@page "/alarms-historian"
@* Live status of the local node's IAlarmHistorianSink (queue depth, drain state) via the
   HistorianAdapterActor.GetStatus query landed in F11. *@
@attribute [Authorize(Policy = AdminUiPolicies.AuthenticatedRead)]
@rendermode RenderMode.InteractiveServer
@using Akka.Actor
@using Akka.Hosting
@using ZB.MOM.WW.OtOpcUa.AdminUI.Clients
@using ZB.MOM.WW.OtOpcUa.Core.AlarmHistorian
@using ZB.MOM.WW.OtOpcUa.Runtime
@using ZB.MOM.WW.OtOpcUa.Runtime.Historian
@inject IRequiredActor<HistorianAdapterActorKey> HistorianActor
@implements IAsyncDisposable

<PageErrorBoundary>
<div class="d-flex justify-content-between align-items-center mb-3">
    <h4 class="mb-0">Alarms historian sink</h4>
</div>

<div class="text-muted small mb-3">Polling every @((int)(_interval == TimeSpan.Zero ? PollSeconds : _interval.TotalSeconds)) s.</div>

@if (_reading is { Availability: HistorianSinkAvailability.NotOnThisRole })
{
    <section class="panel notice rise mt-3" style="animation-delay:.04s">@_reading.Message Checking again every @((int)HistorianSinkStatusReader.NotRegisteredPollInterval.TotalSeconds) s in case the node is still starting.</section>
}
else if (_status is null && _reading is { Availability: HistorianSinkAvailability.Unavailable })
{
    <section class="panel notice notice-alert rise mt-3" style="animation-delay:.04s">@_reading.Message Retrying every @PollSeconds s.</section>
}
else if (_status is null)
{
    <p class="mt-3">Loading…</p>
}
else
{
    @if (_reading is { Availability: HistorianSinkAvailability.Unavailable })
    {
        <section class="panel notice notice-alert rise mt-3" style="animation-delay:.04s">
            @_reading.Message Showing the last status read at @_statusReadUtc?.ToString("u").
        </section>
    }
    <section class="card-grid rise mt-3" style="animation-delay:.08s">
        <div class="metric-card">
            <div class="panel-head">Queue</div>
            <div class="kv"><span class="k">Depth</span><span class="v numeric">@_status.QueueDepth</span></div>
            <div class="kv"><span class="k">Dead-lettered</span><span class="v numeric">@_status.DeadLetterDepth</span></div>
            <div class="kv"><span class="k">Evicted (lifetime)</span><span class="v numeric">@_status.EvictedCount</span></div>
        </div>

        <div class="metric-card">
            <div class="panel-head">Drain state</div>
            <div class="kv"><span class="k">State</span><span class="v"><span class="@StateChipClass(_status.DrainState)">@_status.DrainState</span></span></div>
            <div class="kv"><span class="k">Last drain</span><span class="v">@(_status.LastDrainUtc?.ToString("u") ?? "—")</span></div>
            <div class="kv"><span class="k">Last success</span><span class="v">@(_status.LastSuccessUtc?.ToString("u") ?? "—")</span></div>
            @if (!string.IsNullOrWhiteSpace(_status.LastError))
            {
                <div class="kv"><span class="k">Last error</span><span class="v text-danger small" title="@_status.LastError">@DisplayText.Abbreviate(_status.LastError, 80)</span></div>
            }
        </div>
    </section>
}
</PageErrorBoundary>

@code {
    private const int PollSeconds = 5;

    // The Fleet.razor lifecycle (R04 L3): IAsyncDisposable, a _disposed flag, an overlap guard and a
    // page-lifetime CTS, so a queued tick after teardown neither Asks nor renders.
    private HistorianSinkStatus? _status;
    private DateTime? _statusReadUtc;
    private HistorianSinkReading? _reading;
    private Timer? _timer;
    private int _tickRunning;
    private TimeSpan _interval;
    private readonly CancellationTokenSource _cts = new();
    private volatile bool _disposed;

    protected override async Task OnInitializedAsync()
    {
        await RefreshAsync();
        // "Not registered" is usually permanent (an admin-only node) but can also be a driver node still
        // starting up, so it keeps a slow re-poll instead of stopping for good (review r0 M6).
        _interval = HistorianSinkStatusReader.PollIntervalFor(_reading?.Availability);
        _timer = new Timer(_ => _ = InvokeAsync(RefreshAsync), null, _interval, _interval);
    }

    private async Task RefreshAsync()
    {
        if (_disposed || Interlocked.Exchange(ref _tickRunning, 1) == 1) return;
        try
        {
            _reading = await HistorianSinkStatusReader.ReadAsync(
                () => HistorianActor.ActorRef, HistorianSinkStatusReader.AskTimeout, _cts.Token);
            if (_reading.Status is not null)
            {
                _status = _reading.Status;
                _statusReadUtc = DateTime.UtcNow;
            }
        }
        catch (Exception ex) when (ex is OperationCanceledException or ObjectDisposedException)
        {
            return; // the page went away mid-Ask
        }
        finally
        {
            Volatile.Write(ref _tickRunning, 0);
        }

        if (_disposed) return;
        var interval = HistorianSinkStatusReader.PollIntervalFor(_reading?.Availability);
        if (_timer is not null && interval != _interval)
        {
            _interval = interval;
            try { _timer.Change(interval, interval); }
            catch (ObjectDisposedException) { return; }
        }

        StateHasChanged();
    }

    private static string StateChipClass(HistorianDrainState state) => state switch
    {
        HistorianDrainState.Disabled => "chip chip-idle",
        HistorianDrainState.Idle => "chip chip-idle",
        HistorianDrainState.Draining => "chip chip-ok",
        HistorianDrainState.BackingOff => "chip chip-caution",
        _ => "chip chip-idle",
    };

    public async ValueTask DisposeAsync()
    {
        _disposed = true;
        _cts.Cancel();
        // Drains an in-flight callback (System.Threading.Timer async dispose, .NET 6+). The callback only
        // schedules the tick, so a tick may still hold _cts — skip the dispose then (see Hosts.razor).
        if (_timer is not null) await _timer.DisposeAsync();
        if (Volatile.Read(ref _tickRunning) == 0) _cts.Dispose();
    }
}