// Runs one simulation to completion in Node (Dawn WebGPU) and returns the pressure signal.

import { create, globals } from "webgpu";
import { defaultParams, type PhysParams } from "../params.ts";
import { Simulation } from "../sim/simulation.ts";

let devicePromise: Promise<GPUDevice> | null = null;

export function getDevice(): Promise<GPUDevice> {
  if (!devicePromise) {
    Object.assign(globalThis, globals);
    devicePromise = (async () => {
      const gpu = create([]);
      const adapter = await gpu.requestAdapter();
      if (!adapter) throw new Error("No WebGPU adapter");
      const device = await adapter.requestDevice();
      device.addEventListener("uncapturederror", (ev) => {
        console.error("WebGPU error:", (ev as GPUUncapturedErrorEvent).error.message);
      });
      return device;
    })();
  }
  return devicePromise;
}

export interface RunResult {
  params: PhysParams;
  audio: Float32Array;
  fs: number;
  steps: number;
  seconds: number;
  grid: { nx: number; ny: number };
  dt: number;
  maxContactForce: number;
}

export async function runSimulation(overrides: Partial<PhysParams>, log: (s: string) => void = () => {}): Promise<RunResult> {
  const params: PhysParams = { ...defaultParams, ...overrides };
  const device = await getDevice();
  const sim = new Simulation(device, params);
  const t0 = performance.now();
  let lastLog = t0;
  let maxContactForce = 0;
  while (sim.phase !== "done") {
    await sim.runBatch();
    const st = sim.status();
    if (st.stick) maxContactForce = Math.max(maxContactForce, st.stick.maxForce);
    const now = performance.now();
    if (now - lastLog > 5000) {
      lastLog = now;
      log(`  ${st.phase} t=${st.t.toFixed(2)} s, ${(sim.totalSteps / ((now - t0) / 1000) / 1e3).toFixed(0)} k steps/s`);
    }
  }
  log("  loop finished");
  const seconds = (performance.now() - t0) / 1000;
  const result: RunResult = {
    params,
    audio: sim.processedAudio().slice(),
    fs: sim.fs,
    steps: sim.totalSteps,
    seconds,
    grid: { nx: sim.grid.nx, ny: sim.grid.ny },
    dt: sim.dt,
    maxContactForce,
  };
  // Buffers are left to the garbage collector: explicit destroy() aborts inside the Dawn bindings.
  return result;
}