#!/usr/bin/env node

'use strict';

/**
 * This module is started with src/bin/run.sh. It sets up a Express HTTP and a Socket.IO Server.
 * Static file Requests are answered directly from this module, Socket.IO messages are passed
 * to MessageHandler and minfied requests are passed to minified.
 */

/*
 * 2011 Peter 'Pita' Martischka (Primary Technology Ltd)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const log4js = require('log4js');
log4js.replaceConsole();

// wtfnode should be loaded after log4js.replaceConsole() so that it uses log4js for logging, and it
// should be above everything else so that it can hook in before resources are used.
const wtfnode = require('wtfnode');

/*
 * early check for version compatibility before calling
 * any modules that require newer versions of NodeJS
 */
const NodeVersion = require('./utils/NodeVersion');
NodeVersion.enforceMinNodeVersion('10.17.0');
NodeVersion.checkDeprecationStatus('10.17.0', '1.8.8');

const UpdateCheck = require('./utils/UpdateCheck');
const db = require('./db/DB');
const express = require('./hooks/express');
const hooks = require('../static/js/pluginfw/hooks');
const npm = require('npm/lib/npm.js');
const pluginDefs = require('../static/js/pluginfw/plugin_defs');
const plugins = require('../static/js/pluginfw/plugins');
const settings = require('./utils/Settings');
const util = require('util');

const logger = log4js.getLogger('server');

const State = {
  INITIAL: 1,
  STARTING: 2,
  RUNNING: 3,
  STOPPING: 4,
  STOPPED: 5,
  EXITING: 6,
  WAITING_FOR_EXIT: 7,
  STATE_TRANSITION_FAILED: 8,
};

let state = State.INITIAL;

class Gate extends Promise {
  constructor() {
    let res;
    super((resolve) => { res = resolve; });
    this.resolve = res;
  }
}

const removeSignalListener = (signal, listener) => {
  logger.debug(`Removing ${signal} listener because it might interfere with shutdown tasks. ` +
               `Function code:\n${listener.toString()}\n` +
               `Current stack:\n${(new Error()).stack.split('\n').slice(1).join('\n')}`);
  process.off(signal, listener);
};

let startDoneGate;
exports.start = async () => {
  switch (state) {
    case State.INITIAL:
      break;
    case State.STARTING:
      await startDoneGate;
      // Retry. Don't fall through because it might have transitioned to STATE_TRANSITION_FAILED.
      return await exports.start();
    case State.RUNNING:
      return express.server;
    case State.STOPPING:
    case State.STOPPED:
    case State.EXITING:
    case State.WAITING_FOR_EXIT:
    case State.STATE_TRANSITION_FAILED:
      throw new Error('restart not supported');
    default:
      throw new Error(`unknown State: ${state.toString()}`);
  }
  logger.info('Starting Etherpad...');
  startDoneGate = new Gate();
  state = State.STARTING;
  try {
    // Check if Etherpad version is up-to-date
    UpdateCheck.check();

    // start up stats counting system
    const stats = require('./stats');
    stats.gauge('memoryUsage', () => process.memoryUsage().rss);
    stats.gauge('memoryUsageHeap', () => process.memoryUsage().heapUsed);

    process.on('uncaughtException', (err) => exports.exit(err));
    // As of v14, Node.js does not exit when there is an unhandled Promise rejection. Convert an
    // unhandled rejection into an uncaught exception, which does cause Node.js to exit.
    process.on('unhandledRejection', (err) => { throw err; });

    for (const signal of ['SIGINT', 'SIGTERM']) {
      // Forcibly remove other signal listeners to prevent them from terminating node before we are
      // done cleaning up. See https://github.com/andywer/threads.js/pull/329 for an example of a
      // problematic listener. This means that exports.exit is solely responsible for performing all
      // necessary cleanup tasks.
      for (const listener of process.listeners(signal)) {
        removeSignalListener(signal, listener);
      }
      process.on(signal, exports.exit);
      // Prevent signal listeners from being added in the future.
      process.on('newListener', (event, listener) => {
        if (event !== signal) return;
        removeSignalListener(signal, listener);
      });
    }

