<form method="POST">
    <h3>Editing: SingleProductTemplate.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php
namespace Automattic\WooCommerce\Blocks\Templates;

use Automattic\WooCommerce\Blocks\Templates\SingleProductTemplateCompatibility;
use Automattic\WooCommerce\Blocks\Utils\BlockTemplateUtils;

/**
 * SingleProductTemplate class.
 *
 * @internal
 */
class SingleProductTemplate extends AbstractTemplate {

	/**
	 * The slug of the template.
	 *
	 * @var string
	 */
	const SLUG = 'single-product';

	/**
	 * Initialization method.
	 */
	public function init() {
		add_action( 'template_redirect', array( $this, 'render_block_template' ) );
		add_filter( 'get_block_templates', array( $this, 'update_single_product_content' ), 11, 3 );
	}

	/**
	 * Returns the title of the template.
	 *
	 * @return string
	 */
	public function get_template_title() {
		return _x( 'Single Product', 'Template name', 'woocommerce' );
	}

	/**
	 * Returns the description of the template.
	 *
	 * @return string
	 */
	public function get_template_description() {
		return __( 'Displays a single product.', 'woocommerce' );
	}

	/**
	 * Renders the default block template from Woo Blocks if no theme templates exist.
	 */
	public function render_block_template() {
		if ( ! is_embed() &amp;&amp; is_singular( 'product' ) ) {
			global $post;

			$valid_slugs = array( self::SLUG );
			if ( 'product' === $post-&gt;post_type &amp;&amp; $post-&gt;post_name ) {
				$valid_slugs[] = 'single-product-' . $post-&gt;post_name;
			}
			$templates = get_block_templates( array( 'slug__in' =&gt; $valid_slugs ) );

			if ( isset( $templates[0] ) &amp;&amp; BlockTemplateUtils::template_has_legacy_template_block( $templates[0] ) ) {
				add_filter( 'woocommerce_disable_compatibility_layer', '__return_true' );
			}

			add_filter( 'woocommerce_has_block_template', '__return_true', 10, 0 );
		}
	}

	/**
	 * Add the block template objects to be used.
	 *
	 * @param array  $query_result Array of template objects.
	 * @param array  $query Optional. Arguments to retrieve templates.
	 * @param string $template_type wp_template or wp_template_part.
	 * @return array
	 */
	public function update_single_product_content( $query_result, $query, $template_type ) {
		$query_result = array_map(
			function ( $template ) {
				if ( str_contains( $template-&gt;slug, self::SLUG ) ) {
					// We don't want to add the compatibility layer on the Editor Side.
					// The second condition is necessary to not apply the compatibility layer on the REST API. Gutenberg uses the REST API to clone the template.
					// More details: https://github.com/woocommerce/woocommerce-blocks/issues/9662.
					if ( ( ! is_admin() &amp;&amp; ! ( defined( 'REST_REQUEST' ) &amp;&amp; REST_REQUEST ) ) &amp;&amp; ! BlockTemplateUtils::template_has_legacy_template_block( $template ) ) {
						// Add the product class to the body. We should move this to a more appropriate place.
						add_filter(
							'body_class',
							function ( $classes ) {
								return array_merge( $classes, wc_get_product_class() );
							}
						);

						global $product;

						if ( ! $product instanceof \WC_Product ) {
							$product_id = get_the_ID();
							if ( $product_id ) {
								wc_setup_product_data( $product_id );
							}
						}

						if ( post_password_required() ) {
							$template-&gt;content = $this-&gt;add_password_form( $template-&gt;content );
						} else {
							$template-&gt;content = SingleProductTemplateCompatibility::add_compatibility_layer( $template-&gt;content );
						}
					}
				}
				return $template;
			},
			$query_result
		);
		return $query_result;
	}

