<?php
declare(strict_types=1);

namespace WebCalendar\WP;

defined( 'ABSPATH' ) || exit;

/**
 * Manages per-user iCal feed tokens stored in wp_usermeta.
 */
class FeedTokenManager {

	private const META_KEY     = 'webcal_feed_token';
	private const TOKEN_LENGTH = 32;

	/**
	 * Get the feed token for a user, creating one if it doesn't exist.
	 *
	 * @param int $user_id WordPress user ID.
	 * @return string 32-character alphanumeric token.
	 */
	public function get_token( int $user_id ): string {
		$token = get_user_meta( $user_id, self::META_KEY, true );
		if ( is_string( $token ) && strlen( $token ) === self::TOKEN_LENGTH ) {
			return $token;
		}

		return $this->regenerate_token( $user_id );
	}

	/**
	 * Replace the feed token for a user and return the new one.
	 *
	 * @param int $user_id WordPress user ID.
	 * @return string New 32-character alphanumeric token.
	 */
	public function regenerate_token( int $user_id ): string {
		$token = wp_generate_password( self::TOKEN_LENGTH, false, false );
		update_user_meta( $user_id, self::META_KEY, $token );
		return $token;
	}

	/**
	 * Look up the user ID for a given feed token.
	 *
	 * @param string $token Feed token to look up.
	 * @return int|null User ID if found, null otherwise.
	 */
	public function get_user_id_by_token( string $token ): ?int {
		if ( strlen( $token ) !== self::TOKEN_LENGTH ) {
			return null;
		}

		/** @var array<int|string> $users */
		$users = get_users(
			[
				'meta_key'   => self::META_KEY,
				'meta_value' => $token,
				'number'     => 1,
				'fields'     => 'ID',
			]
		);

		if ( empty( $users ) ) {
			return null;
		}

		$id = reset( $users );
		return is_numeric( $id ) ? (int) $id : null;
	}

	/**
	 * Delete the feed token for a user.
	 *
	 * @param int $user_id WordPress user ID.
	 */
	public function delete_token( int $user_id ): void {
		delete_user_meta( $user_id, self::META_KEY );
	}
}