/*******************************************************************************
 * Copyright (c) 2016 EclipseSource.
 *
 * Distributed under MIT license
 * See https://github.com/ralfstx/minimal-json/blob/master/LICENSE
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 ******************************************************************************/
package net.sourceforge.plantuml.json;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Reader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import net.sourceforge.plantuml.json.JsonObject.Member;

/**
 * Represents a JSON object, a set of name/value pairs, where the names are
 * strings and the values are JSON values.
 * <p>
 * Members can be added using the <code>add(String, ...)</code> methods which
 * accept instances of {@link JsonValue}, strings, primitive numbers, and
 * boolean values. To modify certain values of an object, use the
 * <code>set(String, ...)</code> methods. Please note that the <code>add</code>
 * methods are faster than <code>set</code> as they do not search for existing
 * members. On the other hand, the <code>add</code> methods do not prevent
 * adding multiple members with the same name. Duplicate names are discouraged
 * but not prohibited by JSON.
 * </p>
 * <p>
 * Members can be accessed by their name using {@link #get(String)}. A list of
 * all names can be obtained from the method {@link #names()}. This class also
 * supports iterating over the members in document order using an
 * {@link #iterator()} or an enhanced for loop:
 * </p>
 * 
 * <pre>
 * for (Member member : jsonObject) {
 *   String name = member.getName();
 *   JsonValue value = member.getValue();
 *   ...
 * }
 * </pre>
 * <p>
 * Even though JSON objects are unordered by definition, instances of this class
 * preserve the order of members to allow processing in document order and to
 * guarantee a predictable output.
 * </p>
 * <p>
 * Note that this class is <strong>not thread-safe</strong>. If multiple threads
 * access a <code>JsonObject</code> instance concurrently, while at least one of
 * these threads modifies the contents of this object, access to the instance
 * must be synchronized externally. Failure to do so may lead to an inconsistent
 * state.
 * </p>
 * <p>
 * This class is <strong>not supposed to be extended</strong> by clients.
 * </p>
 */
@SuppressWarnings("serial") // use default serial UID
public class JsonObject extends JsonValue implements Iterable<Member> {
	
	/**
	 * Added for PlantUML
	 */
	public JsonValue cloneMe() {
		final JsonObject copy = new JsonObject();
		for (int i=0; i<names.size(); i++)
			copy.add(this.names.get(i), this.values.get(i).cloneMe());
		return copy;
	}


	private final List<String> names;
	private final List<JsonValue> values;
	private transient HashIndexTable table;

	/**
	 * Creates a new empty JsonObject.
	 */
	public JsonObject() {
		names = new ArrayList<>();
		values = new ArrayList<>();
		table = new HashIndexTable();
	}

	/**
	 * Creates a new JsonObject, initialized with the contents of the specified JSON
	 * object.
	 *
	 * @param object the JSON object to get the initial contents from, must not be
	 *               <code>null</code>
	 */
	public JsonObject(JsonObject object) {
		this(object, false);
	}

	private JsonObject(JsonObject object, boolean unmodifiable) {
		if (object == null) {
			throw new NullPointerException("object is null");
		}
		if (unmodifiable) {
			names = Collections.unmodifiableList(object.names);
			values = Collections.unmodifiableList(object.values);
		} else {
			names = new ArrayList<>(object.names);
			values = new ArrayList<>(object.values);
		}
		table = new HashIndexTable();
		updateHashIndex();
	}

	/**
	 * Reads a JSON object from the given reader.
	 * <p>
	 * Characters are read in chunks and buffered internally, therefore wrapping an
	 * existing reader in an additional <code>BufferedReader</code> does
	 * <strong>not</strong> improve reading performance.
	 * </p>
	 *
	 * @param reader the reader to read the JSON object from
	 * @return the JSON object that has been read
	 * @throws IOException                   if an I/O error occurs in the reader
	 * @throws ParseException                if the input is not valid JSON
	 * @throws UnsupportedOperationException if the input does not contain a JSON
	 *                                       object
	 * @deprecated Use {@link Json#parse(Reader)}{@link JsonValue#asObject()
	 *             .asObject()} instead
	 */
	@Deprecated
	public static JsonObject readFrom(Reader reader) throws IOException {
		return JsonValue.readFrom(reader).asObject();
	}

