namespace HSchool.Content;

/// <summary>
/// Selected packs cannot be ordered: a required pack is missing, or they require each other.
/// Distinct from <see cref="ContentLoadException"/> so the create dialog can name the pack.
/// </summary>
public sealed class PackDependencyException : Exception
{
    public const string MissingCode = "missing-mod";

    public const string CycleCode = "mod-cycle";

    private PackDependencyException(string message, string code, string? missingPackId)
        : base(message)
    {
        Code = code;
        MissingPackId = missingPackId;
    }

    public string Code { get; }

    public string? MissingPackId { get; }

    public static PackDependencyException Missing(string missingPackId, string requiredBy) =>
        new(
            $"Pack '{requiredBy}' requires '{missingPackId}', which was not selected.",
            MissingCode,
            missingPackId);

    public static PackDependencyException Cycle() =>
        new("Selected packs have a cyclic dependency.", CycleCode, missingPackId: null);
}