using System.Text.Json.Nodes;
using Monitor.Measurement;
using Monitor.Protocol;
using Monitor.TestSupport;

namespace Monitor.Backend.Tests;

/// <summary>真实的后端 + 真实的 Agent（进程内）+ 假 Probe：覆盖 Agent 与 Backend 的链路、Probe 与 Agent 的点对点会话和数据面。</summary>
[Collection("backend")]
public sealed class AgentEndToEndTests
{
    private readonly BackendFixture _backend;

    public AgentEndToEndTests(BackendFixture backend)
    {
        _backend = backend;
    }

    private async Task<(AgentHarness Agent, ProbeSimulator Probe, LineTask Udp)> LineAsync()
    {
        AgentHarness agent = await AgentHarness.StartAsync(_backend);
        await agent.OverrideLineTasksAsync(rateHz: 30);
        ProbeSimulator probe = await agent.ConnectProbeAsync();
        LineTaskSet set = await probe.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo" && t.Port == agent.App.UdpPorts[0]));
        return (agent, probe, set.Tasks.Single(t => t.Kind == "udp_echo"));
    }

    private async Task<JsonNode> AgentViewAsync(AgentHarness agent) => await _backend.GetJsonAsync(_backend.Admin, "/api/admin/agents/" + agent.Id);

    [Fact]
    public async Task Agent_ConnectsAndReportsItsRealPorts_AndTheProbeSessionIsVisibleToTheBackend()
    {
        await using AgentHarness agent = await AgentHarness.StartAsync(_backend);
        JsonNode view = await AgentViewAsync(agent);
        Assert.Equal("active", view["status"]!.GetValue<string>());
        Assert.False(view["probe_connected"]!.GetValue<bool>());

        await using ProbeSimulator probe = await agent.ConnectProbeAsync();
        await BackendFixture.EventuallyAsync(async () => (await AgentViewAsync(agent))["probe_connected"]!.GetValue<bool>());
    }

    [Fact]
    public async Task LocalLimits_RejectTasksOutsideTheAllowedPorts_AndTheReasonReachesTheAdmin()
    {
        // 默认模板的端口（7443/7444）不在这个 Agent 实际监听的端口里：任务被拒绝，原因是 policy_denied
        await using AgentHarness agent = await AgentHarness.StartAsync(_backend);
        await BackendFixture.EventuallyAsync(async () => (await AgentViewAsync(agent))["rejected"]!.AsArray().Count == 2);
        JsonNode rejected = (await AgentViewAsync(agent))["rejected"]!;
        Assert.All(rejected.AsArray(), item => Assert.Equal("policy_denied", item!["reason"]!.GetValue<string>()));

        // 覆盖成实际端口之后恢复
        await agent.OverrideLineTasksAsync();
        await BackendFixture.EventuallyAsync(async () => (await AgentViewAsync(agent))["rejected"]!.AsArray().Count == 0);
    }

    [Fact]
    public async Task UdpEcho_EndToEnd_FragmentsAreMergedWithAgentTimestamps_AndStoredByTheBackend()
    {
        (AgentHarness agent, ProbeSimulator probe, LineTask udp) = await LineAsync();
        await using (agent)
        await using (probe)
        {
            (int sent, int received) = await probe.RunUdpEchoAsync(udp, 40, TimeSpan.FromMilliseconds(40));
            Assert.Equal(40, sent);
            Assert.Equal(40, received);

            JsonNode stored = null!;
            await BackendFixture.EventuallyAsync(async () =>
            {
                stored = await _backend.GetJsonAsync(_backend.Admin, $"/api/admin/raw/chunks?agent_id={agent.Id}");
                return stored["items"]!.AsArray().Count >= 1;
            }, because: (await _backend.GetJsonAsync(_backend.Admin, $"/api/admin/events?agent_id={agent.Id}")).ToJsonString() + $" fragments={agent.App.Counters.Fragments} discarded={agent.App.Counters.FragmentsDiscarded} outbox={agent.App.Link.Outbox.PendingCount}");
            JsonNode chunk = stored["items"]![0]!;
            Assert.True(chunk["kind"] is not null, stored.ToJsonString());
            Assert.Equal("udp_echo", chunk["kind"]!.GetValue<string>());
            Assert.True(agent.App.Counters.Fragments >= 1);
            Assert.True(agent.App.Counters.PacketsIn >= 40);
        }
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public async Task TcpEcho_EndToEnd_AuthenticatedFirstFrame_PlainOrTls(bool tls)
    {
        (AgentHarness agent, ProbeSimulator probe, _) = await LineAsync();
        await using (agent)
        await using (probe)
        {
            LineTask tcp = (await probe.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "tcp_echo" && t.Port == agent.App.TcpPorts[0]))).Tasks.Single(t => t.Kind == "tcp_echo");
            (int sent, int received) = await probe.RunTcpEchoAsync(tcp, agent.App.TcpPorts[0], 15, TimeSpan.FromMilliseconds(60), tls);
            Assert.Equal(15, sent);
            Assert.Equal(15, received);
            await BackendFixture.EventuallyAsync(async () => (await _backend.GetJsonAsync(_backend.Admin, $"/api/admin/raw/chunks?agent_id={agent.Id}"))["items"]!.AsArray().Any(c => c!["kind"]!.GetValue<string>() == "tcp_echo"));
        }
    }

