// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_NET_LOG_NET_EXPORT_FILE_WRITER_H_
#define COMPONENTS_NET_LOG_NET_EXPORT_FILE_WRITER_H_

#include <memory>
#include <string>

#include "base/command_line.h"
#include "base/files/file.h"
#include "base/files/file_path.h"
#include "base/functional/callback.h"
#include "base/gtest_prod_util.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/threading/thread_checker.h"
#include "base/values.h"
#include "mojo/public/cpp/bindings/remote.h"
#include "net/log/net_log_capture_mode.h"
#include "services/network/public/mojom/network_service.mojom.h"

namespace base {
class TaskRunner;
}  // namespace base

namespace network {
namespace mojom {
class NetworkContext;
}
}  // namespace network

namespace net_log {

// NetExportFileWriter is used exclusively as a support class for
// chrome://net-export/. There's a single instance created globally that acts as
// the interface to all NetExportMessageHandlers which can tell it to start or
// stop logging in response to user actions from chrome://net-export/ UIs.
// Because there's only one instance, the logging state can be shared between
// multiple instances of the chrome://net-export/ UI. Internally, it manages a
// pipe to an instance of network::NetLogExporter and handles the
// attaching/detaching of it to the NetLog. This class is used by the iOS and
// non-iOS implementations of chrome://net-export/.
//
// NetExportFileWriter maintains the current logging state using the members
// |state_|, |log_exists_|, |log_capture_mode_known_|, |log_capture_mode_|.
// Its three main commands are Initialize(), StartNetLog(), and StopNetLog().
// These are the only functions that may cause NetExportFileWriter to change
// state. Initialize() must be called before NetExportFileWriter can process any
// other commands. A portion of the initialization needs to run on the
// |file_task_runner_|.
//
// This class is created and destroyed on the UI thread, and all public entry
// points are to be called on the UI thread. Internally, the class may run some
// code on the |file_task_runner_|.
class NetExportFileWriter {
 public:
  // Special value meaning "can use an unlimited number of bytes".
  static constexpr uint64_t kNoLimit =
      network::mojom::NetLogExporter::kUnlimitedFileSize;

  // The observer interface to be implemented by code that wishes to be notified
  // of NetExportFileWriter's state changes.
  class StateObserver {
   public:
    virtual void OnNewState(const base::Value::Dict& state) = 0;
  };

  // Struct used to store the results of setting up the default log directory
  // and log path.
  struct DefaultLogPathResults {
    bool default_log_path_success;
    base::FilePath default_log_path;
    bool log_exists;
  };

  using FilePathCallback = base::OnceCallback<void(const base::FilePath&)>;
  using DirectoryGetter = base::RepeatingCallback<bool(base::FilePath*)>;

  // Constructs a NetExportFileWriter. Only one instance is created in browser
  // process.
  NetExportFileWriter();

  NetExportFileWriter(const NetExportFileWriter&) = delete;
  NetExportFileWriter& operator=(const NetExportFileWriter&) = delete;

  ~NetExportFileWriter();

  // Attaches a StateObserver. |observer| will be notified of state changes to
  // NetExportFileWriter. State changes may occur in response to Initiailze(),
  // StartNetLog(), or StopNetLog(). StateObserver::OnNewState() will be called
  // asynchronously relative to the command that caused the state change.
  // |observer| must remain alive until RemoveObserver() is called.
  void AddObserver(StateObserver* observer);

  // Detaches a StateObserver.
  void RemoveObserver(StateObserver* observer);

  // Initializes NetExportFileWriter if not initialized. Calling this function
  // again is OK.
  void Initialize();

  // Starts collecting NetLog data into the file at |log_path|. If |log_path| is
  // empty, the default log path is used. If NetExportFileWriter is already
  // logging, this is a no-op and |capture_mode| is ignored.
  //
  // |max_file_size| places a bound on how large the log file can grow. To make
  // it grow unboundedly pass kNoLimit.
  //
  // |network_context| will be used to append net info (from net::GetInfo())
  // at end of logging once StopNetLog is called.
  void StartNetLog(const base::FilePath& log_path,
                   net::NetLogCaptureMode capture_mode,
                   uint64_t max_file_size,
                   const base::CommandLine::StringType& command_line_string,
                   const std::string& channel_string,
                   network::mojom::NetworkContext* network_context);