	/**
	 * Reads a JSON object from the given string.
	 *
	 * @param string the string that contains the JSON object
	 * @return the JSON object that has been read
	 * @throws ParseException                if the input is not valid JSON
	 * @throws UnsupportedOperationException if the input does not contain a JSON
	 *                                       object
	 * @deprecated Use {@link Json#parse(String)}{@link JsonValue#asObject()
	 *             .asObject()} instead
	 */
	@Deprecated
	public static JsonObject readFrom(String string) {
		return JsonValue.readFrom(string).asObject();
	}

	/**
	 * Returns an unmodifiable JsonObject for the specified one. This method allows
	 * to provide read-only access to a JsonObject.
	 * <p>
	 * The returned JsonObject is backed by the given object and reflect changes
	 * that happen to it. Attempts to modify the returned JsonObject result in an
	 * <code>UnsupportedOperationException</code>.
	 * </p>
	 *
	 * @param object the JsonObject for which an unmodifiable JsonObject is to be
	 *               returned
	 * @return an unmodifiable view of the specified JsonObject
	 */
	public static JsonObject unmodifiableObject(JsonObject object) {
		return new JsonObject(object, true);
	}

	/**
	 * Appends a new member to the end of this object, with the specified name and
	 * the JSON representation of the specified <code>int</code> value.
	 * <p>
	 * This method <strong>does not prevent duplicate names</strong>. Calling this
	 * method with a name that already exists in the object will append another
	 * member with the same name. In order to replace existing members, use the
	 * method <code>set(name, value)</code> instead. However, <strong> <em>add</em>
	 * is much faster than <em>set</em></strong> (because it does not need to search
	 * for existing members). Therefore <em>add</em> should be preferred when
	 * constructing new objects.
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject add(String name, int value) {
		add(name, Json.value(value));
		return this;
	}

	/**
	 * Appends a new member to the end of this object, with the specified name and
	 * the JSON representation of the specified <code>long</code> value.
	 * <p>
	 * This method <strong>does not prevent duplicate names</strong>. Calling this
	 * method with a name that already exists in the object will append another
	 * member with the same name. In order to replace existing members, use the
	 * method <code>set(name, value)</code> instead. However, <strong> <em>add</em>
	 * is much faster than <em>set</em></strong> (because it does not need to search
	 * for existing members). Therefore <em>add</em> should be preferred when
	 * constructing new objects.
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject add(String name, long value) {
		add(name, Json.value(value));
		return this;
	}

	/**
	 * Appends a new member to the end of this object, with the specified name and
	 * the JSON representation of the specified <code>float</code> value.
	 * <p>
	 * This method <strong>does not prevent duplicate names</strong>. Calling this
	 * method with a name that already exists in the object will append another
	 * member with the same name. In order to replace existing members, use the
	 * method <code>set(name, value)</code> instead. However, <strong> <em>add</em>
	 * is much faster than <em>set</em></strong> (because it does not need to search
	 * for existing members). Therefore <em>add</em> should be preferred when
	 * constructing new objects.
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject add(String name, float value) {
		add(name, Json.value(value));
		return this;
	}

	/**
	 * Appends a new member to the end of this object, with the specified name and
	 * the JSON representation of the specified <code>double</code> value.
	 * <p>
	 * This method <strong>does not prevent duplicate names</strong>. Calling this
	 * method with a name that already exists in the object will append another
	 * member with the same name. In order to replace existing members, use the
	 * method <code>set(name, value)</code> instead. However, <strong> <em>add</em>
	 * is much faster than <em>set</em></strong> (because it does not need to search
	 * for existing members). Therefore <em>add</em> should be preferred when
	 * constructing new objects.
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject add(String name, double value) {
		add(name, Json.value(value));
		return this;
	}

