chore: initial project import

backend/src/Monitor.Backend.Application/Agents/AgentRuntime.cs

@@ -0,0 +1,102 @@
+using System.Collections.Concurrent;
+using Fleet.Core;
+using Monitor.Protocol;
+
+namespace Monitor.Backend.Application;
+
+/// <summary>Agent 眼中的一个已连接 Probe（Agent 在事件和心跳里上报）。</summary>
+public sealed record ConnectedProbeInfo(string Id, string? Version, string? Remote, long SinceMs);
+
+/// <summary>Agent 的运行时状态（只在内存中）：连着哪些 Probe、最近的进程内计数、端点变化次数。</summary>
+public sealed class AgentRuntimeState
+{
+    private readonly object _gate = new();
+    private int _endpointChanges;
+    private IReadOnlyList<ConnectedProbeInfo> _probes = [];
+
+    /// <summary>当前连着这个 Agent 的 Probe（每个 Probe 一项）。</summary>
+    public IReadOnlyList<ConnectedProbeInfo> Probes => Volatile.Read(ref _probes);
+
+    public bool ProbeConnected => Probes.Count > 0;
+
+    public bool IsConnected(string probeId) => Probes.Any(p => p.Id == probeId);
+
+    /// <summary>事件 <c>probe_connected</c>：事件里带着 Probe 的版本和地址；心跳里的完整快照随后会再校正一次。</summary>
+    public void AddProbe(ConnectedProbeInfo info)
+    {
+        lock (_gate)
+        {
+            Volatile.Write(ref _probes, [.. _probes.Where(p => p.Id != info.Id), info]);
+        }
+    }
+
+    public void RemoveProbe(string id)
+    {
+        lock (_gate)
+        {
+            Volatile.Write(ref _probes, [.. _probes.Where(p => p.Id != id)]);
+        }
+    }
+
+    /// <summary>心跳里的完整快照：覆盖事件推算出的结果。</summary>
+    public void ReplaceProbes(IEnumerable<ConnectedProbeInfo> probes)
+    {
+        lock (_gate)
+        {
+            Volatile.Write(ref _probes, [.. probes.OrderBy(p => p.SinceMs).ThenBy(p => p.Id, StringComparer.Ordinal)]);
+        }
+    }
+
+    public void ClearProbes() => ReplaceProbes([]);
+
+    /// <summary>最新的主机资源占用快照，以及收到它的时间。</summary>
+    public HostSnapshot? Host { get; set; }
+
+    public long HostReceivedAtMs { get; set; }
+
+    public AgentHeartbeatExtra? LastHeartbeat { get; set; }
+
+    public long LastHeartbeatAtMs { get; set; }
+
+    public int EndpointChanges => Volatile.Read(ref _endpointChanges);
+
+    public void CountEndpointChange() => Interlocked.Increment(ref _endpointChanges);
+}
+
+public sealed class AgentRuntime
+{
+    private readonly ConcurrentDictionary<NodeId, AgentRuntimeState> _states = new();
+
+    public AgentRuntimeState Get(NodeId agent) => _states.GetOrAdd(agent, _ => new AgentRuntimeState());
+
+    public bool TryGet(NodeId agent, out AgentRuntimeState state) => _states.TryGetValue(agent, out state!);
+
+    public void Remove(NodeId agent) => _states.TryRemove(agent, out _);
+
+    /// <summary>某个 Probe 现在连着哪些 Agent。</summary>
+    public IReadOnlyList<(NodeId Agent, ConnectedProbeInfo Probe)> ConnectionsOf(string probeId)
+    {
+        var result = new List<(NodeId, ConnectedProbeInfo)>();
+        foreach ((NodeId agent, AgentRuntimeState state) in _states)
+        {
+            foreach (ConnectedProbeInfo probe in state.Probes)
+            {
+                if (probe.Id == probeId)
+                {
+                    result.Add((agent, probe));
+                }
+            }
+        }
+
+        return result;
+    }
+
+    /// <summary>Agent 断开时，它对 Probe 会话的认知也随之失效。</summary>
+    public void MarkOffline(NodeId agent)
+    {
+        if (_states.TryGetValue(agent, out AgentRuntimeState? state))
+        {
+            state.ClearProbes();
+        }
+    }
+}