using System.Text.Json;
using Fleet.Core;
using Fleet.Rpc;

namespace Fleet.Server;

public sealed record EnrollmentContext(string? RemoteIp, JsonElement? ProductMeta);

/// <summary>
/// 节点的真实来源地址：前面有反向代理时，套接字上只有代理的地址，产品在这里决定信不信转发头。
/// 没有注册就用套接字地址。
/// </summary>
public interface IClientAddressSource
{
    /// <param name="socket">套接字上看到的对端地址。</param>
    /// <param name="header">按名字取请求头的所有值。</param>
    string? Resolve(System.Net.IPAddress? socket, Func<string, IEnumerable<string>> header);
}

/// <summary>
/// 服务器的身份密钥：操作员用 passkey 把它的公钥签进操作员集合。有它的时候，认证挑战会带上服务器的签名，节点据此确认对面是真的服务器，
/// 并在这条链路上用应用层加密。没有注册就是旧的行为（没有服务器身份）。
/// </summary>
public interface IServerIdentity
{
    byte[] PublicKeySpki { get; }

    /// <summary>对一段内容签名（<c>Fleet.Identity.ServerHello.Payload</c> 给出的）。</summary>
    byte[] Sign(ReadOnlySpan<byte> payload);
}

/// <summary>操作员集合的链（passkey 签的，创世在前）。没有初始化信任根时是空的。节点注册时用它确认「这个面板确实是我的操作员的」。</summary>
public interface IOperatorTrustSource
{
    ValueTask<IReadOnlyList<SignedStatementDto>> ChainAsync(CancellationToken ct);
}

/// <summary>产品挂钩：节点注册成功之后调用。</summary>
public interface IEnrollmentHook
{
    ValueTask OnEnrolledAsync(NodeRecord node, EnrollmentContext context, CancellationToken ct);
}

public enum NodeEventKind
{
    Online,
    Offline,
    Hello,
    Heartbeat,
}

 /// <param name="RemoteIp">这条连接的来源地址（经过 <see cref="IClientAddressSource"/>）；没有就是 null。</param>
public sealed record NodeEvent(NodeEventKind Kind, NodeRecord Node, long AtMs, HelloParams? Hello = null, JsonElement? Extra = null, string? Reason = null, string? RemoteIp = null);

public interface INodeEventSink
{
    ValueTask OnEventAsync(NodeEvent nodeEvent, CancellationToken ct);
}

/// <summary>期望状态提供者：为每个节点计算期望状态的完整快照（天然幂等）。</summary>
public interface IStateProvider
{
    /// <summary>状态文档类型，例如 <c>task_set</c>。</summary>
    string Type { get; }

    ValueTask<StateDocument?> GetAsync(NodeRecord node, CancellationToken ct);

    /// <summary>节点应用之后回调，<c>rejected[]</c> 带结构化原因。</summary>
    ValueTask OnAppliedAsync(NodeRecord node, long version, StateSyncResult result, CancellationToken ct);
}

public sealed record StateDocument(long Version, JsonElement Doc);

public enum InboxOutcome
{
    Stored,
    Duplicate,
    Rejected,
}

/// <summary>收件箱：持久化之后才返回 Stored，框架随后才回复 ACK。</summary>
public interface IInbox
{
    byte Channel { get; }

    ValueTask<InboxOutcome> HandleAsync(NodeRecord node, Guid msgId, ReadOnlyMemory<byte> payload, CancellationToken ct);
}

/// <summary>通知 Fleet：某个节点的期望状态变了，需要重新计算并推送。</summary>
public interface IStateNotifier
{
    void NotifyChanged(NodeId node);

    void NotifyAllChanged();
}