ParameterizedTypeHandlerMap.java

/*
 * Copyright (C) 2008 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 com.smartandroid.sa.json;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

import com.smartandroid.sa.json.internal.$Gson$Types;

/**
 * A map that provides ability to associate handlers for a specific type or all
 * of its sub-types
 * 
 * @author Inderjeet Singh
 * @author Joel Leitch
 * 
 * @param <T>
 *            The handler that will be looked up by type
 */
final class ParameterizedTypeHandlerMap<T> {
	private static final Logger logger = Logger
			.getLogger(ParameterizedTypeHandlerMap.class.getName());
	/**
	 * Map that is meant for storing default type adapters
	 */
	private final Map<Type, T> systemMap = new HashMap<Type, T>();
	private final Map<Type, T> userMap = new HashMap<Type, T>();
	/**
	 * List of default type hierarchy adapters
	 */
	private final List<Pair<Class<?>, T>> systemTypeHierarchyList = new ArrayList<Pair<Class<?>, T>>();
	private final List<Pair<Class<?>, T>> userTypeHierarchyList = new ArrayList<Pair<Class<?>, T>>();
	private boolean modifiable = true;

	public synchronized void registerForTypeHierarchy(Class<?> typeOfT,
			T value, boolean isSystem) {
		Pair<Class<?>, T> pair = new Pair<Class<?>, T>(typeOfT, value);
		registerForTypeHierarchy(pair, isSystem);
	}

	public synchronized void registerForTypeHierarchy(Pair<Class<?>, T> pair,
			boolean isSystem) {
		if (!modifiable) {
			throw new IllegalStateException(
					"Attempted to modify an unmodifiable map.");
		}
		List<Pair<Class<?>, T>> typeHierarchyList = isSystem ? systemTypeHierarchyList
				: userTypeHierarchyList;
		int index = getIndexOfSpecificHandlerForTypeHierarchy(pair.first,
				typeHierarchyList);
		if (index >= 0) {
			logger.log(Level.WARNING,
					"Overriding the existing type handler for {0}", pair.first);
			typeHierarchyList.remove(index);
		}
		index = getIndexOfAnOverriddenHandler(pair.first, typeHierarchyList);
		if (index >= 0) {
			throw new IllegalArgumentException(
					"The specified type handler for type "
							+ pair.first
							+ " hides the previously registered type hierarchy handler for "
							+ typeHierarchyList.get(index).first
							+ ". Gson does not allow this.");
		}
		// We want stack behavior for adding to this list. A type adapter added
		// subsequently should
		// override a previously registered one.
		typeHierarchyList.add(0, pair);
	}

	private static <T> int getIndexOfAnOverriddenHandler(Class<?> type,
			List<Pair<Class<?>, T>> typeHierarchyList) {
		for (int i = typeHierarchyList.size() - 1; i >= 0; --i) {
			Pair<Class<?>, T> entry = typeHierarchyList.get(i);
			if (type.isAssignableFrom(entry.first)) {
				return i;
			}
		}
		return -1;
	}

	public synchronized void register(Type typeOfT, T value, boolean isSystem) {
		if (!modifiable) {
			throw new IllegalStateException(
					"Attempted to modify an unmodifiable map.");
		}
		if (hasSpecificHandlerFor(typeOfT)) {
			logger.log(Level.WARNING,
					"Overriding the existing type handler for {0}", typeOfT);
		}
		Map<Type, T> map = isSystem ? systemMap : userMap;
		map.put(typeOfT, value);
	}

	public synchronized void registerIfAbsent(
			ParameterizedTypeHandlerMap<T> other) {
		if (!modifiable) {
			throw new IllegalStateException(
					"Attempted to modify an unmodifiable map.");
		}
		for (Map.Entry<Type, T> entry : other.userMap.entrySet()) {
			if (!userMap.containsKey(entry.getKey())) {
				register(entry.getKey(), entry.getValue(), false);
			}
		}
		for (Map.Entry<Type, T> entry : other.systemMap.entrySet()) {
			if (!systemMap.containsKey(entry.getKey())) {
				register(entry.getKey(), entry.getValue(), true);
			}
		}
		// Quite important to traverse the typeHierarchyList from stack bottom
		// first since
		// we want to register the handlers in the same order to preserve
		// priority order
		for (int i = other.userTypeHierarchyList.size() - 1; i >= 0; --i) {
			Pair<Class<?>, T> entry = other.userTypeHierarchyList.get(i);
			int index = getIndexOfSpecificHandlerForTypeHierarchy(entry.first,
					userTypeHierarchyList);
			if (index < 0) {
				registerForTypeHierarchy(entry, false);
			}
		}
		for (int i = other.systemTypeHierarchyList.size() - 1; i >= 0; --i) {
			Pair<Class<?>, T> entry = other.systemTypeHierarchyList.get(i);
			int index = getIndexOfSpecificHandlerForTypeHierarchy(entry.first,
					systemTypeHierarchyList);
			if (index < 0) {
				registerForTypeHierarchy(entry, true);
			}
		}
	}

