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

using namespace std;

#define TOTAL 10000
#define TRANSFER 100

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

// The mutex that we will use to lock access to the bank accounts
pthread_mutex_t mutex_bank;


// --------------------------------------------------
// 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_bank);

        // Read balance for each account
        int old_savings = savings;
        int old_checking = checking;

        // Update balance for each account
        savings = old_savings +  TRANSFER;

        if ( i % 3 ) {
            sleep(1);
        }

        checking = old_checking - TRANSFER;

        print();

        pthread_mutex_unlock (&mutex_bank);

        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_bank);

        // Read balance for each account
        int old_checking = checking;
        int old_savings = savings;

        // Update balance for each account
        checking = old_checking + TRANSFER;
        if ( i % 2 ) {
            sleep(1);
        }
        savings = old_savings -  TRANSFER;

        print();

        pthread_mutex_unlock (&mutex_bank);

        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;
    
    // Initialize the mutex
    pthread_mutex_init(&mutex_bank, 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, NULL);
    pthread_join(saver_thread, NULL);

    // Destory the mutex
    pthread_mutex_destroy(&mutex_bank);

    return 0;
}