src/net/instaweb/rewriter/support_noscript_filter.cc

/*
 * Copyright 2012 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.
 */
// Author: sriharis@google.com (Srihari Sukumaran)

#include "net/instaweb/rewriter/public/support_noscript_filter.h"

#include "net/instaweb/public/global_constants.h"
#include "net/instaweb/rewriter/public/mobilize_rewrite_filter.h"
#include "net/instaweb/rewriter/public/request_properties.h"
#include "net/instaweb/rewriter/public/rewrite_driver.h"
#include "net/instaweb/rewriter/public/rewrite_options.h"
#include "net/instaweb/rewriter/public/rewrite_query.h"
#include "net/instaweb/rewriter/public/split_html_beacon_filter.h"
#include "pagespeed/kernel/base/scoped_ptr.h"
#include "pagespeed/kernel/base/string.h"
#include "pagespeed/kernel/base/string_util.h"
#include "pagespeed/kernel/html/html_element.h"
#include "pagespeed/kernel/html/html_keywords.h"
#include "pagespeed/kernel/html/html_name.h"
#include "pagespeed/kernel/html/html_node.h"
#include "pagespeed/kernel/http/google_url.h"

namespace net_instaweb {

SupportNoscriptFilter::SupportNoscriptFilter(RewriteDriver* rewrite_driver)
    : rewrite_driver_(rewrite_driver),
      should_insert_noscript_(true) {
}

SupportNoscriptFilter::~SupportNoscriptFilter() {
}

void SupportNoscriptFilter::DetermineEnabled(GoogleString* disabled_reason) {
  // Insert a NOSCRIPT tag only if at least one of the filters requiring
  // JavaScript for execution is enabled.
  should_insert_noscript_ = IsAnyFilterRequiringScriptExecutionEnabled();
  set_is_enabled(should_insert_noscript_);
}

void SupportNoscriptFilter::StartElement(HtmlElement* element) {
  if (should_insert_noscript_ && element->keyword() == HtmlName::kBody) {
    scoped_ptr<GoogleUrl> url_with_psa_off(
        rewrite_driver_->google_url().CopyAndAddQueryParam(
            RewriteQuery::kPageSpeed, RewriteQuery::kNoscriptValue));
    GoogleString escaped_url;
    HtmlKeywords::Escape(url_with_psa_off->Spec(), &escaped_url);
    // TODO(sriharis): Replace the usage of HtmlCharactersNode with HtmlElement
    // and Attribute.
    HtmlCharactersNode* noscript_node = rewrite_driver_->NewCharactersNode(
        element, StringPrintf(kNoScriptRedirectFormatter,
                              escaped_url.c_str(), escaped_url.c_str()));
    rewrite_driver_->PrependChild(element, noscript_node);
    should_insert_noscript_ = false;
  }
  // TODO(sriharis):  Handle the case where there is no body -- insert a body in
  // EndElement of kHtml?
}

bool SupportNoscriptFilter::IsAnyFilterRequiringScriptExecutionEnabled() const {
  const RewriteOptions* options = rewrite_driver_->options();
  const RequestProperties* request_properties =
      rewrite_driver_->request_properties();
  RewriteOptions::FilterVector js_filters;
  options->GetEnabledFiltersRequiringScriptExecution(&js_filters);
  for (int i = 0, n = js_filters.size(); i < n; ++i) {
    RewriteOptions::Filter filter = js_filters[i];
    bool filter_enabled = true;
    switch (filter) {
      case RewriteOptions::kDeferIframe:
      case RewriteOptions::kDeferJavascript:
      case RewriteOptions::kSplitHtml:
        // We don't need to insert a noscript redirect if we are just
        // instrumenting the page, instead of actually running split HTML.
        filter_enabled =
            (request_properties->SupportsJsDefer(
                 options->enable_aggressive_rewriters_for_mobile()) &&
             !SplitHtmlBeaconFilter::ShouldApply(rewrite_driver_));
        break;
      case RewriteOptions::kDedupInlinedImages:
      case RewriteOptions::kDelayImages:
      case RewriteOptions::kLazyloadImages:
      case RewriteOptions::kLocalStorageCache:
        filter_enabled = request_properties->SupportsImageInlining();
        break;
      case RewriteOptions::kFlushSubresources:
        filter_enabled = rewrite_driver_->flushed_early();;
        break;
      case RewriteOptions::kCachePartialHtml:
        filter_enabled = rewrite_driver_->flushing_cached_html();
        break;
      case RewriteOptions::kMobilize:
        filter_enabled =
            MobilizeRewriteFilter::IsApplicableFor(rewrite_driver_);
        break;
      default:
        break;
      }
    if (filter_enabled) {
      return true;
    }
  }
  return false;
}

}  // namespace net_instaweb