/*
 * 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 cn.emay.sdk.util.json.gson.internal.bind;

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import cn.emay.sdk.util.json.gson.Gson;
import cn.emay.sdk.util.json.gson.JsonElement;
import cn.emay.sdk.util.json.gson.JsonPrimitive;
import cn.emay.sdk.util.json.gson.JsonSyntaxException;
import cn.emay.sdk.util.json.gson.TypeAdapter;
import cn.emay.sdk.util.json.gson.TypeAdapterFactory;
import cn.emay.sdk.util.json.gson.internal.$Gson$Types;
import cn.emay.sdk.util.json.gson.internal.ConstructorConstructor;
import cn.emay.sdk.util.json.gson.internal.JsonReaderInternalAccess;
import cn.emay.sdk.util.json.gson.internal.ObjectConstructor;
import cn.emay.sdk.util.json.gson.internal.Streams;
import cn.emay.sdk.util.json.gson.reflect.TypeToken;
import cn.emay.sdk.util.json.gson.stream.JsonReader;
import cn.emay.sdk.util.json.gson.stream.JsonToken;
import cn.emay.sdk.util.json.gson.stream.JsonWriter;

/**
 * Adapts maps to either JSON objects or JSON arrays.
 *
 * <h3>Maps as JSON objects</h3> For primitive keys or when complex map key
 * serialization is not enabled, this converts Java {@link Map Maps} to JSON
 * Objects. This requires that map keys can be serialized as strings; this is
 * insufficient for some key types. For example, consider a map whose keys are
 * points on a grid. The default JSON form encodes reasonably:
 * 
 * <pre>
 * {
 * 	&#64;code
 * 	Map<Point, String> original = new LinkedHashMap<Point, String>();
 * 	original.put(new Point(5, 6), "a");
 * 	original.put(new Point(8, 8), "b");
 * 	System.out.println(gson.toJson(original, type));
 * }
 * </pre>
 * 
 * The above code prints this JSON object:
 * 
 * <pre>
 *    {@code
 *   {
 *     "(5,6)": "a",
 *     "(8,8)": "b"
 *   }
 * }
 * </pre>
 * 
 * But GSON is unable to deserialize this value because the JSON string name is
 * just the {@link Object#toString() toString()} of the map key. Attempting to
 * convert the above JSON to an object fails with a parse exception:
 * 
 * <pre>
 * com.google.gson.JsonParseException: Expecting object found: "(5,6)"
 *   at com.google.gson.JsonObjectDeserializationVisitor.visitFieldUsingCustomHandler
 *   at com.google.gson.ObjectNavigator.navigateClassFields
 *   ...
 * </pre>
 *
 * <h3>Maps as JSON arrays</h3> An alternative approach taken by this type
 * adapter when it is required and complex map key serialization is enabled is
 * to encode maps as arrays of map entries. Each map entry is a two element
 * array containing a key and a value. This approach is more flexible because
 * any type can be used as the map's key; not just strings. But it's also less
 * portable because the receiver of such JSON must be aware of the map entry
 * convention.
 *
 * <p>
 * Register this adapter when you are creating your GSON instance.
 * 
 * <pre>
 * {
 * 	&#64;code
 * 	Gson gson = new GsonBuilder().registerTypeAdapter(Map.class, new MapAsArrayTypeAdapter()).create();
 * }
 * </pre>
 * 
 * This will change the structure of the JSON emitted by the code above. Now we
 * get an array. In this case the arrays elements are map entries:
 * 
 * <pre>
 *    {@code
 *   [
 *     [
 *       {
 *         "x": 5,
 *         "y": 6
 *       },
 *       "a",
 *     ],
 *     [
 *       {
 *         "x": 8,
 *         "y": 8
 *       },
 *       "b"
 *     ]
 *   ]
 * }
 * </pre>
 * 
 * This format will serialize and deserialize just fine as long as this adapter
 * is registered.
 */
public final class MapTypeAdapterFactory implements TypeAdapterFactory {
	private final ConstructorConstructor constructorConstructor;
	final boolean complexMapKeySerialization;

	public MapTypeAdapterFactory(ConstructorConstructor constructorConstructor, boolean complexMapKeySerialization) {
		this.constructorConstructor = constructorConstructor;
		this.complexMapKeySerialization = complexMapKeySerialization;
	}

	@Override
	public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
		Type type = typeToken.getType();

		Class<? super T> rawType = typeToken.getRawType();
		if (!Map.class.isAssignableFrom(rawType)) {
			return null;
		}

		Class<?> rawTypeOfSrc = $Gson$Types.getRawType(type);
		Type[] keyAndValueTypes = $Gson$Types.getMapKeyAndValueTypes(type, rawTypeOfSrc);
		TypeAdapter<?> keyAdapter = getKeyAdapter(gson, keyAndValueTypes[0]);
		TypeAdapter<?> valueAdapter = gson.getAdapter(TypeToken.get(keyAndValueTypes[1]));
		ObjectConstructor<T> constructor = constructorConstructor.get(typeToken);

