<?php
/**
 * Taxonomy and term helpers.
 *
 * @package SeebAbilities
 */

namespace SeebAbilities\Support;

use WP_Error;
use WP_Taxonomy;

defined( 'ABSPATH' ) || exit;

/**
 * Term helpers.
 */
final class Terms {

	/**
	 * Returns a taxonomy that is shown in the REST API.
	 *
	 * @param string $name Taxonomy name.
	 *
	 * @return WP_Taxonomy|WP_Error
	 */
	public static function taxonomy( string $name ) {

		$taxonomy = get_taxonomy( $name );

		if ( ! $taxonomy instanceof WP_Taxonomy || empty( $taxonomy->show_in_rest ) ) {
			/* translators: %s: taxonomy name */
			return Helpers::not_found( sprintf( __( 'Taxonomy "%s" does not exist or is not available.', 'seeb-abilities' ), $name ) );
		}

		return $taxonomy;
	}

	/**
	 * Resolves term IDs, slugs or names to term IDs. Integers must be existing term IDs. Strings
	 * are matched by slug, then by name, and are created when missing and the user can create terms.
	 *
	 * @param string $taxonomy Taxonomy name.
	 * @param array  $terms    Term IDs, slugs or names.
	 *
	 * @return int[]|WP_Error
	 */
	public static function resolve( string $taxonomy, array $terms ) {

		$tax_object = get_taxonomy( $taxonomy );
		$ids        = [];

		foreach ( $terms as $term ) {

			if ( is_int( $term ) ) {
				$found = get_term( $term, $taxonomy );

				if ( ! $found || is_wp_error( $found ) ) {
					/* translators: 1: term ID, 2: taxonomy name */
					return Helpers::not_found( sprintf( __( 'Term %1$d does not exist in taxonomy "%2$s".', 'seeb-abilities' ), $term, $taxonomy ) );
				}

				$ids[] = $found->term_id;
				continue;
			}

			$term = trim( (string) $term );

			if ( '' === $term ) {
				continue;
			}

			$found = get_term_by( 'slug', sanitize_title( $term ), $taxonomy );

			if ( ! $found ) {
				$found = get_term_by( 'name', $term, $taxonomy );
			}

			if ( $found ) {
				$ids[] = $found->term_id;
				continue;
			}

			if ( ! current_user_can( $tax_object->cap->edit_terms ) ) {
				/* translators: 1: term name, 2: taxonomy name */
				return Helpers::forbidden( sprintf( __( 'Term "%1$s" does not exist in taxonomy "%2$s" and you are not allowed to create it.', 'seeb-abilities' ), $term, $taxonomy ) );
			}

			$created = wp_insert_term( wp_slash( $term ), $taxonomy );

			if ( is_wp_error( $created ) ) {
				return $created;
			}

			$ids[] = (int) $created['term_id'];
		}

		return array_values( array_unique( $ids ) );
	}

	/**
	 * Checks that the user can assign terms of the taxonomy to posts of the post type.
	 *
	 * @param string $taxonomy  Taxonomy name.
	 * @param string $post_type Post type.
	 *
	 * @return true|WP_Error
	 */
	public static function check_assign( string $taxonomy, string $post_type ) {

		$tax_object = self::taxonomy( $taxonomy );

		if ( is_wp_error( $tax_object ) ) {
			return $tax_object;
		}

		if ( ! is_object_in_taxonomy( $post_type, $taxonomy ) ) {
			/* translators: 1: taxonomy name, 2: post type */
			return Helpers::error( 'invalid_taxonomy', sprintf( __( 'Taxonomy "%1$s" is not registered for post type "%2$s".', 'seeb-abilities' ), $taxonomy, $post_type ) );
		}

		if ( ! current_user_can( $tax_object->cap->assign_terms ) ) {
			/* translators: %s: taxonomy name */
			return Helpers::forbidden( sprintf( __( 'You are not allowed to assign terms of taxonomy "%s".', 'seeb-abilities' ), $taxonomy ) );
		}

		return true;
	}

	/**
	 * Sets terms of several taxonomies on a post.
	 *
	 * @param int   $post_id Post ID.
	 * @param array $terms   Term IDs, slugs or names keyed by taxonomy.
	 * @param bool  $append  Whether to keep the existing terms.
	 *
	 * @return true|WP_Error
	 */
	public static function set_post_terms( int $post_id, array $terms, bool $append = false ) {

		$post_type = (string) get_post_type( $post_id );

		foreach ( $terms as $taxonomy => $values ) {

			$check = self::check_assign( (string) $taxonomy, $post_type );

			if ( is_wp_error( $check ) ) {
				return $check;
			}

			$ids = self::resolve( (string) $taxonomy, (array) $values );

			if ( is_wp_error( $ids ) ) {
				return $ids;
			}

			$result = wp_set_object_terms( $post_id, $ids, (string) $taxonomy, $append );

			if ( is_wp_error( $result ) ) {
				return $result;
			}
		}

		return true;
	}
}