    [Fact]
    public async Task TcpDataPlane_ClosesConnectionsWithoutAValidFirstFrame()
    {
        (AgentHarness agent, ProbeSimulator probe, _) = await LineAsync();
        await using (agent)
        await using (probe)
        {
            using var client = new System.Net.Sockets.TcpClient();
            await client.ConnectAsync(System.Net.IPAddress.Loopback, agent.App.TcpPorts[0]);
            await client.GetStream().WriteAsync(new byte[TcpWire.AuthBytes]); // 全零：magic 不对
            byte[] buffer = new byte[16];
            Assert.Equal(0, await client.GetStream().ReadAsync(buffer).AsTask().WaitAsync(TimeSpan.FromSeconds(10)));
            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Counters.DroppedInvalid >= 1));
        }
    }

    [Fact]
    public async Task DataPlane_DropsForgedReplayedAndGarbagePackets_WithoutAnswering()
    {
        (AgentHarness agent, ProbeSimulator probe, LineTask udp) = await LineAsync();
        await using (agent)
        await using (probe)
        {
            long before = agent.App.Counters.DroppedInvalid;
            await probe.SendRawUdpAsync([1, 2, 3]);
            await probe.SendRawUdpAsync(new byte[64]);
            await probe.SendForgedEchoAsync(udp, 1);
            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Counters.DroppedInvalid - before >= 3), because: "garbage and forged packets are counted");

            // 重放：同一个序号发两次，只有第一次被接受
            await probe.SendEchoAsync(udp, 500);
            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Counters.PacketsOut >= 1));
            long dropped = agent.App.Counters.DroppedInvalid;
            await probe.SendEchoAsync(udp, 500);
            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Counters.DroppedInvalid > dropped), because: "a replayed packet is dropped");
        }
    }

    [Fact]
    public async Task ARestartedProbe_NeverInheritsTheAgentRecordsOfItsPreviousSession()
    {
        (AgentHarness agent, ProbeSimulator first, LineTask udp) = await LineAsync();
        await using (agent)
        {
            await first.RunUdpEchoAsync(udp, 20, TimeSpan.FromMilliseconds(40));
            RowStore records = agent.App.Streams.Records(udp.StreamId, "msg")!;
            Assert.True(records.Contains(5), "the agent recorded t2/t3 for the first session's packets");
            await first.DisposeAsync();

            // The probe process restarts: a new session with its own streams; sequence numbers start from 0 again
            await using ProbeSimulator second = first.Restarted();
            await second.ConnectAsync("127.0.0.1", agent.App.ControlPort, agent.TlsSpki, agent.App.UdpPorts[0], agent.NodeId);
            LineTaskSet set = await second.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo" && t.Port == agent.App.UdpPorts[0]));
            LineTask udp2 = set.Tasks.Single(t => t.Kind == "udp_echo");
            Assert.NotEqual(udp.StreamId, udp2.StreamId);

            // The previous session's streams are released with it ...
            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Streams.Records(udp.StreamId, "msg") is null), because: "the previous session's streams must be released");

            // ... and a packet the new session never sent has no agent record: if the old t2/t3 survived, a lost uplink packet would look like a downlink loss
            RowStore fresh = agent.App.Streams.Records(udp2.StreamId, "msg")!;
            Assert.False(fresh.Contains(3));
            Assert.False(fresh.Contains(5));
        }
    }

    [Fact]
    public async Task SeveralProbes_AreReportedTogether_CanBeDroppedOneByOne_AndARevokedOneIsKickedOut()
    {
        await using AgentHarness agent = await AgentHarness.StartAsync(_backend);
        await agent.OverrideLineTasksAsync(rateHz: 30);
        await using ProbeSimulator a = await agent.ConnectProbeAsync();
        await using ProbeSimulator b = await agent.ConnectProbeAsync();

