package net.sourceforge.pain.logic.fn;

import net.sourceforge.pain.data.type.*;

/**
 * PAiN  Date: 14.04.2003  Time: 0:50:45
 */
public final class RelocateFn {

	public static void relocate(Located obj, Space dst) {
		removeFromSpace(obj);		// removing obj from src space
		addToSpace(dst, obj);		// adding obj to dst space
	}

	public static void removeFromSpace(Located obj) {
		final Space space = obj.getLocation();
		final Located prev = obj.getPrevInSpace();
		final Located next = obj.getNextInSpace();
		if (prev != obj) { // backward iteration has no nulls! see Located.java
			final Located firstInSpace = space.getFirstInSpace();
			if (next != null) {
				next.setPrevInSpace(prev);
			} else { // obj is last, and obj was prev for first
				firstInSpace.setPrevInSpace(prev);
			}
			if (obj != firstInSpace) { //last in list should have next = null
				prev.setNextInSpace(next);
			} else {
				space.setFirstInSpace(next);
			}

		} else { // there only one obj in space
			space.setFirstInSpace(null);
		}
		obj.setLocation(null);
		obj.setNextInSpace(null);
		obj.setPrevInSpace(null);
	}

	/** used for new created objects*/
	public static void addToSpace(Space space, Located obj) {
		Located first = space.getFirstInSpace();
		if (first != null) {
			final Located prev = first.getPrevInSpace(); // last in list
			prev.setNextInSpace(obj);
			obj.setPrevInSpace(prev);
		} else {
			space.setFirstInSpace(obj);
			first = obj;
		}
		first.setPrevInSpace(obj);  //backward list should be without nulls!
		obj.setNextInSpace(null); // forward list finished on null!
		obj.setLocation(space);
	}


}