	/**
	 * Appends a new member to the end of this object, with the specified name and
	 * the JSON representation of the specified <code>boolean</code> value.
	 * <p>
	 * This method <strong>does not prevent duplicate names</strong>. Calling this
	 * method with a name that already exists in the object will append another
	 * member with the same name. In order to replace existing members, use the
	 * method <code>set(name, value)</code> instead. However, <strong> <em>add</em>
	 * is much faster than <em>set</em></strong> (because it does not need to search
	 * for existing members). Therefore <em>add</em> should be preferred when
	 * constructing new objects.
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject add(String name, boolean value) {
		add(name, Json.value(value));
		return this;
	}

	/**
	 * Appends a new member to the end of this object, with the specified name and
	 * the JSON representation of the specified string.
	 * <p>
	 * This method <strong>does not prevent duplicate names</strong>. Calling this
	 * method with a name that already exists in the object will append another
	 * member with the same name. In order to replace existing members, use the
	 * method <code>set(name, value)</code> instead. However, <strong> <em>add</em>
	 * is much faster than <em>set</em></strong> (because it does not need to search
	 * for existing members). Therefore <em>add</em> should be preferred when
	 * constructing new objects.
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject add(String name, String value) {
		add(name, Json.value(value));
		return this;
	}

	/**
	 * Appends a new member to the end of this object, with the specified name and
	 * the specified JSON value.
	 * <p>
	 * This method <strong>does not prevent duplicate names</strong>. Calling this
	 * method with a name that already exists in the object will append another
	 * member with the same name. In order to replace existing members, use the
	 * method <code>set(name, value)</code> instead. However, <strong> <em>add</em>
	 * is much faster than <em>set</em></strong> (because it does not need to search
	 * for existing members). Therefore <em>add</em> should be preferred when
	 * constructing new objects.
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add, must not be <code>null</code>
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject add(String name, JsonValue value) {
		if (name == null) {
			throw new NullPointerException("name is null");
		}
		if (value == null) {
			throw new NullPointerException("value is null");
		}
		table.add(name, names.size());
		names.add(name);
		values.add(value);
		return this;
	}

	/**
	 * Sets the value of the member with the specified name to the JSON
	 * representation of the specified <code>int</code> value. If this object does
	 * not contain a member with this name, a new member is added at the end of the
	 * object. If this object contains multiple members with this name, only the
	 * last one is changed.
	 * <p>
	 * This method should <strong>only be used to modify existing objects</strong>.
	 * To fill a new object with members, the method <code>add(name, value)</code>
	 * should be preferred which is much faster (as it does not need to search for
	 * existing members).
	 * </p>
	 *
	 * @param name  the name of the member to replace
	 * @param value the value to set to the member
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject set(String name, int value) {
		set(name, Json.value(value));
		return this;
	}

	/**
	 * Sets the value of the member with the specified name to the JSON
	 * representation of the specified <code>long</code> value. If this object does
	 * not contain a member with this name, a new member is added at the end of the
	 * object. If this object contains multiple members with this name, only the
	 * last one is changed.
	 * <p>
	 * This method should <strong>only be used to modify existing objects</strong>.
	 * To fill a new object with members, the method <code>add(name, value)</code>
	 * should be preferred which is much faster (as it does not need to search for
	 * existing members).
	 * </p>
	 *
	 * @param name  the name of the member to replace
	 * @param value the value to set to the member
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject set(String name, long value) {
		set(name, Json.value(value));
		return this;
	}

	/**
	 * Sets the value of the member with the specified name to the JSON
	 * representation of the specified <code>float</code> value. If this object does
	 * not contain a member with this name, a new member is added at the end of the
	 * object. If this object contains multiple members with this name, only the
	 * last one is changed.
	 * <p>
	 * This method should <strong>only be used to modify existing objects</strong>.
	 * To fill a new object with members, the method <code>add(name, value)</code>
	 * should be preferred which is much faster (as it does not need to search for
	 * existing members).
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject set(String name, float value) {
		set(name, Json.value(value));
		return this;
	}

