Class Log

src/main/java/field/utility/Log.java:21–158

A Microscopically small logging framework

 * A Microscopically small logging framework
 */
public class Log {

	static protected ConcurrentLinkedDeque<Pair<Pattern, BiConsumer<String, Object>>> active = new ConcurrentLinkedDeque<>();
	static protected Cache<String, String> earlyFail = CacheBuilder.newBuilder().concurrencyLevel(2).maximumSize(100).build();

	// we default to logging everything
	static protected
	BiConsumer<String, Supplier<Object>> _fallthrough = (x, y) -> println(x, y==null ? null : y.get());

	// Use --------------------------------

	static public void log(String channel, Supplier<Object> message) {
		boolean found = false;
		if (earlyFail.getIfPresent(channel) == null) {
			for (Pair<Pattern, BiConsumer<String, Object>> p : active) {
				if (p.first.matcher(channel).matches()) {
					Object m = message.get();
					if (m != null) p.second.accept(channel, m);
					found = true;
					break;
				}
			}
			if (!found) earlyFail.put(channel, channel);
		}
		if (!found && _fallthrough != null) _fallthrough.accept(channel, message);
	}

	// Configure --------------------------------

	/**
	 * adds a pattern to be logged. This rule is of higher priority than anything previously called "on" (and lower than anything subsequently
	 * called "on").
	 */
	static public void add(String pattern, BiConsumer<String, Object> to) {
		earlyFail.invalidateAll();
		active.addFirst(new Pair<>(Pattern.compile(pattern), to));
	}

	/**
	 * adds a pattern to be logged. This rule is of higher priority than anything previously called "on" (and lower than anything subsequently
	 * called "on"). Previous rules identical to "pattern" are removed.
	 */
	static public void on(String pattern, BiConsumer<String, Object> to) {
		off(pattern);
		add(pattern, to);
	}

	/**
	 * turns a pattern off, by removing anything else associated with this pattern. If other rules (including the default) capture this output it
	 * will still be logged
	 */
	static public void off(String pattern) {
		earlyFail.invalidateAll();
		Iterator<Pair<Pattern, BiConsumer<String, Object>>> i = active.iterator();
		while (i.hasNext()) {
			if (i.next().first.equals(pattern)) i.remove();
		}
	}