	public synchronized void register(ParameterizedTypeHandlerMap<T> other) {
		if (!modifiable) {
			throw new IllegalStateException(
					"Attempted to modify an unmodifiable map.");
		}
		for (Map.Entry<Type, T> entry : other.userMap.entrySet()) {
			register(entry.getKey(), entry.getValue(), false);
		}
		for (Map.Entry<Type, T> entry : other.systemMap.entrySet()) {
			register(entry.getKey(), entry.getValue(), true);
		}
		// Quite important to traverse the typeHierarchyList from stack bottom
		// first since
		// we want to register the handlers in the same order to preserve
		// priority order
		for (int i = other.userTypeHierarchyList.size() - 1; i >= 0; --i) {
			Pair<Class<?>, T> entry = other.userTypeHierarchyList.get(i);
			registerForTypeHierarchy(entry, false);
		}
		for (int i = other.systemTypeHierarchyList.size() - 1; i >= 0; --i) {
			Pair<Class<?>, T> entry = other.systemTypeHierarchyList.get(i);
			registerForTypeHierarchy(entry, true);
		}
	}

	public synchronized void registerIfAbsent(Type typeOfT, T value) {
		if (!modifiable) {
			throw new IllegalStateException(
					"Attempted to modify an unmodifiable map.");
		}
		if (!userMap.containsKey(typeOfT)) {
			register(typeOfT, value, false);
		}
	}

	public synchronized void makeUnmodifiable() {
		modifiable = false;
	}

	public synchronized T getHandlerFor(Type type, boolean systemOnly) {
		T handler;
		if (!systemOnly) {
			handler = userMap.get(type);
			if (handler != null) {
				return handler;
			}
		}
		handler = systemMap.get(type);
		if (handler != null) {
			return handler;
		}
		Class<?> rawClass = $Gson$Types.getRawType(type);
		if (rawClass != type) {
			handler = getHandlerFor(rawClass, systemOnly);
			if (handler != null) {
				return handler;
			}
		}
		// check if something registered for type hierarchy
		handler = getHandlerForTypeHierarchy(rawClass, systemOnly);
		return handler;
	}

	private T getHandlerForTypeHierarchy(Class<?> type, boolean systemOnly) {
		if (!systemOnly) {
			for (Pair<Class<?>, T> entry : userTypeHierarchyList) {
				if (entry.first.isAssignableFrom(type)) {
					return entry.second;
				}
			}
		}
		for (Pair<Class<?>, T> entry : systemTypeHierarchyList) {
			if (entry.first.isAssignableFrom(type)) {
				return entry.second;
			}
		}
		return null;
	}

	public synchronized boolean hasSpecificHandlerFor(Type type) {
		return userMap.containsKey(type) || systemMap.containsKey(type);
	}

	private static <T> int getIndexOfSpecificHandlerForTypeHierarchy(
			Class<?> type, List<Pair<Class<?>, T>> typeHierarchyList) {
		for (int i = typeHierarchyList.size() - 1; i >= 0; --i) {
			if (type.equals(typeHierarchyList.get(i).first)) {
				return i;
			}
		}
		return -1;
	}

	public synchronized ParameterizedTypeHandlerMap<T> copyOf() {
		ParameterizedTypeHandlerMap<T> copy = new ParameterizedTypeHandlerMap<T>();
		// Instead of individually registering entries in the map, make an
		// efficient copy
		// of the list and map

		// TODO (inder): Performance optimization. We can probably just share
		// the
		// systemMap and systemTypeHierarchyList instead of making copies
		copy.systemMap.putAll(systemMap);
		copy.userMap.putAll(userMap);
		copy.systemTypeHierarchyList.addAll(systemTypeHierarchyList);
		copy.userTypeHierarchyList.addAll(userTypeHierarchyList);
		return copy;
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder("{userTypeHierarchyList:{");
		appendList(sb, userTypeHierarchyList);
		sb.append("},systemTypeHierarchyList:{");
		appendList(sb, systemTypeHierarchyList);
		sb.append("},userMap:{");
		appendMap(sb, userMap);
		sb.append("},systemMap:{");
		appendMap(sb, systemMap);
		sb.append("}");
		return sb.toString();
	}

	private void appendList(StringBuilder sb, List<Pair<Class<?>, T>> list) {
		boolean first = true;
		for (Pair<Class<?>, T> entry : list) {
			if (first) {
				first = false;
			} else {
				sb.append(',');
			}
			sb.append(typeToString(entry.first)).append(':');
			sb.append(entry.second);
		}
	}

	private void appendMap(StringBuilder sb, Map<Type, T> map) {
		boolean first = true;
		for (Map.Entry<Type, T> entry : map.entrySet()) {
			if (first) {
				first = false;
			} else {
				sb.append(',');
			}
			sb.append(typeToString(entry.getKey())).append(':');
			sb.append(entry.getValue());
		}
	}

	private String typeToString(Type type) {
		return $Gson$Types.getRawType(type).getSimpleName();
	}
}