	/**
	 * Sets the value of the member with the specified name to the JSON
	 * representation of the specified <code>double</code> value. If this object
	 * does not contain a member with this name, a new member is added at the end of
	 * the object. If this object contains multiple members with this name, only the
	 * last one is changed.
	 * <p>
	 * This method should <strong>only be used to modify existing objects</strong>.
	 * To fill a new object with members, the method <code>add(name, value)</code>
	 * should be preferred which is much faster (as it does not need to search for
	 * existing members).
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject set(String name, double value) {
		set(name, Json.value(value));
		return this;
	}

	/**
	 * Sets the value of the member with the specified name to the JSON
	 * representation of the specified <code>boolean</code> value. If this object
	 * does not contain a member with this name, a new member is added at the end of
	 * the object. If this object contains multiple members with this name, only the
	 * last one is changed.
	 * <p>
	 * This method should <strong>only be used to modify existing objects</strong>.
	 * To fill a new object with members, the method <code>add(name, value)</code>
	 * should be preferred which is much faster (as it does not need to search for
	 * existing members).
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject set(String name, boolean value) {
		set(name, Json.value(value));
		return this;
	}

	/**
	 * Sets the value of the member with the specified name to the JSON
	 * representation of the specified string. If this object does not contain a
	 * member with this name, a new member is added at the end of the object. If
	 * this object contains multiple members with this name, only the last one is
	 * changed.
	 * <p>
	 * This method should <strong>only be used to modify existing objects</strong>.
	 * To fill a new object with members, the method <code>add(name, value)</code>
	 * should be preferred which is much faster (as it does not need to search for
	 * existing members).
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject set(String name, String value) {
		set(name, Json.value(value));
		return this;
	}

	/**
	 * Sets the value of the member with the specified name to the specified JSON
	 * value. If this object does not contain a member with this name, a new member
	 * is added at the end of the object. If this object contains multiple members
	 * with this name, only the last one is changed.
	 * <p>
	 * This method should <strong>only be used to modify existing objects</strong>.
	 * To fill a new object with members, the method <code>add(name, value)</code>
	 * should be preferred which is much faster (as it does not need to search for
	 * existing members).
	 * </p>
	 *
	 * @param name  the name of the member to add
	 * @param value the value of the member to add, must not be <code>null</code>
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject set(String name, JsonValue value) {
		if (name == null) {
			throw new NullPointerException("name is null");
		}
		if (value == null) {
			throw new NullPointerException("value is null");
		}
		int index = indexOf(name);
		if (index != -1) {
			values.set(index, value);
		} else {
			table.add(name, names.size());
			names.add(name);
			values.add(value);
		}
		return this;
	}

	/**
	 * Removes a member with the specified name from this object. If this object
	 * contains multiple members with the given name, only the last one is removed.
	 * If this object does not contain a member with the specified name, the object
	 * is not modified.
	 *
	 * @param name the name of the member to remove
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject remove(String name) {
		if (name == null) {
			throw new NullPointerException("name is null");
		}
		int index = indexOf(name);
		if (index != -1) {
			table.remove(index);
			names.remove(index);
			values.remove(index);
		}
		return this;
	}

	/**
	 * Checks if a specified member is present as a child of this object. This will
	 * not test if this object contains the literal <code>null</code>,
	 * {@link JsonValue#isNull()} should be used for this purpose.
	 *
	 * @param name the name of the member to check for
	 * @return whether or not the member is present
	 */
	public boolean contains(String name) {
		return names.contains(name);
	}

