// host-services.js
// Copyright (C) 2022 DTP Technologies, LLC
// License: Apache-2.0

'use strict';

const os = require('os');
const diskusage = require('diskusage-ng');

const path = require('path');
const fs = require('fs');
const si = require('systeminformation');

require('dotenv').config({ path: path.resolve(__dirname, '..', '..', '.env') });

const dgram = require('dgram');
const numeral = require('numeral');

const {
  SitePlatform,
  SiteAsync,
  SiteLog,
  SiteError,
} = require(path.join(__dirname, '..', '..', 'lib', 'site-lib'));

const { CronJob } = require('cron');

const CRON_TIMEZONE = 'America/New_York';

module.pkg = require(path.resolve(__dirname, '..', '..', 'package.json'));
module.config = {
  componentName: 'host-services',
  root: path.resolve(__dirname, '..', '..'),
};

module.log = new SiteLog(module, module.config.componentName);

class CacheStats {

  constructor ( ) {
    this.itemCount = 0;
    this.dataSize = 0;

    this.expireCount = 0;
    this.expireDataSize = 0;

    this.hitCount = 0;
    this.hitDataSize = 0;

    this.missCount = 0;
    this.missDataSize = 0;
  }

  add (size) {
    this.itemCount += 1;
    this.dataSize += (size / 1024.0);
  }

  remove (size) {
    this.itemCount -= 1;
    this.dataSize -= size / 1024.0;
  }

  hit (size) {
    this.hitCount += 1;
    this.hitDataSize += (size / 1024.0);
  }

  miss (size) {
    this.missCount += 1;
    this.missDataSize += (size / 1024.0);
  }

  expire (size) {
    this.expireCount += 1;
    this.expireDataSize += size;
  }

  report ( ) {
    const report = {
      itemCount: this.itemCount,
      dataSize: this.dataSize,

      expireCount: this.expireCount,
      expireDataSize: this.expireDataSize,

      hitCount: this.hitCount,
      hitDataSize: this.hitDataSize,

      missCount: this.missCount,
      missDataSize: this.missDataSize,
    };

    this.resetCounters();

    return report;
  }

  resetCounters ( ) {
    this.expireCount = 0;
    this.expireDataSize = 0;

    this.hitCount = 0;
    this.hitDataSize = 0;
    
    this.missCount = 0;
    this.missDataSize = 0;
  }
}

class HostCacheTransaction {

  get tid ( ) { return this.message.tid; }
  get cmd ( ) { return this.message.cmd; }
  get params ( ) { return this.message.params; }

  get address ( ) { return this.rinfo.address; }
  get port ( ) { return this.rinfo.port; }
  get size ( ) { return this.rinfo.size; }

  constructor (message, rinfo) {
    this.created = Date.now(); // timestamp, not Date instance

    this.message = message;
    this.rinfo = rinfo;

    this.flags = {
      isFetched: false,
      isCached: false,
      isResolved: false,
      isError: false,
    };
  }

  async getFile ( ) {
    const { minio: minioService } = module.services;
    const filePath = path.join(
      process.env.DTP_HOST_CACHE_PATH,
      this.params.bucket,
      this.params.key,
    );
    const res = {
      cmd: this.cmd,
      success: true,
      message: undefined,
      file: {
        stats: undefined,
        path: undefined,
      },
    };
  
    try {
      res.file.stats = await fs.promises.stat(filePath);
      if (!res.file.stats.isFile()) {
        throw new SiteError(500, 'invalid object requested');
      }
      res.file.path = filePath;
      this.flags.isCached = true;
      module.cacheStats.hit(res.file.stats.size);
      return module.manager.resolveTransaction(this, res);
    } catch (error) {
      if (error.code !== 'ENOENT') {
        module.log.error('failed to stat requested object', { transaction: this, error });
        res.success = false;
        res.statusCode = 500;
        res.message = error.message;
        this.error = error;
        this.flags.isError = true;
        return module.manager.resolveTransaction(this, res);
      }
      // fall through to MinIO fetch since file not found in cache
    }
  
    try {
      await minioService.downloadFile({
        bucket: this.params.bucket,
        key: this.params.key,
        filePath,
      });
      res.file.path = filePath;
      res.file.stats = await fs.promises.stat(filePath);
      if (!res.file.stats.isFile()) {
        throw new SiteError(500, 'invalid object requested');
      }
      this.flags.isFetched = true;
      module.cacheStats.add(res.file.stats.size);
      module.cacheStats.miss(res.file.stats.size);
      return module.manager.resolveTransaction(this, res);
    } catch (error) {
      if (error.code !== 'NotFound') {
        module.log.error('failed to fetch requested object from MinIO', { transaction: this, error });
        res.success = false;
        res.statusCode = 500;
        res.message = error.message;
        this.error = error;
        this.flags.isError = true;
        return module.manager.resolveTransaction(this, res);
      }
    }
  
