package ch.qos.logback.core.issue;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Example code illustrating locking policies in the JDK.
 * See http://jira.qos.ch/browse/LBCORE-97 for a discussion.
 * 
 * @author Joern Huxhorn
 */
public class LBCORE97 {

  static int THREAD_COUNT = 10;
  
  public static void main(String args[]) throws InterruptedException {
    
    System.out.println("Environment:");
    System.out.println("java.runtime.name    = "
        + System.getProperty("java.runtime.name"));
    System.out.println("java.runtime.version = "
        + System.getProperty("java.runtime.version"));
    System.out.println("java.vendor          = "
        + System.getProperty("java.vendor"));
    System.out.println("java.version         = "
        + System.getProperty("java.version"));
    System.out.println("java.vm.name         = "
        + System.getProperty("java.vm.name"));
    System.out.println("java.vm.info         = "
        + System.getProperty("java.vm.info"));

    System.out.println("os.name              = "
        + System.getProperty("os.name"));
    System.out.println("os.version           = "
        + System.getProperty("os.version"));
    System.out.println("os.arch              = "
        + System.getProperty("os.arch"));
    System.out.println("##########################################");

    usingSynchronized(THREAD_COUNT);
    usingUnfairLock(THREAD_COUNT);
    usingFairLock(THREAD_COUNT);
  }

  public static void execute(String text, Thread[] threads)
      throws InterruptedException {
    System.out.println("About to execute " + text + "...");
    int threadCount = threads.length;
    for (int i = 0; i < threadCount; i++) {
      threads[i].start();
    }

    Thread.sleep(10000);

    for (int i = 0; i < threadCount; i++) {
      threads[i].interrupt();
    }
    Thread.sleep(1000); // wait a moment for termination, to lazy for join ;)
  }

  public static void print(String text, Runnable[] runnables) {
    System.out.println("Results for " + text + ":");
    for (int i = 0; i < runnables.length; i++) {
      System.out.println("runnables[" + i + "]: " + runnables[i]);
    }
    System.out.println("##########################################");
  }

  public static void usingSynchronized(int threadCount)
      throws InterruptedException {
    Object lockObject = new Object();
    Runnable[] runnables = new Runnable[threadCount];
    Thread[] threads = new Thread[threadCount];

    for (int i = 0; i < threadCount; i++) {
      runnables[i] = new SynchronizedRunnable(lockObject);
      threads[i] = new Thread(runnables[i]);
    }
    String text = "usingSynchronized";
    execute(text, threads);
    print(text, runnables);
  }

  public static void usingUnfairLock(int threadCount)
      throws InterruptedException {
    Lock lock = new ReentrantLock();
    Runnable[] runnables = new Runnable[threadCount];
    Thread[] threads = new Thread[threadCount];

    for (int i = 0; i < threadCount; i++) {
      runnables[i] = new LockRunnable(lock);
      threads[i] = new Thread(runnables[i]);
    }

    String text = "usingUnfairLock";
    execute(text, threads);
    print(text, runnables);
  }

  public static void usingFairLock(int threadCount) throws InterruptedException {
    Lock lock = new ReentrantLock(true);
    Runnable[] runnables = new Runnable[threadCount];
    Thread[] threads = new Thread[threadCount];

    for (int i = 0; i < threadCount; i++) {
      runnables[i] = new LockRunnable(lock);
      threads[i] = new Thread(runnables[i]);
    }

    String text = "usingFairLock";
    execute(text, threads);
    print(text, runnables);
  }

  public static class SynchronizedRunnable implements Runnable {
    private final Object lockObject;
    private int counter;
    private boolean running;

    public SynchronizedRunnable(Object lockObject) {
      this.lockObject = lockObject;
      this.counter = 0;
      this.running = false;
    }

    public void run() {
      running = true;
      for (;;) {
        synchronized (lockObject) {
          counter++;
          try {
            Thread.sleep(10);
          } catch (InterruptedException ex) {
            break;
          }
        }
      }
      running = false;
    }

    public String toString() {
      return "SynchronizedRunnable[counter=" + counter + ", running=" + running
          + "]";
    }
  }

  public static class LockRunnable implements Runnable {
    private final Lock lock;
    private int counter;
    private boolean running;

    public LockRunnable(Lock lock) {
      this.lock = lock;
      this.counter = 0;
      this.running = false;
    }

    public void run() {
      running = true;
      for (;;) {
        lock.lock();
        try {
          counter++;
          Thread.sleep(10);
        } catch (InterruptedException ex) {
          break;
        } finally {
          lock.unlock();
        }
      }
      running = false;
    }

    public String toString() {
      return "LockRunnable[counter=" + counter + ", running=" + running + "]";
    }
  }
}
