code: /*
   * Copyright (C) 2011 Google Inc.
   *
   * Licensed under the Apache 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.apache.org/licenses/LICENSE-2.0
   *
   * 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 tools.com.google.gson.internal.bind;
  
  import tools.com.google.gson.Gson;
  import tools.com.google.gson.JsonDeserializationContext;
  import tools.com.google.gson.JsonDeserializer;
  import tools.com.google.gson.JsonElement;
  import tools.com.google.gson.JsonParseException;
  import tools.com.google.gson.JsonSerializationContext;
  import tools.com.google.gson.JsonSerializer;
  import tools.com.google.gson.TypeAdapter;
  import tools.com.google.gson.TypeAdapterFactory;
  import tools.com.google.gson.internal.$Gson$Preconditions;
  import tools.com.google.gson.internal.Streams;
  import tools.com.google.gson.reflect.TypeToken;
  import tools.com.google.gson.stream.JsonReader;
  import tools.com.google.gson.stream.JsonWriter;
  import java.io.IOException;
  import java.lang.reflect.Type;
  
  /**
   * Adapts a Gson 1.x tree-style adapter as a streaming TypeAdapter. Since the
   * tree adapter may be serialization-only or deserialization-only, this class
   * has a facility to lookup a delegate type adapter on demand.
   */
  public final class TreeTypeAdapter<T> extends TypeAdapter<T> {
    private final JsonSerializer<T> serializer;
    private final JsonDeserializer<T> deserializer;
    final Gson gson;
    private final TypeToken<T> typeToken;
    private final TypeAdapterFactory skipPast;
    private final GsonContextImpl context = new GsonContextImpl();
  
    /** The delegate is lazily created because it may not be needed, and creating it may fail. */
    private TypeAdapter<T> delegate;
  
    public TreeTypeAdapter(JsonSerializer<T> serializer, JsonDeserializer<T> deserializer,
        Gson gson, TypeToken<T> typeToken, TypeAdapterFactory skipPast) {
      this.serializer = serializer;
      this.deserializer = deserializer;
      this.gson = gson;
      this.typeToken = typeToken;
      this.skipPast = skipPast;
    }
  
    @Override public T read(JsonReader in) throws IOException {
      if (deserializer == null) {
        return delegate().read(in);
      }
      JsonElement value = Streams.parse(in);
      if (value.isJsonNull()) {
        return null;
      }
      return deserializer.deserialize(value, typeToken.getType(), context);
    }
  
    @Override public void write(JsonWriter out, T value) throws IOException {
      if (serializer == null) {
        delegate().write(out, value);
        return;
      }
      if (value == null) {
        out.nullValue();
        return;
      }
      JsonElement tree = serializer.serialize(value, typeToken.getType(), context);
      Streams.write(tree, out);
    }
  
    private TypeAdapter<T> delegate() {
      TypeAdapter<T> d = delegate;
      return d != null
          ? d
          : (delegate = gson.getDelegateAdapter(skipPast, typeToken));
    }
  
    /**
     * Returns a new factory that will match each type against {@code exactType}.
     */
    public static TypeAdapterFactory newFactory(TypeToken<?> exactType, Object typeAdapter) {
      return new SingleTypeFactory(typeAdapter, exactType, false, null);
    }
  
    /**
     * Returns a new factory that will match each type and its raw type against
     * {@code exactType}.
     */
    public static TypeAdapterFactory newFactoryWithMatchRawType(
        TypeToken<?> exactType, Object typeAdapter) {
      // only bother matching raw types if exact type is a raw type
      boolean matchRawType = exactType.getType() == exactType.getRawType();
      return new SingleTypeFactory(typeAdapter, exactType, matchRawType, null);
    }
  
    /**
     * Returns a new factory that will match each type's raw type for assignability
     * to {@code hierarchyType}.
     */
    public static TypeAdapterFactory newTypeHierarchyFactory(
        Class<?> hierarchyType, Object typeAdapter) {
      return new SingleTypeFactory(typeAdapter, null, false, hierarchyType);
    }
  
    private static final class SingleTypeFactory implements TypeAdapterFactory {
      private final TypeToken<?> exactType;
      private final boolean matchRawType;
      private final Class<?> hierarchyType;
      private final JsonSerializer<?> serializer;
      private final JsonDeserializer<?> deserializer;
  
      SingleTypeFactory(Object typeAdapter, TypeToken<?> exactType, boolean matchRawType,
          Class<?> hierarchyType) {
        serializer = typeAdapter instanceof JsonSerializer
            ? (JsonSerializer<?>) typeAdapter
            : null;
        deserializer = typeAdapter instanceof JsonDeserializer
            ? (JsonDeserializer<?>) typeAdapter
            : null;
        $Gson$Preconditions.checkArgument(serializer != null || deserializer != null);
        this.exactType = exactType;
        this.matchRawType = matchRawType;
        this.hierarchyType = hierarchyType;
      }
  
      @SuppressWarnings("unchecked") // guarded by typeToken.equals() call
      @Override
      public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
        boolean matches = exactType != null
            ? exactType.equals(type) || matchRawType && exactType.getType() == type.getRawType()
            : hierarchyType.isAssignableFrom(type.getRawType());
        return matches
            ? new TreeTypeAdapter<T>((JsonSerializer<T>) serializer,
                (JsonDeserializer<T>) deserializer, gson, type, this)
            : null;
      }
    }
  
    private final class GsonContextImpl implements JsonSerializationContext, JsonDeserializationContext {
      @Override public JsonElement serialize(Object src) {
        return gson.toJsonTree(src);
      }
      @Override public JsonElement serialize(Object src, Type typeOfSrc) {
        return gson.toJsonTree(src, typeOfSrc);
      }
      @SuppressWarnings("unchecked")
      @Override public <R> R deserialize(JsonElement json, Type typeOfT) throws JsonParseException {
        return (R) gson.fromJson(json, typeOfT);
      }
    };
  }
  