// 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/safe_browsing/client_side_model_loader.h"

#include "base/bind.h"
#include "base/command_line.h"
#include "base/memory/scoped_ptr.h"
#include "base/message_loop/message_loop.h"
#include "base/metrics/histogram.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/time/time.h"
#include "chrome/browser/safe_browsing/protocol_manager.h"
#include "chrome/common/chrome_switches.h"
#include "chrome/common/safe_browsing/client_model.pb.h"
#include "chrome/common/safe_browsing/csd.pb.h"
#include "chrome/common/safe_browsing/safebrowsing_messages.h"
#include "components/variations/variations_associated_data.h"
#include "net/http/http_response_headers.h"
#include "net/http/http_status_code.h"
#include "net/url_request/url_fetcher.h"
#include "net/url_request/url_request_context_getter.h"
#include "net/url_request/url_request_status.h"
#include "url/gurl.h"

namespace safe_browsing {

// Model Loader strings
const size_t ModelLoader::kMaxModelSizeBytes = 150 * 1024;
const int ModelLoader::kClientModelFetchIntervalMs = 3600 * 1000;
const char ModelLoader::kClientModelUrlPrefix[] =
    "https://ssl.gstatic.com/safebrowsing/csd/";
const char ModelLoader::kClientModelNamePattern[] =
    "client_model_v5%s_variation_%d.pb";
const char ModelLoader::kClientModelFinchExperiment[] =
    "ClientSideDetectionModel";
const char ModelLoader::kClientModelFinchParam[] =
    "ModelNum";
const char kUmaModelDownloadResponseMetricName[] =
    "SBClientPhishing.ClientModelDownloadResponseOrErrorCode";


// static
int ModelLoader::GetModelNumber() {
  std::string num_str = variations::GetVariationParamValue(
      kClientModelFinchExperiment, kClientModelFinchParam);
  int model_number = 0;
  if (!base::StringToInt(num_str, &model_number)) {
    model_number = 0;  // Default model
  }
  return model_number;
}

// static
std::string ModelLoader::FillInModelName(bool is_extended_reporting,
                                         int model_number) {
  return base::StringPrintf(kClientModelNamePattern,
                            is_extended_reporting ? "_ext" : "", model_number);
}

// static
bool ModelLoader::ModelHasValidHashIds(const ClientSideModel& model) {
  const int max_index = model.hashes_size() - 1;
  for (int i = 0; i < model.rule_size(); ++i) {
    for (int j = 0; j < model.rule(i).feature_size(); ++j) {
      if (model.rule(i).feature(j) < 0 ||
          model.rule(i).feature(j) > max_index) {
        return false;
      }
    }
  }
  for (int i = 0; i < model.page_term_size(); ++i) {
    if (model.page_term(i) < 0 || model.page_term(i) > max_index) {
      return false;
    }
  }
  return true;
}

// Model name and URL are a function of is_extended_reporting and Finch.
ModelLoader::ModelLoader(base::Closure update_renderers_callback,
                         net::URLRequestContextGetter* request_context_getter,
                         bool is_extended_reporting)
    : name_(FillInModelName(is_extended_reporting, GetModelNumber())),
      url_(kClientModelUrlPrefix + name_),
      update_renderers_callback_(update_renderers_callback),
      request_context_getter_(request_context_getter),
      weak_factory_(this) {
  DCHECK(url_.is_valid());
}

// For testing only
ModelLoader::ModelLoader(base::Closure update_renderers_callback,
                         const std::string& model_name)
    : name_(model_name),
      url_(kClientModelUrlPrefix + name_),
      update_renderers_callback_(update_renderers_callback),
      request_context_getter_(NULL),
      weak_factory_(this) {
  DCHECK(url_.is_valid());
}

ModelLoader::~ModelLoader() {
}

void ModelLoader::StartFetch() {
  // Start fetching the model either from the cache or possibly from the
  // network if the model isn't in the cache.

