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/*
 * Copyright (C) 2010-2015 AludraTest.org and the contributors.
 *
 * 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.aludratest.cloud.config;

/**
 * Helper class for Preferences consumers which can be used to have getter methods which validate the existence of a configuration
 * property when trying to retrieve it. Clients can wrap an existing Preferences object with this class and use its methods. 

 * Queried child nodes are automatically wrapped and returned as ValidatingPreferencesWrapper.
 * 
 * @author falbrech
 * 
 */
public final class ValidatingPreferencesWrapper implements Preferences {

	private Preferences delegate;

	private ValidatingPreferencesWrapper parent;

	/**
	 * Creates a new ValidatingPreferencesWrapper object which wraps the given Preferences object.
	 * 
	 * @param delegate
	 *            Preferences node to wrap.
	 */
	public ValidatingPreferencesWrapper(Preferences delegate) {
		this.delegate = delegate;
	}

	private ValidatingPreferencesWrapper(Preferences delegate, ValidatingPreferencesWrapper parent) {
		this(delegate);
		this.parent = parent;
	}

	/**
	 * Returns the String representation of the given configuration key's value. If the configuration key does not exist on this
	 * Preferences node, or if its value is null, a ConfigException is thrown.
	 * 
	 * @param key
	 *            Configuration key to retrieve the value of.
	 * 
	 * @return The value of the configuration key, as a String.
	 * @throws ConfigException
	 *             If no value is set for the given key.
	 */
	public String getRequiredStringValue(String key) throws ConfigException {
		return assertNotNull(key, getStringValue(key));
	}

	/**
	 * Returns the int representation of the given configuration key's value. If the configuration key does not exist on this
	 * Preferences node, or if its value is null, a ConfigException is thrown.
	 * 
	 * @param key
	 *            Configuration key to retrieve the value of.
	 * 
	 * @return The value of the configuration key, as an int.
	 * @throws ConfigException
	 *             If no value is set for the given key.
	 */
	public int getRequiredIntValue(String key) throws ConfigException {
		return assertNotNull(key, getIntValue(key));
	}

	/**
	 * Returns the double representation of the given configuration key's value. If the configuration key does not exist on this
	 * Preferences node, or if its value is null, a ConfigException is thrown.
	 * 
	 * @param key
	 *            Configuration key to retrieve the value of.
	 * 
	 * @return The value of the configuration key, as a double.
	 * @throws ConfigException
	 *             If no value is set for the given key.
	 */
	public double getRequiredDoubleValue(String key) throws ConfigException {
		return assertNotNull(key, getDoubleValue(key));
	}

	/**
	 * Returns the float representation of the given configuration key's value. If the configuration key does not exist on this
	 * Preferences node, or if its value is null, a ConfigException is thrown.
	 * 
	 * @param key
	 *            Configuration key to retrieve the value of.
	 * 
	 * @return The value of the configuration key, as a float.
	 * @throws ConfigException
	 *             If no value is set for the given key.
	 */
	public float getRequiredFloatValue(String key) throws ConfigException {
		return assertNotNull(key, getFloatValue(key));
	}

	/**
	 * Returns the boolean representation of the given configuration key's value. If the configuration key does not exist on this
	 * Preferences node, or if its value is null, a ConfigException is thrown.
	 * 
	 * @param key
	 *            Configuration key to retrieve the value of.
	 * 
	 * @return The value of the configuration key, as a boolean.
	 * @throws ConfigException
	 *             If no value is set for the given key.
	 */
	public boolean getRequiredBooleanValue(String key) throws ConfigException {
		return assertNotNull(key, getBooleanValue(key));
	}

	/**
	 * Returns the char representation of the given configuration key's value. If the configuration key does not exist on this
	 * Preferences node, or if its value is null, a ConfigException is thrown.
	 * 
	 * @param key
	 *            Configuration key to retrieve the value of.
	 * 
	 * @return The value of the configuration key, as a char.
	 * @throws ConfigException
	 *             If no value is set for the given key.
	 */
	public char getRequiredCharValue(String key) throws ConfigException {
		return assertNotNull(key, getCharValue(key));
	}

	@Override
	public String getStringValue(String key) {
		return delegate.getStringValue(key);
	}

	@Override
	public int getIntValue(String key) {
		return delegate.getIntValue(key);
	}

	@Override
	public boolean getBooleanValue(String key) {
		return delegate.getBooleanValue(key);
	}

	@Override
	public float getFloatValue(String key) {
		return delegate.getFloatValue(key);
	}

	@Override
	public double getDoubleValue(String key) {
		return delegate.getDoubleValue(key);
	}

	@Override
	public char getCharValue(String key) {
		return delegate.getCharValue(key);
	}

	@Override
	public String getStringValue(String key, String defaultValue) {
		return delegate.getStringValue(key, defaultValue);
	}

	@Override
	public int getIntValue(String key, int defaultValue) {
		return delegate.getIntValue(key, defaultValue);
	}

	@Override
	public boolean getBooleanValue(String key, boolean defaultValue) {
		return delegate.getBooleanValue(key, defaultValue);
	}

	@Override
	public float getFloatValue(String key, float defaultValue) {
		return delegate.getFloatValue(key, defaultValue);
	}

	@Override
	public double getDoubleValue(String key, double defaultValue) {
		return delegate.getDoubleValue(key, defaultValue);
	}

	@Override
	public char getCharValue(String key, char defaultValue) {
		return delegate.getCharValue(key, defaultValue);
	}

	@Override
	public String[] getKeyNames() {
		return delegate.getKeyNames();
	}

	@Override
	public ValidatingPreferencesWrapper getChildNode(String name) {
		return new ValidatingPreferencesWrapper(delegate.getChildNode(name), this);
	}

	@Override
	public String[] getChildNodeNames() {
		return delegate.getChildNodeNames();
	}

	@Override
	public Preferences getParent() {
		return parent;
	}

	/**
	 * Helper method which asserts that a property value is not null and not empty.
	 * 
	 * @param key
	 *            the name of the property to check
	 * @param value
	 *            the property value to check
	 * @return the value specified as parameter
	 * @throws ConfigException
	 *             If the value IS null or empty.
	 */
	private static  T assertNotNull(String key, T value) throws ConfigException {
		if (value == null || "".equals(value)) {
			throw new ConfigException("Missing configuration property: " + key);
		}
		return value;
	}
}