// Copyright (c) 2010 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 "base/file_util.h"
#include "base/logging.h"
#include "base/path_service.h"
#include "base/process_util.h"
#include "base/singleton.h"
#include "base/string16.h"
#include "base/string_util.h"
#include "base/utf_string_conversions.h"
#include "base/version.h"
#include "chrome/common/chrome_constants.h"
#include "chrome/common/chrome_paths.h"
#include "chrome/common/chrome_version_info.h"
#include "chrome/common/service_process_util.h"

namespace {

// This should be more than enough to hold a version string assuming each part
// of the version string is an int64.
const uint32 kMaxVersionStringLength = 256;

// The structure that gets written to shared memory.
struct ServiceProcessSharedData {
  char service_process_version[kMaxVersionStringLength];
  base::ProcessId service_process_pid;
};

// Gets the name of the shared memory used by the service process to write its
// version. The name is not versioned.
std::string GetServiceProcessSharedMemName() {
  return GetServiceProcessScopedName("_service_shmem");
}

// Reads the named shared memory to get the shared data. Returns false if no
// matching shared memory was found.
bool GetServiceProcessSharedData(std::string* version, base::ProcessId* pid) {
  scoped_ptr<base::SharedMemory> shared_mem_service_data;
  shared_mem_service_data.reset(new base::SharedMemory());
  ServiceProcessSharedData* service_data = NULL;
  if (shared_mem_service_data.get() &&
      shared_mem_service_data->Open(GetServiceProcessSharedMemName(), true) &&
      shared_mem_service_data->Map(sizeof(ServiceProcessSharedData))) {
    service_data = reinterpret_cast<ServiceProcessSharedData*>(
        shared_mem_service_data->memory());
    // Make sure the version in shared memory is null-terminated. If it is not,
    // treat it as invalid.
    if (version && memchr(service_data->service_process_version, '\0',
                          sizeof(service_data->service_process_version)))
      *version = service_data->service_process_version;
    if (pid)
      *pid = service_data->service_process_pid;
    return true;
  }
  return false;
}

enum ServiceProcessRunningState {
  SERVICE_NOT_RUNNING,
  SERVICE_OLDER_VERSION_RUNNING,
  SERVICE_SAME_VERSION_RUNNING,
  SERVICE_NEWER_VERSION_RUNNING,
};

ServiceProcessRunningState GetServiceProcessRunningState(
    std::string* service_version_out) {
  std::string version;
  GetServiceProcessSharedData(&version, NULL);
  if (version.empty())
    return SERVICE_NOT_RUNNING;

  // At this time we have a version string. Set the out param if it exists.
  if (service_version_out)
    *service_version_out = version;

  scoped_ptr<Version> service_version(Version::GetVersionFromString(version));
  // If the version string is invalid, treat it like an older version.
  if (!service_version.get())
    return SERVICE_OLDER_VERSION_RUNNING;

  // Get the version of the currently *running* instance of Chrome.
  chrome::VersionInfo version_info;
  if (!version_info.is_valid()) {
    NOTREACHED() << "Failed to get current file version";
    // Our own version is invalid. This is an error case. Pretend that we
    // are out of date.
    return SERVICE_NEWER_VERSION_RUNNING;
  }
  scoped_ptr<Version> running_version(Version::GetVersionFromString(
      version_info.Version()));
  if (!running_version.get()) {
    NOTREACHED() << "Failed to parse version info";
    // Our own version is invalid. This is an error case. Pretend that we
    // are out of date.
    return SERVICE_NEWER_VERSION_RUNNING;
  }

  if (running_version->CompareTo(*service_version) > 0) {
    return SERVICE_OLDER_VERSION_RUNNING;
  } else if (service_version->CompareTo(*running_version) > 0) {
    return SERVICE_NEWER_VERSION_RUNNING;
  }
  return SERVICE_SAME_VERSION_RUNNING;
}


