/**
 * Created by nuintun on 2016/1/14.
 */

var spawn = require('./spawn');
var exec = require('child_process').exec;

/**
 *
 * @param pid
 * @param signal
 * @param callback
 */
module.exports = function (pid, signal, callback){
  var tree = {};
  var pidsToProcess = {};

  tree[pid] = [];
  pidsToProcess[pid] = 1;

  if (typeof signal === 'function') {
    signal = 'SIGKILL';
    callback = signal;
  }

  switch (process.platform) {
    // win32
    case 'win32':
      exec('taskkill /pid ' + pid + ' /T /F', callback);
      break;
    // darwin
    case 'darwin':
      buildProcessTree(pid, tree, pidsToProcess, function (parentPid){
        return spawn('pgrep', ['-P', parentPid]);
      }, function (){
        killAll(tree, signal, callback);
      });
      break;
    // linux
    default:
      buildProcessTree(pid, tree, pidsToProcess, function (parentPid){
        return spawn('ps', ['-o', 'pid', '--no-headers', '--ppid', parentPid]);
      }, function (){
        killAll(tree, signal, callback);
      });
      break;
  }
};

function killAll(tree, signal, callback){
  var killed = {};

  try {
    Object.keys(tree).forEach(function (pid){
      tree[pid].forEach(function (pidpid){
        if (!killed[pidpid]) {
          killPid(pidpid, signal);
          killed[pidpid] = 1;
        }
      });
      if (!killed[pid]) {
        killPid(pid, signal);
        killed[pid] = 1;
      }
    });
  } catch (error) {
    if (callback) {
      return callback(error);
    } else {
      throw error;
    }
  }
  if (callback) {
    return callback();
  }
}

function killPid(pid, signal){
  try {
    process.kill(parseInt(pid, 10), signal);
  }
  catch (error) {
    if (error.code !== 'ESRCH') throw error;
  }
}

function buildProcessTree(parentPid, tree, pidsToProcess, spawnChildProcessesList, callback){
  var allData = '';
  var ps = spawnChildProcessesList(parentPid);

  ps.stdout.on('data', function (data){
    allData += data.toString('ascii');
  });

  var onClose = function (code){
    delete pidsToProcess[parentPid];

    if (code != 0) {
      // no more parent processes
      if (Object.keys(pidsToProcess).length == 0) {
        callback();
      }
      return;
    }

    allData.match(/\d+/g).forEach(function (pid){
      pid = parseInt(pid, 10);
      tree[parentPid].push(pid);
      tree[pid] = [];
      pidsToProcess[pid] = 1;
      buildProcessTree(pid, tree, pidsToProcess, spawnChildProcessesList, callback);
    });
  };

  ps.on('close', onClose);
}