bundleplugin/src/main/java/aQute/lib/justif/Justif.java

package aQute.lib.justif;

import java.util.*;


public class Justif {
	int []tabs;
	
	public Justif(int width, int ... tabs) {
		this.tabs = tabs;
	}

	/**
	 * Routine to wrap a stringbuffer. Basically adds line endings but has the
	 * following control characters:
	 * <ul>
	 * <li>Space at the beginnng of a line is repeated when wrapped for indent.</li>
	 * <li>A tab will mark the current position and wrapping will return to that
	 * position</li>
	 * <li>A form feed in a tabbed colum will break but stay in the column</li>
	 * </ul>
	 * 
	 * @param sb
	 */
	public void wrap(StringBuilder sb) {
		List<Integer> indents = new ArrayList<Integer>();
		
		int indent = 0;
		int linelength = 0;
		int lastSpace = 0;
		int r = 0;
		boolean begin = true;

		while (r < sb.length()) {
			switch (sb.charAt(r++)) {
			case '\n':
				linelength = 0;
				
				indent = indents.isEmpty() ? 0 : indents.remove(0);
				begin = true;
				lastSpace = 0;
				break;

			case ' ':
				if (begin)
					indent++;
				lastSpace = r - 1;
				linelength++;
				break;

			case '\t':
				indents.add(indent);
				indent = linelength;
				sb.deleteCharAt(--r);
				
				if (r < sb.length()) {
					char digit = sb.charAt(r);
					if (Character.isDigit(digit)) {
						sb.deleteCharAt(r--);

						int column = (digit - '0');
						if (column < tabs.length)
							indent = tabs[column];
						else
							indent = column * 8;

						int diff = indent - linelength;
						if (diff > 0) {
							for (int i=0; i<diff; i++) {
								sb.insert(r, ' ');
							}
							r += diff;
							linelength += diff;
						}
					}
				}
				break;

			case '\f':
				linelength = 100000; // force a break
				lastSpace = r-1;

				//$FALL-THROUGH$

			default:
				linelength++;
				begin = false;
				if (lastSpace != 0 && linelength > 60) {
					sb.setCharAt(lastSpace, '\n');
					linelength = 0;

					for (int i = 0; i < indent; i++) {
						sb.insert(lastSpace + 1, ' ');
						linelength++;
					}
					r += indent;
					lastSpace = 0;
				}
			}
		}
	}


}