d20-charsheet/src/org/leumasjaffe/format/StringFormatter.java

package org.leumasjaffe.format;

import java.util.HashMap;
import java.util.Objects;

import lombok.AccessLevel;
import lombok.experimental.FieldDefaults;

@FieldDefaults(level=AccessLevel.PRIVATE, makeFinal=true)
public class StringFormatter {
	private static final class NameMap extends HashMap<String, Object> {
		/**
		 * 
		 */
		private static final long serialVersionUID = -2243574068000774442L;

		NameMap(Object... args) {
			for (Object arg : args) {
				Objects.requireNonNull(arg);
				if (arg instanceof Named) {
					put(((Named) arg).getName(), arg);
				}
			}
		}
	}
	
	String fmt;
	
	public StringFormatter(String logFmtString) {
		this.fmt = logFmtString;
	}
	
	public String format(Object... args) {
		final StringBuilder str = new StringBuilder(fmt.length());
		
		int currentIdx = 0;
		final NameMap named = new NameMap(args);
		
		int lpos = 0;
		for (int pos = fmt.indexOf('{'); pos != -1; lpos = pos+1, pos = fmt.indexOf('{', lpos)) {
			str.append(fmt.substring(lpos, pos));
			int epos = fmt.indexOf('}', pos);

			if (fmt.charAt(pos+1) == '{') { 
				str.append(fmt.substring(++pos, ++epos));
			} else if (epos == pos+1) {
				str.append(args[currentIdx++]);
			} else {
				final String token = fmt.substring(pos+1, epos);
				if (Character.isDigit(token.charAt(0))) {
					str.append(args[Integer.parseInt(token)]);
				} else { // In theory, I could add a format-mode here too
					str.append(named.get(token));
				}
			}
			pos = epos;
		}
		str.append(fmt.substring(lpos));
		return str.toString();
	}
}