'use strict';

const nodeFs = require('node:fs');
const nodePath = require('node:path');
const { spawn: nodeSpawn } = require('node:child_process');

const HELPER_FILENAME = 'aware-cam-proxy.exe';
const MAX_USERNAME_LENGTH = 254;
const MAX_HOST_LENGTH = 253;
const DEVICE_ID_PATTERN = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
const DNS_LABEL_PATTERN = /^[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?$/;
const ALTA_SUFFIXES = ['.avasecurity.com', '.avigilon.com'];

class ProxyLaunchError extends Error {
  constructor(message, code) {
    super(message);
    this.name = 'ProxyLaunchError';
    this.code = code;
  }
}

function validateDeploymentHost(value) {
  if (typeof value !== 'string' || value.length === 0 || value.length > MAX_HOST_LENGTH) {
    throw new ProxyLaunchError('Deployment host is invalid.', 'INVALID_DEPLOYMENT_HOST');
  }

  const host = value.toLowerCase();
  const labels = host.split('.');
  const hasAltaSuffix = ALTA_SUFFIXES.some((suffix) => host.endsWith(suffix));
  if (!hasAltaSuffix || labels.some((label) => !DNS_LABEL_PATTERN.test(label))) {
    throw new ProxyLaunchError('Deployment host is invalid.', 'INVALID_DEPLOYMENT_HOST');
  }

  return host;
}

function validateDeviceId(value) {
  if (typeof value !== 'string' || value.length !== 36 || !DEVICE_ID_PATTERN.test(value)) {
    throw new ProxyLaunchError('Device identifier is invalid.', 'INVALID_DEVICE_ID');
  }
  return value.toLowerCase();
}

function validateUsername(value) {
  if (typeof value !== 'string' || value.length === 0 || value.length > MAX_USERNAME_LENGTH || value.trim().length === 0) {
    throw new ProxyLaunchError('Alta username is invalid.', 'INVALID_USERNAME');
  }
  if (/[\u0000-\u001f\u007f-\u009f]/.test(value)) {
    throw new ProxyLaunchError('Alta username must not contain control characters.', 'INVALID_USERNAME');
  }
  return value;
}

function safeProcessError(error) {
  const source = error && typeof error.message === 'string' ? error.message : 'Unknown process error';
  return source.replace(/[\u0000-\u001f\u007f-\u009f]/g, ' ').slice(0, 512);
}

function safeMetadata(entry, status = entry.status) {
  return {
    processId: entry.processId,
    deviceId: entry.deviceId,
    startedAt: entry.startedAt,
    status
  };
}

function createProxyManager({
  appDirectory,
  fs = nodeFs,
  spawn = nodeSpawn,
  platform = process.platform,
  now = Date.now
} = {}) {
  if (platform !== 'win32') {
    throw new ProxyLaunchError('Proxy helper is supported only on the Windows platform.', 'UNSUPPORTED_PLATFORM');
  }
  if (typeof appDirectory !== 'string' || !nodePath.win32.isAbsolute(appDirectory)) {
    throw new ProxyLaunchError('Approved application directory must be an absolute path.', 'INVALID_APP_DIRECTORY');
  }
  if (typeof fs.existsSync !== 'function' || typeof spawn !== 'function' || typeof now !== 'function') {
    throw new TypeError('Invalid proxy manager dependency.');
  }

  const helperPath = nodePath.win32.join(appDirectory, HELPER_FILENAME);
  const trackedChildren = new Map();

  function removeIfOwned(processId, child) {
    const current = trackedChildren.get(processId);
    if (current && current.child === child) trackedChildren.delete(processId);
  }

  function launchProxy(request) {
    if (!request || typeof request !== 'object' || Array.isArray(request)) {
      throw new ProxyLaunchError('Proxy launch request is invalid.', 'INVALID_REQUEST');
    }

    const deploymentHost = validateDeploymentHost(request.deploymentHost);
    const deviceId = validateDeviceId(request.deviceId);
    const username = validateUsername(request.username);

    if (!fs.existsSync(helperPath)) {
      throw new ProxyLaunchError('Proxy helper was not found in the approved application directory.', 'HELPER_NOT_FOUND');
    }

    let child;
    try {
      child = spawn(
        helperPath,
        ['-a', deploymentHost, '-u', username, '-d', deviceId],
        {
          shell: false,
          detached: true,
          stdio: 'inherit',
          windowsHide: false
        }
      );
    } catch (error) {
      throw new ProxyLaunchError(
        `Failed to launch proxy helper: ${safeProcessError(error)}`,
        'SPAWN_FAILED'
      );
    }

    if (!child || !Number.isSafeInteger(child.pid) || child.pid <= 0 || typeof child.kill !== 'function') {
      throw new ProxyLaunchError('Proxy helper did not return a valid child process.', 'INVALID_CHILD_PROCESS');
    }
    if (trackedChildren.has(child.pid)) {
      try {
        child.kill('SIGTERM');
      } catch {
        // The new child is deliberately not tracked when its PID collides.
      }
      throw new ProxyLaunchError('Proxy helper returned a process identifier already in use.', 'DUPLICATE_PROCESS_ID');
    }

    const entry = {
      child,
      processId: child.pid,
      deviceId,
      startedAt: now(),
      status: 'running'
    };
    trackedChildren.set(entry.processId, entry);

    if (typeof child.once === 'function') {
      child.once('exit', () => removeIfOwned(entry.processId, child));
      child.once('error', () => removeIfOwned(entry.processId, child));
    }

    return { success: true, ...safeMetadata(entry) };
  }

  function stopProxy(processId) {
    if (!Number.isSafeInteger(processId) || processId <= 0) {
      throw new ProxyLaunchError('Process identifier is invalid.', 'INVALID_PROCESS_ID');
    }

    const entry = trackedChildren.get(processId);
    if (!entry) return { success: false, processId, status: 'not-tracked' };

    try {
      const requested = entry.child.kill('SIGTERM');
      if (!requested) {
        removeIfOwned(processId, entry.child);
        return {
          success: true,
          processId,
          deviceId: entry.deviceId,
          status: 'already-exited'
        };
      }

      removeIfOwned(processId, entry.child);
      return {
        success: true,
        processId,
        deviceId: entry.deviceId,
        status: 'stop-requested'
      };
    } catch (error) {
      const permissionDenied = error && (error.code === 'EPERM' || error.code === 'EACCES');
      return {
        success: false,
        processId,
        deviceId: entry.deviceId,
        status: permissionDenied ? 'permission-denied' : 'stop-failed',
        message: permissionDenied
          ? 'Unable to stop the tracked proxy process: permission denied.'
          : 'Unable to stop the tracked proxy process.'
      };
    }
  }

  function listTrackedProxies() {
    return Array.from(trackedChildren.values(), (entry) => safeMetadata(entry));
  }

  return Object.freeze({ launchProxy, stopProxy, listTrackedProxies });
}

module.exports = {
  HELPER_FILENAME,
  MAX_USERNAME_LENGTH,
  ProxyLaunchError,
  createProxyManager,
  validateDeploymentHost,
  validateDeviceId,
  validateUsername
};