<?php
/**
 * The JSON-LD graph of one page.
 *
 * @package ElevenRank
 * @since   1.0.0
 */

namespace ElevenRank\Modules\Schema;

defined( 'ABSPATH' ) || exit;

/**
 * A list of nodes that all have an `@id`, with no id used twice, and without empty properties.
 *
 * @since 1.0.0
 */
final class Graph {

	/**
	 * Nodes by `@id`, in the order they were added.
	 *
	 * @since 1.0.0
	 *
	 * @var array<string, array<string, mixed>>
	 */
	private $nodes = array();

	/**
	 * Adds a node. A node whose `@id` is already in the graph is not added again.
	 *
	 * @since 1.0.0
	 *
	 * @param array<string, mixed>|null $node Node, or null for "nothing to add".
	 * @return bool Whether the node was added.
	 */
	public function add( ?array $node ): bool {
		if ( null === $node || empty( $node['@id'] ) || ! is_string( $node['@id'] ) || isset( $this->nodes[ $node['@id'] ] ) ) {
			return false;
		}

		$clean = self::clean( $node );

		if ( ! is_array( $clean ) || ! isset( $clean['@type'] ) ) {
			return false;
		}

		$this->nodes[ $node['@id'] ] = $clean;

		return true;
	}

	/**
	 * Whether a node with this id is in the graph.
	 *
	 * @since 1.0.0
	 *
	 * @param string $id The `@id`.
	 * @return bool
	 */
	public function has( string $id ): bool {
		return isset( $this->nodes[ $id ] );
	}

	/**
	 * One node.
	 *
	 * @since 1.0.0
	 *
	 * @param string $id The `@id`.
	 * @return array<string, mixed>|null
	 */
	public function get( string $id ): ?array {
		return $this->nodes[ $id ] ?? null;
	}

	/**
	 * The nodes as a list.
	 *
	 * @since 1.0.0
	 *
	 * @return array<int, array<string, mixed>>
	 */
	public function nodes(): array {
		return array_values( $this->nodes );
	}

	/**
	 * Removes empty strings, nulls and empty lists, at every depth. Numbers, `0` and `false` stay.
	 *
	 * @since 1.0.0
	 *
	 * @param mixed $value Any value.
	 * @return mixed The cleaned value; null when nothing is left.
	 */
	public static function clean( $value ) {
		if ( is_array( $value ) ) {
			$out     = array();
			$is_list = array_keys( $value ) === range( 0, count( $value ) - 1 );

			foreach ( $value as $key => $item ) {
				$item = self::clean( $item );

				if ( null === $item ) {
					continue;
				}

				if ( $is_list ) {
					$out[] = $item;
				} else {
					$out[ $key ] = $item;
				}
			}

			return $out ? $out : null;
		}

		if ( null === $value || '' === $value ) {
			return null;
		}

		return $value;
	}
}