org.jclouds.googlecloud.config.ListPageAdapterFactory.java Source code

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Here is the source code for org.jclouds.googlecloud.config.ListPageAdapterFactory.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.jclouds.googlecloud.config;

import java.io.IOException;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import org.jclouds.googlecloud.domain.ForwardingListPage;
import org.jclouds.googlecloud.domain.ListPage;

import com.google.common.collect.ImmutableList;
import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;

public final class ListPageAdapterFactory implements TypeAdapterFactory {
    static final class ListPageAdapter extends TypeAdapter<ListPage<?>> {
        private final TypeAdapter<?> itemAdapter;

        ListPageAdapter(TypeAdapter<?> itemAdapter) {
            this.itemAdapter = itemAdapter;
            nullSafe();
        }

        public void write(JsonWriter out, ListPage<?> value) throws IOException {
            throw new UnsupportedOperationException("We only read ListPages!");
        }

        public ListPage<?> read(JsonReader in) throws IOException {
            ImmutableList.Builder<Object> items = ImmutableList.builder();
            String nextPageToken = null;
            in.beginObject();
            while (in.hasNext()) {
                String name = in.nextName();
                if (name.equals("items")) {
                    if (in.peek() == JsonToken.BEGIN_ARRAY) {
                        readItems(in, items);
                    } else { // aggregated
                        readAggregate(in, items);
                    }
                } else if (name.equals("nextPageToken")) {
                    nextPageToken = in.nextString();
                } else {
                    in.skipValue();
                }
            }
            in.endObject();
            return ForwardingListPage.create(items.build(), nextPageToken);
        }

        private void readItems(JsonReader in, ImmutableList.Builder<Object> items) throws IOException {
            in.beginArray();
            while (in.hasNext()) {
                Object item = itemAdapter.read(in);
                if (item != null) {
                    items.add(item);
                }
            }
            in.endArray();
        }

        private void readAggregate(JsonReader in, ImmutableList.Builder<Object> items) throws IOException {
            in.beginObject(); // enter zone name -> type -> items map
            while (in.hasNext()) {
                String scope = in.nextName(); // skip zone name
                in.beginObject(); // enter zone map
                while (in.hasNext()) {
                    String resourceTypeOrWarning = in.nextName();
                    if (!resourceTypeOrWarning.equals("warning")) {
                        readItems(in, items);
                    } else {
                        in.skipValue();
                    }
                }
                in.endObject(); // end zone map
            }
            in.endObject(); // end item wrapper
        }
    }

    @SuppressWarnings("unchecked")
    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> ownerType) {
        Type type = ownerType.getType();
        if (ownerType.getRawType() != ListPage.class || !(type instanceof ParameterizedType)) {
            return null;
        }
        Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
        TypeAdapter<?> itemAdapter = gson.getAdapter(TypeToken.get(elementType));
        return (TypeAdapter<T>) new ListPageAdapter(itemAdapter);
    }
}