        // The agent reports both sessions with version and address; the probe view shows the agent it is connected to
        JsonNode view = null!;
        await BackendFixture.EventuallyAsync(
            async () =>
            {
                view = await AgentViewAsync(agent);
                return view["probes"]!.AsArray().Count == 2;
            },
            because: "the agent reports every connected probe");
        Assert.All(view["probes"]!.AsArray(), p => Assert.Equal("0.0.0-sim", p!["version"]!.GetValue<string>()));
        Assert.Equal("127.0.0.1", view["probes"]![0]!["remote"]!.GetValue<string>());
        JsonNode probeView = await _backend.GetJsonAsync(_backend.Admin, "/api/admin/probes/" + a.ProbeId);
        Assert.Equal(agent.Id, probeView["connections"]![0]!["agent_id"]!.GetValue<string>());

        // Both get their own task set (own streams)
        LineTaskSet setA = await a.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo"));
        LineTaskSet setB = await b.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo"));
        Assert.NotEqual(setA.Tasks.Single(t => t.Kind == "udp_echo").StreamId, setB.Tasks.Single(t => t.Kind == "udp_echo").StreamId);

        // Drop one: the other stays
        using HttpResponseMessage dropped = await _backend.Admin.PostAsync($"/api/admin/agents/{agent.Id}/probes/{a.ProbeId}/disconnect", null);
        Assert.Equal(System.Net.HttpStatusCode.NoContent, dropped.StatusCode);
        await BackendFixture.EventuallyAsync(async () => (await AgentViewAsync(agent))["probes"]!.AsArray().Count == 1, because: "only the dropped probe leaves");
        Assert.True(b.IsConnected);
        using HttpResponseMessage again = await _backend.Admin.PostAsync($"/api/admin/agents/{agent.Id}/probes/{a.ProbeId}/disconnect", null);
        Assert.Equal(System.Net.HttpStatusCode.Conflict, again.StatusCode);

        // Revoke the remaining one: the agent closes its session
        using HttpResponseMessage revoked = await _backend.Admin.PostAsync($"/api/admin/probes/{b.ProbeId}/revoke", null);
        revoked.EnsureSuccessStatusCode();
        await BackendFixture.EventuallyAsync(async () => (await AgentViewAsync(agent))["probes"]!.AsArray().Count == 0, because: "a revoked probe is disconnected");
    }

    [Fact]
    public async Task PeerHandshake_RejectsAProbeWhoseKeyTheBackendNeverIssued()
    {
        await using AgentHarness agent = await AgentHarness.StartAsync(_backend);
        await agent.CreateProbeAsync();
        await using var stranger = new ProbeSimulator("prb_stranger", Fleet.Identity.NodeIdentity.Generate());
        await Assert.ThrowsAnyAsync<Exception>(() => stranger.ConnectAsync("127.0.0.1", agent.App.ControlPort, agent.TlsSpki, agent.App.UdpPorts[0], agent.NodeId));

        // 证书指纹不对（中间人）也不会连上
        await using ProbeSimulator probe = await agent.CreateProbeAsync();
        await Assert.ThrowsAnyAsync<Exception>(() => probe.ConnectAsync("127.0.0.1", agent.App.ControlPort, new byte[32], agent.App.UdpPorts[0], agent.NodeId));
    }

    [Fact]
    public async Task ProbeDisconnect_IsReportedToTheBackend()
    {
        (AgentHarness agent, ProbeSimulator probe, _) = await LineAsync();
        await using (agent)
        {
            await BackendFixture.EventuallyAsync(async () => (await AgentViewAsync(agent))["probe_connected"]!.GetValue<bool>());
            await probe.DisposeAsync();
            await BackendFixture.EventuallyAsync(async () => !(await AgentViewAsync(agent))["probe_connected"]!.GetValue<bool>());
        }
    }

    [Fact]
    public async Task LineTaskSet_FollowsTheDesiredState_AndIsPushedToTheProbe()
    {
        (AgentHarness agent, ProbeSimulator probe, LineTask udp) = await LineAsync();
        await using (agent)
        await using (probe)
        {
            JsonNode tasks = await _backend.GetJsonAsync(_backend.Admin, "/api/admin/tasks");
            JsonNode mine = tasks["items"]!.AsArray().Single(t => t!["agent_id"]?.GetValue<string>() == agent.Id && t["kind"]!.GetValue<string>() == "udp_echo")!;
            using HttpResponseMessage disabled = await _backend.Admin.PatchAsync("/api/admin/tasks/" + mine["id"]!.GetValue<string>(), BackendFixture.Json(new JsonObject { ["enabled"] = false }, "application/merge-patch+json"));
            disabled.EnsureSuccessStatusCode();

            LineTaskSet next = await probe.WaitForTasksAsync(s => s.Tasks.All(t => t.Kind != "udp_echo") && s.Tasks.Count >= 0 && s.Version > 0);
            Assert.DoesNotContain(next.Tasks, t => t.Id == udp.Id);
        }
    }

