using Dalamud.Bindings.ImGui;
using Dalamud.Plugin.SelfTest;

namespace HellionChat.SelfTests;

// Optional metric capture. Accumulates 1000 steady-state frames of ImGui IO
// counters plus the plugin's full-Draw wall-time (Plugin.LastDrawMs),
// then writes a single perf-baseline.json into the plugin ConfigDirectory so
// the cycle-notes author can copy the baseline figures without a separate
// profiling harness. The step only records — it never fails on a threshold
// (the budgets are evaluated by a human against the JSON ("optional,
// manual"). It returns Waiting until the sample window fills, mirroring the
// per-frame poll idiom of ThemeSwitchSelfTestStep.
internal sealed class PerformanceBaselineStep : ISelfTestStep
{
    // Steady-state window. 1000 frames ≈ 16s at 60fps, long enough to
    // average out GC blips without making the manual step tedious.
    private const int TargetFrames = 1000;

    // Rough draw-call proxy: ImGui emits 6 indices per quad, so vertices/6 is an
    // intentional under-count of draw work, not the exact quad count.
    private const int VerticesPerQuadProxy = 6;

    private readonly Plugin _plugin;

    private int _frames;
    private ulong _lastFrameCount;
    private double _drawMsSum;
    private double _drawMsMax;
    private long _vertexSum;
    private long _vertexMax;
    private double _deltaMsSum;
    private double _deltaMsMax;
    private string? _logPath;

    public PerformanceBaselineStep(Plugin plugin)
    {
        _plugin = plugin;
    }

    public string Name => "Hellion Chat - Performance baseline capture";

    public SelfTestStepResult RunStep()
    {
        var io = ImGui.GetIO();

        // Count each real frame once. Without the FrameCount gate a step that
        // is polled more than once per frame would inflate the sample count.
        var frameCount = Plugin.Interface.UiBuilder.FrameCount;
        if (frameCount != _lastFrameCount)
        {
            _lastFrameCount = frameCount;
            _frames++;

            var drawMs = _plugin.LastDrawMs;
            _drawMsSum += drawMs;
            if (drawMs > _drawMsMax)
                _drawMsMax = drawMs;

            long vertices = io.MetricsRenderVertices;
            _vertexSum += vertices;
            if (vertices > _vertexMax)
                _vertexMax = vertices;

            var deltaMs = io.DeltaTime * 1000f;
            _deltaMsSum += deltaMs;
            if (deltaMs > _deltaMsMax)
                _deltaMsMax = deltaMs;
        }

        if (_frames < TargetFrames)
        {
            ImGui.Text(
                $"Sampling steady-state… {_frames}/{TargetFrames} frames. "
                    + "Keep the chat window visible and idle."
            );
            return SelfTestStepResult.Waiting;
        }

        _logPath ??= WriteBaselineLog();
        ImGui.Text($"Baseline captured ({TargetFrames} frames). Wrote: {_logPath}");
        return SelfTestStepResult.Pass;
    }

    public void CleanUp()
    {
        _frames = 0;
        _lastFrameCount = 0;
        _drawMsSum = 0;
        _drawMsMax = 0;
        _vertexSum = 0;
        _vertexMax = 0;
        _deltaMsSum = 0;
        _deltaMsMax = 0;
        _logPath = null;
    }

    private string WriteBaselineLog()
    {
        // Disk write happens here, never in the per-frame hot path.
        return PerformanceBaselineLog.Write(
            avgDrawMs: _drawMsSum / TargetFrames,
            maxDrawMs: _drawMsMax,
            avgDrawCallsProxy: _vertexSum / (double)TargetFrames / VerticesPerQuadProxy,
            maxDrawCallsProxy: _vertexMax / (double)VerticesPerQuadProxy,
            avgDeltaMs: _deltaMsSum / TargetFrames,
            maxDeltaMs: _deltaMsMax,
            frames: TargetFrames
        );
    }
}