/**
    * Copyright 2005-2013 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.krad.datadictionary.uif;
  
  import org.apache.commons.lang.StringUtils;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.kuali.rice.core.api.config.property.ConfigContext;
  import org.kuali.rice.krad.datadictionary.DataDictionaryException;
  import org.kuali.rice.krad.service.KRADServiceLocatorWeb;
  import org.kuali.rice.krad.uif.UifConstants;
  import org.kuali.rice.krad.uif.UifConstants.ViewType;
  import org.kuali.rice.krad.uif.service.ViewTypeService;
  import org.kuali.rice.krad.uif.util.ViewModelUtils;
  import org.kuali.rice.krad.uif.view.View;
  import org.kuali.rice.krad.util.KRADConstants;
  import org.springframework.beans.PropertyValues;
  import org.springframework.beans.factory.config.BeanDefinition;
  import org.springframework.beans.factory.support.KualiDefaultListableBeanFactory;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Map.Entry;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  
  /**
   * Indexes {@code View} bean entries for retrieval
   *
   * <p>
   * This is used to retrieve a {@code View} instance by its unique id.
   * Furthermore, view of certain types (that have a {@code ViewTypeService}
   * are indexed by their type to support retrieval of views based on parameters.
   * </p>
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class UifDictionaryIndex implements Runnable {
      private static final Log LOG = LogFactory.getLog(UifDictionaryIndex.class);
  
      private KualiDefaultListableBeanFactory ddBeans;
  
      // view entries keyed by view id with value the spring bean name
      private Map<String, String> viewBeanEntriesById;
  
      // view entries indexed by type
      private Map<String, ViewTypeDictionaryIndex> viewEntriesByType;
  
      // views that are loaded eagerly
      private Map<String, UifViewPool> viewPools;
  
      // threadpool size
      private static final int THREADS = 4;
      private boolean poolSizeSet;
      private Integer threadPoolSize;
  
      public UifDictionaryIndex(KualiDefaultListableBeanFactory ddBeans) {
          this.ddBeans = ddBeans;
      }
  
      @Override
      public void run() {
          LOG.info("Starting View Index Building");
          try {
              Integer size = new Integer(ConfigContext.getCurrentContextConfig().getProperty(
                      KRADConstants.KRAD_DICTIONARY_INDEX_POOL_SIZE));
              threadPoolSize = size;
              poolSizeSet = true;
          } catch (NumberFormatException nfe) {
              // ignore this, instead the pool will be set to DEFAULT_SIZE
          }
          buildViewIndicies();
          LOG.info("Completed View Index Building");
      }
  
      /**
       * Retrieves the View instance with the given id
       *
       * <p>
       * First an attempt is made to get a preloaded view (if one exists). If found it is pulled from
       * the pool and a replacement is built on another thread. If a preloaded view does not exist, one is built
       * by Spring from the bean factory
       * </p>
       *
      * @param viewId - the unique id for the view
      * @return View instance with the given id
      * @throws org.kuali.rice.krad.datadictionary.DataDictionaryException if view doesn't exist for id
      */
     public View getViewById(final String viewId) {
         // check for preloaded view
         if (viewPools.containsKey(viewId)) {
 
             final UifViewPool viewPool = viewPools.get(viewId);
             synchronized (viewPool) {
                 if (!viewPool.isEmpty()) {
                     View view = viewPool.getViewInstance();
 
                     // replace view in the pool
                     Runnable createView = new Runnable() {
                         public void run() {
                             View newViewInstance = getViewInstanceFromFactory(viewId);
                             viewPool.addViewInstance(newViewInstance);
                         }
                     };
 
                     Thread t = new Thread(createView);
                     t.start();
 
                     return view;
                 } else {
                     LOG.info("Pool size for view with id: "
                             + viewId
                             + " is empty. Considering increasing max pool size.");
                 }
             }
         }
 
         // no pooling, get new instance from factory
         return getViewInstanceFromFactory(viewId);
     }
 
     /**
      * Retrieves a view object from the bean factory based on view id
      *
      * @param viewId - id of the view to retrieve
      * @return View instance for view with specified id
      * @throws org.kuali.rice.krad.datadictionary.DataDictionaryException if view doesn't exist for id
      */
     protected View getViewInstanceFromFactory(String viewId) {
         String beanName = viewBeanEntriesById.get(viewId);
         if (StringUtils.isBlank(beanName)) {
             throw new DataDictionaryException("Unable to find View with id: " + viewId);
         }
 
         return ddBeans.getBean(beanName, View.class);
     }
 
     /**
      * Retrieves a {@code View} instance that is of the given type based on
      * the index key
      *
      * @param viewTypeName - type name for the view
      * @param indexKey - Map of index key parameters, these are the parameters the
      * indexer used to index the view initially and needs to identify
      * an unique view instance
      * @return View instance that matches the given index or Null if one is not
      *         found
      */
     public View getViewByTypeIndex(ViewType viewTypeName, Map<String, String> indexKey) {
         String index = buildTypeIndex(indexKey);
 
