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/**
 * 
 */
package clime.messadmin.utils;

import java.text.FieldPosition;
import java.text.NumberFormat;
import java.text.ParsePosition;
import java.util.Locale;

/**
 * Formats a number of bytes, adding a suffix
 * @author Cédrik LIME
 */
public class BytesFormat extends NumberFormat {
	protected static final int DEFAULT_FRACTIONS_DIGITS = 2;

	protected static final double KB = 1024;
	protected static final double MB = KB * 1024;
	protected static final double GB = MB * 1024;
	protected static final double TB = GB * 1024;

	protected static final String B_STR = "B";
	protected static final String KB_STR = "KB";
	protected static final String MB_STR = "MB";
	protected static final String GB_STR = "GB";
	protected static final String TB_STR = "TB";

	protected String B_suffix;
	protected String KB_suffix;
	protected String MB_suffix;
	protected String GB_suffix;
	protected String TB_suffix;

	protected Locale locale;

	/**
	 * 
	 */
	public BytesFormat(Locale locale, String separator) {
		super();
		this.locale = locale;
		if (separator == null) {
			separator = "";
		}
		B_suffix = separator + B_STR;
		KB_suffix = separator + KB_STR;
		MB_suffix = separator + MB_STR;
		GB_suffix = separator + GB_STR;
		TB_suffix = separator + TB_STR;
	}

	public static BytesFormat getBytesInstance(String separator) {
		return new BytesFormat(Locale.getDefault(), separator); // super-class is not thread-safe
	}
	public static BytesFormat getBytesInstance(Locale locale, String separator) {
		return new BytesFormat(locale, separator); // super-class is not thread-safe
	}

	/**
	 * {@inheritDoc}
	 */
	public StringBuffer format(double number, StringBuffer toAppendTo, FieldPosition pos) {
		if (number > Long.MAX_VALUE) {
			throw new IllegalArgumentException("Can not format double numbers greater than Long.MAX_VALUE");//$NON-NLS-1$
		}
		return format((long)number, toAppendTo, pos);
	}

	/**
	 * {@inheritDoc}
	 */
	public StringBuffer format(long number, StringBuffer toAppendTo, FieldPosition pos) {
		bytesToHumanString(number, DEFAULT_FRACTIONS_DIGITS, toAppendTo);
		return toAppendTo;
	}

	/**
	 * {@inheritDoc}
	 */
	public Number parse(String text, ParsePosition parsePosition) {
		throw new UnsupportedOperationException();
	}

	/**
	 * Smart formatter for bytes
	 * @param bytes
	 * @param toAppendTo  buffer where to put the formated, human-readable String
	 */
	protected void bytesToHumanString(long bytes, int fractionsDigits, StringBuffer toAppendTo) {
		if (bytes < 0) {
			toAppendTo.append(bytes);
			return;
		}
		double result = bytes;
		String suffix = "";//$NON-NLS-1$
		// Could use a ChoiceFormat() + MessageFormat() instead,
		// but this is faster
		if (bytes < KB) {
			result = bytes;
			suffix = B_suffix;
		} else if (bytes >= KB && bytes < MB) {
			result = round(bytes / KB, fractionsDigits);
			suffix = KB_suffix;
		} else if (bytes >= MB && bytes < GB) {
			result = round(bytes / MB, fractionsDigits);
			suffix = MB_suffix;
		} else if (bytes >= GB && bytes < TB) {
			result = round(bytes / GB, fractionsDigits);
			suffix = GB_suffix;
		} else {
			result = round(bytes / TB, fractionsDigits);
			suffix = TB_suffix;
		}
		NumberFormat nf = NumberFormat.getNumberInstance(locale);
		nf.setMinimumFractionDigits(0);
		nf.setMaximumFractionDigits(fractionsDigits);
		nf.setGroupingUsed(super.isGroupingUsed());
		toAppendTo.append(nf.format(result)).append(suffix);
	}

    private double round(double value, int fractionsDigits) {
    	double powValue = Math.pow(10, fractionsDigits);
		return Math.round(value * powValue) / powValue;
	}
}