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package org.apache.juneau.serializer;

import static org.apache.juneau.internal.CollectionUtils.*;

import java.util.*;
import java.util.concurrent.*;

import org.apache.juneau.*;
import org.apache.juneau.http.*;

/**
 * Represents a group of {@link Serializer Serializers} that can be looked up by media type.
 *
 * <h5 class='topic'>Description</h5>
 *
 * Provides the following features:
 * <ul class='spaced-list'>
 *    <li>
 *       Finds serializers based on HTTP <code>Accept</code> header values.
 *    <li>
 *       Sets common properties on all serializers in a single method call.
 *    <li>
 *       Clones existing groups and all serializers within the group in a single method call.
 * </ul>
 *
 * <h5 class='topic'>Match ordering</h5>
 *
 * Serializers are matched against <code>Accept</code> strings in the order they exist in this group.
 *
 * <p>
 * Adding new entries will cause the entries to be prepended to the group.
 * This allows for previous serializers to be overridden through subsequent calls.
 *
 * <p>
 * For example, calling <code>g.append(S1.<jk>class</jk>,S2.<jk>class</jk>).append(S3.<jk>class</jk>,S4.<jk>class</jk>)</code>
 * will result in the order <code>S3, S4, S1, S2</code>.
 *
 * <h5 class='section'>Example:</h5>
 * <p class='bcode w800'>
 *    <jc>// Construct a new serializer group</jc>
 *    SerializerGroup g = SerializerGroup.<jsm>create</jsm>();
 *       .append(JsonSerializer.<jk>class</jk>, XmlSerializer.<jk>class</jk>); <jc>// Add some serializers to it</jc>
 *       .ws().pojoSwaps(CalendarSwap.ISO8601DT.<jk>class</jk>) <jc>// Change settings for all serializers in the group.</jc>
 *       .build();
 *
 *    <jc>// Find the appropriate serializer by Accept type</jc>
 *    WriterSerializer s = g.getWriterSerializer(<js>"text/foo, text/json;q=0.8, text/*;q:0.6, *\/*;q=0.0"</js>);
 *
 *    <jc>// Serialize a bean to JSON text </jc>
 *    AddressBook addressBook = <jk>new</jk> AddressBook();  <jc>// Bean to serialize.</jc>
 *    String json = s.serialize(addressBook);
 * </p>
 */
public final class SerializerGroup extends BeanTraverseContext {

   /**
    * An unmodifiable empty serializer group.
    */
   public static final SerializerGroup EMPTY = create().build();

   // Maps Accept headers to matching serializers.
   private final ConcurrentHashMap<String,SerializerMatch> cache = new ConcurrentHashMap<>();

   private final MediaTypeRange[] mediaTypeRanges;
   private final Serializer[] mediaTypeRangeSerializers;

   private final List<MediaType> mediaTypesList;
   private final List<Serializer> serializers;

   /**
    * Instantiates a new clean-slate {@link SerializerGroupBuilder} object.
    *
    * <p>
    * This is equivalent to simply calling <code><jk>new</jk> SerializerGroupBuilder()</code>.
    *
    * @return A new {@link SerializerGroupBuilder} object.
    */
   public static SerializerGroupBuilder create() {
      return new SerializerGroupBuilder();
   }

   /**
    * Returns a builder that's a copy of the settings on this serializer group.
    *
    * @return A new {@link SerializerGroupBuilder} initialized to this group.
    */
   @Override /* Context */
   public SerializerGroupBuilder builder() {
      return new SerializerGroupBuilder(this);
   }

   /**
    * Constructor.
    *
    * @param ps
    *    The modifiable properties that were used to initialize the serializers.
    *    A snapshot of these will be made so that we can clone and modify this group.
    * @param serializers
    *    The serializers defined in this group.
    *    The order is important because they will be tried in reverse order (e.g.newer first) in which they will be tried
    *    to match against media types.
    */
   public SerializerGroup(PropertyStore ps, Serializer[] serializers) {
      super(ps);
      this.serializers = immutableList(serializers);

      List<MediaTypeRange> lmtr = new ArrayList<>();
      LinkedHashSet<MediaType> lmt = new LinkedHashSet<>();
      List<Serializer> l = new ArrayList<>();
      for (Serializer s : serializers) {
         for (MediaTypeRange m: s.getMediaTypeRanges()) {
            lmtr.add(m);
            l.add(s);
         }
         for (MediaType mt : s.getAcceptMediaTypes())
            lmt.add(mt);
      }

      this.mediaTypeRanges = lmtr.toArray(new MediaTypeRange[lmt.size()]);
      this.mediaTypesList = unmodifiableList(new ArrayList<>(lmt));
      this.mediaTypeRangeSerializers = l.toArray(new Serializer[l.size()]);
   }

