// 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/renderer/translate_helper.h"

#include "base/compiler_specific.h"
#include "base/message_loop.h"
#include "base/metrics/histogram.h"
#include "base/utf_string_conversions.h"
#include "chrome/common/chrome_constants.h"
#include "chrome/common/render_messages.h"
#include "chrome/renderer/autofill/autofill_agent.h"
#include "content/renderer/render_view.h"
#include "third_party/WebKit/Source/WebKit/chromium/public/WebDocument.h"
#include "third_party/WebKit/Source/WebKit/chromium/public/WebElement.h"
#include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
#include "third_party/WebKit/Source/WebKit/chromium/public/WebScriptSource.h"
#include "third_party/WebKit/Source/WebKit/chromium/public/WebView.h"
#include "third_party/cld/encodings/compact_lang_det/win/cld_unicodetext.h"
#include "v8/include/v8.h"
#include "webkit/glue/dom_operations.h"

using WebKit::WebDocument;
using WebKit::WebElement;
using WebKit::WebFrame;
using WebKit::WebScriptSource;
using WebKit::WebString;
using WebKit::WebView;

// The delay in millliseconds that we'll wait before checking to see if the
// translate library injected in the page is ready.
static const int kTranslateInitCheckDelayMs = 150;

// The maximum number of times we'll check to see if the translate library
// injected in the page is ready.
static const int kMaxTranslateInitCheckAttempts = 5;

// The delay we wait in milliseconds before checking whether the translation has
// finished.
static const int kTranslateStatusCheckDelayMs = 400;

// Language name passed to the Translate element for it to detect the language.
static const char* const kAutoDetectionLanguage = "auto";

////////////////////////////////////////////////////////////////////////////////
// TranslateHelper, public:
//
TranslateHelper::TranslateHelper(RenderView* render_view,
                                 autofill::AutofillAgent* autofill)
    : RenderViewObserver(render_view),
      translation_pending_(false),
      page_id_(-1),
      autofill_(autofill),
      ALLOW_THIS_IN_INITIALIZER_LIST(method_factory_(this)) {
}

TranslateHelper::~TranslateHelper() {
}

void TranslateHelper::PageCaptured(const string16& contents) {
  WebDocument document = render_view()->webview()->mainFrame()->document();
  // If the page explicitly specifies a language, use it, otherwise we'll
  // determine it based on the text content using the CLD.
  std::string language = GetPageLanguageFromMetaTag(&document);
  if (language.empty()) {
    base::TimeTicks begin_time = base::TimeTicks::Now();
    language = DetermineTextLanguage(contents);
    UMA_HISTOGRAM_MEDIUM_TIMES("Renderer4.LanguageDetection",
                               base::TimeTicks::Now() - begin_time);
  }

  Send(new ViewHostMsg_TranslateLanguageDetermined(
      routing_id(), language, IsPageTranslatable(&document)));
}

void TranslateHelper::CancelPendingTranslation() {
  method_factory_.RevokeAll();
  translation_pending_ = false;
  page_id_ = -1;
  source_lang_.clear();
  target_lang_.clear();
}

// static
bool TranslateHelper::IsPageTranslatable(WebDocument* document) {
  std::vector<WebElement> meta_elements;
  webkit_glue::GetMetaElementsWithAttribute(document,
                                            ASCIIToUTF16("name"),
                                            ASCIIToUTF16("google"),
                                            &meta_elements);
  std::vector<WebElement>::const_iterator iter;
  for (iter = meta_elements.begin(); iter != meta_elements.end(); ++iter) {
    WebString attribute = iter->getAttribute("value");
    if (attribute.isNull())  // We support both 'value' and 'content'.
      attribute = iter->getAttribute("content");
    if (attribute.isNull())
      continue;
    if (LowerCaseEqualsASCII(attribute, "notranslate"))
      return false;
  }
  return true;
}

// static
std::string TranslateHelper::GetPageLanguageFromMetaTag(WebDocument* document) {
  // The META language tag looks like:
  // <meta http-equiv="content-language" content="en">
  // It can contain more than one language:
  // <meta http-equiv="content-language" content="en, fr">
  std::vector<WebElement> meta_elements;
  webkit_glue::GetMetaElementsWithAttribute(document,
                                            ASCIIToUTF16("http-equiv"),
                                            ASCIIToUTF16("content-language"),
                                            &meta_elements);
  if (meta_elements.empty())
    return std::string();

  // We don't expect more than one such tag. If there are several, just use the
  // first one.
  WebString attribute = meta_elements[0].getAttribute("content");
  if (attribute.isEmpty())
    return std::string();

  // The value is supposed to be ASCII.
  if (!IsStringASCII(attribute))
    return std::string();

  std::string language = StringToLowerASCII(UTF16ToASCII(attribute));
  size_t coma_index = language.find(',');
  if (coma_index != std::string::npos) {
    // There are more than 1 language specified, just keep the first one.
    language = language.substr(0, coma_index);
  }
  TrimWhitespaceASCII(language, TRIM_ALL, &language);
  return language;
}

