// Copyright (c) 2012 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 "chrome/browser/prerender/prerender_field_trial.h"

#include "base/command_line.h"
#include "base/logging.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/histogram.h"
#include "chrome/browser/metrics/metrics_service.h"
#include "chrome/browser/prefs/pref_service.h"
#include "chrome/browser/prerender/prerender_manager.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/common/chrome_switches.h"
#include "chrome/common/chrome_version_info.h"
#include "content/browser/renderer_host/resource_dispatcher_host.h"

namespace prerender {

namespace {

const char kPrerenderFromOmniboxTrialName[] = "PrerenderFromOmnibox";

void SetupPrefetchFieldTrial() {
  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
  if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
      channel == chrome::VersionInfo::CHANNEL_BETA) {
    return;
  }

  const base::FieldTrial::Probability divisor = 1000;
  const base::FieldTrial::Probability prefetch_probability = 500;
  scoped_refptr<base::FieldTrial> trial(
      new base::FieldTrial("Prefetch", divisor,
                           "ContentPrefetchPrefetchOff", 2012, 6, 30));
  const int kPrefetchOnGroup = trial->AppendGroup("ContentPrefetchPrefetchOn",
                                                  prefetch_probability);
  ResourceDispatcherHost::set_is_prefetch_enabled(
      trial->group() == kPrefetchOnGroup);
}

void SetupPrerenderFieldTrial() {
  base::FieldTrial::Probability divisor = 1000;
  base::FieldTrial::Probability exp1_probability = 200;
  base::FieldTrial::Probability control1_probability = 200;
  base::FieldTrial::Probability no_use1_probability = 100;
  base::FieldTrial::Probability exp2_probability = 200;
  base::FieldTrial::Probability control2_probability = 200;
  base::FieldTrial::Probability no_use2_probability = 100;
  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
  if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
      channel == chrome::VersionInfo::CHANNEL_BETA) {
    exp1_probability = 495;
    control1_probability = 5;
    no_use1_probability = 0;
    exp2_probability = 495;
    control2_probability = 5;
    no_use2_probability = 0;
  }
  CHECK_EQ(divisor, exp1_probability + control1_probability +
           no_use1_probability + exp2_probability +
           control2_probability + no_use2_probability);
  scoped_refptr<base::FieldTrial> trial(
      new base::FieldTrial("Prerender", divisor,
                           "ContentPrefetchPrerender1", 2012, 6, 30));

  const int kPrerenderExperiment1Group = trial->kDefaultGroupNumber;
  const int kPrerenderControl1Group =
      trial->AppendGroup("ContentPrefetchPrerenderControl1",
                         control1_probability);
  const int kPrerenderNoUse1Group =
      trial->AppendGroup("ContentPrefetchPrerenderNoUse1",
                         no_use1_probability);
  const int kPrerenderExperiment2Group =
      trial->AppendGroup("ContentPrefetchPrerender2",
                         exp2_probability);
  const int kPrerenderControl2Group =
      trial->AppendGroup("ContentPrefetchPrerenderControl2",
                         control2_probability);
  const int kPrerenderNoUse2Group =
      trial->AppendGroup("ContentPrefetchPrerenderNoUse2",
                         no_use2_probability);
  const int trial_group = trial->group();
  if (trial_group == kPrerenderExperiment1Group ||
      trial_group == kPrerenderExperiment2Group) {
    PrerenderManager::SetMode(
        PrerenderManager::PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP);
  } else if (trial_group == kPrerenderControl1Group ||
             trial_group == kPrerenderControl2Group) {
    PrerenderManager::SetMode(
        PrerenderManager::PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP);
  } else if (trial_group == kPrerenderNoUse1Group ||
             trial_group == kPrerenderNoUse2Group) {
    PrerenderManager::SetMode(
        PrerenderManager::PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP);
  } else {
    NOTREACHED();
  }
}

}  // end namespace

void ConfigurePrerenderFromOmnibox();

void ConfigurePrefetchAndPrerender(const CommandLine& command_line) {
  enum PrerenderOption {
    PRERENDER_OPTION_AUTO,
    PRERENDER_OPTION_DISABLED,
    PRERENDER_OPTION_ENABLED,
    PRERENDER_OPTION_PREFETCH_ONLY,
  };