	/**
	 * Copies all members of the specified object into this object. When the
	 * specified object contains members with names that also exist in this object,
	 * the existing values in this object will be replaced by the corresponding
	 * values in the specified object.
	 *
	 * @param object the object to merge
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject merge(JsonObject object) {
		if (object == null) {
			throw new NullPointerException("object is null");
		}
		for (Member member : object) {
			this.set(member.name, member.value);
		}
		return this;
	}

	/**
	 * Copies all members of the specified object into this object. When the
	 * specified object contains members with names that also exist in this object,
	 * the existing values in this object will be replaced by the corresponding
	 * values in the specified object, except for the case that both values are
	 * JsonObjects themselves, which will trigger another merge of these objects.
	 *
	 * @param object the object to deep merge
	 * @return the object itself, to enable method chaining
	 */
	public JsonObject deepMerge(JsonObject object) {
		if (object == null) {
			throw new NullPointerException("object is null");
		}
		for (Member member : object) {
			final String name = member.name;
			JsonValue value = member.value;
			if (value instanceof JsonObject) {
				final JsonValue existingValue = this.get(member.name);
				if (existingValue instanceof JsonObject) {
					value = ((JsonObject) existingValue).deepMerge((JsonObject) value);
				}
			}
			this.set(name, value);
		}
		return this;
	}

	/**
	 * Returns the value of the member with the specified name in this object. If
	 * this object contains multiple members with the given name, this method will
	 * return the last one.
	 *
	 * @param name the name of the member whose value is to be returned
	 * @return the value of the last member with the specified name, or
	 *         <code>null</code> if this object does not contain a member with that
	 *         name
	 */
	public JsonValue get(String name) {
		if (name == null) {
			throw new NullPointerException("name is null");
		}
		int index = indexOf(name);
		return index != -1 ? values.get(index) : null;
	}

	/**
	 * Returns the <code>int</code> value of the member with the specified name in
	 * this object. If this object does not contain a member with this name, the
	 * given default value is returned. If this object contains multiple members
	 * with the given name, the last one will be picked. If this member's value does
	 * not represent a JSON number or if it cannot be interpreted as Java
	 * <code>int</code>, an exception is thrown.
	 *
	 * @param name         the name of the member whose value is to be returned
	 * @param defaultValue the value to be returned if the requested member is
	 *                     missing
	 * @return the value of the last member with the specified name, or the given
	 *         default value if this object does not contain a member with that name
	 */
	public int getInt(String name, int defaultValue) {
		JsonValue value = get(name);
		return value != null ? value.asInt() : defaultValue;
	}

	/**
	 * Returns the <code>long</code> value of the member with the specified name in
	 * this object. If this object does not contain a member with this name, the
	 * given default value is returned. If this object contains multiple members
	 * with the given name, the last one will be picked. If this member's value does
	 * not represent a JSON number or if it cannot be interpreted as Java
	 * <code>long</code>, an exception is thrown.
	 *
	 * @param name         the name of the member whose value is to be returned
	 * @param defaultValue the value to be returned if the requested member is
	 *                     missing
	 * @return the value of the last member with the specified name, or the given
	 *         default value if this object does not contain a member with that name
	 */
	public long getLong(String name, long defaultValue) {
		JsonValue value = get(name);
		return value != null ? value.asLong() : defaultValue;
	}

	/**
	 * Returns the <code>float</code> value of the member with the specified name in
	 * this object. If this object does not contain a member with this name, the
	 * given default value is returned. If this object contains multiple members
	 * with the given name, the last one will be picked. If this member's value does
	 * not represent a JSON number or if it cannot be interpreted as Java
	 * <code>float</code>, an exception is thrown.
	 *
	 * @param name         the name of the member whose value is to be returned
	 * @param defaultValue the value to be returned if the requested member is
	 *                     missing
	 * @return the value of the last member with the specified name, or the given
	 *         default value if this object does not contain a member with that name
	 */
	public float getFloat(String name, float defaultValue) {
		JsonValue value = get(name);
		return value != null ? value.asFloat() : defaultValue;
	}

