import { spawnSync } from 'node:child_process';
import * as fs from 'node:fs';
import * as os from 'node:os';
import * as path from 'node:path';
import { fileURLToPath } from 'node:url';
import type { SampledPoint } from './pointcloudSample.js';

function scriptPath(): string {
  const here = path.dirname(fileURLToPath(import.meta.url));
  return path.join(here, '..', 'scripts', 'deviation_heatmap_gpu.py');
}

function resolvePython3(): string {
  const fromEnv = process.env.PYTHON3_PATH?.trim();
  if (fromEnv) return fromEnv;
  for (const p of ['/usr/bin/python3', '/usr/local/bin/python3']) {
    try {
      if (fs.existsSync(p)) return p;
    } catch {
      /* ignore */
    }
  }
  return 'python3';
}

export function deviationGpuEnabled(): boolean {
  const v = process.env.ASSEMBLY_USE_GPU?.trim().toLowerCase();
  return v === '1' || v === 'true' || v === 'yes';
}

export type GpuDeviationResult = {
  colors: Float32Array;
  vertexCount: number;
  dispMin: number;
  dispMax: number;
};

/**
 * 调用 scripts/deviation_heatmap_gpu.py（PyTorch CUDA KNN）。
 * 返回 null 时由调用方回退 CPU。
 */
export function tryRunDeviationGpu(
  cadFilePath: string,
  sampled: SampledPoint[],
): GpuDeviationResult | null {
  if (!deviationGpuEnabled()) return null;
  const script = scriptPath();
  if (!fs.existsSync(script)) return null;
  if (sampled.length === 0) return null;

  const py = resolvePython3();
  const tmp = fs.mkdtempSync(path.join(os.tmpdir(), 'dev-gpu-'));
  const ptsFile = path.join(tmp, 'points.bin');
  const buf = Buffer.allocUnsafe(sampled.length * 12);
  for (let i = 0; i < sampled.length; i++) {
    const o = i * 12;
    buf.writeFloatLE(sampled[i]!.x, o);
    buf.writeFloatLE(sampled[i]!.y, o + 4);
    buf.writeFloatLE(sampled[i]!.z, o + 8);
  }
  fs.writeFileSync(ptsFile, buf);

  try {
    const r = spawnSync(
      py,
      [script, '--cad', cadFilePath, '--points', ptsFile, '--out-dir', tmp],
      {
        encoding: 'utf-8',
        maxBuffer: 64 * 1024 * 1024,
        timeout: 30 * 60 * 1000,
        env: { ...process.env, PYTHONUNBUFFERED: '1' },
      },
    );

    if (r.error) {
      console.warn('[DeviationGPU]', r.error.message);
      return null;
    }
    if (r.status === 2) {
      console.warn('[DeviationGPU] 回退 CPU：', (r.stdout || '').trim().slice(-500) || 'exit 2');
      return null;
    }
    if (r.status !== 0) {
      console.warn('[DeviationGPU] 失败 status=', r.status, (r.stderr || r.stdout || '').slice(0, 800));
      return null;
    }

    const resultJsonPath = path.join(tmp, 'result.json');
    if (!fs.existsSync(resultJsonPath)) return null;
    const meta = JSON.parse(fs.readFileSync(resultJsonPath, 'utf-8')) as {
      ok?: boolean;
      vertexCount?: number;
      dispMin?: number;
      dispMax?: number;
    };
    if (!meta.ok || !meta.vertexCount) return null;

    const colorsPath = path.join(tmp, 'colors.bin');
    if (!fs.existsSync(colorsPath)) return null;
    const cBuf = fs.readFileSync(colorsPath);
    const expectedBytes = meta.vertexCount * 3 * 4;
    if (cBuf.length !== expectedBytes) {
      console.warn('[DeviationGPU] colors.bin 长度异常', cBuf.length, '!=', expectedBytes);
      return null;
    }
    const colors = new Float32Array(cBuf.buffer, cBuf.byteOffset, meta.vertexCount * 3);

    return {
      colors,
      vertexCount: meta.vertexCount,
      dispMin: meta.dispMin ?? 0,
      dispMax: meta.dispMax ?? 1,
    };
  } finally {
    try {
      fs.rmSync(tmp, { recursive: true, force: true });
    } catch {
      /* ignore */
    }
  }
}