/*
 * Copyright [1999-2015] Wellcome Trust Sanger Institute and the EMBL-European Bioinformatics Institute
 * Copyright [2016-2017] EMBL-European Bioinformatics Institute
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.ensembl.healthcheck.configurationmanager;

import java.lang.reflect.InvocationHandler;

import uk.co.flamingpenguin.jewel.cli.OptionNotPresentException;

/**
 * 
 * A configuration object that gets its information from System properties.
 * 
 * Use the newInstance method for instantiation.
 * 
 */
public class ConfigurationBySystemEnvironment<T> extends
		AbstractAliasAwareWithStanardInvocationHanderConfigurationBacking<T> {

	/**
	 * <p>
	 * Use this method to create instances of this configuration object.
	 * </p>
	 * 
	 * <pre>
	 * ConfigurationUserParameters configuration = (ConfigurationUserParameters) ConfigurationBySystemEnvironment
	 * 		.newInstance(ConfigurationUserParameters.class);
	 * </pre>
	 * 
	 * @param configurationInterfaceToProxy
	 *            : The class object of the configuration interface that this
	 *            configuration object will proxy
	 * 
	 * @return an instance of the configuration class passed. Should be casted
	 *         to the type that was requested as shown in the code example
	 *         above.
	 * 
	 */
	public static Object newInstance(Class configurationInterfaceToProxy) {

		InvocationHandler handler;

		handler = new ConfigurationBySystemEnvironment(
				configurationInterfaceToProxy);

		Object configuration = java.lang.reflect.Proxy.newProxyInstance(
				configurationInterfaceToProxy.getClassLoader(),
				new Class[] { configurationInterfaceToProxy }, handler);

		return configuration;
	}

	public ConfigurationBySystemEnvironment(Class<T> configurationClass) {
		super(configurationClass);
	}

	protected String mockDirectGetMethod(String varRequested) {

		String result = System.getProperty(varRequested);

		if (result == null) {
			throw new OptionNotPresentException("varRequested does not exist!");
		}

		return result;
	}

	protected boolean mockDirectIsMethod(String varRequested) {

		boolean result = true;

		try {
			mockDirectGetMethod(varRequested);
		} catch (OptionNotPresentException e) {
			result = false;
		}

		return result;
	}

	public String toString() {
		return this.getClass().getSimpleName();
	}

}