package Sequenic.T2ext.Selection;

import java.util.IdentityHashMap;
import java.util.Map;

import Sequenic.T2.Coverage.BasicPath;
import Sequenic.T2.Seq.Trace;
import Sequenic.T2.StreamTraces.TraceFilter;

/**
 * Note: Do NOT use the same instance for both selecting and synthesizing.
 * 
 * Suppose a certain BasicPath is not modification-traversing, but can not be synthesized.
 * If synthesizeCoverage is called first the backing selector will be invoked and it will return null.
 * If isModificationTraversing is subsequently invoked, the cached result is retrieved and
 * the BasicPath will be marked as modification-traversing, even if it is not.
 * 
 * Conversely, if isModificationTraversing is invoked first the BasicPath will be cached to 
 * as the 'result'. if synthesizeCoverage is subsequently called, the BasicPath will be returned
 * unmodified, even if it would otherwise be modified by the backing selector.
 * 
 * 
 * @author jeiels
 *
 */
final class CachedSelector implements ISelector, TraceFilter {

	private final ISelector selector;
	private final Map<BasicPath,Boolean> cacheBoolean;
	
	private static final int defaultSize = 351;
	
	CachedSelector(final ISelector selector)
	{
		this.selector = selector;
		
		cacheBoolean = new IdentityHashMap<BasicPath, Boolean>(defaultSize);		
	}
	
	static CachedSelector create(final ISelector selector, boolean justSelect)
	{
		if(justSelect)
			return new CachedSelector(selector);
		throw new UnsupportedOperationException("Cached selector does not synthesize");
	}
	
	public boolean isModificationTraversing(BasicPath bp)
	{
		Boolean b = cacheBoolean.get(bp);
		if(b==null)
			cacheBoolean.put(bp, b=selector.isModificationTraversing(bp));
		return b;
	}

	public BasicPath synthesizeCoverage(BasicPath bp)
	{
		throw new UnsupportedOperationException("Cached selector does not synthesize");
	}

	public boolean add(Trace t)
	{
		final Map<BasicPath,Boolean> cacheBoolean = this.cacheBoolean;
		for(BasicPath p : t.coverage()) 
		{
			Boolean b = cacheBoolean.get(p);
			if(b==null)
				cacheBoolean.put(p, b=selector.isModificationTraversing(p));
			else if(b)
				return true;
		}
		return false;

	}
	
}