CollectionFormatter.java

package aQute.bnd.build.model.conversions;

import java.util.Collection;

public class CollectionFormatter<T> implements Converter<String,Collection< ? extends T>> {

	private final String						separator;
	private final Converter<String, ? super T>	itemFormatter;
	private final String						emptyOutput;
	private final boolean						leadingSpace;
	private final String						initial;
	private final String						suffix;

	public CollectionFormatter(String separator) {
		this(separator, (String) null);
	}

	public CollectionFormatter(String separator, String emptyOutput) {
		this(separator, new DefaultFormatter(), emptyOutput);
	}

	public CollectionFormatter(String separator, Converter<String, ? super T> itemFormatter) {
		this(separator, itemFormatter, null);
	}

	public CollectionFormatter(String separator, Converter<String, ? super T> itemFormatter, String emptyOutput) {
		this(separator, itemFormatter, emptyOutput, false, "\\\n\t", "");
	}

	public CollectionFormatter(String separator, Converter<String, ? super T> itemFormatter, String emptyOutput,
			String prefix, String suffix) {
		this(separator, itemFormatter, emptyOutput, false, prefix, suffix);
	}

	/**
	 * @param separator Separator between items
	 * @param itemFormatter Formatter for each item
	 * @param emptyOutput Output to produce for empty inputs
	 * @param leadingSpace Whether to lead with a space before the first item
	 * @param prefix Prefix for the first item in lists containing more than one
	 *            items.
	 * @param suffix Suffix to add at the end of the list
	 */
	public CollectionFormatter(String separator, Converter<String, ? super T> itemFormatter, String emptyOutput,
			boolean leadingSpace, String prefix, String suffix) {
		this.separator = separator;
		this.itemFormatter = itemFormatter;
		this.emptyOutput = emptyOutput;
		this.leadingSpace = leadingSpace;
		this.initial = prefix;
		this.suffix = suffix;
	}

	public String convert(Collection< ? extends T> input) throws IllegalArgumentException {
		String result = null;
		if (input != null) {
			if (input.isEmpty()) {
				result = emptyOutput;
			} else {
				StringBuilder buffer = new StringBuilder();
				if (leadingSpace)
					buffer.append(' ');

				if (input.size() == 1) {
					T item = input.iterator().next();
					buffer.append(itemFormatter.convert(item));
				} else {
					String del = initial == null ? "" : initial;
					for (T item : input) {
						buffer.append(del);
						buffer.append(itemFormatter.convert(item));
						del = separator;
					}
				}

				if (suffix != null)
					buffer.append(suffix);
				result = buffer.toString();
			}
		}
		return result;
	}

	@Override
	public String error(String msg) {
		return msg;
	}
}