    await util.promisify(npm.load)();
    await db.init();
    await plugins.update();
    const installedPlugins = Object.values(pluginDefs.plugins)
        .filter((plugin) => plugin.package.name !== 'ep_etherpad-lite')
        .map((plugin) => `${plugin.package.name}@${plugin.package.version}`)
        .join(', ');
    logger.info(`Installed plugins: ${installedPlugins}`);
    logger.debug(`Installed parts:\n${plugins.formatParts()}`);
    logger.debug(`Installed hooks:\n${plugins.formatHooks()}`);
    await hooks.aCallAll('loadSettings', {settings});
    await hooks.aCallAll('createServer');
  } catch (err) {
    logger.error('Error occurred while starting Etherpad');
    state = State.STATE_TRANSITION_FAILED;
    startDoneGate.resolve();
    return await exports.exit(err);
  }

  logger.info('Etherpad is running');
  state = State.RUNNING;
  startDoneGate.resolve();

  // Return the HTTP server to make it easier to write tests.
  return express.server;
};

let stopDoneGate;
exports.stop = async () => {
  switch (state) {
    case State.STARTING:
      await exports.start();
      // Don't fall through to State.RUNNING in case another caller is also waiting for startup.
      return await exports.stop();
    case State.RUNNING:
      break;
    case State.STOPPING:
      await stopDoneGate;
      // fall through
    case State.INITIAL:
    case State.STOPPED:
    case State.EXITING:
    case State.WAITING_FOR_EXIT:
    case State.STATE_TRANSITION_FAILED:
      return;
    default:
      throw new Error(`unknown State: ${state.toString()}`);
  }
  logger.info('Stopping Etherpad...');
  const stopDoneGate = new Gate();
  state = State.STOPPING;
  try {
    let timeout = null;
    await Promise.race([
      hooks.aCallAll('shutdown'),
      new Promise((resolve, reject) => {
        timeout = setTimeout(() => reject(new Error('Timed out waiting for shutdown tasks')), 3000);
      }),
    ]);
    clearTimeout(timeout);
  } catch (err) {
    logger.error('Error occurred while stopping Etherpad');
    state = State.STATE_TRANSITION_FAILED;
    stopDoneGate.resolve();
    return await exports.exit(err);
  }
  logger.info('Etherpad stopped');
  state = State.STOPPED;
  stopDoneGate.resolve();
};

let exitGate;
let exitCalled = false;
exports.exit = async (err = null) => {
  /* eslint-disable no-process-exit */
  if (err === 'SIGTERM') {
    // Termination from SIGTERM is not treated as an abnormal termination.
    logger.info('Received SIGTERM signal');
    err = null;
  } else if (err != null) {
    logger.error(err.stack || err.toString());
    process.exitCode = 1;
    if (exitCalled) {
      logger.error('Error occurred while waiting to exit. Forcing an immediate unclean exit...');
      process.exit(1);
    }
  }
  exitCalled = true;
  switch (state) {
    case State.STARTING:
    case State.RUNNING:
    case State.STOPPING:
      await exports.stop();
      // Don't fall through to State.STOPPED in case another caller is also waiting for stop().
      // Don't pass err to exports.exit() because this err has already been processed. (If err is
      // passed again to exit() then exit() will think that a second error occurred while exiting.)
      return await exports.exit();
    case State.INITIAL:
    case State.STOPPED:
    case State.STATE_TRANSITION_FAILED:
      break;
    case State.EXITING:
      await exitGate;
      // fall through
    case State.WAITING_FOR_EXIT:
      return;
    default:
      throw new Error(`unknown State: ${state.toString()}`);
  }
  logger.info('Exiting...');
  exitGate = new Gate();
  state = State.EXITING;
  exitGate.resolve();
  // Node.js should exit on its own without further action. Add a timeout to force Node.js to exit
  // just in case something failed to get cleaned up during the shutdown hook. unref() is called on
  // the timeout so that the timeout itself does not prevent Node.js from exiting.
  setTimeout(() => {
    logger.error('Something that should have been cleaned up during the shutdown hook (such as ' +
                 'a timer, worker thread, or open connection) is preventing Node.js from exiting');
    wtfnode.dump();
    logger.error('Forcing an unclean exit...');
    process.exit(1);
  }, 5000).unref();
  logger.info('Waiting for Node.js to exit...');
  state = State.WAITING_FOR_EXIT;
  /* eslint-enable no-process-exit */
};

if (require.main === module) exports.start();