strangler-fig-demo/new/src/New.Domain/ValueObjects/ContactDetails.cs

using System.Text.RegularExpressions;

namespace New.Domain.ValueObjects;

/// <summary>How the applicant prefers to be contacted.</summary>
public enum CorrespondenceChannel
{
    Post,
    Email,
}

/// <summary>
/// Email/phone plus the applicant's preferred channel. The one real invariant:
/// choosing <see cref="CorrespondenceChannel.Email"/> requires a non-empty,
/// well-formed email address - you can't ask to be emailed with no email on file.
/// </summary>
public sealed record ContactDetails
{
    private static readonly Regex SimpleEmailPattern =
        new(@"^[^@\s]+@[^@\s]+\.[^@\s]+$", RegexOptions.Compiled);

    public string? Email { get; }
    public string? Phone { get; }
    public CorrespondenceChannel PreferredChannel { get; }

    public ContactDetails(string? email, string? phone, CorrespondenceChannel preferredChannel)
    {
        if (preferredChannel == CorrespondenceChannel.Email && !IsWellFormedEmail(email))
        {
            throw new DomainInvariantViolationException(
                "ContactDetails.EmailRequiredForEmailChannel",
                "Preferring email as the correspondence channel requires a non-empty, well-formed email address.");
        }

        Email = email;
        Phone = phone;
        PreferredChannel = preferredChannel;
    }

    private static bool IsWellFormedEmail(string? email) =>
        !string.IsNullOrWhiteSpace(email) && SimpleEmailPattern.IsMatch(email);
}