<?php
/**
 * Sends a test email and explains the result.
 *
 * @package ForensixDigital
 */

declare(strict_types=1);

namespace ForensixDigital\Apps\Mail;

defined( 'ABSPATH' ) || exit;

/**
 * The test goes to the address of the person who clicked, never to a free-form address. Only
 * the server's own replies are kept from the SMTP conversation, so the password cannot leak.
 */
final class TestMail {

	public const LAST = 'forensix_mail_last_test';

	/**
	 * Sends the test.
	 *
	 * @param string $to Recipient.
	 * @return array{ok: bool, message: string, details: array<int, string>}
	 */
	public static function send( string $to ): array {
		$error   = '';
		$replies = array();

		// phpcs:disable WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase -- PHPMailer's own property names.
		$capture = static function ( \WP_Error $failure ) use ( &$error ): void {
			$error = $failure->get_error_message();
		};
		$listen  = static function ( $phpmailer ) use ( &$replies ): void {
			if ( ! $phpmailer instanceof \PHPMailer\PHPMailer\PHPMailer || 'smtp' !== $phpmailer->Mailer ) {
				return;
			}
			$phpmailer->SMTPDebug   = 2;
			$phpmailer->Debugoutput = static function ( $line ) use ( &$replies ): void {
				$line = trim( (string) $line );
				if ( str_contains( $line, 'SERVER -> CLIENT:' ) ) {
					$replies[] = sanitize_text_field( (string) preg_replace( '/^.*?SERVER -> CLIENT:\s*/', '', $line ) );
				}
			};
		};
		// phpcs:enable WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase

		add_action( 'wp_mail_failed', $capture );
		add_action( 'phpmailer_init', $listen, 99 );
		$sent = wp_mail(
			$to,
			/* translators: %s: site name. */
			sprintf( __( 'Test email from %s', 'forensix-digital' ), wp_specialchars_decode( get_bloginfo( 'name' ), ENT_QUOTES ) ),
			__( 'This is a test message from Forensix Digital. If you can read it, your site can send email.', 'forensix-digital' )
		);
		remove_action( 'wp_mail_failed', $capture );
		remove_action( 'phpmailer_init', $listen, 99 );

		$result = array(
			'ok'      => $sent,
			'message' => $sent
				/* translators: %s: email address. */
				? sprintf( __( 'The test email was handed over for delivery to %s. Check that inbox, and the spam folder.', 'forensix-digital' ), $to )
				: self::explain( $error ),
			'details' => array_slice( array_values( array_filter( $replies ) ), -4 ),
		);
		update_option(
			self::LAST,
			array(
				'time' => time(),
				'ok'   => $sent,
			),
			false
		);
		return $result;
	}

	/**
	 * A plain-language reason for a failure.
	 *
	 * @param string $error The mailer's message.
	 */
	public static function explain( string $error ): string {
		$lower = strtolower( $error );
		if ( str_contains( $lower, 'could not authenticate' ) || str_contains( $lower, 'authentication' ) ) {
			return __( 'The mail server did not accept the user name or password. Check both, and use an app password if your provider needs one.', 'forensix-digital' );
		}
		if ( str_contains( $lower, 'connect' ) ) {
			return __( 'Your site could not reach the mail server. Check the server name, the port and the encryption. Some hosts block outgoing mail ports; your host can tell you.', 'forensix-digital' );
		}
		if ( str_contains( $lower, 'from' ) && str_contains( $lower, 'address' ) ) {
			return __( 'The mail server did not accept the sender address. Use an address that belongs to your mail account.', 'forensix-digital' );
		}
		return __( 'The email could not be sent. Check the settings and try again.', 'forensix-digital' );
	}
}