/*
 * 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.google.gson;

import com.google.gson.internal.$Gson$Preconditions;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;

/**
 * A class representing an object type in Json. An object consists of name-value pairs where names
 * are strings, and values are any other type of {@link JsonElement}. This allows for a creating a
 * tree of JsonElements. The member elements of this object are maintained in order they were added.
 *
 * @author Inderjeet Singh
 * @author Joel Leitch
 */
public final class JsonObject extends JsonElement {
  // We are using a linked hash map because it is important to preserve
  // the order in which elements are inserted. This is needed to ensure
  // that the fields of an object are inserted in the order they were
  // defined in the class.
  private final Map<String, JsonElement> members = new LinkedHashMap<String, JsonElement>();

  /**
   * Creates an empty JsonObject.
   */
  public JsonObject() {
  }

  /**
   * Adds a member, which is a name-value pair, to self. The name must be a String, but the value
   * can be an arbitrary JsonElement, thereby allowing you to build a full tree of JsonElements
   * rooted at this node.
   *
   * @param property name of the member.
   * @param value the member object.
   */
  public void add(String property, JsonElement value) {
    if (value == null) {
      value = JsonNull.INSTANCE;
    }
    members.put($Gson$Preconditions.checkNotNull(property), value);
  }

  /**
   * Removes the {@code property} from this {@link JsonObject}.
   *
   * @param property name of the member that should be removed.
   * @return the {@link JsonElement} object that is being removed.
   * @since 1.3
   */
  public JsonElement remove(String property) {
    return members.remove(property);
  }

  /**
   * Convenience method to add a primitive member. The specified value is converted to a
   * JsonPrimitive of String.
   *
   * @param property name of the member.
   * @param value the string value associated with the member.
   */
  public void addProperty(String property, String value) {
    add(property, createJsonElement(value));
  }

  /**
   * Convenience method to add a primitive member. The specified value is converted to a
   * JsonPrimitive of Number.
   *
   * @param property name of the member.
   * @param value the number value associated with the member.
   */
  public void addProperty(String property, Number value) {
    add(property, createJsonElement(value));
  }

  /**
   * Convenience method to add a boolean member. The specified value is converted to a
   * JsonPrimitive of Boolean.
   *
   * @param property name of the member.
   * @param value the number value associated with the member.
   */
  public void addProperty(String property, Boolean value) {
    add(property, createJsonElement(value));
  }

  /**
   * Convenience method to add a char member. The specified value is converted to a
   * JsonPrimitive of Character.
   *
   * @param property name of the member.
   * @param value the number value associated with the member.
   */
  public void addProperty(String property, Character value) {
    add(property, createJsonElement(value));
  }

  /**
   * Creates the proper {@link JsonElement} object from the given {@code value} object.
   *
   * @param value the object to generate the {@link JsonElement} for
   * @return a {@link JsonPrimitive} if the {@code value} is not null, otherwise a {@link JsonNull}
   */
  private JsonElement createJsonElement(Object value) {
    return value == null ? JsonNull.INSTANCE : new JsonPrimitive(value);
  }

  /**
   * Returns a set of members of this object. The set is ordered, and the order is in which the
   * elements were added.
   *
   * @return a set of members of this object.
   */
  public Set<Map.Entry<String, JsonElement>> entrySet() {
    return members.entrySet();
  }

  /**
   * Convenience method to check if a member with the specified name is present in this object.
   *
   * @param memberName name of the member that is being checked for presence.
   * @return true if there is a member with the specified name, false otherwise.
   */
  public boolean has(String memberName) {
    return members.containsKey(memberName);
  }

  /**
   * Returns the member with the specified name.
   *
   * @param memberName name of the member that is being requested.
   * @return the member matching the name. Null if no such member exists.
   */
  public JsonElement get(String memberName) {
    if (members.containsKey(memberName)) {
      JsonElement member = members.get(memberName);
      return member == null ? JsonNull.INSTANCE : member;
    }
    return null;
  }

  /**
   * Convenience method to get the specified member as a JsonPrimitive element.
   *
   * @param memberName name of the member being requested.
   * @return the JsonPrimitive corresponding to the specified member.
   */
  public JsonPrimitive getAsJsonPrimitive(String memberName) {
    return (JsonPrimitive) members.get(memberName);
  }

  /**
   * Convenience method to get the specified member as a JsonArray.
   *
   * @param memberName name of the member being requested.
   * @return the JsonArray corresponding to the specified member.
   */
  public JsonArray getAsJsonArray(String memberName) {
    return (JsonArray) members.get(memberName);
  }

  /**
   * Convenience method to get the specified member as a JsonObject.
   *
   * @param memberName name of the member being requested.
   * @return the JsonObject corresponding to the specified member.
   */
  public JsonObject getAsJsonObject(String memberName) {
    return (JsonObject) members.get(memberName);
  }

  @Override
  public boolean equals(Object o) {
    return (o == this) || (o instanceof JsonObject
        && ((JsonObject) o).members.equals(members));
  }

  @Override
  public int hashCode() {
    return members.hashCode();
  }
}
