using SFML.Graphics;
using SFML.Window;
using SFML.System;
using System.Diagnostics;
using FluidSim.Scenarios;
using FluidSim.Audio;

namespace FluidSim;

public class Program
{
    private const int SampleRate = 44100;
    private static volatile bool running = true;
    // Global step counter – incremented every simulation step
    private static long stepCount = 0;

    public static void Main()
    {
        var mode = new VideoMode(new Vector2u(1280, 720));
        var window = new RenderWindow(mode, "Fluid Simulation");
        window.SetVerticalSyncEnabled(true);
        window.Closed += (_, _) => { running = false; window.Close(); };

        var soundEngine = new SoundEngine(bufferCapacity: 2048);
        soundEngine.Volume = 70;
        soundEngine.Start();

        var stopwatch = Stopwatch.StartNew();

        // --- Warmup: fill audio buffer with silence ---
        int warmupSamples = SampleRate / 2;                // 0.5 s
        float[] warmup = new float[warmupSamples];
        for (int i = 0; i < warmupSamples; i++)
            warmup[i] = 0;
        soundEngine.WriteSamples(warmup, warmupSamples);

        // Reset timer after warmup – this is the “real‑time zero”
        stopwatch.Restart();
        stepCount = 0;                                     // simulation steps start now

        // --- Initialise the simulation scenario ---
        Simulation.Initialize(SampleRate);

        const int chunkSize = 2048;
        float[] buffer = new float[chunkSize];

        double lastLogTime = 0.0;                         // for periodic speed printout

        while (window.IsOpen)
        {
            window.DispatchEvents();

            // --- Compute how many audio samples are needed since last frame ---
            double currentTime = stopwatch.Elapsed.TotalSeconds;
            double elapsed = currentTime;                  // since stopwatch was reset
            int samplesNeeded = (int)(elapsed * SampleRate) - (int)(stepCount);
            // (stepCount is total generated samples, so we just need the remainder)

            // --- Generate the required number of simulation steps ---
            while (samplesNeeded > 0 && running)
            {
                int toGenerate = Math.Min(samplesNeeded, chunkSize);
                for (int i = 0; i < toGenerate; i++)
                {
                    buffer[i] = Simulation.Process();
                    stepCount++;
                }
                soundEngine.WriteSamples(buffer, toGenerate);
                samplesNeeded -= toGenerate;
            }

            // --- Display speed ---
            double simTime = stepCount / (double)SampleRate;
            double wallTime = stopwatch.Elapsed.TotalSeconds;
            double speed = (wallTime > 0) ? simTime / wallTime : 0.0;

            // Update window title with instant speed
            window.SetTitle($"FluidSim | Speed: {speed:F3}× | Steps: {stepCount}");

            // Console log once per second
            if (wallTime - lastLogTime >= 1.0)
            {
                Console.WriteLine($"Speed: {speed:F3}×  ({stepCount} steps, {wallTime:F2}s wall)");
                lastLogTime = wallTime;
            }

            // --- Rendering (placeholder) ---
            window.Clear(Color.Black);
            window.Display();
        }

        // --- Cleanup ---
        soundEngine.Dispose();
        window.Dispose();
    }
}