feat: add metadata url transformer

src/Url/MetadataUrlTransformer.php

@@ -0,0 +1,92 @@
+<?php
+
+namespace WPContentSync\Url;
+
+final class MetadataUrlTransformer {
+	private UrlTransformer $url_transformer;
+
+	public function __construct( UrlTransformer $url_transformer ) {
+		$this->url_transformer = $url_transformer;
+	}
+
+	/**
+	 * Transform URLs within a metadata value.
+	 *
+	 * @param mixed                $value    Metadata value.
+	 * @param UrlMappingCollection $mappings URL mappings.
+	 * @return mixed
+	 */
+	public function transformValue( $value, UrlMappingCollection $mappings ) {
+		if ( is_array( $value ) ) {
+			return $this->transformArray( $value, $mappings );
+		}
+
+		if ( ! is_string( $value ) ) {
+			return $value;
+		}
+
+		if ( $this->isSerialized( $value ) ) {
+			// phpcs:ignore -- Required to transform serialized metadata while preserving valid string lengths.
+			$unserialized = unserialize( $value, array( 'allowed_classes' => false ) );
+
+			// phpcs:ignore -- Required to reserialize metadata with updated string lengths.
+			return serialize( $this->transformValue( $unserialized, $mappings ) );
+		}
+
+		if ( $this->isJsonObjectOrArray( $value ) ) {
+			$decoded = json_decode( $value, true );
+
+			if ( is_array( $decoded ) && JSON_ERROR_NONE === json_last_error() ) {
+				$encoded = wp_json_encode( $this->transformArray( $decoded, $mappings ) );
+
+				if ( is_string( $encoded ) ) {
+					return $encoded;
+				}
+			}
+		}
+
+		return $this->url_transformer->transformString( $value, $mappings );
+	}
+
+	/**
+	 * Transform URLs within a metadata array.
+	 *
+	 * @param array<mixed>         $value    Metadata array.
+	 * @param UrlMappingCollection $mappings URL mappings.
+	 * @return array<mixed>
+	 */
+	private function transformArray( array $value, UrlMappingCollection $mappings ): array {
+		$transformed = array();
+
+		foreach ( $value as $key => $item ) {
+			$transformed[ $key ] = $this->transformValue( $item, $mappings );
+		}
+
+		return $transformed;
+	}
+
+	private function isSerialized( string $value ): bool {
+		$trimmed = trim( $value );
+
+		if ( 'N;' === $trimmed ) {
+			return true;
+		}
+
+		if ( 'b:0;' === $trimmed ) {
+			return true;
+		}
+
+		if ( ! preg_match( '/^(?:a|O|s|i|d|b):/', $trimmed ) ) {
+			return false;
+		}
+
+		// phpcs:ignore -- Validation must parse PHP serialized metadata.
+		return false !== @unserialize( $trimmed, array( 'allowed_classes' => false ) );
+	}
+
+	private function isJsonObjectOrArray( string $value ): bool {
+		$trimmed = trim( $value );
+
+		return '' !== $trimmed && in_array( $trimmed[0], array( '{', '[' ), true );
+	}
+}