// 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 <windows.h>
#include <shlwapi.h>

#include "base/command_line.h"
#include "base/debug/trace_event.h"
#include "base/environment.h"
#include "base/file_version_info.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/rand_util.h"  // For PreRead experiment.
#include "base/sha1.h"  // For PreRead experiment.
#include "base/strings/string16.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
#include "base/version.h"
#include "base/win/windows_version.h"
#include "chrome/app/breakpad_win.h"
#include "chrome/app/client_util.h"
#include "chrome/app/image_pre_reader_win.h"
#include "chrome/common/chrome_constants.h"
#include "chrome/common/chrome_result_codes.h"
#include "chrome/common/chrome_switches.h"
#include "chrome/common/env_vars.h"
#include "chrome/installer/util/browser_distribution.h"
#include "chrome/installer/util/channel_info.h"
#include "chrome/installer/util/google_update_constants.h"
#include "chrome/installer/util/google_update_settings.h"
#include "chrome/installer/util/install_util.h"
#include "chrome/installer/util/util_constants.h"

namespace {
// The entry point signature of chrome.dll.
typedef int (*DLL_MAIN)(HINSTANCE, sandbox::SandboxInterfaceInfo*);

typedef void (*RelaunchChromeBrowserWithNewCommandLineIfNeededFunc)();

// Returns true if the build date for this module precedes the expiry date
// for the pre-read experiment.
bool PreReadExperimentIsActive() {
  const int kPreReadExpiryYear = 2014;
  const int kPreReadExpiryMonth = 7;
  const int kPreReadExpiryDay = 1;
  const char kBuildTimeStr[] = __DATE__ " " __TIME__;

  // Get the timestamp of the build.
  base::Time build_time;
  bool result = base::Time::FromString(kBuildTimeStr, &build_time);
  DCHECK(result);

  // Get the timestamp at which the experiment expires.
  base::Time::Exploded exploded = {0};
  exploded.year = kPreReadExpiryYear;
  exploded.month = kPreReadExpiryMonth;
  exploded.day_of_month = kPreReadExpiryDay;
  base::Time expiration_time = base::Time::FromLocalExploded(exploded);

  // Return true if the build time predates the expiration time..
  return build_time < expiration_time;
}

// Get random unit values, i.e., in the range (0, 1), denoting a die-toss for
// being in an experiment population and experimental group thereof.
void GetPreReadPopulationAndGroup(double* population, double* group) {
  // By default we use the metrics id for the user as stable pseudo-random
  // input to a hash.
  base::string16 metrics_id;
  GoogleUpdateSettings::GetMetricsId(&metrics_id);

  // If this user has not metrics id, we fall back to a purely random value
  // per browser session.
  const size_t kLength = 16;
  std::string random_value(metrics_id.empty() ? base::RandBytesAsString(kLength)
                                              : base::WideToUTF8(metrics_id));

  // To interpret the value as a random number we hash it and read the first 8
  // bytes of the hash as a unit-interval representing a die-toss for being in
  // the experiment population and the second 8 bytes as a die-toss for being
  // in various experiment groups.
  unsigned char sha1_hash[base::kSHA1Length];
  base::SHA1HashBytes(
      reinterpret_cast<const unsigned char*>(random_value.c_str()),
      random_value.size() * sizeof(random_value[0]),
      sha1_hash);
  COMPILE_ASSERT(2 * sizeof(uint64) < sizeof(sha1_hash), need_more_data);
  const uint64* random_bits = reinterpret_cast<uint64*>(&sha1_hash[0]);

  // Convert the bits into unit-intervals and return.
  *population = base::BitsToOpenEndedUnitInterval(random_bits[0]);
  *group = base::BitsToOpenEndedUnitInterval(random_bits[1]);
}

// Gets the amount of pre-read to use as well as the experiment group in which
// the user falls.
size_t InitPreReadPercentage() {
  // By default use the old behaviour: read 100%.
  const int kDefaultPercentage = 100;
  const char kDefaultFormatStr[] = "%d-pct-default";
  const char kControlFormatStr[] = "%d-pct-control";
  const char kGroupFormatStr[] = "%d-pct";

  COMPILE_ASSERT(kDefaultPercentage <= 100, default_percentage_too_large);
  COMPILE_ASSERT(kDefaultPercentage % 5 == 0, default_percentage_not_mult_5);

  // Roll the dice to determine if this user is in the experiment and if so,
  // in which experimental group.
  double population = 0.0;
  double group = 0.0;
  GetPreReadPopulationAndGroup(&population, &group);

