package models.objectOrientedTransfer;

import java.util.ArrayList;
import java.util.List;

/**
 * A dependency-composed closed delta
 * 
 * @author Nitta
 * 
 */
public class DeltaComplex {
	private Delta frontierDelta;
	private DeltaComplex subComplex = null;
	
	public DeltaComplex(Delta delta) {
		this.frontierDelta = delta;
	}
	
	public DeltaComplex(Delta frontierDelta, DeltaComplex subComplex) {
		this.frontierDelta = frontierDelta;
		this.subComplex = subComplex;
	}
	
	/**
	 * dependency composition
	 * (this = delta | this)
	 * 
	 * @param delta
	 */
	public void attach(Delta delta) {
		this.subComplex = this.copy();
		this.frontierDelta = delta;
	}
	
	/**
	 * if this = d1 | d2 | ... | dn
	 * 
	 * @return [d1, d2, ..., dn]
	 */
	public List<Delta> split() {
		if (subComplex == null) {
			List<Delta> deltaSequence = new ArrayList<>();
			deltaSequence.add(frontierDelta);
			return deltaSequence;
		}
		List<Delta> deltaSequence = subComplex.split();
		deltaSequence.add(0, frontierDelta);
		return deltaSequence;
	}
	
	public Delta collapse() {
		Delta allDelta = null;
		for (Delta delta: this.split()) {
			if (allDelta == null) {
				allDelta = delta;
			} else {
				allDelta = allDelta.combine(delta);
			}
		}
		return allDelta;
	}
	
	public DeltaComplex copy() {
		if (subComplex == null) {
			return new DeltaComplex(frontierDelta.copy());
		}
		return new DeltaComplex(frontierDelta.copy(), subComplex.copy());
	}
}