#nullable enable
using System;
using System.Collections.Generic;
using Cysharp.Threading.Tasks;

namespace ShrinkContext
{
    public enum ShrinkFiberState
    {
        Inactive = 0,
        Loading = 1,
        Active = 2,
        Unloading = 3,
    }

    /// <summary>
    /// 纤程（论文定义 44）：组件的一次运行时实例化。
    /// 生命周期由 Target（期望提供者集合，null 即 ⊥）与惯性状态机驱动：
    /// 一旦进入转换即运行至完成，之后才响应新的目标变化（算法 5）。
    /// </summary>
    public sealed class ShrinkFiber
    {
        internal ShrinkFiber(long uid, IShrinkComponent component, ShrinkFiber? parent, object? config)
        {
            Uid = uid;
            Component = component;
            Parent = parent;
            Config = config;
            InjectSet = new HashSet<string>(component.Inject ?? Array.Empty<string>(), StringComparer.Ordinal);
            ProvideSet = new HashSet<string>(component.Provide ?? Array.Empty<string>(), StringComparer.Ordinal);
        }

        public long Uid { get; }

        public string Name => Component.Name;

        public IShrinkComponent Component { get; }

        /// <summary>实例化该纤程时的父纤程（根级为 null）；父纤程卸载会级联到本纤程。</summary>
        public ShrinkFiber? Parent { get; }

        /// <summary>本纤程运行所在的派生子上下文。</summary>
        public ShrinkCtx Ctx { get; internal set; } = null!;

        public object? Config { get; }

        public ShrinkFiberState State { get; internal set; } = ShrinkFiberState.Inactive;

        /// <summary>是否到达过 Active（用于断言“从未激活”）。</summary>
        public bool EverActive { get; internal set; }

        /// <summary>最近一次 apply 抛出的异常；成功激活后清空。</summary>
        public Exception? LastError { get; internal set; }

        /// <summary>已提交视图（算法 5 reload 提交 / 算法 6 读取）：依赖键 → 绑定快照。</summary>
        public IReadOnlyDictionary<string, ShrinkBinding>? Committed => _committed;

        /// <summary>进行中转换的句柄；任务在纤程到达静止态（Active 或 Inactive）时完成。</summary>
        public UniTask Inertia { get; internal set; }

        internal Dictionary<string, ShrinkBinding>? _committed;
        internal long[]? Target;
        internal bool InTransition;
        internal bool Retired;
        internal HashSet<string> InjectSet { get; }
        internal HashSet<string> ProvideSet { get; }
    }
}