package ReadersWriters;

import ReadersWriters.MemorySegment;
import ReadersWriters.MemoryWrapper;
import ReadersWriters.Process;

public class SolutionWithSynchronization implements MemoryWrapper{

    private MemorySegment _memory = null;
    private boolean writing;
    private int readers = 0;

    public SolutionWithSynchronization(){
    _memory = new MemorySegment();
    }

    public void read(Process p){
        p.setState("wantread");
        beforeRead();
        p.setState("reading");
        _memory.read();
        p.setState("idle");
        afterRead();
    }

    public void write(Process p){
        p.setState("wantwrite");
        beforeWrite();
        p.setState("writing");
        _memory.write();
        p.setState("idle");
        afterWrite();
    }

    private synchronized void beforeRead() {
        while(!okToRead()){
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        readers++;
    }

    public boolean okToRead(){
        return !writing;
    }

    private synchronized void beforeWrite() {
        while(!okToWrite())
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        writing = true;
    }

    public boolean okToWrite(){
        return !writing && readers == 0;
    }

    private synchronized void afterRead() {
        readers--;
        notifyAll();

    }

    private synchronized void afterWrite() {
        writing = false;
        notifyAll();
    }
}