/*
 * Copyright 2010 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: sligocki@google.com (Shawn Ligocki)

#ifndef NET_INSTAWEB_REWRITER_PUBLIC_REWRITE_DRIVER_FACTORY_H_
#define NET_INSTAWEB_REWRITER_PUBLIC_REWRITE_DRIVER_FACTORY_H_

#include <set>
#include <vector>

#include "net/instaweb/rewriter/public/central_controller_interface.h"
#include "net/instaweb/rewriter/public/central_controller_interface_adapter.h"
#include "pagespeed/kernel/base/abstract_mutex.h"
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/function.h"
#include "pagespeed/kernel/base/null_statistics.h"
#include "pagespeed/kernel/base/scoped_ptr.h"
#include "pagespeed/kernel/base/statistics.h"
#include "pagespeed/kernel/base/string.h"
#include "pagespeed/kernel/base/string_util.h"
#include "pagespeed/kernel/base/thread_system.h"
#include "pagespeed/kernel/thread/queued_worker_pool.h"

namespace pagespeed { namespace js { struct JsTokenizerPatterns; } }

namespace net_instaweb {

class CacheHtmlInfoFinder;
class CriticalCssFinder;
class CriticalImagesFinder;
class CriticalLineInfoFinder;
class CriticalSelectorFinder;
class FileSystem;
class FlushEarlyInfoFinder;
class ExperimentMatcher;
class Hasher;
class MessageHandler;
class MobilizeCachedFinder;
class NamedLockManager;
class NonceGenerator;
class ProcessContext;
class PropertyCache;
class ServerContext;
class RewriteDriver;
class RewriteOptions;
class RewriteOptionsManager;
class RewriteStats;
class SHA1Signature;
class Scheduler;
class StaticAssetManager;
class Timer;
class UrlAsyncFetcher;
class UrlNamer;
class UsageDataReporter;
class UserAgentMatcher;
class UserAgentNormalizer;

// Manages the construction and ownership of most objects needed to create
// RewriteDrivers. If you have your own versions of these classes (specific
// implementations of UrlAsyncFetcher, Hasher, etc.) you can make your own
// subclass of RewriteDriverFactory to use these by default.
class RewriteDriverFactory {
 public:
  // Helper for users of defer_cleanup; see below.
  template<class T> class Deleter;

  enum WorkerPoolCategory {
    kHtmlWorkers,
    kRewriteWorkers,
    kLowPriorityRewriteWorkers,
    // Make sure to insert new values above this line.
    kNumWorkerPools
  };

  // Takes ownership of thread_system.
  RewriteDriverFactory(const ProcessContext& process_context,
                       ThreadSystem* thread_system);

  // Initializes default options we want to hard-code into the
  // base-class to get consistency across deployments.  Subclasses
  // that override NewRewriteOptions() should call this method from
  // their constructor.  It is safe to call this multiple times.
  void InitializeDefaultOptions();

  // Static version of the above. If you are using that you may also need
  // to call reset_default_options.
  static void InitializeDefaultOptions(RewriteOptions* options);

  virtual ~RewriteDriverFactory();

  // The RewriteDriverFactory will create objects of default type through the
  // New* method from drived classes.  Here are the objects that can be
  // replaced before creating the RewriteDriver.
  // Note: RewriteDriver takes ownership of these.
  void set_html_parse_message_handler(MessageHandler* message_handler);
  void set_message_handler(MessageHandler* message_handler);
  void set_file_system(FileSystem* file_system);
  void set_hasher(Hasher* hasher);
  void set_nonce_generator(NonceGenerator* nonce_generator);
  void set_url_namer(UrlNamer* url_namer);
  void set_signature(SHA1Signature* signature);
  void set_timer(Timer* timer);
  void set_usage_data_reporter(UsageDataReporter* reporter);

  // Set up a directory for slurped files for HTML and resources.  If
  // read_only is true, then it will only read from these files, and
  // this will eliminate the usage of any other url_fetcher.  If
  // read_only is false, then the existing url fetcher will be used as
  // a fallback if the slurped file is not found, and slurped files will
  // be subsequently written so they don't have to be fetched from
  // the Internet again.
  //
  // You must set the slurp directory prior to calling ComputeUrlAsyncFetcher.
  void set_slurp_directory(const StringPiece& directory);
  void set_slurp_read_only(bool read_only);
  void set_slurp_print_urls(bool read_only);

  // Setting HTTP caching on causes both the fetcher and the async
  // fecher to return cached versions.
  void set_force_caching(bool u) { force_caching_ = u; }

