Decorator pattern for serializing blocks

gb5187.php

<?php

// https://github.com/WordPress/wordpress-develop/pull/5187

namespace GH5187;

interface Block_Content {
	public function content( string $content, array $block ): string;
}

final class Serialized_Blocks {
	public function __construct(
		private readonly array $blocks,
		private Block_Content $content,
	) {}

	public function serialized(): string {
		$result = '';
		foreach ( $this->blocks as $block ) {
			$result .= $this->block( $block );
		};
		return $result;
	}

	private function block( $block ): string {
		if ( ! is_array( $block['attrs'] ) ) {
			$block['attrs'] = array();
		}

		$block_content = '';

		$index = 0;

		foreach ( $block['innerContent'] as $chunk ) {
			$block_content .= is_string( $chunk ) ? $chunk : $this->block( $block['innerBlocks'][ $index++ ] );
		}

		return $this->content->content( $block_content, $block );
	}
}

class Callback implements Block_Content {
	public function __construct(
		private $callback,
		private Block_Content $origin,
	) {}

	public function content( string $content, array $block ): string {
		$block = call_user_func( $this->callback, $block );

		return $this->origin->content( $content, $block );
	}
}

class Delimited implements Block_Content {
	public function content( string $content, array $block ): string {
		return get_comment_delimited_block_content(
			$block['blockName'],
			$block['attrs'],
			$content,
		);
	}
}

/*
$blocks = [...];

$content.   = new Serialized_Blocks( $blocks, new Delimited() );
$serialized = $content->serialized();

$fn         = fn ( array $block ) => ...;
$content    = new Serialized_Blocks( $blocks, new Callback( $fn, new Delimited() ) );
$serialized = new $content->serialized();
*/