#nullable enable

using System;
using System.Collections.Generic;
using System.Linq;

namespace ShrinkApp
{
    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
    public sealed class ShrinkAppInstallerRegistryAttribute : Attribute
    {
        public ShrinkAppInstallerRegistryAttribute(params Type[] installerTypes)
        {
            InstallerTypes = installerTypes ?? Array.Empty<Type>();
        }

        public Type[] InstallerTypes { get; }
    }

    internal static class ShrinkAppGeneratedRegistry
    {
        public static IReadOnlyList<Type> GetInstallerTypes()
        {
            var types = new List<Type>();
            var seen = new HashSet<Type>();
            foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
            {
                object[] attributes;
                try
                {
                    attributes = assembly.GetCustomAttributes(typeof(ShrinkAppInstallerRegistryAttribute), false);
                }
                catch
                {
                    continue;
                }

                foreach (var attribute in attributes.OfType<ShrinkAppInstallerRegistryAttribute>())
                {
                    foreach (var installerType in attribute.InstallerTypes ?? Array.Empty<Type>())
                    {
                        if (installerType == null || !seen.Add(installerType))
                            continue;

                        types.Add(installerType);
                    }
                }
            }

            return types;
        }
    }
}