// Author: Matheus Eduardo Garbelini
// Code: Philosophers dinner

import java.util.Random;

public class Deadlock {

    static CrazyThread[] Threads; // Stores the thread classes
    static Object[] Locks; // Stores the locks
    static String[] LocksFlags;


    public static void main(String[] args) {

        // Initialize n threads, where n is the number of cores on current machine
        int ncores = Runtime.getRuntime().availableProcessors();
        System.out.println("Number of available cores: " + ncores);

        Locks = new Object[ncores];
        Threads = new CrazyThread[ncores];
        LocksFlags = new String[ncores];

        // Initialize threads
        for (int i = 0; i < ncores; i++) {
            LocksFlags[i] = "_";
            Locks[i] = new Object();
            Threads[i] = new CrazyThread();
            Threads[i].ncore = i;
            Threads[i].maxcores = ncores;
            System.out.println("Core number: " + i);
        }
        // Start threads
        for (int i = 0; i < ncores; i++) {
            Threads[i].start();
        }

    }


    public static class CrazyThread extends Thread {
        public int ncore;
        public int maxcores;
        public Random random = new Random(); // Each seed is different at class allocation (nanoTime used)

        public void run() {

            while (true) {
                int start_delay = random.nextInt(10);
                int busy_delay = random.nextInt(100);
                threadSleep(start_delay);

                synchronized (Locks[ncore]) {
                    LocksFlags[ncore] = String.valueOf(ncore); // Set flag for first lock
                    printThreads(); // print locks status
                    int next_lock = (ncore + 1) % maxcores;
                    synchronized (Locks[next_lock]) {
                        LocksFlags[next_lock] = String.valueOf(ncore); // Set flag for second lock
                        printThreads(); // print locks status
                        threadSleep(busy_delay);
                    }
                    LocksFlags[next_lock] = "_";
                }
                LocksFlags[ncore] = "_";
                printThreads(); // Print freed locks

            }

        }

        void threadSleep(int ms) {
            try { // Yes, java requires to use an exception even to sleep a thread, oh my god!!!
                Thread.sleep(ms);
            } catch (Exception e) {
            }
        }

        void printThreads() {
            String threadsText = "";
            for (int i = 0; i < maxcores; i++) {
                if (i == 0)
                    threadsText += "["; // first lock flag

                threadsText += LocksFlags[i];

                if (i == maxcores - 1)
                    threadsText += "]";
                else
                    threadsText += ",";
            }

            System.out.println(threadsText);
        }
    }
}