// static
std::string TranslateHelper::DetermineTextLanguage(const string16& text) {
  std::string language = chrome::kUnknownLanguageCode;
  int num_languages = 0;
  int text_bytes = 0;
  bool is_reliable = false;
  Language cld_language =
      DetectLanguageOfUnicodeText(NULL, text.c_str(), true, &is_reliable,
                                  &num_languages, NULL, &text_bytes);
  // We don't trust the result if the CLD reports that the detection is not
  // reliable, or if the actual text used to detect the language was less than
  // 100 bytes (short texts can often lead to wrong results).
  if (is_reliable && text_bytes >= 100 && cld_language != NUM_LANGUAGES &&
      cld_language != UNKNOWN_LANGUAGE && cld_language != TG_UNKNOWN_LANGUAGE) {
    // We should not use LanguageCode_ISO_639_1 because it does not cover all
    // the languages CLD can detect. As a result, it'll return the invalid
    // language code for tradtional Chinese among others.
    // |LanguageCodeWithDialect| will go through ISO 639-1, ISO-639-2 and
    // 'other' tables to do the 'right' thing. In addition, it'll return zh-CN
    // for Simplified Chinese.
    language = LanguageCodeWithDialects(cld_language);
  }
  return language;
}

////////////////////////////////////////////////////////////////////////////////
// TranslateHelper, protected:
//
bool TranslateHelper::IsTranslateLibAvailable() {
  bool lib_available = false;
  if (!ExecuteScriptAndGetBoolResult(
      "typeof cr != 'undefined' && typeof cr.googleTranslate != 'undefined' && "
      "typeof cr.googleTranslate.translate == 'function'", &lib_available)) {
    NOTREACHED();
    return false;
  }
  return lib_available;
}

bool TranslateHelper::IsTranslateLibReady() {
  bool lib_ready = false;
  if (!ExecuteScriptAndGetBoolResult("cr.googleTranslate.libReady",
                                     &lib_ready)) {
    NOTREACHED();
    return false;
  }
  return lib_ready;
}

bool TranslateHelper::HasTranslationFinished() {
  bool translation_finished = false;
  if (!ExecuteScriptAndGetBoolResult("cr.googleTranslate.finished",
                                     &translation_finished)) {
    NOTREACHED() << "crGoogleTranslateGetFinished returned unexpected value.";
    return true;
  }

  return translation_finished;
}

bool TranslateHelper::HasTranslationFailed() {
  bool translation_failed = false;
  if (!ExecuteScriptAndGetBoolResult("cr.googleTranslate.error",
                                     &translation_failed)) {
    NOTREACHED() << "crGoogleTranslateGetError returned unexpected value.";
    return true;
  }

  return translation_failed;
}

bool TranslateHelper::StartTranslation() {
  bool translate_success = false;
  if (!ExecuteScriptAndGetBoolResult("cr.googleTranslate.translate('" +
                                     source_lang_ + "','" + target_lang_ + "')",
                                     &translate_success)) {
    NOTREACHED();
    return false;
  }
  return translate_success;
}

std::string TranslateHelper::GetOriginalPageLanguage() {
  std::string lang;
  ExecuteScriptAndGetStringResult("cr.googleTranslate.sourceLang", &lang);
  return lang;
}

bool TranslateHelper::DontDelayTasks() {
  return false;
}

////////////////////////////////////////////////////////////////////////////////
// TranslateHelper, private:
//

bool TranslateHelper::OnMessageReceived(const IPC::Message& message) {
  bool handled = true;
  IPC_BEGIN_MESSAGE_MAP(TranslateHelper, message)
    IPC_MESSAGE_HANDLER(ViewMsg_TranslatePage, OnTranslatePage)
    IPC_MESSAGE_HANDLER(ViewMsg_RevertTranslation, OnRevertTranslation)
    IPC_MESSAGE_UNHANDLED(handled = false)
  IPC_END_MESSAGE_MAP()
  return handled;
}

void TranslateHelper::OnTranslatePage(int page_id,
                                      const std::string& translate_script,
                                      const std::string& source_lang,
                                      const std::string& target_lang) {
  if (render_view()->page_id() != page_id)
    return;  // We navigated away, nothing to do.

  if (translation_pending_ && page_id == page_id_ &&
      target_lang_ == target_lang) {
    // A similar translation is already under way, nothing to do.
    return;
  }

  // Any pending translation is now irrelevant.
  CancelPendingTranslation();

  // Set our states.
  translation_pending_ = true;
  page_id_ = page_id;
  // If the source language is undetermined, we'll let the translate element
  // detect it.
  source_lang_ = (source_lang != chrome::kUnknownLanguageCode) ?
                  source_lang : kAutoDetectionLanguage;
  target_lang_ = target_lang;

  if (!IsTranslateLibAvailable()) {
    // Evaluate the script to add the translation related method to the global
    // context of the page.
    ExecuteScript(translate_script);
    DCHECK(IsTranslateLibAvailable());
  }