   /**
    * Searches the group for a serializer that can handle the specified <code>Accept</code> value.
    *
    * <p>
    * The <code>accept</code> value complies with the syntax described in RFC2616, Section 14.1, as described below:
    * <p class='bcode w800'>
    *    Accept         = "Accept" ":"
    *                      #( media-range [ accept-params ] )
    *
    *    media-range    = ( "*\/*"
    *                      | ( type "/" "*" )
    *                      | ( type "/" subtype )
    *                      ) *( ";" parameter )
    *    accept-params  = ";" "q" "=" qvalue *( accept-extension )
    *    accept-extension = ";" token [ "=" ( token | quoted-string ) ]
    * </p>
    *
    * <p>
    * The returned object includes both the serializer and media type that matched.
    *
    * @param acceptHeader The HTTP <l>Accept</l> header string.
    * @return The serializer and media type that matched the accept header, or <jk>null</jk> if no match was made.
    */
   public SerializerMatch getSerializerMatch(String acceptHeader) {
      SerializerMatch sm = cache.get(acceptHeader);
      if (sm != null)
         return sm;

      Accept a = Accept.forString(acceptHeader);
      int match = a.findMatch(mediaTypeRanges);
      if (match >= 0) {
         sm = new SerializerMatch(mediaTypeRanges[match].getMediaType(), mediaTypeRangeSerializers[match]);
         cache.putIfAbsent(acceptHeader, sm);
      }

      return cache.get(acceptHeader);
   }

   /**
    * Same as {@link #getSerializerMatch(String)} but matches using a {@link MediaType} instance.
    *
    * @param mediaType The HTTP media type.
    * @return The serializer and media type that matched the media type, or <jk>null</jk> if no match was made.
    */
   public SerializerMatch getSerializerMatch(MediaType mediaType) {
      return getSerializerMatch(mediaType.toString());
   }

   /**
    * Same as {@link #getSerializerMatch(String)} but returns just the matched serializer.
    *
    * @param acceptHeader The HTTP <l>Accept</l> header string.
    * @return The serializer that matched the accept header, or <jk>null</jk> if no match was made.
    */
   public Serializer getSerializer(String acceptHeader) {
      SerializerMatch sm = getSerializerMatch(acceptHeader);
      return sm == null ? null : sm.getSerializer();
   }

   /**
    * Same as {@link #getSerializerMatch(MediaType)} but returns just the matched serializer.
    *
    * @param mediaType The HTTP media type.
    * @return The serializer that matched the accept header, or <jk>null</jk> if no match was made.
    */
   public Serializer getSerializer(MediaType mediaType) {
      if (mediaType == null)
         return null;
      return getSerializer(mediaType.toString());
   }

   /**
    * Same as {@link #getSerializer(String)}, but casts it to a {@link WriterSerializer}.
    *
    * @param acceptHeader The HTTP <l>Accept</l> header string.
    * @return The serializer that matched the accept header, or <jk>null</jk> if no match was made.
    */
   public WriterSerializer getWriterSerializer(String acceptHeader) {
      return (WriterSerializer)getSerializer(acceptHeader);
   }

   /**
    * Same as {@link #getSerializer(MediaType)}, but casts it to a {@link WriterSerializer}.
    *
    * @param mediaType The HTTP media type.
    * @return The serializer that matched the accept header, or <jk>null</jk> if no match was made.
    */
   public WriterSerializer getWriterSerializer(MediaType mediaType) {
      return (WriterSerializer)getSerializer(mediaType);
   }

   /**
    * Same as {@link #getSerializer(String)}, but casts it to an {@link OutputStreamSerializer}.
    *
    * @param acceptHeader The HTTP <l>Accept</l> header string.
    * @return The serializer that matched the accept header, or <jk>null</jk> if no match was made.
    */
   public OutputStreamSerializer getStreamSerializer(String acceptHeader) {
      return (OutputStreamSerializer)getSerializer(acceptHeader);
   }

   /**
    * Same as {@link #getSerializer(MediaType)}, but casts it to a {@link OutputStreamSerializer}.
    *
    * @param mediaType The HTTP media type.
    * @return The serializer that matched the accept header, or <jk>null</jk> if no match was made.
    */
   public OutputStreamSerializer getStreamSerializer(MediaType mediaType) {
      return (OutputStreamSerializer)getSerializer(mediaType);
   }

   /**
    * Returns the media types that all serializers in this group can handle.
    *
    * <p>
    * Entries are ordered in the same order as the serializers in the group.
    *
    * @return An unmodifiable list of media types.
    */
   public List<MediaType> getSupportedMediaTypes() {
      return mediaTypesList;
   }

   /**
    * Returns a copy of the serializers in this group.
    *
    * @return An unmodifiable list of serializers in this group.
    */
   public List<Serializer> getSerializers() {
      return serializers;
   }
}