/**
    * 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.properties;
  
  import java.util.List;
  import java.util.Properties;
  
  import org.kuali.common.util.Assert;
  import org.kuali.common.util.PropertyUtils;
  import org.kuali.common.util.cache.Cache;
  import org.kuali.common.util.cache.SimpleCache;
  import org.kuali.common.util.property.processor.NoOpProcessor;
  import org.kuali.common.util.property.processor.OverridingProcessor;
  import org.kuali.common.util.property.processor.PropertyProcessor;
  import org.kuali.common.util.resolver.PropertiesValueResolver;
  import org.kuali.common.util.resolver.ValueResolver;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class DefaultPropertiesService implements PropertiesService {
  
  	private static final Logger logger = LoggerFactory.getLogger(DefaultPropertiesService.class);
  
  	private static final Cache<String, Properties> CACHE = new SimpleCache<String, Properties>();
  	private static final PropertyProcessor DEFAULT_POST_PROCESSOR = NoOpProcessor.INSTANCE;
  
  	private final Properties overrides;
  	private final PropertyProcessor postProcessor;
  
  	public DefaultPropertiesService(Properties overrides) {
  		this(overrides, DEFAULT_POST_PROCESSOR);
  	}
  
  	public DefaultPropertiesService(Properties overrides, PropertyProcessor postProcessor) {
  		Assert.noNulls(overrides, postProcessor);
  		this.overrides = PropertyUtils.toImmutable(overrides);
  		this.postProcessor = postProcessor;
  	}
  
  	protected PropertiesLoader getLoader(Location location, Cache<String, Properties> cache, Properties combined) {
  		return new CachingLoader(location, CACHE);
  	}
  
  	@Override
  	public Properties getProperties(List<Location> locations) {
  
  		// Allocate a new properties object
  		Properties properties = new Properties();
  
  		// Cycle through our list of locations
  		for (Location location : locations) {
  
  			// Override anything we've loaded with properties from overrides
  			Properties combined = PropertyUtils.combine(properties, overrides);
  
  			// Use the combined properties to resolve values
  			ValueResolver resolver = new PropertiesValueResolver(combined);
  
  			// Resolve the location using the resolver
  			String resolvedLocation = resolver.resolve(location.getValue());
  
  			// If the resolved location is different from the original location, create a new location object
  			Location actualLocation = getLocation(location, location.getValue(), resolvedLocation);
  
  			// Setup a loader capable of correctly handling things
  			// It might be perfectly acceptable for the location to not even exist
  			// The location might point to the default location for user specified overrides and the user hasn't provided any (for example)
  			// The loader is allowed to ignore missing locations, emit a log message about missing locations, or throw an exception
  			PropertiesLoader loader = getLoader(actualLocation, CACHE, combined);
  
  			// This may return an empty properties object depending on the configuration of the corresponding Location object
  			Properties loaded = loader.load();
  
  			// Any freshly loaded properties "win" over previous properties
  			new OverridingProcessor(loaded).process(properties);
  		}
  
  		// Do any post processing as needed
  		postProcessor.process(properties);
  
  		// This is expensive, only do this in debug mode
  		if (logger.isDebugEnabled()) {
  			logger.debug("Displaying {} property values:\n\n{}", properties.size(), PropertyUtils.toString(properties));
  		}
  
  		// Return what we've found
 		return properties;
 	}
 
 	private Location getLocation(Location location, String originalLocation, String resolvedLocation) {
 		if (originalLocation.equals(resolvedLocation)) {
 			return location;
 		} else {
 			return Location.builder(location, resolvedLocation).build();
 		}
 	}
 
 	public void clearCache() {
 		CACHE.clear();
 	}
 
 	public Properties getOverrides() {
 		return overrides;
 	}
 
 	public PropertyProcessor getPostProcessor() {
 		return postProcessor;
 	}
 
 }