package com.jotuntech.sketcher.common;

import java.util.zip.Deflater;

public class DiffPacker {
	private Deflater deflater;
	private byte[] encodedDiff;

	public DiffPacker() {
		deflater = new Deflater(Deflater.BEST_COMPRESSION, true);
	}

	public int pack(short[] diffAlpha, short[] diffRed, short[] diffGreen, short[] diffBlue, byte[] output) {
		return pack(diffAlpha, diffRed, diffGreen, diffBlue, output, 0, output.length);
	}

	public int pack(short[] diffAlpha, short[] diffRed, short[] diffGreen, short[] diffBlue, byte[] output, int ofs, int len) {
		/* Create buffers, or enlarge them if they are too small */
		if(encodedDiff == null || encodedDiff.length < diffAlpha.length * 8) {
			encodedDiff = new byte[diffAlpha.length * 8];
		}

		int lastAlpha = 0, lastRed = 0, lastGreen = 0, lastBlue = 0;
		for(int diffOffset = 0, alphaOffset = 0, redOffset = diffAlpha.length * 2, greenOffset = diffAlpha.length * 4, blueOffset = diffAlpha.length * 6; diffOffset < diffAlpha.length; diffOffset++, alphaOffset++, redOffset++, greenOffset++, blueOffset++) {
			short alpha = (short) (diffAlpha[diffOffset] - lastAlpha);
			short red = (short) (diffRed[diffOffset] - lastRed);
			short green = (short) (diffGreen[diffOffset] - lastGreen);
			short blue = (short) (diffBlue[diffOffset] - lastBlue);

			encodedDiff[alphaOffset++] = (byte) (0xFF & (alpha >> 8));
			encodedDiff[alphaOffset] = (byte) (0xFF & alpha);
			encodedDiff[redOffset++] = (byte) (0xFF & (red >> 8));
			encodedDiff[redOffset] = (byte) (0xFF & red);
			encodedDiff[greenOffset++] = (byte) (0xFF & (green >> 8));
			encodedDiff[greenOffset] = (byte) (0xFF & green);
			encodedDiff[blueOffset++] = (byte) (0xFF & (blue >> 8));
			encodedDiff[blueOffset] = (byte) (0xFF & blue);

			lastAlpha = diffAlpha[diffOffset];
			lastRed = diffRed[diffOffset];
			lastGreen = diffGreen[diffOffset];
			lastBlue = diffBlue[diffOffset];
		}

		/* Deflate encoded diffs */
		deflater.reset();
		deflater.setInput(encodedDiff, 0, diffAlpha.length * 8);
		deflater.finish();
		int compressedLength = 0;
		while(!deflater.finished() && compressedLength < len) {
			compressedLength += deflater.deflate(output, ofs + compressedLength, len - compressedLength);
		}
		return compressedLength;
	}
}