//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.websocket.jsr356.metadata;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  import org.eclipse.jetty.websocket.api.InvalidWebSocketException;
  
  /**
   * An durable collection of {@link CoderMetadata}.
   * <p>
   * This is a write-only collection, and cannot be modified once initialized.
   * 
   * @param <T>
   *            The type of coder ({@link javax.websocket.Decoder} or {@link javax.websocket.Encoder}
   * @param <M>
   *            The metadata for the coder
   */
  public abstract class CoderMetadataSet<T, M extends CoderMetadata<T>> implements Iterable<M>
  {
      /**
       * Collection of metadatas
       */
      private final List<M> metadatas;
      /**
       * Collection of declared Coder classes
       */
      private final List<Class<? extends T>> coders;
      /**
       * Mapping of supported Type to metadata list index
       */
      private final Map<Class<?>, Integer> typeMap;
      /**
       * Mapping of Coder class to list of supported metadata
       */
      private final Map<Class<? extends T>, List<Integer>> implMap;
  
      protected CoderMetadataSet()
      {
          metadatas = new ArrayList<>();
          coders = new ArrayList<>();
          typeMap = new ConcurrentHashMap<>();
          implMap = new ConcurrentHashMap<>();
      }
  
      public void add(Class<? extends T> coder)
      {
          List<M> metadatas = discover(coder);
          trackMetadata(metadatas);
      }
  
      public List<M> addAll(Class<? extends T>[] coders)
      {
          List<M> metadatas = new ArrayList<>();
  
          for (Class<? extends T> coder : coders)
          {
              metadatas.addAll(discover(coder));
          }
  
          trackMetadata(metadatas);
          return metadatas;
      }
  
      public List<M> addAll(List<Class<? extends T>> coders)
      {
          List<M> metadatas = new ArrayList<>();
  
          for (Class<? extends T> coder : coders)
          {
              metadatas.addAll(discover(coder));
          }
  
          trackMetadata(metadatas);
          return metadatas;
      }
  
      /**
       * Coder Specific discovery of Metadata for a specific coder.
      * 
      * @param coder
      *            the coder to discover metadata in.
      * @return the list of metadata discovered
      * @throws InvalidWebSocketException
      *             if unable to discover some metadata. Sucha as: a duplicate {@link CoderMetadata#getObjectType()} encountered, , or if unable to find the
      *             concrete generic class reference for the coder, or if the provided coder is not valid per spec.
      */
     protected abstract List<M> discover(Class<? extends T> coder);
 
     public Class<? extends T> getCoder(Class<?> type)
     {
         M metadata = getMetadataByType(type);
         if (metadata == null)
         {
             return null;
         }
         return metadata.getCoderClass();
     }
 
     public List<Class<? extends T>> getList()
     {
         return coders;
     }
 
     public List<M> getMetadataByImplementation(Class<? extends T> clazz)
     {
         List<Integer> indexes = implMap.get(clazz);
         if (indexes == null)
         {
             return null;
         }
         List<M> ret = new ArrayList<>();
         for (Integer idx : indexes)
         {
             ret.add(metadatas.get(idx));
         }
         return ret;
     }
 
     public M getMetadataByType(Class<?> type)
     {
         Integer idx = typeMap.get(type);
         if (idx == null)
         {
             // Quick lookup failed, try slower lookup via isAssignable instead
             idx = getMetadataByAssignableType(type);
             if (idx != null)
             {
                 // add new entry map
                 typeMap.put(type,idx);
             }
         }
 
         // If idx is STILL null, we've got no match
         if (idx == null)
         {
             return null;
         }
         return metadatas.get(idx);
     }
 
     private Integer getMetadataByAssignableType(Class<?> type)
     {
         for (Map.Entry<Class<?>, Integer> entry : typeMap.entrySet())
         {
             if (entry.getKey().isAssignableFrom(type))
             {
                 return entry.getValue();
             }
         }
 
         return null;
     }
 
     @Override
     public Iterator<M> iterator()
     {
         return metadatas.iterator();
     }
 
     @Override
     public String toString()
     {
         StringBuilder builder = new StringBuilder();
         builder.append(this.getClass().getSimpleName());
         builder.append("[metadatas=");
         builder.append(metadatas.size());
         builder.append(",coders=");
         builder.append(coders.size());
         builder.append("]");
         return builder.toString();
     }
 
     protected void trackMetadata(List<M> metadatas)
     {
         for (M metadata : metadatas)
         {
             trackMetadata(metadata);
         }
     }
 
     protected void trackMetadata(M metadata)
     {
         synchronized (metadatas)
         {
             // Validate
             boolean duplicate = false;
 
             // Is this metadata already declared?
             if (metadatas.contains(metadata))
             {
                 duplicate = true;
             }
 
             // Is this type already declared?
             Class<?> type = metadata.getObjectType();
             if (typeMap.containsKey(type))
             {
                 duplicate = true;
             }
 
             if (duplicate)
             {
                 StringBuilder err = new StringBuilder();
                 err.append("Duplicate decoder for type: ");
                 err.append(type);
                 err.append(" (class ").append(metadata.getCoderClass().getName());
 
                 // Get prior one
                 M dup = getMetadataByType(type);
                 err.append(" duplicates ");
                 err.append(dup.getCoderClass().getName());
                 err.append(")");
                 throw new IllegalStateException(err.toString());
             }
 
             // Track
             Class<? extends T> coderClass = metadata.getCoderClass();
             int newidx = metadatas.size();
             metadatas.add(metadata);
             coders.add(coderClass);
             typeMap.put(type,newidx);
 
             List<Integer> indexes = implMap.get(coderClass);
             if (indexes == null)
             {
                 indexes = new ArrayList<>();
             }
             if (indexes.contains(newidx))
             {
                 // possible duplicate, TODO: how?
             }
             indexes.add(newidx);
             implMap.put(coderClass,indexes);
         }
     }
 }