  // We limit experiment populations to 1% of the Stable and 10% of each of
  // the other channels.
  const string16 channel(GoogleUpdateSettings::GetChromeChannel(
      GoogleUpdateSettings::IsSystemInstall()));
  double threshold = (channel == installer::kChromeChannelStable) ? 0.01 : 0.10;

  // If the experiment has expired use the default pre-read level. Otherwise,
  // those not in the experiment population also use the default pre-read level.
  size_t value = kDefaultPercentage;
  const char* format_str = kDefaultFormatStr;
  if (PreReadExperimentIsActive() && (population <= threshold)) {
    // We divide the experiment population into groups pre-reading at 5 percent
    // increments in the range [0, 100].
    value = static_cast<size_t>(group * 21.0) * 5;
    DCHECK_LE(value, 100u);
    DCHECK_EQ(0u, value % 5);
    format_str =
        (value == kDefaultPercentage) ? kControlFormatStr : kGroupFormatStr;
  }

  // Generate the group name corresponding to this percentage value.
  std::string group_name;
  base::SStringPrintf(&group_name, format_str, value);

  // Persist the group name to the environment so that it can be used for
  // reporting.
  scoped_ptr<base::Environment> env(base::Environment::Create());
  env->SetVar(chrome::kPreReadEnvironmentVariable, group_name);

  // Return the percentage value to be used.
  return value;
}

// Expects that |dir| has a trailing backslash. |dir| is modified so it
// contains the full path that was tried. Caller must check for the return
// value not being null to determine if this path contains a valid dll.
HMODULE LoadChromeWithDirectory(string16* dir) {
  ::SetCurrentDirectoryW(dir->c_str());
  const CommandLine& cmd_line = *CommandLine::ForCurrentProcess();
#if !defined(CHROME_MULTIPLE_DLL)
  const wchar_t* dll_name = installer::kChromeDll;
#else
  const wchar_t* dll_name = cmd_line.HasSwitch(switches::kProcessType) ?
      installer::kChromeChildDll : installer::kChromeDll;
#endif
  dir->append(dll_name);

#if !defined(WIN_DISABLE_PREREAD)
  // We pre-read the binary to warm the memory caches (fewer hard faults to
  // page parts of the binary in).
  if (!cmd_line.HasSwitch(switches::kProcessType)) {
    const size_t kStepSize = 1024 * 1024;
    size_t percentage = InitPreReadPercentage();
    ImagePreReader::PartialPreReadImage(dir->c_str(), percentage, kStepSize);
  }
#endif

  return ::LoadLibraryExW(dir->c_str(), NULL,
                          LOAD_WITH_ALTERED_SEARCH_PATH);
}

void RecordDidRun(const string16& dll_path) {
  bool system_level = !InstallUtil::IsPerUserInstall(dll_path.c_str());
  GoogleUpdateSettings::UpdateDidRunState(true, system_level);
}

void ClearDidRun(const string16& dll_path) {
  bool system_level = !InstallUtil::IsPerUserInstall(dll_path.c_str());
  GoogleUpdateSettings::UpdateDidRunState(false, system_level);
}

}  // namespace

string16 GetExecutablePath() {
  wchar_t path[MAX_PATH];
  ::GetModuleFileNameW(NULL, path, MAX_PATH);
  if (!::PathRemoveFileSpecW(path))
    return string16();
  string16 exe_path(path);
  return exe_path.append(1, L'\\');
}

string16 GetCurrentModuleVersion() {
  scoped_ptr<FileVersionInfo> file_version_info(
      FileVersionInfo::CreateFileVersionInfoForCurrentModule());
  if (file_version_info.get()) {
    string16 version_string(file_version_info->file_version());
    if (Version(WideToASCII(version_string)).IsValid())
      return version_string;
  }
  return string16();
}

//=============================================================================

MainDllLoader::MainDllLoader() : dll_(NULL) {
}

MainDllLoader::~MainDllLoader() {
}

// Loading chrome is an interesting affair. First we try loading from the
// current directory to support run-what-you-compile and other development
// scenarios.
// If that fails then we look at the --chrome-version command line flag to
// determine if we should stick with an older dll version even if a new one is
// available to support upgrade-in-place scenarios.
// If that fails then finally we look at the version resource in the current
// module. This is the expected path for chrome.exe browser instances in an
// installed build.
HMODULE MainDllLoader::Load(string16* out_version, string16* out_file) {
  const CommandLine& cmd_line = *CommandLine::ForCurrentProcess();
  const string16 dir(GetExecutablePath());
  *out_file = dir;
  HMODULE dll = LoadChromeWithDirectory(out_file);
  if (!dll) {
    // Loading from same directory (for developers) failed.
    string16 version_string;
    if (cmd_line.HasSwitch(switches::kChromeVersion)) {
      // This is used to support Chrome Frame, see http://crbug.com/88589.
      version_string = cmd_line.GetSwitchValueNative(switches::kChromeVersion);