  // You can call set_base_url_async_fetcher to set up real async fetching
  // for real serving or for modeling of live traffic.
  //
  // These fetchers may be used directly when serving traffic, or they
  // may be aggregated with other fetchers (e.g. for slurping).
  //
  // You cannot set the base URL fetcher once ComputeUrlAsyncFetcher has
  // been called.
  void set_base_url_async_fetcher(UrlAsyncFetcher* url_fetcher);
  // Takes ownership of distributed_fetcher.
  void set_base_distributed_async_fetcher(UrlAsyncFetcher* distributed_fetcher);
  bool set_filename_prefix(StringPiece p);

  // Determines whether Slurping is enabled.
  bool slurping_enabled() const { return !slurp_directory_.empty(); }

  MessageHandler* html_parse_message_handler();
  MessageHandler* message_handler();
  FileSystem* file_system();
  NonceGenerator* nonce_generator();
  // TODO(sligocki): Remove hasher() and force people to make a NewHasher when
  // they need one.
  Hasher* hasher();
  UrlNamer* url_namer();
  UserAgentMatcher* user_agent_matcher();
  StaticAssetManager* static_asset_manager();
  SHA1Signature* signature();
  RewriteOptions* default_options() { return default_options_.get(); }
  virtual RewriteOptionsManager* NewRewriteOptionsManager();

  // These accessors are *not* thread-safe until after the first call, as they
  // do unlocked lazy initialization, so they must be called at least once prior
  // to starting threads. Normally this is done by CreateServerContext() or
  // InitServerContext().
  Timer* timer();
  NamedLockManager* lock_manager();
  QueuedWorkerPool* WorkerPool(WorkerPoolCategory pool);
  Scheduler* scheduler();
  UsageDataReporter* usage_data_reporter();
  const pagespeed::js::JsTokenizerPatterns* js_tokenizer_patterns() const {
    return js_tokenizer_patterns_;
  }
  const std::vector<const UserAgentNormalizer*>& user_agent_normalizers();

  // Computes URL fetchers using the base fetcher, and optionally,
  // slurp_directory and slurp_read_only.  These are not thread-safe;
  // they must be called once prior to spawning threads, e.g. via
  // CreateServerContext.
  virtual UrlAsyncFetcher* ComputeUrlAsyncFetcher();
  virtual UrlAsyncFetcher* ComputeDistributedFetcher();

  // Threadsafe mechanism to create a managed ServerContext.  The
  // ServerContext is owned by the factory, and should not be
  // deleted directly.  Currently it is not possible to delete a
  // server context except by deleting the entire factory.
  //
  // Implemented in terms of NewServerContext().
  //
  // Note that this is a convenience wrapper only. In particular,
  // SystemServerContext creates ServerContexts by calling New and Init
  // separately.
  ServerContext* CreateServerContext();

  // Initializes a ServerContext that has been new'd directly.  This
  // allows 2-phase initialization if required.  There is no need to
  // call this if you use CreateServerContext.
  void InitServerContext(ServerContext* server_context);

  // Called from InitServerContext, but virtualized separately as it is
  // platform-specific.  This method must call on the server context:
  // set_http_cache, set_metadata_cache, set_filesystem_metadata_cache, and
  // MakePropertyCaches.
  virtual void SetupCaches(ServerContext* server_context) = 0;

  // Returns true if this platform uses beacon-based measurements to make
  // run-time decisions.  This is used to determine how to configure various
  // beacon-based filters.
  virtual bool UseBeaconResultsInFilters() const = 0;

  // Provides an optional hook for adding rewrite passes to the HTML filter
  // chain.  This should be used for filters that are specific to a particular
  // RewriteDriverFactory implementation.
  virtual void AddPlatformSpecificRewritePasses(RewriteDriver* driver);

  // Provides an optional hook for adding rewriters to the .pagespeed. resource
  // decoding chain.  This should be used for rewriters that are specific to a
  // particular RewriteDriverFactory implementation.  The caller should only use
  // the resulting driver for reconstructing a .pagespeed. resource, not for
  // transforming HTML.  Therefore, implementations should add any
  // platform-specific rewriter whose id might appear in a .pagespeed. URL.
  // This should be done independent of RewriteOptions, since we only store
  // a single decoding driver globally to save memory.
  virtual void AddPlatformSpecificDecodingPasses(RewriteDriver* driver);

  // Provides an optional hook for customizing the RewriteDriver object
  // using the options set on it. This is called before
  // RewriteDriver::AddFilters() and AddPlatformSpecificRewritePasses().
  virtual void ApplyPlatformSpecificConfiguration(RewriteDriver* driver);