         ViewTypeDictionaryIndex typeIndex = getTypeIndex(viewTypeName);
 
         String viewId = typeIndex.get(index);
         if (StringUtils.isNotBlank(viewId)) {
             return getViewById(viewId);
         }
 
         return null;
     }
 
     /**
      * Indicates whether a {@code View} exists for the given view type and index information
      *
      * @param viewTypeName - type name for the view
      * @param indexKey - Map of index key parameters, these are the parameters the indexer used to index
      * the view initially and needs to identify an unique view instance
      * @return boolean true if view exists, false if not
      */
     public boolean viewByTypeExist(ViewType viewTypeName, Map<String, String> indexKey) {
         boolean viewExist = false;
 
         String index = buildTypeIndex(indexKey);
         ViewTypeDictionaryIndex typeIndex = getTypeIndex(viewTypeName);
 
         String viewId = typeIndex.get(index);
         if (StringUtils.isNotBlank(viewId)) {
             viewExist = true;
         }
 
         return viewExist;
     }
 
     /**
      * Retrieves the configured property values for the view bean definition associated with the given id
      *
      * <p>
      * Since constructing the View object can be expensive, when metadata only is needed this method can be used
      * to retrieve the configured property values. Note this looks at the merged bean definition
      * </p>
      *
      * @param viewId - id for the view to retrieve
      * @return PropertyValues configured on the view bean definition, or null if view is not found
      */
     public PropertyValues getViewPropertiesById(String viewId) {
         String beanName = viewBeanEntriesById.get(viewId);
         if (StringUtils.isBlank(beanName)) {
             BeanDefinition beanDefinition = ddBeans.getMergedBeanDefinition(beanName);
 
             return beanDefinition.getPropertyValues();
         }
 
         return null;
     }
 
     /**
      * Retrieves the configured property values for the view bean definition associated with the given type and
      * index
      *
      * <p>
      * Since constructing the View object can be expensive, when metadata only is needed this method can be used
      * to retrieve the configured property values. Note this looks at the merged bean definition
      * </p>
      *
      * @param viewTypeName - type name for the view
      * @param indexKey - Map of index key parameters, these are the parameters the indexer used to index
      * the view initially and needs to identify an unique view instance
      * @return PropertyValues configured on the view bean definition, or null if view is not found
      */
     public PropertyValues getViewPropertiesByType(ViewType viewTypeName, Map<String, String> indexKey) {
         String index = buildTypeIndex(indexKey);
 
         ViewTypeDictionaryIndex typeIndex = getTypeIndex(viewTypeName);
 
         String beanName = typeIndex.get(index);
         if (StringUtils.isNotBlank(beanName)) {
             BeanDefinition beanDefinition = ddBeans.getMergedBeanDefinition(beanName);
 
             return beanDefinition.getPropertyValues();
         }
 
         return null;
     }
 
     /**
      * Gets all {@code View} prototypes configured for the given view type
      * name
      *
      * @param viewTypeName - view type name to retrieve
      * @return List<View> view prototypes with the given type name, or empty
      *         list
      */
     public List<View> getViewsForType(ViewType viewTypeName) {
         List<View> typeViews = new ArrayList<View>();
 
         // get view ids for the type
         if (viewEntriesByType.containsKey(viewTypeName.name())) {
             ViewTypeDictionaryIndex typeIndex = viewEntriesByType.get(viewTypeName.name());
             for (Entry<String, String> typeEntry : typeIndex.getViewIndex().entrySet()) {
                 View typeView = ddBeans.getBean(typeEntry.getValue(), View.class);
                 typeViews.add(typeView);
             }
         } else {
             throw new DataDictionaryException("Unable to find view index for type: " + viewTypeName);
         }
 
         return typeViews;
     }
 
     /**
      * Initializes the view index {@code Map} then iterates through all the
      * beans in the factory that implement {@code View}, adding them to the
      * index
      */
     protected void buildViewIndicies() {
         viewBeanEntriesById = new HashMap<String, String>();
         viewEntriesByType = new HashMap<String, ViewTypeDictionaryIndex>();
         viewPools = new HashMap<String, UifViewPool>();
 
         int threads = THREADS;
 
         if (poolSizeSet) {
             threads = threadPoolSize;
         }
 
         ExecutorService executor = Executors.newFixedThreadPool(threads);
 
