import { spawn } from 'node:child_process';
import { createWriteStream } from 'node:fs';
import { mkdir } from 'node:fs/promises';
import { dirname } from 'node:path';

export const quote = value => "'" + String(value).replaceAll("'", "'\\''") + "'";

export function command(argv, { signal, outputPath, maxBytes = 100000 } = {}) {
  return new Promise((resolve, reject) => {
    const child = spawn(argv[0], argv.slice(1), { stdio: ['ignore', 'pipe', 'pipe'] });
    let output = '', bytes = 0, truncated = false, killTimer;
    const file = outputPath ? createWriteStream(outputPath, { mode: 0o600 }) : null;
    if (file) child.stdout.pipe(file);
    const collect = chunk => {
      const remaining = Math.max(0, maxBytes - bytes);
      output += chunk.subarray(0, remaining).toString();
      bytes += chunk.length;
      if (bytes > maxBytes) truncated = true;
    };
    if (!file) child.stdout.on('data', collect);
    child.stderr.on('data', collect);
    const abort = () => { child.kill('SIGTERM'); killTimer = setTimeout(() => child.kill('SIGKILL'), 5000); };
    signal?.addEventListener('abort', abort, { once: true });
    if (signal?.aborted) abort();
    child.on('error', reject);
    file?.on('error', reject);
    child.on('close', async (code, terminationSignal) => {
      clearTimeout(killTimer);
      signal?.removeEventListener('abort', abort);
      if (file && !file.writableFinished) await new Promise(r => file.once('finish', r));
      resolve({ output: output + (truncated ? '\n[output truncated]' : ''), exitCode: code ?? 128, signal: terminationSignal });
    });
  });
}

export class ContainerBackend {
  constructor(config, event = () => {}, execute = command) {
    this.config = config; this.event = event; this.execute = execute;
    this.root = `${config.work_root ?? '/workspace'}/.pi-study`;
    this.bare = `${this.root}/shared.git`;
    this.active = new Map(); this.nextTool = 0;
  }
  argv(script) {
    return [...(this.config.docker_prefix ?? ['docker']), 'exec', '--user', this.config.container_user ?? 'agent', this.config.container_name, 'bash', '-lc', script];
  }
  async checked(script, options) {
    const result = await this.execute(this.argv(script), options);
    if (result.exitCode) throw new Error(`Container command failed (${result.exitCode}): ${result.output}`);
    return result;
  }
  agentPath(id) {
    if (!/^agent-\d+$/.test(id)) throw new Error('Invalid agent ID');
    return `${this.root}/agents/${id}`;
  }
  async prepare() {
    const seed = this.config.seed_dir ?? `${this.config.work_root ?? '/workspace'}/solution`;
    await this.checked(`set -euo pipefail\ntest ! -e ${quote(this.root)}\nmkdir -p ${quote(this.root + '/agents')} ${quote(this.root + '/jobs')}\ngit clone --bare --no-hardlinks ${quote(seed)} ${quote(this.bare)}\ngit --git-dir=${quote(this.bare)} rev-parse --verify main\ngit --git-dir=${quote(this.bare)} symbolic-ref HEAD refs/heads/main`);
  }
  async createAgent(id) {
    const path = this.agentPath(id);
    await this.checked(`set -euo pipefail\ngit clone ${quote(this.bare)} ${quote(path)}\ngit -C ${quote(path)} config user.name ${quote(id)}\ngit -C ${quote(path)} config user.email ${quote(id + '@study.invalid')}\ngit -C ${quote(path)} checkout -b ${quote(id)} origin/main`);
  }
  async bash(id, script, { signal, timeout = 120 } = {}) {
    if (signal?.aborted) throw new Error('Tool cancelled');
    const job = `${this.root}/jobs/${id}-${++this.nextTool}.pid`;
    const cancelled = `${job}.cancelled`;
    const seconds = Math.max(1, Math.min(Number(timeout) || 120, 600));
    const wrapped = `set -uo pipefail\ncd ${quote(this.agentPath(id))}\ntest ! -e ${quote(cancelled)} || exit 130\nsetsid timeout --signal=TERM --kill-after=5s ${seconds}s bash -lc ${quote(script)} &\nchild=$!\nprintf '%s' "$child" > ${quote(job)}\nif test -e ${quote(cancelled)}; then kill -TERM -- "-$child" 2>/dev/null || true; sleep 1; kill -KILL -- "-$child" 2>/dev/null || true; fi\nwait "$child"\nstatus=$?\nrm -f ${quote(job)}\nexit "$status"`;
    const kill = async () => {
      await this.execute(this.argv(`touch ${quote(cancelled)}; if test -f ${quote(job)}; then pid=$(cat ${quote(job)}); case "$pid" in ''|*[!0-9]*) exit 1;; esac; kill -TERM -- "-$pid" 2>/dev/null || true; sleep 1; kill -KILL -- "-$pid" 2>/dev/null || true; rm -f ${quote(job)}; fi`));
    };
    this.active.set(job, kill);
    const onAbort = () => { void kill(); };
    signal?.addEventListener('abort', onAbort, { once: true });
    try { return await this.execute(this.argv(wrapped), { signal }); }
    finally { signal?.removeEventListener('abort', onAbort); this.active.delete(job); if (signal?.aborted) await kill(); }
  }
  async revision() {
    const revision = (await this.checked(`git --git-dir=${quote(this.bare)} rev-parse refs/heads/main`)).output.trim();
    if (!/^[0-9a-f]{40,64}$/.test(revision)) throw new Error('Invalid snapshot revision');
    return revision;
  }
  async snapshot(outputPath, revision = null) {
    await mkdir(dirname(outputPath), { recursive: true });
    revision ??= await this.revision();
    if (!/^[0-9a-f]{40,64}$/.test(revision)) throw new Error('Invalid snapshot revision');
    await this.checked(`git --git-dir=${quote(this.bare)} archive --format=tar.gz ${quote(revision)}`, { outputPath });
    return { path: outputPath, revision };
  }
  async stop() { await Promise.allSettled([...this.active.values()].map(kill => kill())); }
}