chore: initial project import

backend/src/Monitor.Backend.Application/Tasks/TaskPlanner.cs

@@ -0,0 +1,93 @@
+using System.Security.Cryptography;
+using System.Text.Json;
+using Fleet.Core;
+using Fleet.Server;
+using Monitor.Protocol;
+
+namespace Monitor.Backend.Application;
+
+public sealed record DesiredTaskSet(long Version, TaskSet Document);
+
+/// <summary>
+/// 为每个 Agent 计算期望状态（<see cref="TaskSet"/>）：有效任务集 + 允许连接的 Probe 公钥。
+/// 只有内容真的变了才递增版本号，所以断线重连后 Agent 收到的永远是当前版本的完整快照。
+/// </summary>
+public sealed class TaskPlanner : IDisposable
+{
+    public const string ProbeAgentsVersionKey = "probe_agents_version";
+
+    private readonly ITaskStore _tasks;
+    private readonly IAgentStore _agents;
+    private readonly IProbeStore _probes;
+    private readonly ISettingsStore _settings;
+    private readonly SemaphoreSlim _gate = new(1, 1);
+
+    public TaskPlanner(ITaskStore tasks, IAgentStore agents, IProbeStore probes, ISettingsStore settings)
+    {
+        _tasks = tasks;
+        _agents = agents;
+        _probes = probes;
+        _settings = settings;
+    }
+
+    /// <summary>pending、disabled 或不存在的 Agent 返回 null（不下发状态）。</summary>
+    public async ValueTask<DesiredTaskSet?> GetDesiredAsync(NodeId agentId, CancellationToken ct)
+    {
+        AgentRecord? agent = await _agents.GetAsync(agentId, ct);
+        if (agent is null || agent.Status != NodeStatus.Active)
+        {
+            return null;
+        }
+
+        IReadOnlyList<TaskRecord> all = await _tasks.ListAsync(ct);
+        IReadOnlyList<ProbeRecord> probes = await _probes.ListAsync(ct);
+        long listVersion = long.TryParse(await _settings.GetAsync(ProbeAgentsVersionKey, ct), out long v) ? v : 0;
+
+        var document = new TaskSet { ProbeAgentsVersion = listVersion };
+        foreach (EffectiveTask task in EffectiveTasks.Compute(all, agent, filterByAgentKinds: true))
+        {
+            document.Tasks.Add(new TaskSpec
+            {
+                Id = task.Id,
+                Scope = task.Scope,
+                Kind = task.Kind,
+                Target = task.Target,
+                Params = new Dictionary<string, JsonElement>(task.Params),
+                Schedule = task.Schedule,
+                Enabled = true,
+            });
+        }
+
+        foreach (ProbeRecord probe in probes.Where(p => p.RevokedAtMs is null))
+        {
+            document.Peers.Add(new PeerSpec { ProbeId = new ProbeId(probe.Id), PublicKey = Convert.ToBase64String(probe.PublicKey) });
+        }
+
+        string hash = Convert.ToHexStringLower(SHA256.HashData(JsonSerializer.SerializeToUtf8Bytes(document, MonitorJsonContext.Default.TaskSet)));
+
+        await _gate.WaitAsync(ct);
+        try
+        {
+            // 重新读取，避免并发的两次计算各自递增
+            AgentRecord current = await _agents.GetAsync(agentId, ct) ?? agent;
+            string? storedHash = await _agents.GetTaskHashAsync(agentId, ct);
+            long version = current.TaskVersion;
+            if (storedHash != hash)
+            {
+                version++;
+                await _agents.SetTaskVersionAsync(agentId, version, hash, ct);
+            }
+
+            document.Version = version;
+            return new DesiredTaskSet(version, document);
+        }
+        finally
+        {
+            _gate.Release();
+        }
+    }
+
+    public void Dispose() => _gate.Dispose();
+
+    public ValueTask<long> BumpProbeAgentsVersionAsync(CancellationToken ct) => _settings.IncrementAsync(ProbeAgentsVersionKey, ct);
+}