import { spawn, execFile, type ChildProcess } from 'node:child_process';
import { randomBytes } from 'node:crypto';
import { existsSync } from 'node:fs';
import { resolve } from 'node:path';
import { promisify } from 'node:util';

const execFileAsync = promisify(execFile);
export const bridgePython =
  process.env.BRIDGE_PYTHON ??
  (existsSync(resolve('.venv/bin/python')) ? resolve('.venv/bin/python') : 'python3');
export async function stopProcess(child: ChildProcess): Promise<void> {
  if (child.exitCode !== null || child.signalCode !== null) return;
  await new Promise<void>((resolve) => {
    const timer = setTimeout(() => child.kill('SIGKILL'), 3000);
    child.once('exit', () => {
      clearTimeout(timer);
      resolve();
    });
    child.kill('SIGTERM');
  });
}
export async function startBridge() {
  const token = randomBytes(32).toString('hex');
  const child = spawn(bridgePython, ['-m', 'mujoco_control_bridge', '--port', '0'], {
    env: { ...process.env, PYTHONPATH: '', PYTHONNOUSERSITE: '1', MUJOCO_CONTROL_TOKEN: token },
    stdio: ['ignore', 'pipe', 'pipe'],
  });
  let output = '',
    errors = '';
  child.stderr.on('data', (chunk: Buffer) => {
    errors = (errors + chunk.toString()).slice(-65536);
  });
  try {
    const endpoint = await new Promise<string>((resolve, reject) => {
      const timeout = setTimeout(() => reject(new Error(`桥接启动超时：${errors}`)), 15000);
      child.once('error', (error) => {
        clearTimeout(timeout);
        reject(error);
      });
      child.once('exit', () => {
        clearTimeout(timeout);
        reject(new Error(`桥接启动失败：${errors}`));
      });
      child.stdout.on('data', (chunk: Buffer) => {
        output += chunk.toString();
        const ready = output.match(/CONTROL_BRIDGE_READY (\{[^\n]+\})/);
        if (ready) {
          clearTimeout(timeout);
          resolve((JSON.parse(ready[1]) as { endpoint: string }).endpoint);
        }
      });
    });
    return {
      endpoint,
      token,
      stop: () => stopProcess(child),
      errors: () => errors,
      python: async (
        script: string,
        python = bridgePython,
        environment: Record<string, string> = {},
      ) => {
        const { stdout, stderr } = await execFileAsync(python, ['-c', script], {
          env: {
            ...process.env,
            PYTHONPATH: '',
            PYTHONNOUSERSITE: '1',
            ...environment,
            MUJOCO_CONTROL_TOKEN: token,
            MUJOCO_CONTROL_ENDPOINT: endpoint,
          },
          timeout: 120000,
          maxBuffer: 4 * 1024 * 1024,
        });
        return { stdout, stderr };
      },
    };
  } catch (error) {
    await stopProcess(child);
    throw error;
  }
}