CacheUtils.java

package info.freelibrary.djatoka.util;

import java.util.ArrayList;
import java.util.List;

public class CacheUtils {

    /**
     * 
     * @param aLevel
     * @param aScale
     * @param aRegion
     * @return
     */
    public static final String getFileName(String aLevel, String aScale,
	    String aRegion) {
	StringBuilder cfName = new StringBuilder("image_");
	String region = isEmpty(aRegion) ? "all" : aRegion.replace(',', '-');

	/*
	 * TODO: Right now this assumes if it gets passed a level that it's not
	 * doing a region... what possibilities do we exclude by doing this?
	 */
	if (aLevel != null && !aLevel.equals("") && !aLevel.equals("-1")) {
	    cfName.append(aLevel);
	}
	else {
	    cfName.append(aScale).append('_').append(region);
	}

	return cfName.append(".jpg").toString();
    }

    public static final int getMaxLevel(int aHeight, int aWidth) {
	return (int) Math.ceil(Math.log(Math.max(aHeight, aWidth))
		/ Math.log(2));
    }

    public static final int getScale(int aLevel) {
	return (int) Math.pow(2, aLevel);
    }
    
    public static final List<String> getCachingQueries(int aHeight, int aWidth) {
	int maxLevel = getMaxLevel(aHeight, aWidth);
	List<String> list = new ArrayList<String>();
	
	for (int level = 0; level <= maxLevel; level++) {
	    String scale = Integer.toString(getScale(level));
	    
	    if (level <= 8) {
		list.add("/all/" + scale);
		continue; // We don't need to get regions for these
	    }
	    
	    int tileSize = getTileSize(level, maxLevel);
	    int x = 0;
	    
	    /* x is left point and y is top point */
	    for (int xSize = 0, y = 0; xSize <= aWidth; xSize += tileSize) {
		if (x * tileSize > (aWidth + tileSize)) {
		    break;
		}
		
		for (int ySize = 0; ySize <= aHeight; ySize += tileSize) {
		    String region = getRegion(level, aWidth, aHeight, x, y++);
		    
		    if (y * tileSize > (aHeight + tileSize)) {
			break;
		    }

		    list.add("/" + region + "/" + scale);
		}
		
		x += 1;
	    }
	}

	return list;
    }
    
    /*
     * All the other code uses width, height (rather than height, width); I
     * should probably change to match their use pattern/order for consistency
     */
    public static final String getRegion(int aLevel, int aWidth, int aHeight, int aX, int aY) {
	int tileSize = getTileSize(aLevel, getMaxLevel(aHeight, aWidth));
	int startX, startY, tileSizeX, tileSizeY;
	
	/* startX is left point and startY is top point */
	if (aLevel > 8) {
	    if (aX == 0) {
		tileSizeX = tileSize - 1;
	    }
	    else {
		tileSizeX = tileSize;
	    }

	    if (aY == 0) {
		tileSizeY = tileSize - 1;
	    }
	    else {
		tileSizeY = tileSize;
	    }

	    startX = aX * tileSize;
	    startY = aY * tileSize;

	    return startY + "," + startX + "," + tileSizeY + "," + tileSizeX;
	}

	return "all";
    }
    
    private static boolean isEmpty(String aString) {
	return aString == null || aString.equals("");
    }
    
    private static int getTileSize(int aLevel, int aMaxLevel) {
	return (int) (Math.pow(2, aMaxLevel) / Math.pow(2, aLevel)) * 256;
    }
}