const { spawn, exec } = require('child_process');
const fs = require('fs').promises;
const path = require('path');
const { EventEmitter } = require('events');

class FirecrackerManager extends EventEmitter {
  constructor() {
    super();
    this.vms = new Map();
    this.basePath = '/tmp/sandboxes';
    this.kernelPath = '/tmp/vmlinux';
    this.rootfsPath = '/tmp/rootfs.ext4';
    this.firecrackerAvailable = false;
  }

  async initialize() {
    await fs.mkdir(this.basePath, { recursive: true });
    
    // Check if Firecracker is available
    try {
      await new Promise((resolve, reject) => {
        exec('firecracker --version', (error, stdout) => {
          if (error) {
            console.warn('⚠️ Firecracker not available');
            this.firecrackerAvailable = false;
            resolve();
          } else {
            console.log('✅ Firecracker available:', stdout.trim());
            this.firecrackerAvailable = true;
            resolve();
          }
        });
      });
    } catch (e) {
      this.firecrackerAvailable = false;
    }

    // Check for KVM device
    try {
      await fs.access('/dev/kvm');
      console.log('✅ KVM device available');
    } catch (e) {
      console.warn('⚠️ /dev/kvm not found - Firecracker requires KVM');
      this.firecrackerAvailable = false;
    }

    console.log(`Firecracker Manager initialized (available: ${this.firecrackerAvailable})`);
  }

  async createVM(vmId, options = {}) {
    if (!this.firecrackerAvailable) {
      throw new Error('Firecracker not available');
    }

    const vmPath = path.join(this.basePath, vmId);
    await fs.mkdir(vmPath, { recursive: true });

    const socketPath = path.join(vmPath, 'firecracker.sock');
    const configPath = path.join(vmPath, 'config.json');

    // Create Firecracker VM configuration
    const config = {
      'boot-source': {
        kernel_image_path: this.kernelPath,
        boot_args: 'console=ttyS0 reboot=k panic=1 pci=off'
      },
      'drives': [{
        drive_id: 'rootfs',
        path_on_host: this.rootfsPath,
        is_root_device: true,
        is_read_only: false
      }],
      'machine-config': {
        vcpu_count: 1,
        mem_size_mib: 512,
        ht_enabled: false
      },
      'network-interfaces': [{
        iface_id: 'eth0',
        guest_mac: '06:00:AC:10:00:02',
        host_dev_name: 'tap0'
      }]
    };

    await fs.writeFile(configPath, JSON.stringify(config, null, 2));

    const vm = {
      vmId,
      path: vmPath,
      socketPath,
      configPath,
      process: null,
      createdAt: Date.now(),
      status: 'created'
    };

    this.vms.set(vmId, vm);
    return vm;
  }

  async startVM(vmId) {
    const vm = this.vms.get(vmId);
    if (!vm) throw new Error('VM not found');

    return new Promise((resolve, reject) => {
      // Start Firecracker process
      const proc = spawn('firecracker', [
        '--api-sock', vm.socketPath,
        '--config-file', vm.configPath
      ], {
        stdio: ['ignore', 'pipe', 'pipe']
      });

      vm.process = proc;
      vm.status = 'running';

      proc.stdout.on('data', (data) => {
        console.log(`[${vmId}][stdout]: ${data.toString().trim()}`);
      });

      proc.stderr.on('data', (data) => {
        console.log(`[${vmId}][stderr]: ${data.toString().trim()}`);
      });

      proc.on('exit', (code) => {
        console.log(`[${vmId}] VM exited with code: ${code}`);
        vm.status = 'stopped';
      });

      // Wait for socket to be ready
      setTimeout(() => {
        resolve(vm);
      }, 2000);
    });
  }

  async executeInVM(vmId, command) {
    const vm = this.vms.get(vmId);
    if (!vm) throw new Error('VM not found');
    if (vm.status !== 'running') throw new Error('VM not running');

    // Send command via Firecracker API
    // This would use the socket API to communicate with the VM
    // Implementation depends on your rootfs setup

    return {
      vmId,
      command,
      status: 'executed'
    };
  }

  async stopVM(vmId) {
    const vm = this.vms.get(vmId);
    if (!vm) return;

    if (vm.process) {
      vm.process.kill('SIGTERM');
    }

    try {
      await fs.rm(vm.path, { recursive: true, force: true });
    } catch (e) {
      console.error('Cleanup error:', e.message);
    }

    this.vms.delete(vmId);
  }
}

module.exports = FirecrackerManager;