}  // namespace

// Return a name that is scoped to this instance of the service process. We
// use the user-data-dir as a scoping prefix.
std::string GetServiceProcessScopedName(const std::string& append_str) {
  FilePath user_data_dir;
  PathService::Get(chrome::DIR_USER_DATA, &user_data_dir);
#if defined(OS_WIN)
  std::string scoped_name = WideToUTF8(user_data_dir.value());
#elif defined(OS_POSIX)
  std::string scoped_name = user_data_dir.value();
#endif  // defined(OS_WIN)
  std::replace(scoped_name.begin(), scoped_name.end(), '\\', '!');
  std::replace(scoped_name.begin(), scoped_name.end(), '/', '!');
  scoped_name.append(append_str);
  return scoped_name;
}

// Return a name that is scoped to this instance of the service process. We
// use the user-data-dir and the version as a scoping prefix.
std::string GetServiceProcessScopedVersionedName(
    const std::string& append_str) {
  std::string versioned_str;
  chrome::VersionInfo version_info;
  DCHECK(version_info.is_valid());
  versioned_str.append(version_info.Version());
  versioned_str.append(append_str);
  return GetServiceProcessScopedName(versioned_str);
}

// Gets the name of the service process IPC channel.
std::string GetServiceProcessChannelName() {
  return GetServiceProcessScopedVersionedName("_service_ipc");
}

base::ProcessId GetServiceProcessPid() {
  base::ProcessId pid = 0;
  GetServiceProcessSharedData(NULL, &pid);
  return pid;
}

ServiceProcessState::ServiceProcessState() : state_(NULL) {
}

ServiceProcessState::~ServiceProcessState() {
  TearDownState();
}

// static
ServiceProcessState* ServiceProcessState::GetInstance() {
  return Singleton<ServiceProcessState>::get();
}

bool ServiceProcessState::Initialize() {
  if (!TakeSingletonLock()) {
    return false;
  }
  // Now that we have the singleton, take care of killing an older version, if
  // it exists.
  if (ShouldHandleOtherVersion() && !HandleOtherVersion())
    return false;

  // TODO(sanjeevr): We can probably use the shared mem as the sole singleton
  // mechanism. For that the shared mem class needs to return whether it created
  // new instance or opened an existing one. Also shared memory on Linux uses
  // a file on disk which is not deleted when the process exits.

  // Now that we have the singleton, let is also write the version we are using
  // to shared memory. This can be used by a newer service to signal us to exit.
  return CreateSharedData();
}

bool ServiceProcessState::HandleOtherVersion() {
  std::string running_version;
  ServiceProcessRunningState state =
      GetServiceProcessRunningState(&running_version);
  switch (state) {
    case SERVICE_SAME_VERSION_RUNNING:
    case SERVICE_NEWER_VERSION_RUNNING:
      return false;
    case SERVICE_OLDER_VERSION_RUNNING:
      // If an older version is running, kill it.
      ForceServiceProcessShutdown(running_version);
      break;
    case SERVICE_NOT_RUNNING:
      break;
  }
  return true;
}

bool ServiceProcessState::CreateSharedData() {
  chrome::VersionInfo version_info;
  if (!version_info.is_valid()) {
    NOTREACHED() << "Failed to get current file version";
    return false;
  }
  if (version_info.Version().length() >= kMaxVersionStringLength) {
    NOTREACHED() << "Version string length is << " <<
        version_info.Version().length() << "which is longer than" <<
        kMaxVersionStringLength;
    return false;
  }

  scoped_ptr<base::SharedMemory> shared_mem_service_data;
  shared_mem_service_data.reset(new base::SharedMemory());
  if (!shared_mem_service_data.get())
    return false;

  uint32 alloc_size = sizeof(ServiceProcessSharedData);
  if (!shared_mem_service_data->CreateNamed(GetServiceProcessSharedMemName(),
                                            true, alloc_size))
    return false;

  if (!shared_mem_service_data->Map(alloc_size))
    return false;

  memset(shared_mem_service_data->memory(), 0, alloc_size);
  ServiceProcessSharedData* shared_data =
      reinterpret_cast<ServiceProcessSharedData*>(
          shared_mem_service_data->memory());
  memcpy(shared_data->service_process_version, version_info.Version().c_str(),
         version_info.Version().length());
  shared_data->service_process_pid = base::GetCurrentProcId();
  shared_mem_service_data_.reset(shared_mem_service_data.release());
  return true;
}


std::string ServiceProcessState::GetAutoRunKey() {
  return GetServiceProcessScopedName("_service_run");
}