    [Fact]
    public async Task Hy2Ladder_EndToEnd_AgentSendsTheTrain_ProbeReportsReceipts_AndTheTestSucceeds()
    {
        await using AgentHarness agent = await AgentHarness.StartAsync(_backend);
        await agent.OverrideLineTasksAsync();
        await using ProbeSimulator probe = await agent.ConnectProbeAsync();
        await BackendFixture.EventuallyAsync(async () => (await AgentViewAsync(agent))["probe_connected"]!.GetValue<bool>());

        using HttpResponseMessage accepted = await _backend.Admin.PostAsync($"/api/admin/lines/{agent.Id}~{probe.ProbeId}/tests", BackendFixture.Json(new JsonObject { ["plan"] = "hy2_ladder", ["params"] = new JsonObject { ["size"] = 1000 } }));
        Assert.True(accepted.StatusCode == System.Net.HttpStatusCode.Accepted, await accepted.Content.ReadAsStringAsync());
        string testId = JsonNode.Parse(await accepted.Content.ReadAsStringAsync())!["id"]!.GetValue<string>();

        JsonNode test = null!;
        await BackendFixture.EventuallyAsync(
            async () =>
            {
                test = await _backend.GetJsonAsync(_backend.Admin, "/api/public/tests/" + testId);
                return test["status"]!.GetValue<string>() is "succeeded" or "failed" or "aborted";
            },
            TimeSpan.FromSeconds(90));
        Assert.True(test["status"]!.GetValue<string>() == "succeeded", test.ToJsonString());
        Assert.Equal(4, probe.Phases.Count);
        Assert.All(probe.Phases, phase => Assert.Equal("udp_train", phase.Kind));

        // 单块最多 50000 条记录：50 和 100 Mbit/s 阶段（10 s、1000 B 的包）各被 Probe 切成多个列块
        Assert.True(agent.App.Counters.Fragments > 4);
        await BackendFixture.EventuallyAsync(
            async () => (await _backend.GetJsonAsync(_backend.Admin, $"/api/admin/raw/chunks?agent_id={agent.Id}"))["items"]!.AsArray().Count(c => c!["kind"]!.GetValue<string>() == "udp_train") == agent.App.Counters.Fragments,
            because: (await _backend.GetJsonAsync(_backend.Admin, $"/api/admin/events?agent_id={agent.Id}")).ToJsonString() + $" fragments={agent.App.Counters.Fragments} discarded={agent.App.Counters.FragmentsDiscarded} pending={agent.App.Link.Outbox.PendingCount}/{agent.App.Link.Outbox.PendingBytes} dropped={agent.App.Link.Outbox.Dropped} link={agent.App.Link.IsConnected}");
    }

    [Fact]
    public async Task Plan_UsingTcpBulk_IsAcceptedByARealAgentAndStartsItsFirstPhase()
    {
        await using AgentHarness agent = await AgentHarness.StartAsync(_backend);
        await using ProbeSimulator probe = await agent.ConnectProbeAsync();
        await BackendFixture.EventuallyAsync(async () => (await AgentViewAsync(agent))["probe_connected"]!.GetValue<bool>());

        // reality_session 需要 connect、tcp_bulk、hold：真实的 Agent 都实现了
        using HttpResponseMessage response = await _backend.Admin.PostAsync($"/api/admin/lines/{agent.Id}~{probe.ProbeId}/tests", BackendFixture.Json(new JsonObject { ["plan"] = "reality_session" }));
        Assert.Equal(System.Net.HttpStatusCode.Accepted, response.StatusCode);
        await BackendFixture.EventuallyAsync(() => Task.FromResult(!probe.Phases.IsEmpty), because: "the first phase should start");
        Assert.True(probe.Phases.TryPeek(out var first));
        Assert.Equal("connect", first.Kind);
    }

    [Fact]
    public async Task Test_IsRefusedWhenNoProbeIsConnected_AndWhenAPhaseExceedsTheLocalLimits()
    {
        await using AgentHarness agent = await AgentHarness.StartAsync(_backend, config => config.Limits.MaxTotalMbps = 20);
        await agent.OverrideLineTasksAsync();

        var phase = new TestPhase { Kind = "udp_train", DurationSeconds = 1, Params = { ["port"] = System.Text.Json.JsonSerializer.SerializeToElement(agent.App.UdpPorts[0]) } };
        var run = new TestRunParams { TestId = new TestId("tst_x"), ProbeId = new ProbeId("prb_nobody"), Plan = "x", Phases = [phase] };
        Assert.Equal("probe_offline", agent.App.Tests.Start(run).Error.Code.Value);

        await using ProbeSimulator probe = await agent.ConnectProbeAsync();
        run.ProbeId = new ProbeId(probe.ProbeId);
        phase.Params["mbps"] = System.Text.Json.JsonSerializer.SerializeToElement(50);
        Assert.Equal("budget_exceeded", agent.App.Tests.Start(run).Error.Code.Value);
    }
}