    res.success = false;
    res.statusCode = 404;
    res.message = 'Not Found';
    this.error = new SiteError(404, 'Not Found');
    this.flags.isError = true;
    return module.manager.resolveTransaction(this, res);
  }

  async cancel (reason) {
    const res = {
      res: this.cmd,
      success: false,
      message: `Operation canceled: ${reason}`,
    };
    return module.manager.resolveTransaction(this, res);
  }

  async sendResponse (res) {
    const NOW = Date.now();
    const duration = this.duration = (NOW - this.created) / 1000.0;

    const { flags } = this;
    flags.isResolved = true;

    const payload = { tid: this.tid, res, flags, duration };
    const reply = Buffer.from(JSON.stringify(payload));
    module.server.send(reply, this.port, this.address);
  }
}

class TransactionManager {
  constructor ( ) {
    this.transactions = { };
  }

  async addTransaction (transaction) {
    if (this.hasPendingRequest(transaction)) {
      this.transactions[transaction.tid] = transaction; // queue it and be done
      return;
    }

    this.transactions[transaction.tid] = transaction; // queue it and process the command
    switch (transaction.cmd) {
      case 'getFile':
        return transaction.getFile();
  
      default:
        break; // unknown/undefined command
    }
  
    this.log.error('invalid host-services command', {
      cmd: transaction.cmd,
      params: transaction.params,
      from: {
        address: transaction.address,
        port: transaction.port,
      },
    });
    await module.manager.cancelTransaction(transaction, 'Rejected');
  }

  hasPendingRequest (transaction) {
    if (!transaction) { return false; }
    const keys = Object.keys(this.transactions);
    const match = keys.find((key) => {
      const cmp = this.transactions[key];
      if (!cmp) { return false; }
      if (cmp.cmd !== transaction.cmd) { return false; }
      if (cmp.params.bucket !== transaction.params.bucket) { return false; }
      if (cmp.params.key !== transaction.params.key) { return false; }
      return true;
    });
    return !!match;
  }

  async resolveTransaction (transaction, res) {
    await transaction.sendResponse(res);
    this.removeTransaction(transaction, 'resolved');
  }

  async cancelTransaction (transaction, reason) {
    await transaction.cancel();
    this.removeTransaction(transaction, reason);
  }

  removeTransaction (transaction) {
    if (this.transactions[transaction.tid]) {
      delete this.transactions[transaction.tid];
    }
  }

  async expireTransactions ( ) {
    const NOW = Date.now();
    const keys = Object.keys(this.transactions);
    let expired = 0;
    await SiteAsync.each(keys, async (key) => {
      const transaction = this.transactions[key];
      const age = NOW - transaction.created;
      if (age > (1000 * 30)) {
        module.log.alert('expiring transaction', { transaction });
        await this.cancelTransaction(transaction, 'expired');
        ++expired;
      }
    }, 8);
    module.log.info('transaction watchdog', { expired });
  }
}

module.onHostCacheMessage = async (message, rinfo) => {
  try {
    message = message.toString('utf8');
    message = JSON.parse(message);
  
    const transaction = new HostCacheTransaction(message, rinfo);
    module.manager.addTransaction(transaction);
  } catch (error) {
    module.log.error('failed to receive UDP message', { message, error });
  }
};

module.startHostCache = async (basePath) => {
  basePath = basePath || process.env.DTP_HOST_CACHE_PATH;

  const NOW = Date.now();
  const dir = await fs.promises.opendir(basePath);

  for await (const dirent of dir) {
    if (dirent.isDirectory()) {
      module.log.debug('cache start descend into directory', { name: dirent.name });
      await module.startHostCache(path.join(basePath, dirent.name));
    }
    if (dirent.isFile()) {
      const filePath = path.join(basePath, dirent.name);
      const stats = await fs.promises.stat(filePath);
      const age = (NOW - stats.atime.valueOf()) / 1000.0; // seconds
      module.log.debug('examining file', { filePath, age: numeral(age).format('hh:mm:ss') });
      if ((age / 60.0) > 60.0) {
        module.log.info('expiring file', { filePath, age: numeral(age).format('hh:mm:ss') });
        await fs.promises.rm(filePath, { force: true });
      } else {
        module.cacheStats.add(stats.size);
      }
    }
  }

  // await dir.close();
  module.log.info('cache startup cleanup complete', { basePath });
};

