using System;

namespace ShrinkModFramework
{
    /// <summary>宿主包装器执行生命周期；Handle 和自动订阅使用 PublicInstance。数据包可返回 null。</summary>
    public interface IShrinkModWrapper : IShrinkMod
    {
        IShrinkMod PublicInstance { get; }
    }

    /// <summary>
    /// 延迟模组组件源。Revision 是来源内容的稳定指纹（外部 DLL 可使用文件哈希）；
    /// 同一 ModId 的 revision/metadata 变化由 ShrinkModContextHost 作为替换事务处理。
    /// </summary>
    public sealed class ShrinkModComponentSource
    {
        public ShrinkModComponentSource(ShrinkModInfo info, string revision, Func<IShrinkMod> factory)
        {
            Info = info ?? throw new ArgumentNullException(nameof(info));
            if (string.IsNullOrWhiteSpace(info.ModId))
                throw new ArgumentException("ModId must not be empty.", nameof(info));
            if (string.IsNullOrWhiteSpace(revision))
                throw new ArgumentException("Revision must not be empty.", nameof(revision));

            Revision = revision.Trim();
            Factory = factory ?? throw new ArgumentNullException(nameof(factory));
        }

        public ShrinkModInfo Info { get; }
        public string Revision { get; }
        public Func<IShrinkMod> Factory { get; }

        internal ShrinkExternalModAssemblyLoader.RevisionState DiscoveryState { get; set; }

        /// <summary>替换清单元数据或生命周期工厂，同时保留授权发现的程序集 revision。</summary>
        public ShrinkModComponentSource WithMetadata(ShrinkModInfo info, string revision,
            Func<IShrinkMod> factory = null) =>
            new ShrinkModComponentSource(info, revision, factory ?? Factory) { DiscoveryState = DiscoveryState };

        /// <summary>创建无入口类型的数据包；可选生命周期工厂用于注册内容和可逆效应。</summary>
        public static ShrinkModComponentSource CreateDataOnly(ShrinkModInfo info, string revision,
            Func<IShrinkMod> factory = null)
        {
            if (info == null) throw new ArgumentNullException(nameof(info));
            if (info.EntryType != null)
                throw new ArgumentException("A data-only mod must have no entry type.", nameof(info));
            return new ShrinkModComponentSource(info, revision, factory ?? (() => new EmptyDataMod()));
        }

        private sealed class EmptyDataMod : ShrinkModBase, IShrinkModWrapper
        {
            public IShrinkMod PublicInstance => null;
        }
    }
}