	/**
	 * Returns the <code>double</code> value of the member with the specified name
	 * in this object. If this object does not contain a member with this name, the
	 * given default value is returned. If this object contains multiple members
	 * with the given name, the last one will be picked. If this member's value does
	 * not represent a JSON number or if it cannot be interpreted as Java
	 * <code>double</code>, an exception is thrown.
	 *
	 * @param name         the name of the member whose value is to be returned
	 * @param defaultValue the value to be returned if the requested member is
	 *                     missing
	 * @return the value of the last member with the specified name, or the given
	 *         default value if this object does not contain a member with that name
	 */
	public double getDouble(String name, double defaultValue) {
		JsonValue value = get(name);
		return value != null ? value.asDouble() : defaultValue;
	}

	/**
	 * Returns the <code>boolean</code> value of the member with the specified name
	 * in this object. If this object does not contain a member with this name, the
	 * given default value is returned. If this object contains multiple members
	 * with the given name, the last one will be picked. If this member's value does
	 * not represent a JSON <code>true</code> or <code>false</code> value, an
	 * exception is thrown.
	 *
	 * @param name         the name of the member whose value is to be returned
	 * @param defaultValue the value to be returned if the requested member is
	 *                     missing
	 * @return the value of the last member with the specified name, or the given
	 *         default value if this object does not contain a member with that name
	 */
	public boolean getBoolean(String name, boolean defaultValue) {
		JsonValue value = get(name);
		return value != null ? value.asBoolean() : defaultValue;
	}

	/**
	 * Returns the <code>String</code> value of the member with the specified name
	 * in this object. If this object does not contain a member with this name, the
	 * given default value is returned. If this object contains multiple members
	 * with the given name, the last one is picked. If this member's value does not
	 * represent a JSON string, an exception is thrown.
	 *
	 * @param name         the name of the member whose value is to be returned
	 * @param defaultValue the value to be returned if the requested member is
	 *                     missing
	 * @return the value of the last member with the specified name, or the given
	 *         default value if this object does not contain a member with that name
	 */
	public String getString(String name, String defaultValue) {
		JsonValue value = get(name);
		return value != null ? value.asString() : defaultValue;
	}

	/**
	 * Returns the number of members (name/value pairs) in this object.
	 *
	 * @return the number of members in this object
	 */
	public int size() {
		return names.size();
	}

	/**
	 * Returns <code>true</code> if this object contains no members.
	 *
	 * @return <code>true</code> if this object contains no members
	 */
	public boolean isEmpty() {
		return names.isEmpty();
	}

	/**
	 * Returns a list of the names in this object in document order. The returned
	 * list is backed by this object and will reflect subsequent changes. It cannot
	 * be used to modify this object. Attempts to modify the returned list will
	 * result in an exception.
	 *
	 * @return a list of the names in this object
	 */
	public List<String> names() {
		return Collections.unmodifiableList(names);
	}

	/**
	 * Returns an iterator over the members of this object in document order. The
	 * returned iterator cannot be used to modify this object.
	 *
	 * @return an iterator over the members of this object
	 */
	public Iterator<Member> iterator() {
		final Iterator<String> namesIterator = names.iterator();
		final Iterator<JsonValue> valuesIterator = values.iterator();
		return new Iterator<JsonObject.Member>() {

			public boolean hasNext() {
				return namesIterator.hasNext();
			}

			public Member next() {
				String name = namesIterator.next();
				JsonValue value = valuesIterator.next();
				return new Member(name, value);
			}

			public void remove() {
				throw new UnsupportedOperationException();
			}

		};
	}

	@Override
	void write(JsonWriter writer) throws IOException {
		writer.writeObjectOpen();
		Iterator<String> namesIterator = names.iterator();
		Iterator<JsonValue> valuesIterator = values.iterator();
		if (namesIterator.hasNext()) {
			writer.writeMemberName(namesIterator.next());
			writer.writeMemberSeparator();
			valuesIterator.next().write(writer);
			while (namesIterator.hasNext()) {
				writer.writeObjectSeparator();
				writer.writeMemberName(namesIterator.next());
				writer.writeMemberSeparator();
				valuesIterator.next().write(writer);
			}
		}
		writer.writeObjectClose();
	}

