// 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 "chrome_frame/simple_resource_loader.h"

#include <algorithm>

#include <atlbase.h>

#include "base/base_paths.h"
#include "base/file_path.h"
#include "base/file_util.h"
#include "base/path_service.h"
#include "base/i18n/file_util_icu.h"
#include "base/i18n/rtl.h"
#include "base/singleton.h"
#include "base/string_util.h"
#include "base/utf_string_conversions.h"
#include "base/win/windows_version.h"

#include "chrome_frame/policy_settings.h"

namespace {

const wchar_t kLocalesDirName[] = L"Locales";

bool IsInvalidTagCharacter(wchar_t tag_character) {
  return !(L'-' == tag_character ||
           IsAsciiDigit(tag_character) ||
           IsAsciiAlpha(tag_character));
}

// A helper function object that performs a lower-case ASCII comparison between
// two strings.
class CompareInsensitiveASCII
    : public std::unary_function<const std::wstring&, bool> {
 public:
  explicit CompareInsensitiveASCII(const std::wstring& value)
      : value_lowered_(WideToASCII(value)) {
    StringToLowerASCII(&value_lowered_);
  }
  bool operator()(const std::wstring& comparand) {
    return LowerCaseEqualsASCII(comparand, value_lowered_.c_str());
  }

 private:
  std::string value_lowered_;
};

// Returns true if the value was added.
bool PushBackIfAbsent(
    const std::wstring& value,
    std::vector<std::wstring>* collection) {
  if (collection->end() ==
      std::find_if(collection->begin(), collection->end(),
                   CompareInsensitiveASCII(value))) {
    collection->push_back(value);
    return true;
  }
  return false;
}

}  // namespace

SimpleResourceLoader::SimpleResourceLoader()
    : locale_dll_handle_(NULL) {
  // Find and load the resource DLL.
  std::vector<std::wstring> language_tags;

  // First, try the locale dictated by policy and its fallback.
  std::wstring application_locale =
      Singleton<PolicySettings>()->ApplicationLocale();
  if (!application_locale.empty()) {
    language_tags.push_back(application_locale);
    std::wstring::size_type dash = application_locale.find(L'-');
    if (std::wstring::npos != dash) {
      if (0 != dash) {
        language_tags.push_back(application_locale.substr(0, dash));
      } else {
        NOTREACHED() << "Group Policy application locale begins with a dash.";
      }
    }
  }

  // Next, try the thread, process, user, system languages.
  GetPreferredLanguages(&language_tags);

  // Finally, fall-back on "en-US" (which may already be present in the vector,
  // but that's okay since we'll exit with success when the first is tried).
  language_tags.push_back(L"en-US");

  FilePath locales_path;
  FilePath locale_dll_path;

  DetermineLocalesDirectory(&locales_path);
  if (LoadLocaleDll(language_tags, locales_path, &locale_dll_handle_,
                    &locale_dll_path)) {
    language_ = locale_dll_path.BaseName().RemoveExtension().value();
  } else {
    NOTREACHED() << "Failed loading any resource dll (even \"en-US\").";
  }
}

SimpleResourceLoader::~SimpleResourceLoader() {
  locale_dll_handle_ = NULL;
}

// static
void SimpleResourceLoader::GetPreferredLanguages(
    std::vector<std::wstring>* language_tags) {
  // The full set of preferred languages and their fallbacks are given priority.
  GetThreadPreferredUILanguages(language_tags);

  // The above gives us nothing pre-Vista, so use ICU to get the system
  // language and add it and its fallback to the end of the list if not present.
  std::wstring language;
  std::wstring region;

  GetICUSystemLanguage(&language, &region);
  if (!region.empty()) {
    std::wstring combined;
    combined.reserve(language.size() + 1 + region.size());
    combined.assign(language).append(L"-").append(region);
    PushBackIfAbsent(combined, language_tags);
  }
  PushBackIfAbsent(language, language_tags);
}

// static
bool SimpleResourceLoader::GetThreadPreferredUILanguages(
    std::vector<std::wstring>* language_tags) {
  typedef BOOL (WINAPI* GetThreadPreferredUILanguages_Fn)(
      DWORD, PULONG, PZZWSTR, PULONG);
  HMODULE kernel32 = GetModuleHandle(L"kernel32.dll");
  DCHECK(kernel32) << "Failed finding kernel32.dll!";
  GetThreadPreferredUILanguages_Fn get_thread_preferred_ui_languages =
      reinterpret_cast<GetThreadPreferredUILanguages_Fn>(
          GetProcAddress(kernel32, "GetThreadPreferredUILanguages"));
  bool have_mui = (NULL != get_thread_preferred_ui_languages);
  if (have_mui) {
    const DWORD kNameAndFallbackFlags =
        MUI_LANGUAGE_NAME | MUI_MERGE_SYSTEM_FALLBACK | MUI_MERGE_USER_FALLBACK;
    ULONG language_count = 0;
    ULONG buffer_length = 0;

    if (get_thread_preferred_ui_languages(
            kNameAndFallbackFlags,
            &language_count,
            NULL,
            &buffer_length) && 0 != buffer_length) {
      std::vector<wchar_t> language_names(buffer_length);

      if (get_thread_preferred_ui_languages(
              kNameAndFallbackFlags,
              &language_count,
              &language_names[0],
              &buffer_length)) {
        std::vector<wchar_t>::const_iterator scan = language_names.begin();
        std::wstring language(&*scan);
        while (!language.empty()) {
          language_tags->push_back(language);
          scan += language.size() + 1;
          language.assign(&*scan);
        }
      }
    }
  }
  return have_mui;
}

