ArgumentPresenterImpl.java

package org.caudexorigo.cli;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

class ArgumentPresenterImpl<O> implements ArgumentPresenter<O>
{
	private final OptionsSpecification<O> m_specification;
	private final Class<O> m_klass;

	public ArgumentPresenterImpl(final Class<O> klass, final OptionsSpecification<O> specification)
	{
		m_specification = specification;
		m_klass = klass;
	}

	/**
	 * @inheritdoc
	 */
	@SuppressWarnings("unchecked")
	public O presentArguments(final TypedArguments arguments)
	{
		final O result = (O) Proxy.newProxyInstance(m_klass.getClassLoader(), new Class[] { m_klass }, new InvocationHandler()
		{
			public Object invoke(final Object proxy, final Method method, final Object[] args) throws Throwable
			{
				if (args != null && args.length != 0)
				{
					throw new UnsupportedOperationException(String.format("Method (%s) with arguments not supported for reading argument values", method.toGenericString()));
				}
				else if (method.isAnnotationPresent(Unparsed.class))
				{
					return arguments.getUnparsedValue();
				}
				else if (!m_specification.isSpecified(method))
				{
					throw new UnsupportedOperationException(String.format("Method (%s) is not annotated for option specification", method.toGenericString()));
				}

				final OptionSpecification specification = m_specification.getSpecification(method);

				if (m_specification.isExistenceChecker(method) || !specification.hasValue())
				{
					return optionPresent(arguments, specification);
				}
				return getValue(arguments, method, specification);
			}

			private Object optionPresent(final TypedArguments arguments, final ArgumentSpecification specification)
			{
				return arguments.contains(specification);
			}

			private Object getValue(final TypedArguments arguments, final Method method, final ArgumentSpecification specification) throws NoSuchMethodException, InstantiationException, IllegalAccessException, InvocationTargetException
			{
				final Object value = arguments.getValue(specification);
				if (value == null)
				{
					throw new OptionNotPresentException(specification);
				}
				return value;
			}
		});
		return result;
	}
}