<?php
/**
 * Parser for the excluded-posts settings field.
 *
 * @package Postlinkly
 * @since   1.13.0
 */

declare(strict_types=1);

namespace Postlinkly\Settings;

/**
 * Turns the excluded-posts field's free text into post IDs.
 *
 * The field accepts post IDs and post URLs in the same box, separated by
 * commas or newlines. URLs exist because an ID is not something a site
 * owner has to hand: excluding a post by ID means hunting for it in the
 * admin first, while its URL is usually already in the clipboard. On a
 * site with thousands of posts that difference decides whether the
 * setting gets used at all.
 *
 * URLs are resolved to IDs here, at save time, and only the IDs are
 * stored. An ID keeps pointing at the same post after a slug change,
 * where a stored URL would quietly stop matching — so an exclusion set up
 * today still holds after the post is renamed tomorrow.
 *
 * @since 1.13.0
 */
final class ExcludedPostsParser {

	/**
	 * Parses the raw field value into post IDs.
	 *
	 * Anything that is not a plain number is treated as a URL and resolved
	 * with `url_to_postid()`. Entries that resolve to nothing are returned
	 * separately rather than dropped: a silently discarded entry leaves the
	 * owner believing a post is excluded when it is not, and the only way
	 * they would find out is by seeing it suggested again.
	 *
	 * @since 1.13.0
	 *
	 * @param string $raw Raw field value.
	 *
	 * @return array{ids: array<int, int>, unresolved: array<int, string>}
	 *         Resolved post IDs in input order with duplicates collapsed,
	 *         and the entries that could not be resolved.
	 */
	public static function parse( string $raw ): array {
		$parts = preg_split( '/[\s,]+/', $raw );
		if ( false === $parts ) {
			return array(
				'ids'        => array(),
				'unresolved' => array(),
			);
		}

		$ids        = array();
		$unresolved = array();

		foreach ( $parts as $part ) {
			$part = trim( $part );
			if ( '' === $part ) {
				continue;
			}

			if ( 1 === preg_match( '/^[0-9]+$/', $part ) ) {
				$id = (int) $part;
				if ( $id > 0 ) {
					$ids[ $id ] = true;
				}
				continue;
			}

			$id = function_exists( 'url_to_postid' ) ? (int) url_to_postid( $part ) : 0;
			if ( $id > 0 ) {
				$ids[ $id ] = true;
				continue;
			}

			$unresolved[ $part ] = true;
		}

		return array(
			// Keys carried the de-duplication; the caller wants a plain list.
			'ids'        => array_map( 'intval', array_keys( $ids ) ),
			'unresolved' => array_keys( $unresolved ),
		);
	}
}