/**
 * When a file is accessed for read or otherwise, it's atime is updated. If the
 * atime of a file exceeds the configured max file idle time, the file is
 * removed.
 * @param {String} basePath 
 */
module.cleanHostCache = async (basePath) => {
  const NOW = Date.now(); // timestamp, not Date instance
  basePath = basePath || process.env.DTP_HOST_CACHE_PATH;
  module.log.info('cache directory cleanup', { path: basePath });

  const dir = await fs.promises.opendir(basePath);
  for await (const dirent of dir) {
    if (dirent.isDirectory()) {
      module.log.debug('cache clean descend into directory', { name: dirent.name });
      await module.cleanHostCache(path.join(basePath, dirent.name));
    }
    if (dirent.isFile()) {
      const filePath = path.join(basePath, dirent.name);
      const stats = await fs.promises.stat(filePath);
      const age = NOW - stats.atime.valueOf();
      module.log.debug('examining file', { filePath, age: numeral(age / 1000.0).format('hh:mm:ss') });
      if ((age / 1000.0 / 60.0) > 60.0) {
        module.log.info('expiring file', { filePath, age: numeral(age / 1000.0).format('hh:mm:ss') });
        await fs.promises.rm(filePath, { force: true });
        module.cacheStats.remove(stats.size);
        module.cacheStats.expire(stats.size);
      }
    }
  }

  module.log.info('cache directory cleanup complete', { basePath });
};

module.expireTransactions = async ( ) => {
  await module.manager.expireTransactions();
};

module.registerHost = async ( ) => {
  const NOW = new Date();

  const mongoose = require('mongoose');
  const NetHost = mongoose.model('NetHost');

  const memory = await si.mem();

  module.host = new NetHost();
  module.host.created = NOW;
  module.host.status = 'starting';
  module.host.hostname = os.hostname();

  module.host.arch = os.arch();
  module.host.cpus = os.cpus().map((cpu) => {
    return {
      model: cpu.model,
      speed: cpu.speed,
    };
  });

  module.host.totalmem = memory.total;
  module.host.freemem = memory.available;

  module.host.platform = os.platform();
  module.host.release = os.release();
  module.host.version = os.version();

  module.host.network = (await si.networkInterfaces()).map((iface) => {
    return {
      iface: iface.iface,
      speed: iface.speed,
      mac: iface.mac,
      ip4: iface.ip4,
      ip4subnet: iface.ip4subnet,
      ip6: iface.ip6,
      ip6subnet: iface.ip6subnet,
      flags: {
        internal: iface.internal,
        virtual: iface.virtual,
      },
    };
  });
  module.log.info('host registration: network', { network: module.host.network });

  await module.host.save();
  module.host = module.host.toObject();
  module.log.info('registered host with platform', { host: module.host._id });
  return module.host;
};

module.reportHostStats = async ( ) => {
  const NOW = new Date();

  const mongoose = require('mongoose');
  const NetHost = mongoose.model('NetHost');
  const NetHostStats = mongoose.model('NetHostStats');

  const memory = await si.mem();

  const network = (await si.networkStats('*')).map((iface) => {
    const record = { iface: iface.iface };

    record.rxDropped = iface.rx_dropped;
    record.rxErrors = iface.rx_errors;

    record.txDropped = iface.tx_dropped;
    record.txErrors = iface.tx_errors;

    if (iface.ms !== 0) {
      record.rxPerSecond = iface.rx_sec / (iface.ms / 1000.0);
      record.txPerSecond = iface.tx_sec / (iface.ms / 1000.0);
    } else {
      record.rxPerSecond = 0;
      record.txPerSecond = 0;
    }

    return record;
  });

  const cpus = os.cpus().map((cpu) => {
    return {
      user: cpu.times.user,
      nice: cpu.times.nice,
      sys: cpu.times.sys,
      idle: cpu.times.idle,
      irq: cpu.times.irq,
    };
  });
  const load = os.loadavg();
  const cache = module.cacheStats.report();
  const disk = {
    cache: await module.getDiskUsage(process.env.DTP_HOST_CACHE_PATH),
  };

  const cpuDeltas = [ ];
  if (module.oldCpuStats) {
    for (let idx = 0; idx < cpus.length; ++idx) {
      cpuDeltas.push({
        user: cpus[idx].user - module.oldCpuStats[idx].user,
        nice: cpus[idx].nice - module.oldCpuStats[idx].nice,
        sys: cpus[idx].sys - module.oldCpuStats[idx].sys,
        idle: cpus[idx].idle - module.oldCpuStats[idx].idle,
        irq: cpus[idx].irq - module.oldCpuStats[idx].irq,
      });
    }
  } else {
    cpus.forEach(( ) => {
      cpuDeltas.push({
        user: 0,
        nice: 0,
        sys: 0,
        idle: 0,
        irq: 0,
      });
    });
  }
  module.oldCpuStats = cpus;

