/**
    * Copyright 2005-2016 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.rice.core.web.util;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static org.springframework.beans.factory.BeanFactoryUtils.beansOfTypeIncludingAncestors;
  
  import java.util.Collection;
  import java.util.Enumeration;
  import java.util.Properties;
  
  import javax.servlet.ServletContext;
  import javax.servlet.ServletContextEvent;
  
  import org.apache.commons.lang.StringUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.beans.factory.ListableBeanFactory;
  import org.springframework.context.ConfigurableApplicationContext;
  import org.springframework.core.env.ConfigurableEnvironment;
  import org.springframework.core.env.MutablePropertySources;
  import org.springframework.core.env.PropertySource;
  import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
  
  import com.google.common.base.Optional;
  import com.google.common.base.Preconditions;
  
  /**
   * Utility class for dealing with {@link PropertySource}s.
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class PropertySources {
  
      private static final Logger logger = LoggerFactory.getLogger(PropertySources.class);
  
      /**
       * Check system properties and servlet context init params for an annotated Spring configuration
       * class located under {@code key}. If present, create a new
       * {@AnnotationConfigWebApplicationContext} and register
       * the annotated configuration class. Refresh the context and then examine it for a
       * {@code PropertySource<?>} bean. There must be exactly one {@code PropertySource<?>} bean
       * present in the application context.
       */
      public static Optional<PropertySource<?>> getPropertySource(ServletContextEvent sce, String key) {
          Optional<String> annotatedClass = getProperty(sce, key);
          if (annotatedClass.isPresent()) {
              AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
              context.setServletContext(sce.getServletContext());
              PropertySource<?> propertySource = getPropertySource(annotatedClass.get(), context);
              return Optional.<PropertySource<?>> of(propertySource);
          } else {
              return Optional.absent();
          }
      }
  
      /**
       * Register {@code propertySource} as the first thing Spring will check when looking up property
       * values.
       */
      public static void addFirst(ConfigurableApplicationContext context, PropertySource<?> propertySource) {
          ConfigurableEnvironment env = context.getEnvironment();
          MutablePropertySources propertySources = env.getPropertySources();
          propertySources.addFirst(propertySource);
      }
  
      protected static PropertySource<?> getPropertySource(String className, AnnotationConfigWebApplicationContext context) {
          try {
              logger.info("Loading [{}] to setup a Spring property source", className);
              Class<?> annotatedClass = Class.forName(className);
              context.register(annotatedClass);
              context.refresh();
              PropertySource<?> propertySource = getPropertySource(context, annotatedClass);
              context.close();
              logger.info("Spring property source was successfully setup");
              return propertySource;
          } catch (Exception e) {
              throw new IllegalStateException("Unexpected error configuring Spring property source", e);
          }
      }
  
      protected static PropertySource<?> getPropertySource(ListableBeanFactory factory, Class<?> annotatedClass) {
          @SuppressWarnings("rawtypes")
          Collection<PropertySource> collection = beansOfTypeIncludingAncestors(factory, PropertySource.class).values();
          checkSizeEqualsOne(collection, annotatedClass);
          return collection.iterator().next();
     }
 
     protected static void checkSizeEqualsOne(Collection<?> collection, Class<?> annotatedClass) {
         Object[] args = {annotatedClass.getCanonicalName(), collection.size()};
         String errorMessage = "[%s] contained %s property source beans.  There must always be exactly 1 property source bean";
         Preconditions.checkState(collection.size() == 1, errorMessage, args);
     }
 
     /**
      * Examine both system properties and servlet context init parameters for the presence of a
      * value under {@code key}.
      */
     public static Optional<String> getProperty(ServletContextEvent sce, String key) {
         checkNotNull(key, "'key' cannot be null");
 
         // If there is a system property value, use it
         String sys = System.getProperty(key);
         if (!StringUtils.isBlank(sys)) {
             logger.info("Found [{}] defined in system properties: [{}]", key, sys);
             return Optional.of(sys);
         }
 
         // If there is a servlet context value, use it. Unless it's blank or an unresolved placeholder
         String web = sce.getServletContext().getInitParameter(key);
         if (StringUtils.isBlank(web) || isPlaceHolder(web)) {
             return Optional.absent();
         } else {
             logger.info("Found [{}] defined in servlet context: [{}]", key, web);
             return Optional.of(web);
         }
     }
 
     /**
      * Convert {@code ServletContext} init parameters into a {@code Properties} object.
      */
     public static Properties convert(ServletContext context) {
         Properties properties = new Properties();
         @SuppressWarnings("unchecked")
         Enumeration<String> paramNames = context.getInitParameterNames();
         while (paramNames.hasMoreElements()) {
             String paramName = paramNames.nextElement();
             properties.put(paramName, context.getInitParameter(paramName));
         }
         return properties;
     }
 
     protected static boolean isPlaceHolder(String value) {
         checkNotNull(value, "'value' cannot be null");
         return value.startsWith("${") && value.endsWith("}");
     }
 
 }