inside any techarticle section if CLASS_CODE missing.
		if ( empty( $data['code'] ) ) {
			foreach ( [ self::CLASS_STEPS, self::CLASS_GOAL, self::CLASS_CONTEXT ] as $section_class ) {
				$root = self::first_class_node( $xpath, $section_class );
				if ( ! $root ) {
					continue;
				}
				foreach ( $xpath->query( './/pre//code', $root ) as $code_node ) {
					$text = self::node_text( $code_node );
					if ( '' !== $text ) {
						$data['code'][] = [ 'text' => $text, 'language' => 'php' ];
					}
				}
			}
		}

		return SlotBag::from_array( $data );
	}

	/**
	 * @param array $data Slot array.
	 */
	public static function slots_from_array( array $data ): SlotBag {
		return SlotBag::from_array( $data );
	}

	/**
	 * Build TechArticle JSON-LD from page context + slots.
	 *
	 * @param array $context headline, url, dates, author, image, about, @id.
	 * @return array
	 */
	public static function to_schema( array $context, SlotBag $slots ): array {
		if ( ! $slots->has_required() ) {
			return [];
		}

		$has_part = [];
		foreach ( $slots->code as $sample ) {
			$has_part[] = [
				'@type'               => 'SoftwareSourceCode',
				'codeSampleType'      => 'full',
				'programmingLanguage' => $sample['language'] ?? 'php',
				'text'                => $sample['text'],
			];
		}

		$howto_steps = [];
		foreach ( $slots->steps as $step ) {
			$entry = [
				'@type' => 'HowToStep',
				'text'  => $step['text'],
			];
			if ( ! empty( $step['name'] ) ) {
				$entry['name'] = $step['name'];
			}
			$howto_steps[] = $entry;
		}

		$howto = [
			'@type' => 'HowTo',
			'step'  => $howto_steps,
		];
		if ( '' !== $slots->goal ) {
			$howto['name'] = $slots->goal;
		}
		$has_part[] = $howto;

		$schema = [
			'@context' => 'https://schema.org',
			'@type'    => 'TechArticle',
			'headline' => (string) ( $context['headline'] ?? '' ),
			'url'      => (string) ( $context['url'] ?? '' ),
			'hasPart'  => $has_part,
		];

		if ( ! empty( $context['@id'] ) ) {
			$schema['@id'] = (string) $context['@id'];
		}
		if ( ! empty( $context['datePublished'] ) ) {
			$schema['datePublished'] = (string) $context['datePublished'];
		}
		if ( ! empty( $context['dateModified'] ) ) {
			$schema['dateModified'] = (string) $context['dateModified'];
		}
		if ( ! empty( $context['author'] ) ) {
			$schema['author'] = $context['author'];
		}
		if ( ! empty( $context['image'] ) ) {
			$schema['image'] = $context['image'];
		}
		if ( ! empty( $context['about'] ) ) {
			$schema['about'] = $context['about'];
		}
		if ( '' !== $slots->goal ) {
			$schema['description'] = $slots->goal;
		} elseif ( '' !== $slots->context ) {
			$schema['description'] = $slots->context;
		}
		if ( '' !== $slots->issues ) {
			$schema['additionalProperty'] = [
				[
					'@type' => 'PropertyValue',
					'name'  => 'commonMistakes',
					'value' => $slots->issues,
				],
			];
		}

		/**
		 * Filter assembled TechArticle schema (mapper path).
		 *
		 * @param array $schema  Schema.
		 * @param array $context Context.
		 * @param SlotBag              $slots   Slots.
		 */
		return apply_filters( 'forwp_seo_techarticle_mapper_schema', $schema, $context, $slots );
	}

	/**
	 * @param array> $blocks Blocks.
	 * @return array>
	 */
	private static function flatten_blocks( array $blocks ): array {
		$flat = [];
		foreach ( $blocks as $block ) {
			$flat[] = $block;
			if ( ! empty( $block['innerBlocks'] ) ) {
				$flat = array_merge( $flat, self::flatten_blocks( $block['innerBlocks'] ) );
			}
		}
		return $flat;
	}

	private static function plain( string $html ): string {
		return trim( wp_strip_all_tags( $html ) );
	}

