<?php
/**
 * Custom GeoJSON properties for feed features.
 *
 * @package Mapsemble
 */

namespace Mapsemble\Feed;

use Mapsemble\MapConfig;

/**
 * Resolves a map's property rows against one post.
 *
 * The values feed Mapsemble's marker-style rules, so the shapes mirror
 * what the Drupal module emits: a meta value as a string, taxonomy terms
 * as one slug or a list of slugs, and nothing at all when a value is
 * empty — a style rule matching "absent" is how "no value" is styled.
 */
class CustomProperties {

	/**
	 * The custom properties for one post.
	 *
	 * @param MapConfig $config  The map.
	 * @param int       $post_id Post id.
	 * @return array<string, string|string[]>
	 */
	public function for_post( MapConfig $config, int $post_id ): array {
		$properties = array();

		foreach ( $config->properties as $row ) {
			if ( ! is_array( $row ) ) {
				continue;
			}
			$name = (string) ( $row['property'] ?? '' );
			$ref  = FieldRef::parse( $row['field'] ?? null );
			if ( '' === $name || null === $ref ) {
				continue;
			}

			$value = FieldRef::KIND_TAX === $ref['kind']
				? $this->term_slugs( $post_id, $ref['name'] )
				: $this->meta_value( $post_id, $ref['name'] );

			if ( null !== $value ) {
				$properties[ $name ] = $value;
			}
		}

		return $properties;
	}

	/**
	 * A post's terms in one taxonomy, flattened when single.
	 *
	 * @param int    $post_id  Post id.
	 * @param string $taxonomy Taxonomy name.
	 * @return string|string[]|null
	 */
	private function term_slugs( int $post_id, string $taxonomy ) {
		$terms = get_the_terms( $post_id, $taxonomy );
		if ( ! is_array( $terms ) || array() === $terms ) {
			return null;
		}
		$slugs = array_map(
			static fn( \WP_Term $term ): string => (string) $term->slug,
			$terms
		);
		return 1 === count( $slugs ) ? $slugs[0] : array_values( $slugs );
	}

	/**
	 * A post's meta value as a string, or null when empty.
	 *
	 * @param int    $post_id Post id.
	 * @param string $key     Meta key.
	 */
	private function meta_value( int $post_id, string $key ): ?string {
		$value = get_post_meta( $post_id, $key, true );
		if ( ! is_scalar( $value ) || '' === (string) $value ) {
			return null;
		}
		return (string) $value;
	}
}