BytesRenderer.java

package fr.openwide.core.wicket.more.rendering;

import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.util.List;
import java.util.Locale;

import org.apache.wicket.util.lang.Bytes;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;

public class BytesRenderer extends Renderer<Bytes> {
	
	private static final long serialVersionUID = -5011963259015482288L;

	private static final double BYTES_IN_KB = 1024;

	private static final double DISPLAY_LIMIT = 1000;

	private static final String OUTPUT_DECIMAL_FORMAT = "#.#";

	private static final String BYTE_UNIT_KEY = "bytes.unit.byte";
	private static final String KB_UNIT_KEY = "bytes.unit.kilobyte";
	private static final String MB_UNIT_KEY = "bytes.unit.megabyte";
	private static final String GB_UNIT_KEY = "bytes.unit.gigabyte";
	private static final String TB_UNIT_KEY = "bytes.unit.terabyte";

	private static final List<String> DEFAULT_UNIT_KEYS = Lists.newArrayList(BYTE_UNIT_KEY, KB_UNIT_KEY, MB_UNIT_KEY, GB_UNIT_KEY, TB_UNIT_KEY);
	
	private static final BytesRenderer INSTANCE = new BytesRenderer();
	
	public static BytesRenderer get() {
		return INSTANCE;
	}
	
	private final List<String> unitKeys;

	private BytesRenderer() {
		this.unitKeys = ImmutableList.copyOf(DEFAULT_UNIT_KEYS);
	};

	protected BytesRenderer(Iterable<String> unitKeys) {
		this.unitKeys = ImmutableList.copyOf(unitKeys);
	}

	@Override
	public String render(Bytes value, Locale locale) {
		double humanReadableSize = Long.valueOf(value.bytes()).doubleValue();
		int unitKeyIndex = 0;
		
		while (humanReadableSize > DISPLAY_LIMIT && unitKeyIndex < unitKeys.size() - 1) {
			humanReadableSize = humanReadableSize / BYTES_IN_KB;
			unitKeyIndex++;
		}
		
		DecimalFormat twoDecimalsFormat = new DecimalFormat(OUTPUT_DECIMAL_FORMAT, DecimalFormatSymbols.getInstance(locale));
		
		return new StringBuilder(twoDecimalsFormat.format(humanReadableSize)).append(" ")
				.append(getString(unitKeys.get(unitKeyIndex), locale))
				.toString();
	}

}