/*******************************************************************************
 * Breakout Cave Survey Visualizer
 *
 * Copyright (C) 2014 James Edwards
 *
 * jedwards8 at fastmail dot fm
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *******************************************************************************/
package org.andork.math3d;

public class LineLineIntersection2d {
	public final double[] m = new double[8];

	public double t0 = Double.NaN;
	public double t1 = Double.NaN;

	/**
	 * the intersection point.
	 */
	public final double[] x = new double[2];

	public boolean findIntersection() {
		double lt0x = m[0];
		double lt0y = m[1];
		double lo0x = m[4];
		double lo0y = m[5];

		if (Math.abs(m[0]) < Math.abs(m[1])) {
			for (int i = 0; i < 8; i += 2) {
				double swap = m[i];
				m[i] = m[i + 1];
				m[i + 1] = swap;
			}
		}

		if (m[0] == 0) {
			return false;
		}

		if (m[1] != 0) {
			double multiplier = -m[1] / m[0];
			m[1] += m[0] * multiplier;
			m[3] += m[2] * multiplier;
			m[5] += m[4] * multiplier;
			m[7] += m[6] * multiplier;
		}

		if (m[3] == 0) {
			return false;
		}

		t1 = (-m[5] - m[7]) / m[3];
		t0 = (-m[2] * t1 - m[4] - m[6]) / m[0];

		x[0] = lo0x + t0 * lt0x;
		x[1] = lo0y + t0 * lt0y;
		return true;
	}

	public void setUp(double lo0x, double lo0y, double lt0x, double lt0y, double lo1x, double lo1y, double lt1x,
			double lt1y) {
		m[0] = lt0x;
		m[1] = lt0y;
		m[2] = -lt1x;
		m[3] = -lt1y;
		m[4] = lo0x;
		m[5] = lo0y;
		m[6] = -lo1x;
		m[7] = -lo1y;
	}

	public void setUp(double[] lo0, double[] lt0, double[] lo1, double[] lt1) {
		m[0] = lt0[0];
		m[1] = lt0[1];
		m[2] = -lt1[0];
		m[3] = -lt1[1];
		m[4] = lo0[0];
		m[5] = lo0[1];
		m[6] = -lo1[0];
		m[7] = -lo1[1];
	}

	/**
	 * Sets the lines to intersect. This method allows you to take lines that
	 * are defined in 2 or more dimensions and pick 2 of those dimensions to
	 * perform the intersection in.
	 *
	 * @param lo0
	 *            a point on the first line.
	 * @param lt0
	 *            the direction of the first line.
	 * @param lo1
	 *            a point on the second line.
	 * @param lt1
	 *            the direction of the second line.
	 * @param da
	 *            the index of the first dimension to use.
	 * @param db
	 *            the index of the second dimension to use.
	 */
	public void setUp(double[] lo0, double[] lt0, double[] lo1, double[] lt1, int da, int db) {
		m[0] = lt0[da];
		m[1] = lt0[db];
		m[2] = -lt1[da];
		m[3] = -lt1[db];
		m[4] = lo0[da];
		m[5] = lo0[db];
		m[6] = -lo1[da];
		m[7] = -lo1[db];
	}
}