package com.gpl.rpg.atcontentstudio.ui.tools;

import java.awt.Composite;
import java.awt.CompositeContext;
import java.awt.RenderingHints;
import java.awt.image.ColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;

/**
 * This Composite emulates the behaviour of Android's ColorMatrixColorFilter,
 * except that you have to use this one a posteriori instead of a filtering paint.
 * 
 * It applies a ColorMatrix to the destination pixels, regardless of potential "source" pixels.
 * Once created and activated through Graphics2D.setComposite(), just paint anything over the pixels you want "filtered".
 * 
 * Works on a per-pixel basis, no sampling of surrounding pixels, or anything.
 * 
 * @author pochat
 *
 */
public class MatrixComposite implements Composite {

	
	final float[] matrix = new float[20];
	
	
	/**
	 * Dismisses the source pixels. Just paint it black, or white, it only affects the dest RGB with the following formulae.
	 * 
	 * R' = a*R + b*G + c*B + d*A + e;
	 * G' = f*R + g*G + h*B + i*A + j;
	 * B' = k*R + l*G + m*B + n*A + o;
	 * A' = p*R + q*G + r*B + s*A + t;
	 * 
	 * @param matrix a flat float[20] array, giving the a..t values;
	 */
	public MatrixComposite(float[] matrix) {
		if (matrix.length != this.matrix.length) {
			throw new Error("MatrixComposite matrix must be of length "+this.matrix.length);
		}
		System.arraycopy(matrix, 0, this.matrix, 0, this.matrix.length);
	}
	
	@Override
	public CompositeContext createContext(ColorModel srcColorModel,
			ColorModel dstColorModel, RenderingHints hints) {
		return new MatrixCompositeContext(this);
	}
	
	class MatrixCompositeContext implements CompositeContext {

		MatrixComposite composite;
		
		public MatrixCompositeContext(MatrixComposite composite) {
			this.composite = composite;
		}
		
		@Override
		public void dispose() {
		}

		@Override
		public void compose(Raster src, Raster dstIn, WritableRaster dstOut) {
			if (src.getSampleModel().getDataType() != DataBuffer.TYPE_INT ||
	                dstIn.getSampleModel().getDataType() != DataBuffer.TYPE_INT ||
	                dstOut.getSampleModel().getDataType() != DataBuffer.TYPE_INT) {
	                throw new IllegalStateException(
	                        "Source and destination must store pixels as INT.");
	            }

	            int width = Math.min(src.getWidth(), dstIn.getWidth());
	            int height = Math.min(src.getHeight(), dstIn.getHeight());

	            float alpha = 1.0f;

	            int[] srcPixel = new int[4];
	            int[] dstPixel = new int[4];
	            int[] srcPixels = new int[width];
	            int[] dstPixels = new int[width];

	            for (int y = 0; y < height; y++) {
	                src.getDataElements(0, y, width, 1, srcPixels);
	                dstIn.getDataElements(0, y, width, 1, dstPixels);
	                for (int x = 0; x < width; x++) {
	                    // pixels are stored as INT_ARGB
	                    // our arrays are [R, G, B, A]
	                    int pixel = srcPixels[x];
	                    srcPixel[0] = (pixel >> 16) & 0xFF;
	                    srcPixel[1] = (pixel >>  8) & 0xFF;
	                    srcPixel[2] = (pixel      ) & 0xFF;
	                    srcPixel[3] = (pixel >> 24) & 0xFF;

	                    pixel = dstPixels[x];
	                    dstPixel[0] = (pixel >> 16) & 0xFF;
	                    dstPixel[1] = (pixel >>  8) & 0xFF;
	                    dstPixel[2] = (pixel      ) & 0xFF;
	                    dstPixel[3] = (pixel >> 24) & 0xFF;

	                    int[] result = applyMatrix(matrix, dstPixel);

	                    // mixes the result with the opacity
	                    dstPixels[x] = ((int) (dstPixel[3] + (result[3] - dstPixel[3]) * alpha) & 0xFF) << 24 |
	                                   ((int) (dstPixel[0] + (result[0] - dstPixel[0]) * alpha) & 0xFF) << 16 |
	                                   ((int) (dstPixel[1] + (result[1] - dstPixel[1]) * alpha) & 0xFF) <<  8 |
	                                    (int) (dstPixel[2] + (result[2] - dstPixel[2]) * alpha) & 0xFF;
	                }
	                dstOut.setDataElements(0, y, width, 1, dstPixels);
	            }
		}
		
		private int[] applyMatrix(float[] matrix, int[] dstPixel) {
			int[] result = new int[4];
			result[0] =  Math.max(0, Math.min(255, (int) (matrix[ 0] * dstPixel[0] + matrix[ 1] * dstPixel[1] + matrix[ 2] * dstPixel[2] + matrix[ 3] * dstPixel[3] + matrix[ 4]) ));
			result[1] =  Math.max(0, Math.min(255, (int) (matrix[ 5] * dstPixel[0] + matrix[ 6] * dstPixel[1] + matrix[ 7] * dstPixel[2] + matrix[ 8] * dstPixel[3] + matrix[ 9]) ));
			result[2] =  Math.max(0, Math.min(255, (int) (matrix[10] * dstPixel[0] + matrix[11] * dstPixel[1] + matrix[12] * dstPixel[2] + matrix[13] * dstPixel[3] + matrix[14]) ));
			result[3] =  Math.max(0, Math.min(255, (int) (matrix[15] * dstPixel[0] + matrix[16] * dstPixel[1] + matrix[17] * dstPixel[2] + matrix[18] * dstPixel[3] + matrix[19]) ));
			return result;
		}
		
	}

}