using MimeKit;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Notifications;

namespace ZB.MOM.WW.ScadaBridge.NotificationService;

/// <summary>
/// Validates the sender and recipient email addresses before an SMTP
/// delivery is attempted, so a malformed address surfaces as a clean error
/// string rather than a <c>ParseException</c> escaping the delivery path.
/// <para>
/// Public so the central Notification Outbox's <c>EmailNotificationDeliveryAdapter</c>
/// can share this exact pre-send validation rather than carry a divergent copy.
/// </para>
/// </summary>
public static class EmailAddressValidator
{
    /// <summary>
    /// Validates the sender and recipient email addresses, returning a
    /// human-readable error string if any is malformed, or null if all parse.
    /// </summary>
    /// <param name="fromAddress">The sender email address to validate.</param>
    /// <param name="recipients">The list of recipient addresses to validate.</param>
    /// <returns>A human-readable error string if any address is malformed; <c>null</c> if all addresses parse successfully.</returns>
    public static string? ValidateAddresses(
        string fromAddress, IReadOnlyList<NotificationRecipient> recipients)
    {
        if (!MailboxAddress.TryParse(fromAddress, out _))
        {
            return $"Invalid sender (from) email address: '{fromAddress}'";
        }

        var invalid = recipients
            .Where(r => !MailboxAddress.TryParse(r.EmailAddress, out _))
            .Select(r => r.EmailAddress)
            .ToList();

        return invalid.Count > 0
            ? $"Invalid recipient email address(es): {string.Join(", ", invalid)}"
            : null;
    }
}
