#include <pthread.h>
#include <iostream>
#include <cassert>

using namespace std;

#define TOTAL 200

int checking = TOTAL/2;
int savings = TOTAL/2;

// Using multiple locks to demonstrate deadlock
pthread_mutex_t mutex_checking;
pthread_mutex_t mutex_savings;


// --------------------------------------------------
// Print bank statement
// --------------------------------------------------
void print() {

  cout << "Statement:" 
       << " checking=" << checking
       << " savings=" << savings << endl;

}

// --------------------------------------------------
// Trying to save money
// --------------------------------------------------
void* saver(void* p_nb_transfers) {

  int nb = *((int*)p_nb_transfers);

  for ( int i = 0; i < nb; i++ ) {
    
    pthread_mutex_lock (&mutex_checking);
    int balance = checking;
    sleep(1);

    pthread_mutex_lock (&mutex_savings);
    savings += balance;
    pthread_mutex_unlock (&mutex_savings);

    checking = 0;
    pthread_mutex_unlock (&mutex_checking);

    print();

    sleep(1);
  }

  // Can use pthread_exit to terminate a thread
  //pthread_exit(0); 
  // Or can simply return from the start function of this thread
  return NULL;

}

// --------------------------------------------------
// Want to spend money
// --------------------------------------------------
void* spender(void* p_nb_transfers) {

  int nb = *((int*)p_nb_transfers);

  for ( int i = 0; i < nb; i++ ) {

    pthread_mutex_lock (&mutex_savings);
    int balance = savings;
    sleep(1);

    pthread_mutex_lock (&mutex_checking);
    checking += balance;
    pthread_mutex_unlock (&mutex_checking);

    savings = 0;
    pthread_mutex_lock (&mutex_savings);

    print();

    sleep(1);
  }

  // Can use pthread_exit to terminate a thread
  //pthread_exit(0); 
  // Or can simply return from the start function of this thread
  return NULL;

}


//-----------------------------------------------------------------------------
int main(int argc, char ** argv)
{

  if ( argc < 2 ) {
    cerr << "Please specify number of bank account transfers to make\n";
    return 0;
  } 

  int nb_transfers = atoi(argv[1]);
  int *p_nb_transfers = &nb_transfers;

  pthread_mutex_init(&mutex_checking, NULL);
  pthread_mutex_init(&mutex_savings, NULL);

  pthread_t spender_thread;
  pthread_t saver_thread;
  
  // Create first thread 
  int rc = pthread_create(&spender_thread, NULL, spender, (void*)p_nb_transfers);
  if ( rc ) {
    cerr << "Failed to create spender thread\n";
    return 1;
  }

  // Create second thread
  rc = pthread_create(&saver_thread, NULL, saver, (void*)p_nb_transfers);
  if ( rc ) {
    cerr << "Failed to create saver thread\n";
    return 1;
  }

  // Wait for threads to finish
  pthread_join(spender_thread, 0);
  pthread_join(saver_thread, 0);

  pthread_mutex_destroy(&mutex_checking);
  pthread_mutex_destroy(&mutex_savings);

  return 0;
}