guesser.java

junit

package org.junit.tests.experimental.theories.extendingwithstubs;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Random;
import java.util.Map.Entry;

import org.hamcrest.BaseDescription;
import org.hamcrest.Description;
import org.junit.internal.AssumptionViolatedException;

public class Guesser<T> extends ReguessableValue {
	static class GuessMap extends HashMap<MethodCall, Object> implements
			InvocationHandler {
		private static final long serialVersionUID= 1L;

		public GuessMap(GuessMap guesses) {
			super(guesses);
		}

		public GuessMap() {
		}

		GuessMap replaceGuess(Object oldValue, Object newValue) {
			GuessMap newGuesses= new GuessMap(this);
			for (Entry<MethodCall, Object> entry : newGuesses.entrySet()) {
				if (entry.getValue().equals(oldValue))
					entry.setValue(newValue);
			}
			return newGuesses;
		}

		protected Object generateGuess(Class<?> returnType) {
			if (returnType.equals(String.class))
				return "GUESS" + new Random().nextInt();
			if (returnType.equals(Integer.class)
					|| returnType.equals(int.class))
				return new Random().nextInt();
			return null;
		}

		Object getGuess(MethodCall call) {
			if (!containsKey(call))
				put(call, generateGuess(call.getReturnType()));
			return get(call);
		}

		public Object invoke(Object proxy, Method method, Object[] args)
				throws Throwable {
			return getGuess(new MethodCall(method, args));
		}
	}

	private final GuessMap guesses;

	private final Class<T> type;

	public Guesser(Class<T> type) {
		this(type, new GuessMap());
	}

	public Guesser(Class<T> type, GuessMap guesses) {
		this.type= type;
		this.guesses= guesses;
	}

	@SuppressWarnings("unchecked")
	public T getProxy() {
		return (T) Proxy.newProxyInstance(getClass().getClassLoader(),
				new Class[] { getType() }, guesses);
	}

	@Override
	public List<ReguessableValue> reguesses(AssumptionViolatedException e) {
		final ArrayList<ReguessableValue> returnThis= new ArrayList<ReguessableValue>();
		e.describeTo(new BaseDescription() {
			@Override
			protected void append(char arg0) {
			}

			boolean expectedSeen= false;
			Object expected= null;

			@Override
			public Description appendValue(Object value) {
				noteValue(value);
				return super.appendValue(value);
			}

			private void noteValue(Object value) {
				if (!expectedSeen) {
					expected= value;
					expectedSeen= true;
					return;
				}

				GuessMap newGuesses= guesses.replaceGuess(expected, value);
				returnThis.add(new Guesser<T>(getType(), newGuesses));
			}
		});
		return returnThis;
	}

	@Override
	public Object getValue() throws CouldNotGenerateValueException {
		return getProxy();
	}

	public Class<T> getType() {
		return type;
	}

	@Override
	public String getDescription() throws CouldNotGenerateValueException {
		return "guesser[" + type + "]";
	}

}