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The Google API Libraries for Google Web Toolkit is a collection of libraries that provide Java language bindings for popular Google JavaScript APIs. These libraries make it quick and easy for developers to use these Google JavaScript APIs with Google Web Toolkit. The libraries are supported by the Google Web Toolkit team.
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/*
 * Copyright 2009 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.gwt.ajaxloader.client;

import com.google.gwt.core.client.JavaScriptException;
import com.google.gwt.core.client.JavaScriptObject;

import java.util.Date;

/**
 * A collection of properties of arbitrary type, for interoperability with
 * non-GWT JavaScript libraries.
 */
public abstract class Properties extends JavaScriptObject {
  /**
   * An exception thrown by the get methods when the key is found but the 
   * value has an unexpected type.
   */
  @SuppressWarnings("serial")
  public static class TypeException extends Exception {
    private TypeException(String key, String expected, String actual) {
      super("Properties.get" + expected + "(" + key + 
          ") failed.  Unexpected type : " + actual + ".");
    }
    
    private TypeException() {
    }
  }
  
  /**
   * Create an empty Properties object.
   * @return An empty Properties object.
   */
  public static Properties create() {
    return JavaScriptObject.createObject().cast();
  }
  
  protected Properties() {
  }

  /**
   * Get a Boolean value mapped to the specified key.
   * 
   * @param key The name of the Boolean property.
   * @return A Boolean value, or null if the key is not found.
   * @throws TypeException if the key is found but the object returned
   * is not a Boolean.
   */
  public final Boolean getBoolean(String key) throws TypeException {
    if (containsKey(key)) {
      String type = typeof(key);
      if (type.equals("boolean")) {
        return nativeGetBoolean(key);
      } else {
        throw new TypeException(key, "Boolean", type);
      }
    } else {
      return null;
    }
  }

  /**
   * Get a Date object mapped to the specified key.
   * 
   * @param key The name of the Date property.
   * @return A Date object, or null if the key is not found.
   * @throws JavaScriptException if the key is found but the object returned
   * is not a Date.
   * @throws TypeException If the key is found but the value is not an object.
   */
  public final Date getDate(String key) 
      throws JavaScriptException, TypeException {
    return JsDate.toJava((JsDate) getObject(key));
  }

  /**
   * Get a Double value mapped to the specified key.
   * 
   * @param key The name of the Double property.
   * @return A Double value, or null if the key is not found.
   * @throws TypeException If the key is found but the value is not a
   * number (integers are fine).
   */
  public final Double getNumber(String key) throws TypeException {
    if (containsKey(key)) {
      String type = typeof(key);
      if (type.equals("number")) {
        return nativeGetNumber(key);
      } else {
        throw new TypeException(key, "Number", type);
      }
    } else {
      return null;
    }
  }

  /**
   * Get a JavaScriptObject mapped to the specified key.
   * 
   * @param key The name of the JavaScriptObject property.
   * @return A JavaScriptObject, or null if the key is not found.
   * @throws TypeException If the key is found but the value is not a
   * JavaScriptObject.
   */
  public final JavaScriptObject getObject(String key) throws TypeException {
    if (containsKey(key)) {
      String type = typeof(key);
      if (type.equals("object")) {
        return nativeGetObject(key);
      } else {
        throw new TypeException(key, "Object", type);
      }
    } else {
      return null;
    }
  }

  /**
   * Get a String mapped to the specified key.
   * 
   * @param key The name of the String property.
   * @return A String, or null if the key is not found.
   * @throws TypeException If the key is found but the value is not a
   * String.
   */
  public final String getString(String key) throws TypeException {
    if (containsKey(key)) {
      String type = typeof(key);
      if (type.equals("string")) {
        return nativeGetString(key);
      } else {
        throw new TypeException(key, "String", type);
      }
    } else {
      return null;
    }
  }
  
  /**
   * Remove the property at the specified key.
   * 
   * @param key The name of the property to remove.
   */
  public final native void remove(String key) /*-{
    delete this[key];
  }-*/;

  /**
   * Set a property.
   * 
   * @param key The name of the property.
   * @param value The value of the property.
   */
  public final void set(String key, Boolean value) {
    if (value == null) {
      remove(key);
    } else {
      setBoolean(key, value);
    }
  }

  /**
   * Set a property.
   * 
   * @param key The name of the property.
   * @param value The value of the property.
   */
  public final void set(String key, Date value) {
    set(key, JsDate.toJs(value));
  }

  /**
   * Set a property.
   * 
   * @param key The name of the property.
   * @param value The value of the property.
   */
  public final void set(String key, Double value) {
    if (value == null) {
      remove(key);
    } else {
      setNumber(key, value);
    }
  }

  /**
   * Set a property.
   * 
   * @param key The name of the property.
   * @param value The value of the property.
   */
  public final native void set(String key, JavaScriptObject value) /*-{
    this[key] = value;
  }-*/;

  /**
   * Set a property.
   * 
   * @param key The name of the property.
   * @param value The value of the property.
   */ 
  public final native void set(String key, String value) /*-{
    this[key] = value;
  }-*/;
  
  /**
   * Executes the JavaScript typeof operator against the property with the
   * given key.  Note that the typeof undefined is "undefined" and the typeof
   * null is "object".
   * 
   * @param key The name of the property to type check.
   * @return The JavaScript type of the property, as defined by the JavaScipt
   * typeof operator.
   */
  public final native String typeof(String key) /*-{
    return typeof this[key];
  }-*/;
  
  private native boolean containsKey(String key) /*-{
    return this[key] != null;
  }-*/;

  private native boolean nativeGetBoolean(String key) /*-{
    return this[key];
  }-*/;

  private native double nativeGetNumber(String key) /*-{
    return this[key];
  }-*/;

  private native JavaScriptObject nativeGetObject(String key) /*-{
    return this[key];
  }-*/;
  
  private native String nativeGetString(String key) /*-{
    return this[key];
  }-*/;
  
  private native void setBoolean(String key, boolean value) /*-{
    this[key] = value;
  }-*/;
  
  private native void setNumber(String key, double value) /*-{
    this[key] = value;
  }-*/;
}