/****************************************************************************
@File Name: test.cpp
@Author: wangzhicheng
@Created Time: Fri 17 Mar 2017 07:21:52 PM CST
****************************************************************************/
#include <iostream>
#include <string>
#include <vector>
#include <thread>
#include <mutex>
#include <chrono>
using namespace std;
static const string BLANK = " ";
struct Employee
{
  string m_id;
  vector<string>lunch_partners;
  mutex m_lock;
  Employee(const string &id):m_id(id)
  {
  }
  void Output(string &strOut)
  {
    strOut = m_id;
    strOut += " lunch parntners = ";
    for(const auto &str:lunch_partners)
    {
      strOut += str;
      strOut += BLANK;
    }
  }
};
void SendMail(const Employee &e0, const Employee &e1)
{
  // e0 send mail to e1
  this_thread::sleep_for(chrono::seconds(1));
}
void assign_lunch_partner(Employee &e0, Employee &e1)
{
  if(&e0 == &e1) return;
  // Locks the given Lockable objects lock1, lock2, ..., lockn using a deadlock avoidance algorithm to avoid deadlock
  lock(e0.m_lock, e1.m_lock);
  lock_guard<mutex>lk0(e0.m_lock, adopt_lock);
  lock_guard<mutex>lk1(e1.m_lock, adopt_lock);
  e0.lunch_partners.emplace_back(e1.m_id);
  e1.lunch_partners.emplace_back(e0.m_id);
  SendMail(e0, e1);
  SendMail(e1, e0);
};
int main()
{
  Employee e0("e0");
  Employee e1("e1");
  Employee e2("e2");
  Employee e3("e3");
  string str;
  vector<thread>threads;
  threads.emplace_back(assign_lunch_partner, ref(e0), ref(e1));
  threads.emplace_back(assign_lunch_partner, ref(e0), ref(e2));
  threads.emplace_back(assign_lunch_partner, ref(e0), ref(e3));
  threads.emplace_back(assign_lunch_partner, ref(e1), ref(e2));
  for(auto &th:threads)
  {
    th.join();
  }
  e0.Output(str);
  cout << str << endl;
  e1.Output(str);
  cout << str << endl;
  e2.Output(str);
  cout << str << endl;
  e3.Output(str);
  cout << str << endl;

  return 0;
}