package com.atlassian.cache.impl;
   
   import java.util.ArrayList;
   import java.util.Collection;
   import java.util.List;
   import java.util.concurrent.ConcurrentHashMap;
   import java.util.concurrent.ConcurrentMap;
   
   import javax.annotation.Nonnull;
  import javax.annotation.Nullable;
  import javax.annotation.ParametersAreNonnullByDefault;
  
  import com.atlassian.cache.Cache;
  import com.atlassian.cache.CacheLoader;
  import com.atlassian.cache.CacheManager;
  import com.atlassian.cache.CacheSettings;
  import com.atlassian.cache.CacheSettingsBuilder;
  import com.atlassian.cache.CacheSettingsDefaultsProvider;
  import com.atlassian.cache.CachedReference;
  import com.atlassian.cache.ManagedCache;
  import com.atlassian.util.concurrent.Function;
  import com.atlassian.util.concurrent.ManagedLock;
  import com.atlassian.util.concurrent.ManagedLocks;
  import com.atlassian.util.concurrent.Supplier;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  /**
   * A partial implementation of {@link CacheManager}.
   *
   * @since 2.0.6
   */
  @ParametersAreNonnullByDefault
  public abstract class AbstractCacheManager implements CacheManager
  {
  
      /**
       * Map of all the caches.
       * Before creating a cache to put into the map, acquire a lock using {@link #cacheCreationLocks}
       * to ensure that a cache is created only once.
       */
      protected final ConcurrentMap<String, Supplier<ManagedCache>> caches = new ConcurrentHashMap<String, Supplier<ManagedCache>>();
  
      /** Used to synchronize the creation of caches. */
      protected final Function<String, ManagedLock> cacheCreationLocks = ManagedLocks.weakManagedLockFactory();
  
      protected final @Nullable CacheSettingsDefaultsProvider cacheSettingsDefaultsProvider;
  
      protected AbstractCacheManager(@Nullable CacheSettingsDefaultsProvider cacheSettingsDefaultsProvider)
      {
          this.cacheSettingsDefaultsProvider = cacheSettingsDefaultsProvider;
      }
  
      @Nonnull
      @SuppressWarnings("unchecked")
      @Override
      public Collection<Cache<?, ?>> getCaches()
      {
          List<Cache<?, ?>> managedCaches = new ArrayList<Cache<?, ?>>(64);
  
          for (final com.atlassian.util.concurrent.Supplier<ManagedCache> cacheRef : caches.values())
          {
              final ManagedCache managedCache = cacheRef.get();
              // Only return instances of Cache. Do not return CachedReference instances
              if (managedCache instanceof Cache)
              {
                  managedCaches.add((Cache<?,?>)managedCache);
              }
          }
          return managedCaches;
      }
  
      @Nonnull
      @Override
      public Collection<ManagedCache> getManagedCaches()
      {
          List<ManagedCache> managedCaches = new ArrayList<ManagedCache>(64);
          for (final com.atlassian.util.concurrent.Supplier<ManagedCache> cacheRef : caches.values())
          {
              final ManagedCache managedCache = cacheRef.get();
              if (managedCache != null)
              {
                  managedCaches.add(managedCache);
              }
          }
          return managedCaches;
      }
  
      @Nullable
      @Override
      public ManagedCache getManagedCache(@Nonnull String name)
      {
          final Supplier<ManagedCache> cacheRef = caches.get(name);
          return (null == cacheRef) ? null : cacheRef.get();
      }
  
      @Override
      public void flushCaches()
      {
         for (final com.atlassian.util.concurrent.Supplier<ManagedCache> cacheRef : caches.values())
         {
             final ManagedCache managedCache = cacheRef.get();
             if (managedCache != null && managedCache.isFlushable())
             {
                 managedCache.clear();
             }
         }
     }
 
     @Nonnull
     @Override
     public <K, V> Cache<K, V> getCache(@Nonnull final String name)
     {
         return getCache(name, null);
     }
 
     @Nonnull
     @Override
     public <K, V> Cache<K, V> getCache(@Nonnull Class<?> owningClass, @Nonnull String name)
     {
         return getCache(cacheName(owningClass, name));
     }
 
     @Nonnull
     @Override
     public <K, V> Cache<K, V> getCache(@Nonnull final String name, @Nonnull final Class<K> keyType, @Nonnull final Class<V> valueType)
     {
         return getCache(name);
     }
 
     @Nonnull
     @Override
     public <K, V> Cache<K, V> getCache(@Nonnull String name, @Nullable CacheLoader<K, V> loader)
     {
         return getCache(name, loader, new CacheSettingsBuilder().build());
     }
 
     @Nonnull
     @Override
     public <V> CachedReference<V> getCachedReference(@Nonnull String name, @Nonnull com.atlassian.cache.Supplier<V> supplier)
     {
         return getCachedReference(name, supplier, new CacheSettingsBuilder().build());
     }
 
     @Nonnull
     @Override
     public <V> CachedReference<V> getCachedReference(@Nonnull Class<?> owningClass,
                                                      @Nonnull String name,
                                                      @Nonnull com.atlassian.cache.Supplier<V> supplier)
     {
         return getCachedReference(owningClass, name, supplier, new CacheSettingsBuilder().build());
     }
 
     @Nonnull
     @Override
     public <V> CachedReference<V> getCachedReference(@Nonnull Class<?> owningClass,
                                                      @Nonnull String name,
                                                      @Nonnull com.atlassian.cache.Supplier<V> supplier,
                                                      @Nonnull CacheSettings settings)
     {
         return getCachedReference(cacheName(owningClass, name), supplier, settings);
     }
 
     private static String cacheName(Class<?> owningClass, String name)
     {
         checkNotNull(name, "name cannot be null");
         return owningClass.getName() + '.' + name;
     }
 
     @Nonnull
     @SuppressWarnings("unchecked")
     @Override
     public <K, V> Cache<K, V> getCache(@Nonnull String name, @Nullable CacheLoader<K, V> loader, @Nonnull CacheSettings settings)
     {
         if (null == loader)
         {
             return (Cache<K, V>) createSimpleCache(name, mergeSettings(name, settings));
         }
         else
         {
             return (Cache<K, V>) createComputingCache(name, mergeSettings(name, settings), loader);
         }
     }
 
     /**
      * Creates a cache that upon a miss is able to populate itself using the loader.
      *
      * @return a non-null cache
      */
     protected abstract <K, V> ManagedCache createComputingCache(@Nonnull String name, @Nonnull CacheSettings settings, @Nullable CacheLoader<K, V> loader);
 
     /**
      * Creates a cache with no loader, i.e. one populated via explicit puts.
      *
      * @param name the name to give the cache (required)
      * @return a non-null cache
      */
     protected abstract ManagedCache createSimpleCache(@Nonnull String name, @Nonnull CacheSettings settings);
 
     protected CacheSettings mergeSettings(String name, CacheSettings settings)
     {
         if (cacheSettingsDefaultsProvider == null)
         {
             return settings;
         }
 
         return cacheSettingsDefaultsProvider.getDefaults(name).override(settings);
     }
 
     @Override
     public void shutdown()
     {
         //By default cacheManages does not have to implements the shutdown method.
     }
 }