         String[] beanNames = ddBeans.getBeanNamesForType(View.class);
         for (final String beanName : beanNames) {
             BeanDefinition beanDefinition = ddBeans.getMergedBeanDefinition(beanName);
             PropertyValues propertyValues = beanDefinition.getPropertyValues();
 
             String id = ViewModelUtils.getStringValFromPVs(propertyValues, "id");
             if (StringUtils.isBlank(id)) {
                 id = beanName;
             }
 
             if (viewBeanEntriesById.containsKey(id)) {
                 throw new DataDictionaryException("Two views must not share the same id. Found duplicate id: " + id);
             }
             viewBeanEntriesById.put(id, beanName);
 
             indexViewForType(propertyValues, id);
 
             // pre-load views if necessary
             String poolSizeStr = ViewModelUtils.getStringValFromPVs(propertyValues, "preloadPoolSize");
             if (StringUtils.isNotBlank(poolSizeStr)) {
                 int poolSize = Integer.parseInt(poolSizeStr);
                 if (poolSize < 1) {
                     continue;
                 }
 
                 final UifViewPool viewPool = new UifViewPool();
                 viewPool.setMaxSize(poolSize);
                 for (int j = 0; j < poolSize; j++) {
                     Runnable createView = new Runnable() {
                         @Override
                         public void run() {
                             View view = (View) ddBeans.getBean(beanName);
                             viewPool.addViewInstance(view);
                         }
                     };
 
                     executor.execute(createView);
                 }
                 viewPools.put(id, viewPool);
             }
         }
         executor.shutdown();
     }
 
     /**
      * Performs additional indexing based on the view type associated with the view instance. The
      * {@code ViewTypeService} associated with the view type name on the instance is invoked to retrieve
      * the parameter key/value pairs from the configured property values, which are then used to build up an index
      * used to key the entry
      *
      * @param propertyValues - property values configured on the view bean definition
      * @param id - id (or bean name if id was not set) for the view
      */
     protected void indexViewForType(PropertyValues propertyValues, String id) {
         String viewTypeName = ViewModelUtils.getStringValFromPVs(propertyValues, "viewTypeName");
         if (StringUtils.isBlank(viewTypeName)) {
             return;
         }
 
         UifConstants.ViewType viewType = ViewType.valueOf(viewTypeName);
 
         ViewTypeService typeService = KRADServiceLocatorWeb.getViewService().getViewTypeService(viewType);
         if (typeService == null) {
             // don't do any further indexing
             return;
         }
 
         // invoke type service to retrieve it parameter name/value pairs
         Map<String, String> typeParameters = typeService.getParametersFromViewConfiguration(propertyValues);
 
         // build the index string from the parameters
         String index = buildTypeIndex(typeParameters);
 
         // get the index for the type and add the view entry
         ViewTypeDictionaryIndex typeIndex = getTypeIndex(viewType);
 
         typeIndex.put(index, id);
     }
 
     /**
      * Retrieves the {@code ViewTypeDictionaryIndex} instance for the given
      * view type name. If one does not exist yet for the given name, a new
      * instance is created
      *
      * @param viewType - name of the view type to retrieve index for
      * @return ViewTypeDictionaryIndex instance
      */
     protected ViewTypeDictionaryIndex getTypeIndex(UifConstants.ViewType viewType) {
         ViewTypeDictionaryIndex typeIndex = null;
 
         if (viewEntriesByType.containsKey(viewType.name())) {
             typeIndex = viewEntriesByType.get(viewType.name());
         } else {
             typeIndex = new ViewTypeDictionaryIndex();
             viewEntriesByType.put(viewType.name(), typeIndex);
         }
 
         return typeIndex;
     }
 
     /**
      * Builds up an index string from the given Map of parameters
      *
      * @param typeParameters - Map of parameters to use for index
      * @return String index
      */
     protected String buildTypeIndex(Map<String, String> typeParameters) {
         String index = "";
 
         for (String parameterName : typeParameters.keySet()) {
             if (StringUtils.isNotBlank(index)) {
                 index += "|||";
             }
             index += parameterName + "^^" + typeParameters.get(parameterName);
         }
 
         return index;
     }
 
 }