//Implementation of Alley class with inner alley
//CP Lab 3
//Course 02158 Concurrent Programming, DTU

//Hans Henrik Lovengreen

public class DoubleAlley extends Alley {
   
    int up = 0, upInner = 0, down = 0;

    DoubleAlley() {
    }

   @Override
    /* Block until car no. may enter alley */
    public synchronized void enter(int no) throws InterruptedException {
        if (no < 3) {
            while (upInner > 0) { wait(); }
            down++;
        } else if (no < 5) {
            while (up   > 0) { wait(); }
            down++;
        } else {
            while (down > 0) { wait(); }
            up++;
            upInner++;
        }
    }

    @Override
    /* Register that car no. has left the alley */
    public synchronized void leave(int no) {
        if (no < 5) {
            down--; 
            if (down == 0) notifyAll();
        } else {
            up--; 
            if (up   == 0) notifyAll();
        }
    }
    
    @Override
    /* Register that car no. has left the inner alley */
    public synchronized void leaveInner(int no) {
        upInner--; 
        if (upInner == 0) notifyAll();
   }

}