  ThreadSystem* thread_system() { return thread_system_.get(); }

  // Return interface to various functions that workers need delegated
  // to a central service. Depending on the implemenation, this may invoke
  // RPCs.
  CentralControllerInterfaceAdapter* central_controller_interface() {
    return central_controller_interface_.get();
  }

  // Returns the set of directories that we (our our subclasses) have created
  // thus far.
  const StringSet& created_directories() const {
    return created_directories_;
  }

  bool async_rewrites() { return true; }

  // Collection of global statistics objects.  This is thread-unsafe:
  // it must be called prior to spawning threads, and after any calls
  // to SetStatistics.  Failing that, it will be initialized in the
  // first call to InitServerContext(), which is thread-safe.
  RewriteStats* rewrite_stats();

  // statistics (default is NullStatistics).  This can be overridden by calling
  // SetStatistics, either from subclasses or externally.
  Statistics* statistics() { return statistics_; }

  // Initializes statistics variables.  This must be done at process
  // startup to enable shared memory segments in Apache to be set up.
  static void InitStats(Statistics* statistics);

  // Initializes static variables.  Initialize/Terminate calls must be paired.
  static void Initialize();
  static void Terminate();

  // Does *not* take ownership of Statistics.
  void SetStatistics(Statistics* stats);

  // Clean up all the factory-owned resources: fetchers, pools,
  // Server Contexts, the Drivers owned by the Server Contexts,
  // and worker threads.
  virtual void ShutDown();

  // Registers the directory as having been created by us.
  void AddCreatedDirectory(const GoogleString& dir);

  // Creates a new empty RewriteOptions object, with no default settings.
  // Generally configurations go factory's default_options() ->
  // ServerContext::global_options() -> RewriteDriverFactory,
  // but this method just provides a blank set of options.
  virtual RewriteOptions* NewRewriteOptions();

  // Creates a new empty RewriteOptions object meant for use for
  // custom options from queries or headers. Default implementation just
  // forwards to NewRewriteOptions().
  virtual RewriteOptions* NewRewriteOptionsForQuery();

  // get/set the version placed into the X-[Mod-]Page(s|-S)peed header.
  const GoogleString& version_string() const { return version_string_; }
  void set_version_string(const StringPiece& version_string) {
    version_string.CopyToString(&version_string_);
  }

  // Causes the given function to be Run after all the threads are shutdown,
  // in order to do any needed resource cleanups. The Deleter<T> template below
  // may be useful for object deletion cleanups.
  void defer_cleanup(Function* f) { deferred_cleanups_.push_back(f); }

  // Queues an object for deletion at the last phase of RewriteDriverFactory
  // destruction.
  template<class T> void TakeOwnership(T* obj) {
    defer_cleanup(new RewriteDriverFactory::Deleter<T>(obj));
  }

  // Base method that returns true if the given ip is a debug ip.
  virtual bool IsDebugClient(const GoogleString& ip) const {
    return false;
  }

  // Creates an ExperimentMatcher, which is used to match clients or sessions to
  // a specific experiment.
  virtual ExperimentMatcher* NewExperimentMatcher();

  // Control the number of simultaneous expensive CPU operations going on at
  // once. Invokes Run on your callback at a time when it is OK to do the
  // expensive operation, or Cancel if you should not perform the operation.
  // Depending on the implemation, may queue the callback for theoretically
  // unbounded time.
  void ScheduleExpensiveOperation(ExpensiveOperationCallback* callback);

 protected:
  bool FetchersComputed() const;
  virtual void StopCacheActivity();
  StringPiece filename_prefix();

  // Used by subclasses to indicate that a ServerContext has been
  // terminated.  Returns true if this was the last server context
  // known to this factory.
  bool TerminateServerContext(ServerContext* server_context);

  // Implementors of RewriteDriverFactory must supply default definitions
  // for each of these methods, although they may be overridden via set_
  // methods above.  These methods all instantiate objects and transfer
  // ownership to the caller.
  virtual UrlAsyncFetcher* DefaultAsyncUrlFetcher() = 0;
  virtual MessageHandler* DefaultHtmlParseMessageHandler() = 0;
  virtual MessageHandler* DefaultMessageHandler() = 0;
  virtual FileSystem* DefaultFileSystem() = 0;
  virtual NonceGenerator* DefaultNonceGenerator();
  virtual Timer* DefaultTimer();
  virtual SHA1Signature* DefaultSignature();

  virtual Hasher* NewHasher() = 0;