  // Stops collecting NetLog data into the file. It is a no-op if
  // NetExportFileWriter is currently not logging.
  //
  // |polled_data| is a JSON dictionary that will be appended to the end of the
  // log; it's for adding additional info to the log that aren't events.
  void StopNetLog(base::Value::Dict polled_data = base::Value::Dict());

  // Creates a `base::Value::Dict` summary of the state of the
  // `NetExportFileWriter`.
  base::Value::Dict GetState() const;

  // Gets the log filepath. |path_callback| will be used to notify the caller
  // when the filepath is retrieved. |path_callback| will be executed with an
  // empty filepath if any of the following occurs:
  // (1) The NetExportFileWriter is not initialized.
  // (2) The log file does not exist.
  // (3) The NetExportFileWriter is currently logging.
  //
  // |path_callback| will be executed at the end of GetFilePathToCompletedLog()
  // asynchronously.
  void GetFilePathToCompletedLog(FilePathCallback path_callback) const;

  // Converts to/from the string representation of a capture mode used by
  // net_export.js.
  static std::string CaptureModeToString(net::NetLogCaptureMode capture_mode);
  static net::NetLogCaptureMode CaptureModeFromString(
      const std::string& capture_mode_string);

  // Overrides the getter used to retrieve the default log base directory during
  // initialization. Should only be used by unit tests.
  void SetDefaultLogBaseDirectoryGetterForTest(const DirectoryGetter& getter);

 private:
  friend class NetExportFileWriterTest;

  // The possible logging states of NetExportFileWriter.
  enum State {
    STATE_UNINITIALIZED,
    // Currently in the process of initializing.
    STATE_INITIALIZING,
    // Not currently logging to file.
    STATE_NOT_LOGGING,
    // Currently in the process of starting the log.
    STATE_STARTING_LOG,
    // Currently logging to file.
    STATE_LOGGING,
    // Currently in the process of stopping the log.
    STATE_STOPPING_LOG,
  };

  void NotifyStateObservers();

  // Posts NotifyStateObservers() to the current thread.
  void NotifyStateObserversAsync();

  // Called internally by Initialize(). Will initialize NetExportFileWriter's
  // state variables after the default log directory is set up and the default
  // log path is determined on the |file_task_runner_|.
  void SetStateAfterSetUpDefaultLogPath(
      const DefaultLogPathResults& set_up_default_log_path_results);

  // Called internally by StartNetLog(). Contains tasks to be done to start
  // logging after the output file has been created.
  void StartNetLogAfterCreateFile(net::NetLogCaptureMode capture_mode,
                                  uint64_t max_file_size,
                                  base::Value::Dict custom_constants,
                                  base::File log_file);

  void OnStartResult(net::NetLogCaptureMode capture_mode, int result);
  void OnStopResult(int result);

  void OnConnectionError();

  // Contains tasks to be done after |net_log_exporter_| has completely
  // stopped writing.
  void ResetExporterThenSetStateNotLogging();

  // Creates a new file for writing at |path|, trying to overwrite any existing
  // file. Called on |file_task_runner_|.
  static base::File CreateOutputFile(base::FilePath path);

  // All members are accessed solely from the main thread (the thread that
  // |thread_checker_| is bound to).
  base::ThreadChecker thread_checker_;

  // Task runners for file-specific and net-specific tasks that must run on a
  // file or net task runner.
  scoped_refptr<base::TaskRunner> file_task_runner_;

  State state_;  // Current logging state of NetExportFileWriter.

  bool log_exists_;  // Whether or not a log file exists on disk.
  bool log_capture_mode_known_;
  net::NetLogCaptureMode log_capture_mode_;

  base::FilePath log_path_;  // base::FilePath to the NetLog file.

  // Used to ask the network service to do the actual exporting.
  mojo::Remote<network::mojom::NetLogExporter> net_log_exporter_;

  // List of StateObservers to notify on state changes.
  base::ObserverList<StateObserver, true>::Unchecked state_observer_list_;

  // Used by unit tests to override the default log base directory retrieved
  // during initialization. This getter is initialized to base::GetTempDir().
  DirectoryGetter default_log_base_dir_getter_;

  base::WeakPtrFactory<NetExportFileWriter> weak_ptr_factory_{this};
};

}  // namespace net_log

#endif  // COMPONENTS_NET_LOG_NET_EXPORT_FILE_WRITER_H_