		@SuppressWarnings({ "unchecked", "rawtypes" })
		// we don't define a type parameter for the key or value types
		TypeAdapter<T> result = new Adapter(gson, keyAndValueTypes[0], keyAdapter, keyAndValueTypes[1], valueAdapter, constructor);
		return result;
	}

	/**
	 * Returns a type adapter that writes the value as a string.
	 */
	private TypeAdapter<?> getKeyAdapter(Gson context, Type keyType) {
		return (keyType == boolean.class || keyType == Boolean.class) ? TypeAdapters.BOOLEAN_AS_STRING : context.getAdapter(TypeToken.get(keyType));
	}

	private final class Adapter<K, V> extends TypeAdapter<Map<K, V>> {
		private final TypeAdapter<K> keyTypeAdapter;
		private final TypeAdapter<V> valueTypeAdapter;
		private final ObjectConstructor<? extends Map<K, V>> constructor;

		public Adapter(Gson context, Type keyType, TypeAdapter<K> keyTypeAdapter, Type valueType, TypeAdapter<V> valueTypeAdapter, ObjectConstructor<? extends Map<K, V>> constructor) {
			this.keyTypeAdapter = new TypeAdapterRuntimeTypeWrapper<K>(context, keyTypeAdapter, keyType);
			this.valueTypeAdapter = new TypeAdapterRuntimeTypeWrapper<V>(context, valueTypeAdapter, valueType);
			this.constructor = constructor;
		}

		@Override
		public Map<K, V> read(JsonReader in) throws IOException {
			JsonToken peek = in.peek();
			if (peek == JsonToken.NULL) {
				in.nextNull();
				return null;
			}

			Map<K, V> map = constructor.construct();

			if (peek == JsonToken.BEGIN_ARRAY) {
				in.beginArray();
				while (in.hasNext()) {
					in.beginArray(); // entry array
					K key = keyTypeAdapter.read(in);
					V value = valueTypeAdapter.read(in);
					V replaced = map.put(key, value);
					if (replaced != null) {
						throw new JsonSyntaxException("duplicate key: " + key);
					}
					in.endArray();
				}
				in.endArray();
			} else {
				in.beginObject();
				while (in.hasNext()) {
					JsonReaderInternalAccess.INSTANCE.promoteNameToValue(in);
					K key = keyTypeAdapter.read(in);
					V value = valueTypeAdapter.read(in);
					V replaced = map.put(key, value);
					if (replaced != null) {
						throw new JsonSyntaxException("duplicate key: " + key);
					}
				}
				in.endObject();
			}
			return map;
		}

		@Override
		public void write(JsonWriter out, Map<K, V> map) throws IOException {
			if (map == null) {
				out.nullValue();
				return;
			}

			if (!complexMapKeySerialization) {
				out.beginObject();
				for (Map.Entry<K, V> entry : map.entrySet()) {
					out.name(String.valueOf(entry.getKey()));
					valueTypeAdapter.write(out, entry.getValue());
				}
				out.endObject();
				return;
			}

			boolean hasComplexKeys = false;
			List<JsonElement> keys = new ArrayList<JsonElement>(map.size());

			List<V> values = new ArrayList<V>(map.size());
			for (Map.Entry<K, V> entry : map.entrySet()) {
				JsonElement keyElement = keyTypeAdapter.toJsonTree(entry.getKey());
				keys.add(keyElement);
				values.add(entry.getValue());
				hasComplexKeys |= keyElement.isJsonArray() || keyElement.isJsonObject();
			}

			if (hasComplexKeys) {
				out.beginArray();
				for (int i = 0; i < keys.size(); i++) {
					out.beginArray(); // entry array
					Streams.write(keys.get(i), out);
					valueTypeAdapter.write(out, values.get(i));
					out.endArray();
				}
				out.endArray();
			} else {
				out.beginObject();
				for (int i = 0; i < keys.size(); i++) {
					JsonElement keyElement = keys.get(i);
					out.name(keyToString(keyElement));
					valueTypeAdapter.write(out, values.get(i));
				}
				out.endObject();
			}
		}

		private String keyToString(JsonElement keyElement) {
			if (keyElement.isJsonPrimitive()) {
				JsonPrimitive primitive = keyElement.getAsJsonPrimitive();
				if (primitive.isNumber()) {
					return String.valueOf(primitive.getAsNumber());
				} else if (primitive.isBoolean()) {
					return Boolean.toString(primitive.getAsBoolean());
				} else if (primitive.isString()) {
					return primitive.getAsString();
				} else {
					throw new AssertionError();
				}
			} else if (keyElement.isJsonNull()) {
				return "null";
			} else {
				throw new AssertionError();
			}
		}
	}
}