package org.simantics.db.common;

import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

import org.simantics.db.AsyncReadGraph;
import org.simantics.db.exception.DatabaseException;

public class GraphSemaphore extends Semaphore {

	private static final long serialVersionUID = 2114861433176831938L;
	
	private final AsyncReadGraph graph;
	
	public GraphSemaphore(AsyncReadGraph graph, int permits) {
		super(permits);
		this.graph = graph;
	}

	public void waitFor(int permits) throws DatabaseException, InterruptedException {
		
    	boolean success = false;
    	success = tryAcquire(permits);
    	if(success) return;
    	
    	while(!success) {
    		
    		if(graph.performPending()) {
    			// Some task was done
    			success = tryAcquire(permits);		
    		} else {
    			// Nothing to do - just wait
            	try {
        			success = tryAcquire(permits, 10, TimeUnit.SECONDS);
        			if(!success) throw new DatabaseException("Timeout while waiting for async request to complete.");
        		} catch (InterruptedException e) {
        			throw new DatabaseException(e);
        		}
    		}
    		    		
    	}

		
	}
	
	

}