  // Creates a new ServerContext* object.  ServerContext itself must be
  // overridden per Factory as it has at least one pure virtual method.
  virtual ServerContext* NewServerContext() = 0;

  // Create a new ServerContext used for decoding only. Unlike NewServerContext,
  // the resulting ServerContext should not be fresh, but should have some of
  // its platform dependencies injected --- but just enough for decoding URLs,
  // and not full operation. At the time of writing it needs the timer,
  // url namer, hasher, message handler, and stats; expensive stuff like
  // cache backends is not needed, however.
  //
  // You may find InitStubDecodingServerContext() useful for doing that, as it
  // will inject all of these from what's available in 'this'.
  virtual ServerContext* NewDecodingServerContext() = 0;

  virtual UrlAsyncFetcher* DefaultDistributedUrlFetcher() { return NULL; }

  virtual CriticalCssFinder* DefaultCriticalCssFinder();
  virtual CriticalImagesFinder* DefaultCriticalImagesFinder(
      ServerContext* server_context);
  virtual CriticalSelectorFinder* DefaultCriticalSelectorFinder(
      ServerContext* server_context);

  // Note: this one may return NULL.
  virtual MobilizeCachedFinder* DefaultMobilizeCachedFinder(
      ServerContext* server_context);

  // Default implementation returns NULL.
  virtual CacheHtmlInfoFinder* DefaultCacheHtmlInfoFinder(
      PropertyCache* cache, ServerContext* server_context);

  // Default implementation returns NULL.
  virtual FlushEarlyInfoFinder* DefaultFlushEarlyInfoFinder();

  // Default implementation returns a valid CriticalSelectorFinder.
  virtual CriticalLineInfoFinder* DefaultCriticalLineInfoFinder(
      ServerContext* server_context);

  // They may also supply a custom lock manager. The default implementation
  // will use the file system.
  virtual NamedLockManager* DefaultLockManager();

  // They may also supply a custom Url namer. The default implementation
  // performs sharding and appends '.pagespeed.<filter>.<hash>.<extension>'.
  virtual UrlNamer* DefaultUrlNamer();

  virtual UserAgentMatcher* DefaultUserAgentMatcher();
  virtual UsageDataReporter* DefaultUsageDataReporter();

  // Provides an optional hook to add user-agent normalizers specific to
  // needs of a specific RewriteDriverFactory implementation. The new entries
  // should be appended to the end of *out (without clearing it), and should
  // still be owned by the RewriteDriverFactory subclass.
  //
  // Default implementation does nothing.
  virtual void AddPlatformSpecificUserAgentNormalizers(
      std::vector<const UserAgentNormalizer*>* out);

  // Subclasses can override this to create an appropriately-sized thread
  // pool for their environment. The default implementation will always
  // make one with a single thread.
  virtual QueuedWorkerPool* CreateWorkerPool(WorkerPoolCategory pool,
                                             StringPiece name);

  // Subclasses can override this method to request load-shedding to happen
  // if the low-priority work pool has too many inactive sequences queued up
  // waiting (the returned value will be a threshold beyond which things
  // will start getting dropped). The default implementation returns
  // kNoLoadShedding, which disables the feature. See also
  // QueuedWorkerPool::set_load_shedding_threshold
  virtual int LowPriorityLoadSheddingThreshold() const;

  // Subclasses can override this to create an appropriate Scheduler
  // subclass if the default isn't acceptable.
  virtual Scheduler* CreateScheduler();

  // Called before creating the url fetchers.
  virtual void FetcherSetupHooks();

  // Override this if you want to change what directory locks go into
  // when using the default filesystem-based lock manager. The default is
  // filename_prefix()
  virtual StringPiece LockFilePrefix();

  // Initializes the StaticAssetManager.
  virtual void InitStaticAssetManager(
      StaticAssetManager* static_asset_manager) {}

  // Sets up enough of platform dependencies in 'context' to be able to use
  // it for decoding URLs, based on this object's values and some stubs.
  void InitStubDecodingServerContext(ServerContext* context);

  // Allow sub-classes to pick which CentralController they want to use.
  virtual CentralControllerInterface* CreateCentralController();

  // For use in tests.
  void RebuildDecodingDriverForTests(ServerContext* server_context);

  void reset_default_options(RewriteOptions* new_defaults);

 private:
  // Creates a StaticAssetManager instance. Default implementation creates an
  // instance that disables serving of filter javascript via gstatic
  // (gstatic.com is the domain google uses for serving static content).
  StaticAssetManager* DefaultStaticAssetManager();

  void SetupSlurpDirectories();

  void InitDecodingDriver(ServerContext* server_context);

