chore: initial project import

backend/src/Monitor.Backend.Application/Query/Lines.cs

@@ -0,0 +1,104 @@
+using Fleet.Core;
+using Monitor.Protocol;
+
+namespace Monitor.Backend.Application;
+
+/// <summary>一条线路 = 一对（Agent，Probe）。存储里它的序列是 <c>line:&lt;probe_id&gt;</c>，对外的 id 是 <c>&lt;agent_id&gt;~&lt;probe_id&gt;</c>。</summary>
+public readonly record struct LineKey(NodeId Agent, ProbeId Probe)
+{
+    public string Series => RawChunkHeader.LinePrefix + Probe.Value;
+
+    public string Id => Agent.Value + "~" + Probe.Value;
+
+    public static bool TryParse(string text, out LineKey key)
+    {
+        int split = text.IndexOf('~', StringComparison.Ordinal);
+        if (split <= 0 || split == text.Length - 1)
+        {
+            key = default;
+            return false;
+        }
+
+        key = new LineKey(new NodeId(text[..split]), new ProbeId(text[(split + 1)..]));
+        return true;
+    }
+}
+
+/// <summary>一条线路的展示视图：Agent 的状态、Probe 记录，以及这一对现在是否连着。</summary>
+public sealed record LineView(AgentView Agent, ProbeRecord Probe)
+{
+    public LineKey Key => new(Agent.Agent.Id, new ProbeId(Probe.Id));
+
+    public bool Connected => Agent.Probes.Any(p => p.Id == Probe.Id);
+
+    public ConnectedProbeInfo? Connection => Agent.Probes.FirstOrDefault(p => p.Id == Probe.Id);
+}
+
+/// <summary>线路目录：把 id 解析成（Agent，Probe），列出所有线路。</summary>
+public sealed class LineService
+{
+    private readonly AgentService _agents;
+    private readonly IProbeStore _probes;
+
+    public LineService(AgentService agents, IProbeStore probes)
+    {
+        _agents = agents;
+        _probes = probes;
+    }
+
+    /// <summary>所有线路：每个 Agent 和每个<b>未吊销</b>的 Probe 配成一对。</summary>
+    public async ValueTask<IReadOnlyList<LineView>> ListAsync(Func<AgentView, bool> include, CancellationToken ct)
+    {
+        IReadOnlyList<AgentView> agents = await _agents.ListAsync(ct);
+        IReadOnlyList<ProbeRecord> probes = [.. (await _probes.ListAsync(ct)).Where(p => p.RevokedAtMs is null)];
+        return [.. agents.Where(include).SelectMany(a => probes.Select(p => new LineView(a, p)))];
+    }
+
+    /// <summary>
+    /// 线路 id 是 <c>agent~probe</c>。只给 Agent id 时：恰好有一个未吊销的 Probe 就用它，否则要求明确指定（<c>probe_required</c>）。
+    /// </summary>
+    public async ValueTask<Result<LineView>> ResolveAsync(string id, CancellationToken ct)
+    {
+        string agentPart = id;
+        string? probePart = null;
+        if (id.Contains('~', StringComparison.Ordinal))
+        {
+            if (!LineKey.TryParse(id, out LineKey key))
+            {
+                return Result<LineView>.Fail(MonitorErrors.AgentNotFound, "line not found");
+            }
+
+            agentPart = key.Agent.Value;
+            probePart = key.Probe.Value;
+        }
+
+        AgentView? agent = await _agents.GetAsync(new NodeId(agentPart), ct);
+        if (agent is null)
+        {
+            return Result<LineView>.Fail(MonitorErrors.AgentNotFound, "line not found");
+        }
+
+        IReadOnlyList<ProbeRecord> probes = await _probes.ListAsync(ct);
+        ProbeRecord? probe;
+        if (probePart is not null)
+        {
+            probe = probes.FirstOrDefault(p => p.Id == probePart);
+            if (probe is null)
+            {
+                return Result<LineView>.Fail(MonitorErrors.ProbeNotFound, "probe not found");
+            }
+        }
+        else
+        {
+            ProbeRecord[] active = [.. probes.Where(p => p.RevokedAtMs is null)];
+            if (active.Length != 1)
+            {
+                return Result<LineView>.Fail(MonitorErrors.ProbeRequired, active.Length == 0 ? "there is no active probe" : "several probes exist: use <agent_id>~<probe_id> as the line id");
+            }
+
+            probe = active[0];
+        }
+
+        return Result<LineView>.Ok(new LineView(agent, probe));
+    }
+}