src/net/instaweb/rewriter/public/critical_css_finder.h

/*
 * Copyright 2013 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: slamm@google.com (Stephen Lamm)

#ifndef NET_INSTAWEB_REWRITER_PUBLIC_CRITICAL_CSS_FINDER_H_
#define NET_INSTAWEB_REWRITER_PUBLIC_CRITICAL_CSS_FINDER_H_

#include "net/instaweb/util/public/property_cache.h"
#include "pagespeed/kernel/base/basictypes.h"

namespace net_instaweb {

class CriticalCssResult;
class RewriteDriver;
class Statistics;
class TimedVariable;

// Finds critical CSS rules (i.e. CSS needed for the initial page load).
class CriticalCssFinder {
 public:
  static const char kCriticalCssValidCount[];
  static const char kCriticalCssExpiredCount[];
  static const char kCriticalCssNotFoundCount[];
  static const char kCriticalCssPropertyName[];

  CriticalCssFinder(const PropertyCache::Cohort* cohort, Statistics* stats);
  virtual ~CriticalCssFinder();

  static void InitStats(Statistics* statistics);

  // Get critical css result from property cache.
  // Ownership of the result is passed to the caller.
  virtual CriticalCssResult* GetCriticalCssFromCache(RewriteDriver* driver);

  // Compute the critical css for the driver's url.
  virtual void ComputeCriticalCss(RewriteDriver* driver) = 0;

  // Copy |critical_css_map| into property cache. Returns true on success.
  virtual bool UpdateCache(RewriteDriver* driver,
                           const CriticalCssResult& result);

  // Collects the critical CSS rules from the property cache and updates the
  // same in the rewrite driver. The ownership of the ruleset stays with the
  // driver.
  virtual void UpdateCriticalCssInfoInDriver(RewriteDriver* driver);

  // Gets the critical CSS rules from the driver if they are present. Otherwise
  // calls UpdateCriticalCssInfoInDriver() to populate the ruleset in the driver
  // and returns the rules. The ownership of the CriticalCssResult is not
  // released and it stays with the driver.
  virtual CriticalCssResult* GetCriticalCss(RewriteDriver* driver);

  const PropertyCache::Cohort* cohort() const { return cohort_; }

 private:
  const PropertyCache::Cohort* cohort_;
  TimedVariable* critical_css_valid_count_;
  TimedVariable* critical_css_expired_count_;
  TimedVariable* critical_css_not_found_count_;

  DISALLOW_COPY_AND_ASSIGN(CriticalCssFinder);
};

}  // namespace net_instaweb

#endif  // NET_INSTAWEB_REWRITER_PUBLIC_CRITICAL_CSS_FINDER_H_