	@Override
	public boolean isObject() {
		return true;
	}

	@Override
	public JsonObject asObject() {
		return this;
	}

	@Override
	public int hashCode() {
		int result = 1;
		result = 31 * result + names.hashCode();
		result = 31 * result + values.hashCode();
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj == null) {
			return false;
		}
		if (getClass() != obj.getClass()) {
			return false;
		}
		JsonObject other = (JsonObject) obj;
		return names.equals(other.names) && values.equals(other.values);
	}

	int indexOf(String name) {
		int index = table.get(name);
		if (index != -1 && name.equals(names.get(index))) {
			return index;
		}
		return names.lastIndexOf(name);
	}

	private synchronized void readObject(ObjectInputStream inputStream) throws IOException, ClassNotFoundException {
		inputStream.defaultReadObject();
		table = new HashIndexTable();
		updateHashIndex();
	}

	private void updateHashIndex() {
		int size = names.size();
		for (int i = 0; i < size; i++) {
			table.add(names.get(i), i);
		}
	}

	/**
	 * Represents a member of a JSON object, a pair of a name and a value.
	 */
	public static class Member {

		private final String name;
		private final JsonValue value;

		Member(String name, JsonValue value) {
			this.name = name;
			this.value = value;
		}

		/**
		 * Returns the name of this member.
		 *
		 * @return the name of this member, never <code>null</code>
		 */
		public String getName() {
			return name;
		}

		/**
		 * Returns the value of this member.
		 *
		 * @return the value of this member, never <code>null</code>
		 */
		public JsonValue getValue() {
			return value;
		}

		@Override
		public int hashCode() {
			int result = 1;
			result = 31 * result + name.hashCode();
			result = 31 * result + value.hashCode();
			return result;
		}

		/**
		 * Indicates whether a given object is "equal to" this JsonObject. An object is
		 * considered equal if it is also a <code>JsonObject</code> and both objects
		 * contain the same members <em>in the same order</em>.
		 * <p>
		 * If two JsonObjects are equal, they will also produce the same JSON output.
		 * </p>
		 *
		 * @param object the object to be compared with this JsonObject
		 * @return <tt>true</tt> if the specified object is equal to this JsonObject,
		 *         <code>false</code> otherwise
		 */
		@Override
		public boolean equals(Object object) {
			if (this == object) {
				return true;
			}
			if (object == null) {
				return false;
			}
			if (getClass() != object.getClass()) {
				return false;
			}
			Member other = (Member) object;
			return name.equals(other.name) && value.equals(other.value);
		}

	}

	static class HashIndexTable {

		private final byte[] hashTable = new byte[32]; // must be a power of two

		HashIndexTable() {
		}

		HashIndexTable(HashIndexTable original) {
			System.arraycopy(original.hashTable, 0, hashTable, 0, hashTable.length);
		}

		void add(String name, int index) {
			int slot = hashSlotFor(name);
			if (index < 0xff) {
				// increment by 1, 0 stands for empty
				hashTable[slot] = (byte) (index + 1);
			} else {
				hashTable[slot] = 0;
			}
		}

		void remove(int index) {
			for (int i = 0; i < hashTable.length; i++) {
				if ((hashTable[i] & 0xff) == index + 1) {
					hashTable[i] = 0;
				} else if ((hashTable[i] & 0xff) > index + 1) {
					hashTable[i]--;
				}
			}
		}

		int get(Object name) {
			int slot = hashSlotFor(name);
			// subtract 1, 0 stands for empty
			return (hashTable[slot] & 0xff) - 1;
		}

		private int hashSlotFor(Object element) {
			return element.hashCode() & hashTable.length - 1;
		}

	}

}
