package class6_1_MultithreadPrimeAppJava_start;
/*
 * Created by yoder on 4/30/2015.
 * Modified every year...
 */

import java.util.ArrayList;
import java.util.List;

/**
 * This worker class creates a worker thread that works on finding prime numbers.
 */
public class PrimeFinder {
    private PrimeApp primeApp;
    private Thread worker;
    private List<Long> primes = new ArrayList<>();

    public PrimeFinder(PrimeApp primeApp) {
        this.primeApp = primeApp;
    }

    public void findPrimes() {
        worker = new Thread(()-> {
            for (long candidate = 100000000; candidate < Long.MAX_VALUE && !worker.isInterrupted(); candidate++) {
                if (isPrime(candidate)) {
                    primes.add(candidate);
                    String text = "Latest prime: " + candidate;
                    primeApp.setRecentPrime(text);
                    System.out.println(text);
                    System.out.println("worker.isInterrupted() = " + worker.isInterrupted());
                }
            }
        });
        worker.start();
    }

    /**
     * Slow O((2^b)) or worse algorithm (where b is the number of bits in candidate)
     *
     * TODO: Implement Miller-Rabin Primality test to get O(n^12) or better performance.
     * http://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_primality_test
     * (Why nine characters for one dash?
     *   Unicode character  Oct     Dec	    Hex	    HTML
     *            en dash   020023	8211	0x2013	&ndash;   )
     *
     * @param candidate candidate to test
     * @return true if candidate is prime.
     */
    private boolean isPrime(long candidate) {
        boolean isPrime = true;
        for(int divisor = 2; divisor < candidate && isPrime; divisor++) {
            if(candidate % divisor == 0) {
                isPrime = false;
            }
        }
        return isPrime;
    }

    public void interrupt() {
        if(worker == null) {
            System.err.println("Cannot stop finding primes. worker variable is null.");
        } else {
            worker.interrupt();
        }
    }
}