/**
    * This file Copyright (c) 2017-2018 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.ui.framework.ioc;
  
  
  import info.magnolia.event.EventBus;
  
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.stream.Stream;
  
  import com.google.common.collect.HashMultimap;
  import com.google.common.collect.Multimap;
  import com.google.inject.Key;
  import com.vaadin.server.VaadinSession;
  
  /**
   * Provides access to {@link VaadinSession} as if it was a key-value store where
   * the key would be a {@link UiContextReference} and the value
   * would be {@link BeanStore} (stores the scoped beans and provides access to them).
   *
   * @see UiScopes
   */
  public class SessionStore {
  
      /**
       * Returns {@link SessionStore} corresponding to current {@link VaadinSession}.
       */
      public static SessionStore access() {
          return access(VaadinSession.getCurrent());
      }
  
      /**
       * Returns {@link SessionStore} corresponding to provided {@link VaadinSession}.
       */
      public static SessionStore access(VaadinSession session) {
          return session.getAttribute(SessionStore.class);
      }
  
      private final VaadinSession vaadinSession;
  
      private final EventBus eventBus;
  
      private final Multimap<UiContextReference, UiContextReference> beanStoreHierarchy = HashMultimap.create();
      private final Map<UiContextReference, UiContextReference> beanStoreParentReferences = new HashMap<>();
  
      public SessionStore(VaadinSession vaadinSession, EventBus eventBus) {
          this.vaadinSession = vaadinSession;
          this.eventBus = eventBus;
      }
  
      public BeanStore createBeanStore(UiContextReference uiContextReference) {
          BeanStore existingBeanStore = getBeanStore(uiContextReference);
          if (existingBeanStore != null) {
              return existingBeanStore;
          }
          return createBeanStore(uiContextReference, Collections.emptyMap());
      }
  
      public BeanStore createBeanStore(UiContextReference key, Map<Key, Object> initialInstances) {
  
          final BeanStoreBeanStore.html#BeanStore">BeanStore beanStore = new BeanStore();
          vaadinSession.setAttribute(key.asString(), beanStore);
          key.getDirectParentReference().ifPresent(parentRef -> {
              beanStoreHierarchy.put(parentRef, key);
             beanStoreParentReferences.put(key, parentRef);
         });
         initialInstances.forEach(beanStore::put);
 
         eventBus.fireEvent(new BeanStoreLifecycleEvent.Create(key, beanStore));
 
         return beanStore;
     }
 
     /**
      * Finds a bean store which corresponds to a scope key.
      * If such store does not exist - creates one.
      */
     public BeanStore getBeanStore(UiContextReference uiContextReference) {
         return (BeanStore) vaadinSession.getAttribute(uiContextReference.asString());
     }
 
     public Optional<UiContextReference> lookupRelatedUiContextReference(Object instance) {
         return beanStoreHierarchy.values().stream()
                 .filter(ref ->
                         Optional.ofNullable(this.getBeanStore(ref))
                                 .map(beanStore -> beanStore.contains(instance))
                                 .orElse(false))
                 .findFirst();
     }
 
     /**
      * Clears a bean store which corresponds to a ui context and removes it.
      */
     public void releaseBeanStore(UiContextReference uiContextReference) {
         final BeanStore store = getBeanStore(uiContextReference);
 
         if (store == null) {
             throw new IllegalArgumentException(String.format("No bean store registered for provided uiContextReference [%s]...", uiContextReference));
         }
 
         eventBus.fireEvent(new BeanStoreLifecycleEvent.BeforeDestroy(uiContextReference, store));
 
         // clean up all the child bean stores and erase information from the hierarchy
         this.beanStoreHierarchy.removeAll(uiContextReference).forEach(this::releaseBeanStore);
         Optional.ofNullable(this.beanStoreParentReferences.remove(uiContextReference))
                 .ifPresent(parentReference -> this.beanStoreHierarchy.remove(parentReference, uiContextReference));
 
         store.clear();
         vaadinSession.setAttribute(uiContextReference.asString(), null);
 
         eventBus.fireEvent(new BeanStoreLifecycleEvent.Destroy(uiContextReference, store));
     }
 
     public static <T> Stream<T> lookUpInstancesOf(UiContextReference uiContextReference, Class<T> clazz) {
         BeanStore beanStore = SessionStore.access().getBeanStore(uiContextReference);
         return Stream.concat(
                 Stream.of(beanStore.getClosestInstance(clazz)),
                 uiContextReference.getParentReferences().stream()
                         .map(parentRef -> SessionStore.access().getBeanStore(parentRef))
                         .filter(Objects::nonNull)
                         .map(parentStore -> parentStore.getClosestInstance(clazz)))
                 .filter(Objects::nonNull);
     }
 }