	/**
	 * Replace the first single product template block with the password form. Remove all other single product template blocks.
	 *
	 * @param array   $parsed_blocks Array of parsed block objects.
	 * @param boolean $is_already_replaced If the password form has already been added.
	 * @return array Parsed blocks
	 */
	private static function replace_first_single_product_template_block_with_password_form( $parsed_blocks, $is_already_replaced ) {
		// We want to replace the first single product template block with the password form. We also want to remove all other single product template blocks.
		// This array doesn't contains all the blocks. For example, it missing the breadcrumbs blocks: it doesn't make sense replace the breadcrumbs with the password form.
		$single_product_template_blocks = array( 'woocommerce/product-image-gallery', 'woocommerce/product-details', 'woocommerce/add-to-cart-form', 'woocommerce/product-meta', 'woocommerce/product-rating', 'woocommerce/product-price', 'woocommerce/related-products' );
		return array_reduce(
			$parsed_blocks,
			function ( $carry, $block ) use ( $single_product_template_blocks ) {
				if ( in_array( $block['blockName'], $single_product_template_blocks, true ) ) {
					if ( $carry['is_already_replaced'] ) {
						return array(
							'blocks'              =&gt; $carry['blocks'],
							'html_block'          =&gt; null,
							'removed'             =&gt; true,
							'is_already_replaced' =&gt; true,

						);
					}

					return array(
						'blocks'              =&gt; $carry['blocks'],
						'html_block'          =&gt; parse_blocks( '&lt;!-- wp:html --&gt;' . get_the_password_form() . '&lt;!-- /wp:html --&gt;' )[0],
						'removed'             =&gt; false,
						'is_already_replaced' =&gt; $carry['is_already_replaced'],
					);

				}

				if ( isset( $block['innerBlocks'] ) &amp;&amp; count( $block['innerBlocks'] ) &gt; 0 ) {
					$index              = 0;
					$new_inner_blocks   = array();
					$new_inner_contents = $block['innerContent'];
					foreach ( $block['innerContent'] as $inner_content ) {
						// Don't process the closing tag of the block.
						if ( count( $block['innerBlocks'] ) === $index ) {
							break;
						}

						$blocks                       = self::replace_first_single_product_template_block_with_password_form( array( $block['innerBlocks'][ $index ] ), $carry['is_already_replaced'] );
						$new_blocks                   = $blocks['blocks'];
						$html_block                   = $blocks['html_block'];
						$is_removed                   = $blocks['removed'];
						$carry['is_already_replaced'] = $blocks['is_already_replaced'];

						if ( isset( $html_block ) ) {
							$new_inner_blocks             = array_merge( $new_inner_blocks, $new_blocks, array( $html_block ) );
							$carry['is_already_replaced'] = true;
						} else {
							$new_inner_blocks = array_merge( $new_inner_blocks, $new_blocks );
						}

						if ( $is_removed ) {
							unset( $new_inner_contents[ $index ] );
							// The last element of the inner contents contains the closing tag of the block. We don't want to remove it.
							if ( $index + 1 &lt; count( $new_inner_contents ) ) {
								unset( $new_inner_contents[ $index + 1 ] );
							}
							$new_inner_contents = array_values( $new_inner_contents );
						}

						$index++;
					}

					$block['innerBlocks']  = $new_inner_blocks;
					$block['innerContent'] = $new_inner_contents;

					return array(
						'blocks'              =&gt; array_merge( $carry['blocks'], array( $block ) ),
						'html_block'          =&gt; null,
						'removed'             =&gt; false,
						'is_already_replaced' =&gt; $carry['is_already_replaced'],
					);
				}

				return array(
					'blocks'              =&gt; array_merge( $carry['blocks'], array( $block ) ),
					'html_block'          =&gt; null,
					'removed'             =&gt; false,
					'is_already_replaced' =&gt; $carry['is_already_replaced'],
				);
			},
			array(
				'blocks'              =&gt; array(),
				'html_block'          =&gt; null,
				'removed'             =&gt; false,
				'is_already_replaced' =&gt; $is_already_replaced,
			)
		);
	}

	/**
	 * Add password form to the Single Product Template.
	 *
	 * @param string $content The content of the template.
	 * @return string
	 */
	public static function add_password_form( $content ) {
		$parsed_blocks     = parse_blocks( $content );
		$blocks            = self::replace_first_single_product_template_block_with_password_form( $parsed_blocks, false );
		$serialized_blocks = serialize_blocks( $blocks['blocks'] );

		return $serialized_blocks;
	}
}
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