package ie.dcu.segment.util;

import ie.dcu.segment.annotate.*;

import java.awt.*;
import java.awt.image.*;
import java.util.List;

import org.eclipse.swt.graphics.Point;

/**
 * Rasterize the annotations using the Graphics2D API. The annotations are drawn
 * onto a byte buffer, with one byte per pixel.
 * 
 * @author Kevin McGuinness
 */
public class AnnotationRasterizer {
	private static final byte[] R = { (byte) 128, (byte) 255, (byte)   0 };
	private static final byte[] G = { (byte) 128, (byte)   0, (byte)   0 };
	private static final byte[] B = { (byte) 128, (byte)   0, (byte) 255 };
	
	private static final Color[] COLORS = {
		new Color(128, 128, 128),
		new Color(255,   0,   0),
		new Color(  0,   0, 255)
	};
	
	private static final ColorModel cm = new IndexColorModel(8,3,R,G,B);
	
	private final int width;
	private final int height;
	private final int npixels;
	private final WritableRaster wr;
	private final BufferedImage im;
	private transient byte[] buff;
	
	public AnnotationRasterizer(int width, int height) {
		this.width = width;
		this.height = height;
		this.npixels = width * height;
		this.wr = cm.createCompatibleWritableRaster(width, height);
		this.im = new BufferedImage(cm, wr, false, null);
	}
	
	
	public byte[] rasterize(AnnotationManager am) {
		paint(am);
		return getDataBuffer();
	}
	
	
	private void paint(AnnotationManager am) {
		
		Graphics2D g = im.createGraphics();
		
		// Clear background
		g.setColor(COLORS[0]);
		g.fillRect(0, 0, width, height);
		
		// For each annotation
		int lastWidth = -1;
		for (Annotation a : am.annotations()) {
			
			List<Point> pts = a.points();
			
			// Skip empty
			if (pts.size() == 0) {
				continue;
			}
			
			// Check if we need to change the stroke
			int width = a.getLineWidth();
			if (width != lastWidth) {
				g.setStroke(createStroke(width));
				lastWidth = width;
			}
			
			// Set the color
			switch (a.getType()) {
			case Foreground:
				g.setColor(COLORS[1]);
				break;
			case Background:
				g.setColor(COLORS[2]);
				break;
			}
			
			// Paint the points
			if (pts.size() > 1) {
				Point last = null;
				for (Point p : pts) {
					if (last != null) {
						g.drawLine(last.x, last.y, p.x, p.y);
					}
					
					last = p;
				}
			} else {
				// If only one point
				Point p = pts.get(0);
				g.drawLine(p.x, p.y, p.x, p.y);
			}
		}
		
		// Commit changes
		g.dispose();
	}
	
	
	private byte[] getDataBuffer() { 
		
		// Optimize the typical case by avoiding a copy if unnecessary.
		DataBuffer buffer = wr.getDataBuffer();
		if (buffer instanceof DataBufferByte) {
			
			// Good, we have a compatible data buffer
			DataBufferByte bytebuf = (DataBufferByte) buffer;
			int banks = bytebuf.getNumBanks();
			if (banks == 1) {
				
				// Smashin, only one data bank is in use
				byte[] buff = bytebuf.getData();
				
				// Sanity check
				if (buff.length == npixels) {
					return buff;
				}
			}
		}
		
		// Handle some unexpected data buffer by copying pixels
		if (buff == null) {
			buff = new byte[npixels];
		}
				
		return (byte[]) wr.getDataElements(0, 0, width, height, buff);
	}
	
	
	
	private static final Stroke createStroke(int width) {
		return new BasicStroke(width, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
	}
	
}