chore: initial project import

backend/agent/src/Monitor.Agent/Chunks/ChunkAssembler.cs

@@ -0,0 +1,75 @@
+using Fleet.Core;
+using Fleet.Link;
+using Monitor.Measurement;
+using Monitor.Protocol;
+
+namespace Monitor.Agent;
+
+/// <summary>
+/// Probe 的列块到达之后：找到对应的流 → 与 Agent 在数据面记录的列合并 → 盖章（块头、时钟锚点）→ 编码 → 放进发件箱（通道 16）。
+/// 找不到对应流的列块（任务已经被撤销、测试已经结束）被丢弃并计数；这只会发生在配置变更的瞬间。
+/// </summary>
+public sealed class ChunkAssembler
+{
+    private readonly StreamRegistry _streams;
+    private readonly MonoClock _clock;
+    private readonly AgentCounters _counters;
+    private readonly Outbox _outbox;
+    private readonly NodeId _agent;
+    private readonly TimeProvider _time;
+    private readonly INodeLog _log;
+
+    public ChunkAssembler(StreamRegistry streams, MonoClock clock, AgentCounters counters, Outbox outbox, NodeId agent, TimeProvider time, INodeLog log)
+    {
+        _streams = streams;
+        _clock = clock;
+        _counters = counters;
+        _outbox = outbox;
+        _agent = agent;
+        _time = time;
+        _log = log;
+    }
+
+    /// <summary>
+    /// 处理某个 Probe 交来的一个列块（已经解码）。返回是否被接受。
+    /// 块头里的 <c>probe_id</c> 以认证过的会话为准（Probe 自报的值不可信），别的 Probe 的流也不会被命中。
+    /// </summary>
+    public bool Accept(RawChunk fragment, ProbeSession probe)
+    {
+        RawChunkHeader header = fragment.Header;
+        StreamInfo? stream = header switch
+        {
+            { TestId: { } test, Phase: { } phase } => _streams.FindByTest(test, phase) is { } found && ReferenceEquals(found.Owner, probe) ? found : null,
+            { TaskId: { } task } => _streams.FindByTask(task, probe),
+            _ => null,
+        };
+        header.ProbeId = new ProbeId(probe.ProbeId);
+        KindSpec? spec = stream is null ? null : Kinds.Find(stream.Kind);
+        if (stream is null || spec is null || spec.Id != header.Kind)
+        {
+            _counters.FragmentDiscarded();
+            return false;
+        }
+
+        Result<IReadOnlyList<RawStream>> merged = FragmentMerger.Merge(spec, fragment, stream.Id, _streams);
+        if (!merged.TryGet(out IReadOnlyList<RawStream>? streams, out FleetError? error))
+        {
+            _log.Warn("fragment discarded", ("kind", spec.Id), ("err", error.Code));
+            _counters.FragmentDiscarded();
+            stream.FragmentDone();
+            return false;
+        }
+
+        RawChunk chunk = ChunkFinalizer.Finalize(spec, fragment, streams, _agent, _clock.Anchor(), stream.Params.Values, stream.Port, ChunkId.New(_time));
+        Emit(chunk);
+        _counters.FragmentAccepted();
+        stream.FragmentDone();
+        return true;
+    }
+
+    /// <summary>Agent 自己采集的块（目标任务）直接发出。</summary>
+    public void Emit(RawChunk chunk)
+    {
+        _outbox.Enqueue(MonitorChannels.RawChunk, chunk.Header.ChunkId.Value, RawChunkCodec.Encode(chunk));
+    }
+}