<?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->looksSerialized( trim( $value ) ) && trim( $value ) !== $value ) {
			return $value;
		}

		if ( $this->looksSerialized( $value ) ) {
			$unserialized = $this->unserializeValue( $value );

			if ( ! $unserialized['valid'] || $this->containsObject( $unserialized['value'] ) ) {
				return $value;
			}

			// phpcs:ignore -- Required to reserialize metadata with updated string lengths.
			return serialize( $this->transformValue( $unserialized['value'], $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 $value;
		}

		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 looksSerialized( string $value ): bool {
		return 'N;' === $value || 'b:0;' === $value || 1 === preg_match( '/^(?:a|O|s|i|d|b):/', $value );
	}

	/**
	 * @return array{valid: bool, value: mixed}
	 */
	private function unserializeValue( string $value ): array {
		if ( 'N;' === $value ) {
			return array(
				'valid' => true,
				'value' => null,
			);
		}

		// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged, WordPress.PHP.DiscouragedPHPFunctions.serialize_unserialize -- Metadata may be stored in PHP serialized format.
		$unserialized = @unserialize( $value, array( 'allowed_classes' => false ) );

		if ( false === $unserialized && 'b:0;' !== $value ) {
			return array(
				'valid' => false,
				'value' => null,
			);
		}

		// phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.serialize_serialize -- Strict validation avoids transforming malformed serialized-looking strings.
		if ( serialize( $unserialized ) !== $value ) {
			return array(
				'valid' => false,
				'value' => null,
			);
		}

		return array(
			'valid' => true,
			'value' => $unserialized,
		);
	}

	private function isJsonObjectOrArray( string $value ): bool {
		$trimmed = trim( $value );

		return '' !== $trimmed && in_array( $trimmed[0], array( '{', '[' ), true );
	}

	/**
	 * @param mixed $value Value to inspect.
	 */
	private function containsObject( $value ): bool {
		if ( is_object( $value ) ) {
			return true;
		}

		if ( ! is_array( $value ) ) {
			return false;
		}

		foreach ( $value as $item ) {
			if ( $this->containsObject( $item ) ) {
				return true;
			}
		}

		return false;
	}
}