// static
void SimpleResourceLoader::GetICUSystemLanguage(std::wstring* language,
                                                std::wstring* region) {
  DCHECK(language);
  DCHECK(region);

  std::string icu_language, icu_region;
  base::i18n::GetLanguageAndRegionFromOS(&icu_language, &icu_region);
  if (!icu_language.empty()) {
    *language = ASCIIToWide(icu_language);
  } else {
    language->clear();
  }
  if (!icu_region.empty()) {
    *region = ASCIIToWide(icu_region);
  } else {
    region->clear();
  }
}

// static
void SimpleResourceLoader::DetermineLocalesDirectory(FilePath* locales_path) {
  DCHECK(locales_path);

  FilePath module_path;
  PathService::Get(base::DIR_MODULE, &module_path);
  *locales_path = module_path.Append(kLocalesDirName);

  // We may be residing in the "locales" directory's parent, or we might be
  // in a sibling directory. Move up one and look for Locales again in the
  // latter case.
  if (!file_util::DirectoryExists(*locales_path)) {
    *locales_path = module_path.DirName();
    *locales_path = locales_path->Append(kLocalesDirName);
  }

  // Don't make a second check to see if the dir is in the parent.  We'll notice
  // and log that in LoadLocaleDll when we actually try loading DLLs.
}

// static
bool SimpleResourceLoader::IsValidLanguageTag(
    const std::wstring& language_tag) {
  // "[a-zA-Z]+(-[a-zA-Z0-9]+)*" is a simplification, but better than nothing.
  // Rather than pick up the weight of a regex processor, just search for a
  // character that isn't in the above set.  This will at least weed out
  // attempts at "../../EvilBinary".
  return language_tag.end() == std::find_if(language_tag.begin(),
                                            language_tag.end(),
                                            &IsInvalidTagCharacter);
}

// static
bool SimpleResourceLoader::LoadLocaleDll(
    const std::vector<std::wstring>& language_tags,
    const FilePath& locales_path,
    HMODULE* dll_handle,
    FilePath* file_path) {
  DCHECK(file_path);

  // The dll should only have resources, not executable code.
  const DWORD load_flags =
      (base::win::GetVersion() >= base::win::VERSION_VISTA ?
          LOAD_LIBRARY_AS_DATAFILE_EXCLUSIVE | LOAD_LIBRARY_AS_IMAGE_RESOURCE :
          DONT_RESOLVE_DLL_REFERENCES);
  const std::wstring dll_suffix(L".dll");
  bool found_dll = false;

  for (std::vector<std::wstring>::const_iterator scan = language_tags.begin(),
         end = language_tags.end();
       scan != end;
       ++scan) {
    if (!IsValidLanguageTag(*scan)) {
      LOG(WARNING) << "Invalid language tag supplied while locating resources:"
                      " \"" << *scan << "\"";
      continue;
    }
    FilePath look_path = locales_path.Append(*scan + dll_suffix);
    HMODULE locale_dll_handle = LoadLibraryEx(look_path.value().c_str(), NULL,
                                              load_flags);
    if (NULL != locale_dll_handle) {
      *dll_handle = locale_dll_handle;
      *file_path = look_path;
      found_dll = true;
      break;
    }
    DPCHECK(ERROR_FILE_NOT_FOUND == GetLastError())
        << "Unable to load generated resources from " << look_path.value();
  }

  DCHECK(found_dll || file_util::DirectoryExists(locales_path))
      << "Could not locate locales DLL directory.";

  return found_dll;
}

std::wstring SimpleResourceLoader::GetLocalizedResource(int message_id) {
  if (!locale_dll_handle_) {
    DLOG(ERROR) << "locale resources are not loaded";
    return std::wstring();
  }

  DCHECK(IS_INTRESOURCE(message_id));

  const ATLSTRINGRESOURCEIMAGE* image = AtlGetStringResourceImage(
      locale_dll_handle_, message_id);
  if (!image) {
    // Fall back on the current module (shouldn't be any strings here except
    // in unittests).
    image = AtlGetStringResourceImage(_AtlBaseModule.GetModuleInstance(),
                                      message_id);
    if (!image) {
      NOTREACHED() << "unable to find resource: " << message_id;
      return std::wstring();
    }
  }
  return std::wstring(image->achString, image->nLength);
}

// static
std::wstring SimpleResourceLoader::GetLanguage() {
  return SimpleResourceLoader::instance()->language_;
}

// static
std::wstring SimpleResourceLoader::Get(int message_id) {
  SimpleResourceLoader* loader = SimpleResourceLoader::instance();
  return loader->GetLocalizedResource(message_id);
}

HMODULE SimpleResourceLoader::GetResourceModuleHandle() {
  return locale_dll_handle_;
}