  // This should only be called during startup. Takes ownership of interface.
  void set_central_controller_interface(CentralControllerInterface* interface);

  scoped_ptr<MessageHandler> html_parse_message_handler_;
  scoped_ptr<MessageHandler> message_handler_;
  scoped_ptr<FileSystem> file_system_;
  UrlAsyncFetcher* url_async_fetcher_;
  UrlAsyncFetcher* distributed_async_fetcher_;
  scoped_ptr<UrlAsyncFetcher> base_url_async_fetcher_;
  scoped_ptr<UrlAsyncFetcher> base_distributed_async_fetcher_;
  scoped_ptr<Hasher> hasher_;
  scoped_ptr<NonceGenerator> nonce_generator_;
  scoped_ptr<SHA1Signature> signature_;
  scoped_ptr<UrlNamer> url_namer_;
  scoped_ptr<UserAgentMatcher> user_agent_matcher_;

  // Lazily filled-in list of UA normalizers, including the default ones
  // this class adds, and any additional ones added by user_agent_normalizers()
  // calling subclass' AddPlatformSpecificUserAgentNormalizers on this.
  std::vector<const UserAgentNormalizer*> user_agent_normalizers_;
  scoped_ptr<StaticAssetManager> static_asset_manager_;
  scoped_ptr<Timer> timer_;
  scoped_ptr<Scheduler> scheduler_;
  scoped_ptr<UsageDataReporter> usage_data_reporter_;
  // RE2 patterns needed for JsTokenizer.
  const pagespeed::js::JsTokenizerPatterns* js_tokenizer_patterns_;

  GoogleString filename_prefix_;
  GoogleString slurp_directory_;
  bool force_caching_;
  bool slurp_read_only_;
  bool slurp_print_urls_;

  scoped_ptr<ThreadSystem> thread_system_;

  // protected by server_context_mutex_;
  typedef std::set<ServerContext*> ServerContextSet;
  ServerContextSet server_contexts_;
  scoped_ptr<AbstractMutex> server_context_mutex_;

  // Stores options with hard-coded defaults and adjustments from
  // the core system, subclasses, and command-line.
  scoped_ptr<RewriteOptions> default_options_;

  // Keep around a RewriteDriver just for decoding resource URLs, using
  // the default options.  This is possible because the id->RewriteFilter
  // table is fully constructed independent of the options; we however
  // still inject options into some of the Decode methods since we also
  // need to honor things like forbids. We also have a special
  // ServerContext just for it, to avoid connecting it to any particular
  // pre-existing one.
  scoped_ptr<ServerContext> decoding_server_context_;
  scoped_ptr<RewriteDriver> decoding_driver_;

  // Manage locks for output resources.
  scoped_ptr<NamedLockManager> lock_manager_;

  scoped_ptr<CentralControllerInterfaceAdapter> central_controller_interface_;

  // Default statistics implementation which can be overridden by children
  // by calling SetStatistics().
  NullStatistics null_statistics_;
  Statistics* statistics_;

  StringSet created_directories_;

  std::vector<QueuedWorkerPool*> worker_pools_;

  // These must be initialized after the RewriteDriverFactory subclass has been
  // constructed so it can use a the statistics() override.
  scoped_ptr<RewriteStats> rewrite_stats_;

  // To assist with subclass destruction-order, subclasses can register
  // functions to run late in the destructor.
  std::vector<Function*> deferred_cleanups_;

  // Version string to put into HTTP response headers.
  // TODO(sligocki): Remove. Redundant with RewriteOptions::x_header_value().
  GoogleString version_string_;

  // The hostname we're running on. Used to set the same field in ServerContext.
  GoogleString hostname_;

  DISALLOW_COPY_AND_ASSIGN(RewriteDriverFactory);
};

// Helper for users of RewriterDriverFactory::defer_cleanup --- instantiates
// into objects that call the appropriate delete operator when Run.
template<class T> class RewriteDriverFactory::Deleter : public Function {
 public:
  explicit Deleter(T* obj) : obj_(obj) {}
  virtual void Run() { delete obj_; }
 private:
  T* obj_;
  DISALLOW_COPY_AND_ASSIGN(Deleter);
};

}  // namespace net_instaweb

#endif  // NET_INSTAWEB_REWRITER_PUBLIC_REWRITE_DRIVER_FACTORY_H_