package org.lwjgl.opengl.glu;

import org.lwjgl.BufferUtils;
import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.GL12;

import java.nio.IntBuffer;

/**
 * Util.java
 * <p/>
 * <p/>
 * Created 7-jan-2004
 *
 * @author Erik Duijs
 */
public class Util {

	/**
	 * temp IntBuffer of one for getting an int from some GL functions
	 */
	private static IntBuffer scratch = BufferUtils.createIntBuffer(16);

	/**
	 * Return ceiling of integer division
	 *
	 * @param a
	 * @param b
	 *
	 * @return int
	 */
	protected static int ceil(int a, int b) {
		return (a % b == 0 ? a / b : a / b + 1);
	}

	/**
	 * Normalize vector
	 *
	 * @param v
	 *
	 * @return float[]
	 */
	protected static float[] normalize(float[] v) {
		float r;

		r = (float)Math.sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]);
		if ( r == 0.0 )
			return v;

		r = 1.0f / r;

		v[0] *= r;
		v[1] *= r;
		v[2] *= r;

		return v;
	}

	/**
	 * Calculate cross-product
	 *
	 * @param v1
	 * @param v2
	 * @param result
	 */
	protected static void cross(float[] v1, float[] v2, float[] result) {
		result[0] = v1[1] * v2[2] - v1[2] * v2[1];
		result[1] = v1[2] * v2[0] - v1[0] * v2[2];
		result[2] = v1[0] * v2[1] - v1[1] * v2[0];
	}

	/**
	 * Method compPerPix.
	 *
	 * @param format
	 *
	 * @return int
	 */
	protected static int compPerPix(int format) {
		/* Determine number of components per pixel */
		switch ( format ) {
			case GL11.GL_COLOR_INDEX:
			case GL11.GL_STENCIL_INDEX:
			case GL11.GL_DEPTH_COMPONENT:
			case GL11.GL_RED:
			case GL11.GL_GREEN:
			case GL11.GL_BLUE:
			case GL11.GL_ALPHA:
			case GL11.GL_LUMINANCE:
				return 1;
			case GL11.GL_LUMINANCE_ALPHA:
				return 2;
			case GL11.GL_RGB:
			case GL12.GL_BGR:
				return 3;
			case GL11.GL_RGBA:
			case GL12.GL_BGRA:
				return 4;
			default :
				return -1;
		}
	}

	/**
	 * Method nearestPower.
	 * <p/>
	 * Compute the nearest power of 2 number.  This algorithm is a little strange, but it works quite well.
	 *
	 * @param value
	 *
	 * @return int
	 */
	protected static int nearestPower(int value) {
		int i;

		i = 1;

		/* Error! */
		if ( value == 0 )
			return -1;

		for ( ; ; ) {
			if ( value == 1 ) {
				return i;
			} else if ( value == 3 ) {
				return i << 2;
			}
			value >>= 1;
			i <<= 1;
		}
	}

	/**
	 * Method bytesPerPixel.
	 *
	 * @param format
	 * @param type
	 *
	 * @return int
	 */
	protected static int bytesPerPixel(int format, int type) {
		int n, m;

		switch ( format ) {
			case GL11.GL_COLOR_INDEX:
			case GL11.GL_STENCIL_INDEX:
			case GL11.GL_DEPTH_COMPONENT:
			case GL11.GL_RED:
			case GL11.GL_GREEN:
			case GL11.GL_BLUE:
			case GL11.GL_ALPHA:
			case GL11.GL_LUMINANCE:
				n = 1;
				break;
			case GL11.GL_LUMINANCE_ALPHA:
				n = 2;
				break;
			case GL11.GL_RGB:
			case GL12.GL_BGR:
				n = 3;
				break;
			case GL11.GL_RGBA:
			case GL12.GL_BGRA:
				n = 4;
				break;
			default :
				n = 0;
		}

		switch ( type ) {
			case GL11.GL_UNSIGNED_BYTE:
				m = 1;
				break;
			case GL11.GL_BYTE:
				m = 1;
				break;
			case GL11.GL_BITMAP:
				m = 1;
				break;
			case GL11.GL_UNSIGNED_SHORT:
				m = 2;
				break;
			case GL11.GL_SHORT:
				m = 2;
				break;
			case GL11.GL_UNSIGNED_INT:
				m = 4;
				break;
			case GL11.GL_INT:
				m = 4;
				break;
			case GL11.GL_FLOAT:
				m = 4;
				break;
			default :
				m = 0;
		}

		return n * m;
	}

	/**
	 * Convenience method for returning an int, rather than getting it out of a buffer yourself.
	 *
	 * @param what
	 *
	 * @return int
	 */
	protected static int glGetIntegerv(int what) {
		scratch.rewind();
		GL11.glGetInteger(what, scratch);
		return scratch.get();
	}

}