<?php
/**
 * A six-digit code sent to the account's email address.
 *
 * @package Adminkeep
 */

namespace Adminkeep\Service\TwoFactor;

use Adminkeep\Service\HtmlEmail;
use WP_User;

defined( 'ABSPATH' ) || exit;

/**
 * The email method.
 *
 * Six digits because that is what people expect from a code and what they can read off a phone
 * notification. Ten minutes and five tries (PendingLogin) make a million combinations a poor bet.
 * The email goes through wp_mail(), so the SMTP feature delivers it. The layout is built here from
 * the same template Nice Emails uses, so the code email looks the same with that feature on or off.
 */
class EmailCode implements Method {

	/** Digits in a code. */
	const LENGTH = 6;

	/**
	 * Identifier.
	 *
	 * @return string
	 */
	public function id() {
		return 'email';
	}

	/**
	 * Label.
	 *
	 * @return string
	 */
	public function label() {
		return __( 'Email code', 'adminkeep' );
	}

	/**
	 * A fresh code, zero-padded.
	 *
	 * @return string
	 */
	public function generate() {
		return str_pad( (string) random_int( 0, ( 10 ** self::LENGTH ) - 1 ), self::LENGTH, '0', STR_PAD_LEFT );
	}

	/**
	 * Hash a code with the pending-login token as salt, so the same code in two pending logins
	 * stores as two different values.
	 *
	 * @param string $secret The code.
	 * @param string $token  The token.
	 * @return string
	 */
	public function hash( $secret, $token ) {
		return wp_hash( $token . ':' . $secret, 'auth' );
	}

	/**
	 * Compare in constant time. Spaces are dropped first because people type "123 456".
	 *
	 * @param mixed  $input What was posted.
	 * @param string $hash  Stored hash.
	 * @param string $token The token.
	 * @return bool
	 */
	public function verify( $input, $hash, $token ) {
		if ( ! is_scalar( $input ) ) {
			return false;
		}

		$code = preg_replace( '/\s+/', '', (string) $input );

		if ( 1 !== preg_match( '/^[0-9]{' . self::LENGTH . '}$/', $code ) ) {
			return false;
		}

		return hash_equals( (string) $hash, $this->hash( $code, $token ) );
	}

	/**
	 * Email the code.
	 *
	 * @param WP_User $user The user.
	 * @param string  $code The code.
	 * @return bool Whether wp_mail() reported success.
	 */
	public function send( WP_User $user, $code ) {
		$site = wp_specialchars_decode( get_bloginfo( 'name' ), ENT_QUOTES );

		/* translators: %s: site name. */
		$subject = sprintf( __( '[%s] Your login code', 'adminkeep' ), $site );

		$minutes = (int) ( PendingLogin::TTL / 60 );

		$text = sprintf(
			/* translators: 1: user display name, 2: the code, 3: minutes the code is valid, 4: site name. */
			__( "Hi %1\$s,\n\nYour login code is:\n\n%2\$s\n\nIt is good for %3\$d minutes and works once. If you did not just enter your password on %4\$s, you can ignore this email; nobody is signed in without the code.", 'adminkeep' ),
			$user->display_name,
			$code,
			$minutes,
			$site
		);

		// Always the Nice Default Emails layout, whether or not that feature is on: it is built
		// here from the same template, and declaring HTML keeps Nice Emails from wrapping it
		// again. A body the template cannot escape (HtmlEmail::body() returns '') falls back to
		// the plain text rather than sending nothing.
		$body    = HtmlEmail::body( $text );
		$message = '' === $body ? $text : HtmlEmail::document( $body );
		$headers = '' === $body ? array() : array( 'Content-Type: text/html; charset=' . get_bloginfo( 'charset' ) );

		// The Email Log drops the body of a message carrying this header (MailRow), so a login
		// code is never readable from the log table.
		$headers[] = 'X-Adminkeep-Secret: 1';

		return (bool) wp_mail( $user->user_email, $subject, $message, $headers );
	}
}