// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/sync/driver/startup_controller.h"

#include <utility>

#include "base/bind.h"
#include "base/command_line.h"
#include "base/location.h"
#include "base/metrics/histogram_macros.h"
#include "base/sequenced_task_runner.h"
#include "base/strings/string_number_conversions.h"
#include "base/threading/sequenced_task_runner_handle.h"
#include "components/sync/driver/sync_driver_switches.h"

namespace syncer {

namespace {

// The amount of time we'll wait to initialize sync if no data type requests
// immediately initialization.
const int kDefaultDeferredInitDelaySeconds = 10;

base::TimeDelta GetDeferredInitDelay() {
  const base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
  if (cmdline->HasSwitch(switches::kSyncDeferredStartupTimeoutSeconds)) {
    int timeout = 0;
    if (base::StringToInt(cmdline->GetSwitchValueASCII(
                              switches::kSyncDeferredStartupTimeoutSeconds),
                          &timeout)) {
      DCHECK_GE(timeout, 0);
      DVLOG(2) << "Sync StartupController overriding startup timeout to "
               << timeout << " seconds.";
      return base::TimeDelta::FromSeconds(timeout);
    }
  }
  return base::TimeDelta::FromSeconds(kDefaultDeferredInitDelaySeconds);
}

bool IsDeferredStartupEnabled() {
  return !base::CommandLine::ForCurrentProcess()->HasSwitch(
      switches::kSyncDisableDeferredStartup);
}

// Enum for UMA defining different events that cause us to exit the "deferred"
// state of initialization and invoke start_engine.
enum DeferredInitTrigger {
  // We have received a signal from a SyncableService requesting that sync
  // starts as soon as possible.
  TRIGGER_DATA_TYPE_REQUEST,
  // No data type requested sync to start and our fallback timer expired.
  TRIGGER_FALLBACK_TIMER,
  MAX_TRIGGER_VALUE
};

}  // namespace

StartupController::StartupController(
    base::RepeatingCallback<ModelTypeSet()> get_preferred_data_types,
    base::RepeatingCallback<bool()> should_start,
    base::RepeatingClosure start_engine)
    : get_preferred_data_types_callback_(std::move(get_preferred_data_types)),
      should_start_callback_(std::move(should_start)),
      start_engine_callback_(std::move(start_engine)),
      bypass_deferred_startup_(false) {}

StartupController::~StartupController() {}

void StartupController::Reset() {
  bypass_deferred_startup_ = false;
  start_up_time_ = base::Time();
  start_engine_time_ = base::Time();
  // Don't let previous timers affect us post-reset.
  weak_factory_.InvalidateWeakPtrs();
}

void StartupController::StartUp(StartUpDeferredOption deferred_option) {
  const bool first_start = start_up_time_.is_null();
  if (first_start) {
    start_up_time_ = base::Time::Now();
  }

  if (deferred_option == STARTUP_DEFERRED && IsDeferredStartupEnabled() &&
      get_preferred_data_types_callback_.Run().Has(SESSIONS)) {
    if (first_start) {
      base::SequencedTaskRunnerHandle::Get()->PostDelayedTask(
          FROM_HERE,
          base::BindOnce(&StartupController::OnFallbackStartupTimerExpired,
                         weak_factory_.GetWeakPtr()),
          GetDeferredInitDelay());
    }
    return;
  }

  if (start_engine_time_.is_null()) {
    start_engine_time_ = base::Time::Now();
    start_engine_callback_.Run();
  }
}

void StartupController::TryStart(bool force_immediate) {
  if (!should_start_callback_.Run()) {
    return;
  }

  // For performance reasons, defer the heavy lifting for sync init unless:
  //
  // - a datatype has requested an immediate start of sync, or
  // - sync needs to start up the engine immediately to provide control state
  //   and encryption information to the UI.
  // Do not start up the sync engine if setup has not completed and isn't
  // in progress, unless told to otherwise.
  StartUp((force_immediate || bypass_deferred_startup_) ? STARTUP_IMMEDIATE
                                                        : STARTUP_DEFERRED);
}

void StartupController::RecordTimeDeferred() {
  DCHECK(!start_up_time_.is_null());
  base::TimeDelta time_deferred = base::Time::Now() - start_up_time_;
  UMA_HISTOGRAM_CUSTOM_TIMES("Sync.Startup.TimeDeferred2", time_deferred,
                             base::TimeDelta::FromSeconds(0),
                             base::TimeDelta::FromMinutes(2), 60);
}

void StartupController::OnFallbackStartupTimerExpired() {
  DCHECK(IsDeferredStartupEnabled());

  if (!start_engine_time_.is_null())
    return;

  DVLOG(2) << "Sync deferred init fallback timer expired, starting engine.";
  RecordTimeDeferred();
  UMA_HISTOGRAM_ENUMERATION("Sync.Startup.DeferredInitTrigger",
                            TRIGGER_FALLBACK_TIMER, MAX_TRIGGER_VALUE);
  // Once the deferred init timer has expired, don't defer startup again (until
  // Reset() or browser restart), even if this startup attempt doesn't succeed.
  bypass_deferred_startup_ = true;
  TryStart(/*force_immediate=*/false);
}

StartupController::State StartupController::GetState() const {
  if (!start_engine_time_.is_null())
    return State::STARTED;
  if (!start_up_time_.is_null())
    return State::STARTING_DEFERRED;
  return State::NOT_STARTED;
}

void StartupController::OnDataTypeRequestsSyncStartup(ModelType type) {
  if (!IsDeferredStartupEnabled()) {
    DVLOG(2) << "Ignoring data type request for sync startup: "
             << ModelTypeToString(type);
    return;
  }

  if (!start_engine_time_.is_null())
    return;

  DVLOG(2) << "Data type requesting sync startup: " << ModelTypeToString(type);
  // Measure the time spent waiting for init and the type that triggered it.
  // We could measure the time spent deferred on a per-datatype basis, but
  // for now this is probably sufficient.
  // TODO(wychen): enum uma should be strongly typed. crbug.com/661401
  UMA_HISTOGRAM_ENUMERATION("Sync.Startup.TypeTriggeringInit",
                            ModelTypeToHistogramInt(type),
                            static_cast<int>(ModelType::NUM_ENTRIES));
  if (!start_up_time_.is_null()) {
    RecordTimeDeferred();
    UMA_HISTOGRAM_ENUMERATION("Sync.Startup.DeferredInitTrigger",
                              TRIGGER_DATA_TYPE_REQUEST, MAX_TRIGGER_VALUE);
  }
  bypass_deferred_startup_ = true;
  TryStart(/*force_immediate=*/false);
}

}  // namespace syncer