/*
* Copyright 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 org.vectomatic.dom.svg.impl;
import org.vectomatic.dom.svg.OMSVGSVGElement;
import org.vectomatic.dom.svg.ui.ExternalSVGResource;
import org.vectomatic.dom.svg.ui.SVGResource;
import org.vectomatic.dom.svg.utils.OMSVGParser;
import com.google.gwt.core.client.JavaScriptObject;
import com.google.gwt.http.client.Request;
import com.google.gwt.http.client.RequestBuilder;
import com.google.gwt.http.client.RequestCallback;
import com.google.gwt.http.client.RequestException;
import com.google.gwt.http.client.Response;
import com.google.gwt.resources.client.ResourceCallback;
import com.google.gwt.resources.client.ResourceException;
import com.google.gwt.safehtml.shared.SafeUri;
import com.google.gwt.safehtml.shared.UriUtils;
/**
* Implementation of ExternalSVGResource derived from Google's original
* ExternalTextResourcePrototype implementation
* @author laaglu
*/
public class ExternalSVGResourcePrototype implements ExternalSVGResource {
/**
* Maps the HTTP callback onto the ResourceCallback.
*/
private class ESRCallback implements RequestCallback {
final ResourceCallback<SVGResource> callback;
public ESRCallback(ResourceCallback<SVGResource> callback) {
this.callback = callback;
}
public void onError(Request request, Throwable exception) {
callback.onError(new ResourceException(
ExternalSVGResourcePrototype.this,
"Unable to retrieve external resource", exception));
}
public void onResponseReceived(Request request, final Response response) {
// Get the contents of the JSON bundle
String responseText = response.getText();
// Call eval() on the object.
JavaScriptObject jso = evalObject(responseText);
if (jso == null) {
callback.onError(new ResourceException(
ExternalSVGResourcePrototype.this,
"eval() returned null"));
return;
}
// Populate the TextResponse cache array
for (int i = 0; i < cache.length; i++) {
final String resourceText = extractString(jso, i);
cache[i] = new SVGResource() {
@Override
public String getName() {
return name;
}
@Override
public OMSVGSVGElement getSvg() {
return OMSVGParser.parse(resourceText);
}
@Override
public SafeUri getSafeUri() {
return UriUtils.fromSafeConstant("data:image/svg+xml;utf8," + resourceText);
}
@Override
public String getUrl() {
return "data:image/svg+xml;utf8," + resourceText;
}
};
}
// Finish by invoking the callback
callback.onSuccess(cache[index]);
}
}
/**
* Evaluate the JSON payload. The regular expression to validate the safety
* of the payload is taken from RFC 4627 (D. Crockford).
*
* @param data
* the raw JSON-encapsulated string bundle
* @return the evaluated JSON object, or <code>null</code> if there is an
* error.
*/
private static native JavaScriptObject evalObject(String data) /*-{
var safe = !(/[^,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]/.test(
data.replace(/"(\\.|[^"\\])*"/g, '')));
if (!safe) {
return null;
}
return eval('(' + data + ')') || null;
}-*/;
/**
* Extract the specified String from a JavaScriptObject that is array-like.
* @param jso
* the JavaScriptObject returned from {@link #evalObject(String)}
* @param index
* the index of the string to extract
* @return the requested string, or <code>null</code> if it does not exist.
*/
private static native String extractString(JavaScriptObject jso, int index) /*-{
return (jso.length > index) && jso[index] || null;
}-*/;
/**
* This is a reference to an array nominally created in the IRB that
* contains the ExternalSVGResource. It is intended to be shared between
* all instances of the ETR that have a common parent IRB.
*/
private final SVGResource[] cache;
private final int index;
private final String name;
private final String url;
/**
* Constructor
* @param name The resource name
* @param url The resource URL
* @param cache A cache of loaded resource
* @param index The index for this resource in the cache
*/
public ExternalSVGResourcePrototype(String name, String url,
SVGResource[] cache, int index) {
this.name = name;
this.url = url;
this.cache = cache;
this.index = index;
}
/**
* Returns the SVG resource name
* @return the SVG resource name
*/
public String getName() {
return name;
}
/**
* Possibly fire off an HTTPRequest for the SVG resource.
* @param callback The request callback
*/
public void getSvg(ResourceCallback<SVGResource> callback)
throws ResourceException {
// If we've already parsed the JSON bundle, short-circuit.
if (cache[index] != null) {
callback.onSuccess(cache[index]);
return;
}
// Otherwise, fire an HTTP request.
RequestBuilder rb = new RequestBuilder(RequestBuilder.GET, url);
try {
rb.sendRequest("", new ESRCallback(callback));
} catch (RequestException e) {
throw new ResourceException(this,
"Unable to initiate request for external resource", e);
}
}
}