  // TODO(nparker): If no profile needs this model, we shouldn't fetch it.
  // Then only re-fetch when a profile setting changes to need it.
  // This will save on the order of ~50KB/week/client of bandwidth.
  fetcher_ = net::URLFetcher::Create(0 /* ID used for testing */, url_,
                                     net::URLFetcher::GET, this);
  fetcher_->SetRequestContext(request_context_getter_);
  fetcher_->Start();
}

void ModelLoader::OnURLFetchComplete(const net::URLFetcher* source) {
  DCHECK_EQ(fetcher_.get(), source);
  DCHECK_EQ(url_, source->GetURL());

  std::string data;
  source->GetResponseAsString(&data);
  net::URLRequestStatus status = source->GetStatus();
  const bool is_success = status.is_success();
  const int response_code = source->GetResponseCode();
  SafeBrowsingProtocolManager::RecordHttpResponseOrErrorCode(
      kUmaModelDownloadResponseMetricName, status, response_code);

  // max_age is valid iff !0.
  base::TimeDelta max_age;
  if (is_success && net::HTTP_OK == response_code &&
      source->GetResponseHeaders()) {
    source->GetResponseHeaders()->GetMaxAgeValue(&max_age);
  }
  scoped_ptr<ClientSideModel> model(new ClientSideModel());
  ClientModelStatus model_status;
  if (!is_success || net::HTTP_OK != response_code) {
    model_status = MODEL_FETCH_FAILED;
  } else if (data.empty()) {
    model_status = MODEL_EMPTY;
  } else if (data.size() > kMaxModelSizeBytes) {
    model_status = MODEL_TOO_LARGE;
  } else if (!model->ParseFromString(data)) {
    model_status = MODEL_PARSE_ERROR;
  } else if (!model->IsInitialized() || !model->has_version()) {
    model_status = MODEL_MISSING_FIELDS;
  } else if (!ModelHasValidHashIds(*model)) {
    model_status = MODEL_BAD_HASH_IDS;
  } else if (model->version() < 0 ||
             (model_.get() && model->version() < model_->version())) {
    model_status = MODEL_INVALID_VERSION_NUMBER;
  } else if (model_.get() && model->version() == model_->version()) {
    model_status = MODEL_NOT_CHANGED;
  } else {
    // The model is valid => replace the existing model with the new one.
    model_str_.assign(data);
    model_.swap(model);
    model_status = MODEL_SUCCESS;
  }
  EndFetch(model_status, max_age);
}

void ModelLoader::EndFetch(ClientModelStatus status, base::TimeDelta max_age) {
  // We don't differentiate models in the UMA stats.
  UMA_HISTOGRAM_ENUMERATION("SBClientPhishing.ClientModelStatus",
                            status,
                            MODEL_STATUS_MAX);
  if (status == MODEL_SUCCESS) {
    update_renderers_callback_.Run();
  }
  int delay_ms = kClientModelFetchIntervalMs;
  // If the most recently fetched model had a valid max-age and the model was
  // valid we're scheduling the next model update for after the max-age expired.
  if (!max_age.is_zero() &&
      (status == MODEL_SUCCESS || status == MODEL_NOT_CHANGED)) {
    // We're adding 60s of additional delay to make sure we're past
    // the model's age.
    max_age += base::TimeDelta::FromMinutes(1);
    delay_ms = max_age.InMilliseconds();
  }

  // Schedule the next model reload.
  ScheduleFetch(delay_ms);
}

void ModelLoader::ScheduleFetch(int64 delay_ms) {
  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
          switches::kSbDisableAutoUpdate))
    return;
  base::MessageLoop::current()->PostDelayedTask(
      FROM_HERE,
      base::Bind(&ModelLoader::StartFetch, weak_factory_.GetWeakPtr()),
      base::TimeDelta::FromMilliseconds(delay_ms));
}

void ModelLoader::CancelFetcher() {
  // Invalidate any scheduled request.
  weak_factory_.InvalidateWeakPtrs();
  // Cancel any request in progress.
  fetcher_.reset();
}

}  // namespace safe_browsing