	/**
	 * @param array> $blocks Inner blocks.
	 */
	private static function plain_from_inner( array $blocks ): string {
		$parts = [];
		foreach ( $blocks as $block ) {
			$name = $block['blockName'] ?? '';
			$html = $block['innerHTML'] ?? '';
			if ( in_array( $name, [ 'core/heading', 'core/paragraph', 'core/list', 'core/code' ], true ) ) {
				$text = self::plain( (string) $html );
				if ( '' !== $text ) {
					$parts[] = $text;
				}
			}
			if ( ! empty( $block['innerBlocks'] ) ) {
				$child = self::plain_from_inner( $block['innerBlocks'] );
				if ( '' !== $child ) {
					$parts[] = $child;
				}
			}
		}
		return trim( implode( "\n", $parts ) );
	}

	private static function first_class_text( \DOMXPath $xpath, string $class ): string {
		$node = self::first_class_node( $xpath, $class );
		if ( ! $node ) {
			return '';
		}

		$parts = [];
		foreach ( $xpath->query( './p|./ul/li|./ol/li|.//p[not(ancestor::*[contains(@class,"forwp-seo-techarticle-step")])]', $node ) as $child ) {
			$text = self::node_text( $child );
			if ( '' !== $text ) {
				$parts[] = $text;
			}
		}

		if ( ! empty( $parts ) ) {
			return trim( implode( ' ', $parts ) );
		}

		// Clone without headings / nested code for a clean fallback.
		$clone = $node->cloneNode( true );
		if ( $clone instanceof \DOMElement ) {
			$headings = [];
			foreach ( $clone->getElementsByTagName( '*' ) as $el ) {
				$tag = strtolower( $el->tagName );
				if ( in_array( $tag, [ 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'pre', 'code' ], true ) ) {
					$headings[] = $el;
				}
			}
			foreach ( $headings as $el ) {
				if ( $el->parentNode ) {
					$el->parentNode->removeChild( $el );
				}
			}
			return self::node_text( $clone );
		}

		return self::node_text( $node );
	}

	private static function first_class_node( \DOMXPath $xpath, string $class ): ?\DOMNode {
		$nodes = self::nodes_by_class( $xpath, $class );
		return $nodes[0] ?? null;
	}

	/**
	 * @return array
	 */
	private static function nodes_by_class( \DOMXPath $xpath, string $class ): array {
		$safe = addcslashes( $class, '"\\' );
		$list = $xpath->query(
			'//*[@id="forwp-seo-root"]//*[contains(concat(" ", normalize-space(@class), " "), " ' . $safe . ' ")]'
		);
		if ( ! $list ) {
			return [];
		}
		$out = [];
		foreach ( $list as $node ) {
			$out[] = $node;
		}
		return $out;
	}

	private static function node_text( \DOMNode $node ): string {
		return trim( preg_replace( '/\s+/u', ' ', $node->textContent ?? '' ) ?? '' );
	}

	/**
	 * Step text without nested code samples.
	 */
	private static function step_text( \DOMXPath $xpath, \DOMNode $node ): string {
		$parts = [];
		foreach ( $xpath->query( './/h3|.//h4|.//p[not(ancestor::pre)]', $node ) as $child ) {
			// Skip if inside a code wrapper.
			$parent = $child->parentNode;
			$skip   = false;
			while ( $parent instanceof \DOMElement ) {
				$class = $parent->getAttribute( 'class' );
				if ( false !== strpos( ' ' . $class . ' ', ' ' . self::CLASS_CODE . ' ' ) ) {
					$skip = true;
					break;
				}
				$parent = $parent->parentNode;
			}
			if ( $skip ) {
				continue;
			}
			$text = self::node_text( $child );
			if ( '' !== $text ) {
				$parts[] = $text;
			}
		}

		if ( ! empty( $parts ) ) {
			return trim( implode( ': ', array_unique( $parts ) ) );
		}

		$clone = $node->cloneNode( true );
		if ( $clone instanceof \DOMElement ) {
			$remove = [];
			foreach ( $clone->getElementsByTagName( '*' ) as $el ) {
				$class = $el instanceof \DOMElement ? $el->getAttribute( 'class' ) : '';
				$tag   = strtolower( $el->tagName );
				if ( 'pre' === $tag || 'code' === $tag || false !== strpos( ' ' . $class . ' ', ' ' . self::CLASS_CODE . ' ' ) ) {
					$remove[] = $el;
				}
			}
			foreach ( $remove as $el ) {
				if ( $el->parentNode ) {
					$el->parentNode->removeChild( $el );
				}
			}
			return self::node_text( $clone );
		}

		return self::node_text( $node );
	}

	/**
	 * Prefer /
 text when CLASS_CODE is on a section wrapper.
	 */
	private static function code_text( \DOMXPath $xpath, \DOMNode $node ): string {
		foreach ( $xpath->query( './/pre//code|.//code', $node ) as $code_node ) {
			$text = self::node_text( $code_node );
			if ( '' !== $text ) {
				return $text;
			}
		}
		return self::node_text( $node );
	}
}