  await NetHostStats.create({
    created: NOW,
    host: module.host._id,
    load,
    cpus: cpuDeltas,
    memory, cache, disk, network,
  });
  await NetHost.updateOne(
    { _id: module.host._id },
    {
      updated: NOW,
      freemem: memory.available,
    },
  );
  module.log.info('platform host report', { host: module.host._id, });
};

module.getDiskUsage = (pathname) => {
  return new Promise((resolve, reject) => {
    diskusage(pathname, (err, usage) => {
      if (err) {
        return reject(err);
      }
      usage.pctUsed = (usage.used / usage.total) * 100.0;
      return resolve(usage);
    });
  });
};

module.setHostStatus = async (status) => {
  if (!module.host) {
    return;
  }

  const NOW = new Date();
  const mongoose = require('mongoose');
  const NetHost = mongoose.model('NetHost');

  await NetHost.updateOne(
    { _id: module.host._id },
    {
      $set: {
        updated: NOW,
        status,
      },
    },
  );
};

module.expireNetHosts = async ( ) => {
  const NOW = new Date();
  const OLDEST = new Date(Date.now() - 1000 * 60 * 2);

  const mongoose = require('mongoose');
  const NetHost = mongoose.model('NetHost');

  const hosts = await NetHost.find({
    status: { $nin: ['inactive', 'crashed'] },
    updated: { $lt: OLDEST }
  });
  module.log.info('expired host cleanup', { hostCount: hosts.length });

  await SiteAsync.each(hosts, async (host) => {
    try {
      await NetHost.updateOne(
        { _id: host._id },
        {
          $set: {
            updated: NOW,
            status: 'crashed',
          },
        },
      );
    } catch (error) {
      module.log.error('failed to clean expired host', { host, error });
    }
  }, 4);
};

(async ( ) => {
  try {
    process.on('unhandledRejection', (error, p) => {
      module.log.error('Unhandled rejection', {
        error: error,
        promise: p,
        stack: error.stack
      });
    });
    
    process.on('warning', (error) => {
      module.log.alert('warning', { error });
    });

    process.once('SIGINT', async ( ) => {
      module.log.info('SIGINT received');
      module.log.info('requesting shutdown...');

      await module.setHostStatus('shutdown');
      const exitCode = await SitePlatform.shutdown();
      await module.setHostStatus('inactive');

      process.nextTick(( ) => {
        process.exit(exitCode);
      });
    });

    module.log.info('ensuring host-services path exists', { path: process.env.DTP_HOST_CACHE_PATH });
    await fs.promises.mkdir(process.env.DTP_HOST_CACHE_PATH, { recursive: true });

    module.networkStats = await si.networkStats('*');

    module.log.info('starting cache service', { path: process.env.DTP_HOST_CACHE_PATH });
    module.cacheStats = new CacheStats();
    await module.startHostCache(process.env.DTP_HOST_CACHE_PATH);
    module.log.info('cache stats at start', { stats: module.cacheStats });

    /*
     * Host Cache server socket setup
     */
    module.log.info('creating server UDP socket');
    module.server = dgram.createSocket('udp4', module.onHostCacheMessage);
    module.log.info('binding server UDP socket');
    module.server.bind(8000);

    /*
     * Site Platform startup
     */
    await SitePlatform.startPlatform(module);

    module.log.info('starting transaction manager');
    module.manager = new TransactionManager();
    module.expireJob = new CronJob('*/5 * * * * *', module.expireTransactions, null, true, CRON_TIMEZONE);

    /*
     * Worker startup
     */
    const cleanCronJob = process.env.DTP_HOST_CACHE_CLEAN_CRON || '*/30 * * * * *';
    module.log.info('starting host cache clean cron', { cleanCronJob });
    module.cleanupJob = new CronJob(cleanCronJob, module.cleanHostCache, null, true, CRON_TIMEZONE);

    module.log.info('starting stats report job');
    module.statsReportJob = new CronJob('*/5 * * * * *', module.reportHostStats, null, true, CRON_TIMEZONE);

    module.log.info('starting host expiration job');
    module.expireHostsJob = new CronJob('*/20 * * * * *', module.expireNetHosts, null, true, CRON_TIMEZONE);

    module.log.info('registering host with DTP Sites platform', { });
    await module.registerHost();
    await module.setHostStatus('active');

    module.log.info(`${module.pkg.name} v${module.pkg.version} ${module.config.componentName} started`);
  } catch (error) {
    module.log.error('failed to start Host Cache worker', { error });
    process.exit(-1);
  }

})();