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/**
 * Copyright 2010-2014 The Kuali Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
 *
 * 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.kuali.common.util.spring.env;

import static com.google.common.base.Preconditions.checkNotNull;

import java.util.Map;
import java.util.Properties;
import java.util.Set;

import org.kuali.common.util.PropertyUtils;
import org.kuali.common.util.log.LoggerUtils;
import org.slf4j.Logger;
import org.springframework.core.env.MapPropertySource;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Maps;

/**
 * 
 * When {@code getProperty(name)} is called, {@code name} is checked. If no value is found, {@code name} is then converted into several aliases representing a few different ways it
 * might be represented as an environment variable. All of the aliases are then also checked.
 * 
 * 
 *  *   foo.barBaz -> env.FOO_BAR_BAZ
 *                 FOO_BAR_BAZ
 *                 env.foo_bar_baz
 *                 foo_bar_baz
 * 
 */
public class SysEnvPropertySource extends MapPropertySource {

	private static final Map> ALIAS_CACHE = Maps.newConcurrentMap();
	private static final String GLOBAL_PROPERTIES_PROPERTY_SOURCE_NAME = "systemPropertiesAndEnvironmentVariables";
	private static final Logger logger = LoggerUtils.make();

	public SysEnvPropertySource() {
		this(GLOBAL_PROPERTIES_PROPERTY_SOURCE_NAME, PropertyUtils.getGlobalProperties());
	}

	public SysEnvPropertySource(String name, Properties source) {
		this(name, convert(source));
	}

	public SysEnvPropertySource(String name, Map source) {
		super(name, source);
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public Object getProperty(String name) {
		checkNotNull(name, "'name' cannot be null");
		Object value = super.getProperty(name);
		if (value != null) {
			return value;
		} else {
			Set aliases = getAliases(name);
			return getProperty(aliases, name);
		}
	}

	protected Object getProperty(Set aliases, String original) {
		for (String alias : aliases) {
			Object value = super.getProperty(alias);
			if (value != null) {
				logger.debug(String.format("PropertySource [%s] does not contain '%s', but found equivalent '%s'", this.getName(), original, alias));
				return value;
			}
		}
		return null;
	}

	/**
	 * 	 *   foo.barBaz -> env.FOO_BAR_BAZ
	 *                 FOO_BAR_BAZ
	 *                 env.foo_bar_baz
	 *                 foo_bar_baz
	 * 
	 */
	protected ImmutableSet getAliases(String name) {
		ImmutableSet aliases = ALIAS_CACHE.get(name);
		if (aliases == null) {
			// foo.barBaz -> env.FOO_BAR_BAZ
			String env1 = EnvUtils.getEnvironmentVariableKey(name);
			// foo.barBaz -> FOO_BAR_BAZ
			String env2 = EnvUtils.toUnderscore(name).toUpperCase();
			// foo.barBaz -> env.foo_bar_baz
			String env3 = env1.toLowerCase();
			// foo.barBaz -> foo_bar_baz
			String env4 = env2.toLowerCase();
			aliases = ImmutableSet.of(env1, env2, env3, env4);
			ALIAS_CACHE.put(name, aliases);
		}
		return aliases;
	}

	protected static Map convert(Properties properties) {
		Map map = Maps.newHashMap();
		for (String key : properties.stringPropertyNames()) {
			map.put(key, properties.getProperty(key));
		}
		return map;
	}

	public void clearAliasCache() {
		ALIAS_CACHE.clear();
	}

}