import { type ChildProcess } from "node:child_process";
import { existsSync, mkdirSync, copyFileSync } from "node:fs";
import { join } from "node:path";
import { CONFIG } from "./config.js";
import * as api from "./firecracker-api.js";
import { deleteTap } from "./network.js";
import { ensureBaseImage, ensureSshKeypair, injectSshKey } from "./rootfs.js";
import { waitForSsh } from "./ssh.js";
import {
  setupNetwork,
  spawnFirecracker,
  bootVM,
  killFirecracker,
} from "./firecracker-vm.js";

function log(msg: string) {
  process.stderr.write(`[snapshot] ${msg}\n`);
}

export function snapshotExists(): boolean {
  return (
    existsSync(CONFIG.snapshot.statePath) &&
    existsSync(CONFIG.snapshot.memPath) &&
    existsSync(CONFIG.snapshot.rootfsPath)
  );
}

export async function createSnapshot() {
  ensureBaseImage();
  ensureSshKeypair();

  const snap = CONFIG.snapshot;
  const socketPath = join(CONFIG.socketDir, "snapshot.sock");

  log("Preparing snapshot rootfs...");
  mkdirSync(CONFIG.socketDir, { recursive: true });
  copyFileSync(CONFIG.baseRootfs, snap.rootfsPath);
  injectSshKey(snap.rootfsPath);

  log("Setting up network...");
  setupNetwork(snap.tapDevice);

  let proc: ChildProcess | null = null;

  try {
    log("Booting VM for snapshot...");
    proc = await spawnFirecracker(socketPath);
    await bootVM({
      socketPath,
      rootfsPath: snap.rootfsPath,
      tapDevice: snap.tapDevice,
      ip: snap.ip,
      octet: snap.octet,
    });

    log("Waiting for SSH...");
    await waitForSsh(snap.ip);

    log("Pausing VM...");
    await api.patchVm(socketPath, "Paused");

    log("Creating snapshot...");
    await api.putSnapshotCreate(socketPath, snap.statePath, snap.memPath);

    log("Snapshot created successfully.");
    log(`  State: ${snap.statePath}`);
    log(`  Memory: ${snap.memPath}`);
    log(`  Rootfs: ${snap.rootfsPath}`);
  } finally {
    await killFirecracker(proc, socketPath, "SIGKILL");
    deleteTap(snap.tapDevice);
  }
}