  PrerenderOption prerender_option = PRERENDER_OPTION_AUTO;
  if (command_line.HasSwitch(switches::kPrerenderMode)) {
    const std::string switch_value =
        command_line.GetSwitchValueASCII(switches::kPrerenderMode);

    if (switch_value == switches::kPrerenderModeSwitchValueAuto) {
      prerender_option = PRERENDER_OPTION_AUTO;
    } else if (switch_value == switches::kPrerenderModeSwitchValueDisabled) {
      prerender_option = PRERENDER_OPTION_DISABLED;
    } else if (switch_value.empty() ||
               switch_value == switches::kPrerenderModeSwitchValueEnabled) {
      // The empty string means the option was provided with no value, and that
      // means enable.
      prerender_option = PRERENDER_OPTION_ENABLED;
    } else if (switch_value ==
               switches::kPrerenderModeSwitchValuePrefetchOnly) {
      prerender_option = PRERENDER_OPTION_PREFETCH_ONLY;
    } else {
      prerender_option = PRERENDER_OPTION_DISABLED;
      LOG(ERROR) << "Invalid --prerender option received on command line: "
                 << switch_value;
      LOG(ERROR) << "Disabling prerendering!";
    }
  }

  switch (prerender_option) {
    case PRERENDER_OPTION_AUTO:
      SetupPrefetchFieldTrial();
      SetupPrerenderFieldTrial();
      break;
    case PRERENDER_OPTION_DISABLED:
      ResourceDispatcherHost::set_is_prefetch_enabled(false);
      PrerenderManager::SetMode(PrerenderManager::PRERENDER_MODE_DISABLED);
      break;
    case PRERENDER_OPTION_ENABLED:
      ResourceDispatcherHost::set_is_prefetch_enabled(true);
      PrerenderManager::SetMode(PrerenderManager::PRERENDER_MODE_ENABLED);
      break;
    case PRERENDER_OPTION_PREFETCH_ONLY:
      ResourceDispatcherHost::set_is_prefetch_enabled(true);
      PrerenderManager::SetMode(PrerenderManager::PRERENDER_MODE_DISABLED);
      break;
    default:
      NOTREACHED();
  }

  UMA_HISTOGRAM_ENUMERATION("Prerender.Sessions",
                            PrerenderManager::GetMode(),
                            PrerenderManager::PRERENDER_MODE_MAX);

  ConfigurePrerenderFromOmnibox();
}

void ConfigurePrerenderFromOmnibox() {
  // Field trial to see if we're enabled.
  const base::FieldTrial::Probability kDivisor = 100;

  base::FieldTrial::Probability kEnabledProbability = 90;
  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
  if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
      channel == chrome::VersionInfo::CHANNEL_BETA) {
    kEnabledProbability = 99;
  }
  scoped_refptr<base::FieldTrial> enabled_trial(
      new base::FieldTrial(kPrerenderFromOmniboxTrialName, kDivisor,
                           "OmniboxPrerenderDisabled", 2012, 8, 30));
  enabled_trial->AppendGroup("OmniboxPrerenderEnabled", kEnabledProbability);
}

bool IsOmniboxEnabled(Profile* profile) {
  if (!profile || profile->IsOffTheRecord())
    return false;

  if (!PrerenderManager::IsPrerenderingPossible())
    return false;

  // Override any field trial groups if the user has set a command line flag.
  if (CommandLine::ForCurrentProcess()->HasSwitch(
      switches::kPrerenderFromOmnibox)) {
    const std::string switch_value =
        CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
            switches::kPrerenderFromOmnibox);

    if (switch_value == switches::kPrerenderFromOmniboxSwitchValueEnabled)
      return true;

    if (switch_value == switches::kPrerenderFromOmniboxSwitchValueDisabled)
      return false;

    DCHECK(switch_value == switches::kPrerenderFromOmniboxSwitchValueAuto);
  }

  const int group =
      base::FieldTrialList::FindValue(kPrerenderFromOmniboxTrialName);
  return group != base::FieldTrial::kNotFinalized &&
         group != base::FieldTrial::kDefaultGroupNumber;
}

}  // namespace prerender