<?php

class GTM_Block_Style {
	private static $instance;
	public $block_styles = [];

	public static function get_instance() {
		if ( ! self::$instance ) {
			self::$instance = new self();
		}

		return self::$instance;
	}

	public function __construct() {
	}

	public function init() {
		add_filter( 'render_block', [$this, 'render_block'], 10, 2 );

		// Ideally styles should be loaded in the head, but blocks may be parsed
		// after that, so loading in the footer for now.
		// See https://core.trac.wordpress.org/ticket/53494.
		add_filter( 'wp_head', [$this, 'render_css'], 11 );
	}

	public function render_block( $block_content, $block ) {
		$block_type = WP_Block_Type_Registry::get_instance()->get_registered( $block['blockName'] );

		// Some blocks has no block stype (such as "core/comments-query-loop"), can skip it.
		// Some blocks has no attrs (core/page-list)
		if ( ! empty( $block_type ) && isset( $block['attrs'] ) ) {
			$attrs       = gtm_apply_block_attribute_defaults( $block['attrs'], $block_type->attributes );
			$block_style = gtm_do_compile_block_style( $block_type, $attrs );

			if ( $block_style !== false ) {

				// Add basic class for using in higher specificity
				// Only in case of the block has some style to be rendered
				if ( ! empty( $block_style['classes'] ) ) {
					array_unshift( $block_style['classes'], 'gtm-style' );
				}

				// Add style id class if there are some style to be rendered
				$style_class = wp_unique_id( 'gtm-style-' );
				if ( ! empty( $block_style['style'] ) ) {
					array_unshift( $block_style['classes'], $style_class );
				}

				if ( ! empty( $block_style['style'] ) ) {
					// Replace block id
					$styles = [];
					foreach ( $block_style['style'] as $selector => $props ) {
						$selector          = str_replace( '{{BLOCK}}', '.' . $style_class . '{{BLOCK}}:not(#\9)', $selector );
						$styles[$selector] = $props;
					}

					$this->block_styles[] = $styles;
				}

				// This assumes the hook only applies to blocks with a single wrapper.
				// I think this is a reasonable limitation for that particular hook.
				if ( ! empty( $block_style['classes'] ) ) {
					$block_content = preg_replace(
						'/' . preg_quote( 'class="', '/' ) . '([^"]*)"/',
						'class="$1 ' . implode( ' ', $block_style['classes'] ) . '"',
						$block_content,
						1
					);
				}
			}
		}

		return $block_content;
	}

	public function render_css() {
		if ( ! empty( $this->block_styles ) ) {
			// Merge all style to single media query
			$all_styles = [];
			foreach ( $this->block_styles as $block_style ) {
				$all_styles = array_merge_recursive( $all_styles, $block_style );
			}

			echo '<style id="gtm-block-styles">';
			$css_template = gtm_css_compileCssTemplate( $all_styles );
			echo wp_strip_all_tags( gtm_css_generateCss( $css_template, ['suppress-import' => false] ) );
			echo '</style>';
		}
	}
}