package com.exh.bevel.algo;

import com.exh.bevel.support.QuadEntry;
import com.exh.bevel.support.QuadList;
import com.exh.bevel.support.Spotlight;
import com.exh.math.primitive.Quad;

/* The main loop for cutting each quad at its point of intersection.
 */
public final class QuadClipper {

	private final QuadList			mPool = new QuadList();
	private final QuadClipList		mSlices = new QuadClipList();

	// Find all intersections, chop them at the dividing line.
	public void on(	final QuadList cmp, final double z, final Spotlight spot,
					final QuadList quadOut) {
		// Step over each element of src, duplicating and
		// running against the src list.  Duplicated results
		// are pushed into the output.
		QuadEntry				src = cmp.head();
		while (src != null) {
			mSlices.start(src.mQ);
			QuadEntry			dst = cmp.head();
			while (dst != null) {
				if (src != dst && src.overlaps(dst)) {
					// Subtract the dst quad from the src
					mSlices.slice(dst.mQ, spot);
				}
				dst = dst.mNext;
			}
			// Create new quads out of the subtraction results.
			mSlices.results(quadOut, mPool);
			src = src.mNext;
		}

		// Once all quads are generated, set the interior z, 'cause
		// that's sorta the point.
		QuadEntry				dst = quadOut.head();
		while (dst != null) {
			final Quad			a = dst.mQ;
			a.mPt[1].z = z;
			a.mPt[2].z = z;
			dst = dst.mNext;
		}
	}
}