using System.Diagnostics.Metrics;

namespace HSchool.Server.Game;

/// <summary>Per-school tick counters surfaced in the Aspire dashboard.</summary>
internal sealed class GameMetrics : IDisposable
{
    public const string MeterName = "HSchool.Server.Game";

    private readonly Meter _meter;
    private readonly Counter<long> _ticks;
    private readonly Histogram<double> _tickDuration;
    private readonly UpDownCounter<long> _connections;

    private int _schools;

    public GameMetrics(IMeterFactory meterFactory)
    {
        _meter = meterFactory.Create(MeterName);
        _ticks = _meter.CreateCounter<long>("hschool.game.ticks", "{tick}", "Simulation steps executed.");
        _tickDuration = _meter.CreateHistogram<double>("hschool.game.tick.duration", "ms", "Wall time of one simulation step.");
        _connections = _meter.CreateUpDownCounter<long>("hschool.game.connections", "{connection}", "Open WebSocket connections.");
        _meter.CreateObservableGauge("hschool.game.schools", () => Volatile.Read(ref _schools), "{school}", "Schools that currently exist.");
    }

    public void RecordTick(double durationMs)
    {
        _ticks.Add(1);
        _tickDuration.Record(durationMs);
    }

    public void ClientConnected() => _connections.Add(1);

    public void ClientDisconnected() => _connections.Add(-1);

    public void SchoolsChanged(int count) => Volatile.Write(ref _schools, count);

    public void Dispose() => _meter.Dispose();
}