ $key ] = true;
				$content = '';
				if ( 'core/block' === $name ) {
					$post = get_post( absint( $attrs['ref'] ) );
					if ( $post && 'wp_block' === $post->post_type && 'publish' === $post->post_status && empty( $post->post_password ) ) {
						$content = $post->post_content;
					}
				} elseif ( 'core/template-part' === $name ) {
					$template = get_block_template( substr( $key, 5 ), 'wp_template_part' );
					$content = $template->content ?? '';
				} elseif ( 'core/pattern' === $name ) {
					$pattern = \WP_Block_Patterns_Registry::get_instance()->get_registered( $attrs['slug'] );
					$content = $pattern['content'] ?? '';
				}
				if ( $content && self::content_contains_form( $content, $state, $depth + 1 ) ) {
					return true;
				}
			}
			if ( ! empty( $block['innerBlocks'] ) && self::blocks_contain_form( $block['innerBlocks'], $state, $depth + 1 ) ) {
				return true;
			}
		}
		return false;
	}
}