      if (!Version(WideToASCII(version_string)).IsValid()) {
        // If a bogus command line flag was given, then abort.
        LOG(ERROR) << "Invalid command line version: " << version_string;
        return NULL;
      }
    }

    // If no version on the command line, then look at the version resource in
    // the current module and try loading that.
    if (version_string.empty())
      version_string = GetCurrentModuleVersion();

    if (version_string.empty()) {
      LOG(ERROR) << "No valid Chrome version found";
      return NULL;
    }

    *out_file = dir;
    *out_version = version_string;
    out_file->append(*out_version).append(1, L'\\');
    dll = LoadChromeWithDirectory(out_file);
    if (!dll) {
      PLOG(ERROR) << "Failed to load Chrome DLL from " << *out_file;
      return NULL;
    }
  }

  DCHECK(dll);

  return dll;
}

// Launching is a matter of loading the right dll, setting the CHROME_VERSION
// environment variable and just calling the entry point. Derived classes can
// add custom code in the OnBeforeLaunch callback.
int MainDllLoader::Launch(HINSTANCE instance,
                          sandbox::SandboxInterfaceInfo* sbox_info) {
  string16 version;
  string16 file;
  dll_ = Load(&version, &file);
  if (!dll_)
    return chrome::RESULT_CODE_MISSING_DATA;

  scoped_ptr<base::Environment> env(base::Environment::Create());
  env->SetVar(chrome::kChromeVersionEnvVar, WideToUTF8(version));
  // TODO(erikwright): Remove this when http://crbug.com/174953 is fixed and
  // widely deployed.
  env->UnSetVar(env_vars::kGoogleUpdateIsMachineEnvVar);

  InitCrashReporter();
  OnBeforeLaunch(file);

  DLL_MAIN entry_point =
      reinterpret_cast<DLL_MAIN>(::GetProcAddress(dll_, "ChromeMain"));
  if (!entry_point)
    return chrome::RESULT_CODE_BAD_PROCESS_TYPE;

  int rc = entry_point(instance, sbox_info);
  return OnBeforeExit(rc, file);
}

void MainDllLoader::RelaunchChromeBrowserWithNewCommandLineIfNeeded() {
  RelaunchChromeBrowserWithNewCommandLineIfNeededFunc relaunch_function =
      reinterpret_cast<RelaunchChromeBrowserWithNewCommandLineIfNeededFunc>(
          ::GetProcAddress(dll_,
                           "RelaunchChromeBrowserWithNewCommandLineIfNeeded"));
  if (!relaunch_function) {
    LOG(ERROR) << "Could not find exported function "
               << "RelaunchChromeBrowserWithNewCommandLineIfNeeded";
  } else {
    relaunch_function();
  }
}

//=============================================================================

class ChromeDllLoader : public MainDllLoader {
 public:
  virtual string16 GetRegistryPath() {
    string16 key(google_update::kRegPathClients);
    BrowserDistribution* dist = BrowserDistribution::GetDistribution();
    key.append(L"\\").append(dist->GetAppGuid());
    return key;
  }

  virtual void OnBeforeLaunch(const string16& dll_path) {
    RecordDidRun(dll_path);
  }

  virtual int OnBeforeExit(int return_code, const string16& dll_path) {
    // NORMAL_EXIT_CANCEL is used for experiments when the user cancels
    // so we need to reset the did_run signal so omaha does not count
    // this run as active usage.
    if (chrome::RESULT_CODE_NORMAL_EXIT_CANCEL == return_code) {
      ClearDidRun(dll_path);
    }
    return return_code;
  }
};

//=============================================================================

class ChromiumDllLoader : public MainDllLoader {
 public:
  virtual string16 GetRegistryPath() {
    BrowserDistribution* dist = BrowserDistribution::GetDistribution();
    return dist->GetVersionKey();
  }
};

MainDllLoader* MakeMainDllLoader() {
#if defined(GOOGLE_CHROME_BUILD)
  return new ChromeDllLoader();
#else
  return new ChromiumDllLoader();
#endif
}