  TranslatePageImpl(0);
}

void TranslateHelper::OnRevertTranslation(int page_id) {
  if (render_view()->page_id() != page_id)
    return;  // We navigated away, nothing to do.

  if (!IsTranslateLibAvailable()) {
    NOTREACHED();
    return;
  }

  WebFrame* main_frame = GetMainFrame();
  if (!main_frame)
    return;

  CancelPendingTranslation();

  main_frame->executeScript(
      WebScriptSource(ASCIIToUTF16("cr.googleTranslate.revert()")));
}

void TranslateHelper::CheckTranslateStatus() {
  // If this is not the same page, the translation has been canceled.  If the
  // view is gone, the page is closing.
  if (page_id_ != render_view()->page_id() || !render_view()->webview())
    return;

  // First check if there was an error.
  if (HasTranslationFailed()) {
    NotifyBrowserTranslationFailed(TranslateErrors::TRANSLATION_ERROR);
    return;  // There was an error.
  }

  if (HasTranslationFinished()) {
    std::string actual_source_lang;
    // Translation was successfull, if it was auto, retrieve the source
    // language the Translate Element detected.
    if (source_lang_ == kAutoDetectionLanguage) {
      actual_source_lang = GetOriginalPageLanguage();
      if (actual_source_lang.empty()) {
        NotifyBrowserTranslationFailed(TranslateErrors::UNKNOWN_LANGUAGE);
        return;
      } else if (actual_source_lang == target_lang_) {
        NotifyBrowserTranslationFailed(TranslateErrors::IDENTICAL_LANGUAGES);
        return;
      }
    } else {
      actual_source_lang = source_lang_;
    }

    if (!translation_pending_) {
      NOTREACHED();
      return;
    }

    translation_pending_ = false;

    if (autofill_)
      autofill_->FrameTranslated(render_view()->webview()->mainFrame());

    // Notify the browser we are done.
    render_view()->Send(new ViewHostMsg_PageTranslated(
        render_view()->routing_id(), render_view()->page_id(),
        actual_source_lang, target_lang_, TranslateErrors::NONE));
    return;
  }

  // The translation is still pending, check again later.
  MessageLoop::current()->PostDelayedTask(FROM_HERE,
      method_factory_.NewRunnableMethod(&TranslateHelper::CheckTranslateStatus),
      DontDelayTasks() ? 0 : kTranslateStatusCheckDelayMs);
}

bool TranslateHelper::ExecuteScript(const std::string& script) {
  WebFrame* main_frame = GetMainFrame();
  if (!main_frame)
    return false;
  main_frame->executeScript(WebScriptSource(ASCIIToUTF16(script)));
  return true;
}

bool TranslateHelper::ExecuteScriptAndGetBoolResult(const std::string& script,
                                                    bool* value) {
  DCHECK(value);
  WebFrame* main_frame = GetMainFrame();
  if (!main_frame)
    return false;

  v8::Handle<v8::Value> v = main_frame->executeScriptAndReturnValue(
      WebScriptSource(ASCIIToUTF16(script)));
  if (v.IsEmpty() || !v->IsBoolean())
    return false;

  *value = v->BooleanValue();
  return true;
}

bool TranslateHelper::ExecuteScriptAndGetStringResult(const std::string& script,
                                                      std::string* value) {
  DCHECK(value);
  WebFrame* main_frame = GetMainFrame();
  if (!main_frame)
    return false;

  v8::Handle<v8::Value> v = main_frame->executeScriptAndReturnValue(
      WebScriptSource(ASCIIToUTF16(script)));
  if (v.IsEmpty() || !v->IsString())
    return false;

  v8::Local<v8::String> v8_str = v->ToString();
  int length = v8_str->Utf8Length() + 1;
  scoped_array<char> str(new char[length]);
  v8_str->WriteUtf8(str.get(), length);
  *value = str.get();
  return true;
}

void TranslateHelper::TranslatePageImpl(int count) {
  DCHECK_LT(count, kMaxTranslateInitCheckAttempts);
  if (page_id_ != render_view()->page_id() || !render_view()->webview())
    return;

  if (!IsTranslateLibReady()) {
    // The library is not ready, try again later, unless we have tried several
    // times unsucessfully already.
    if (++count >= kMaxTranslateInitCheckAttempts) {
      NotifyBrowserTranslationFailed(TranslateErrors::INITIALIZATION_ERROR);
      return;
    }
    MessageLoop::current()->PostDelayedTask(FROM_HERE,
        method_factory_.NewRunnableMethod(&TranslateHelper::TranslatePageImpl,
                                          count),
        DontDelayTasks() ? 0 : count * kTranslateInitCheckDelayMs);
    return;
  }

  if (!StartTranslation()) {
    NotifyBrowserTranslationFailed(TranslateErrors::TRANSLATION_ERROR);
    return;
  }
  // Check the status of the translation.
  MessageLoop::current()->PostDelayedTask(FROM_HERE,
      method_factory_.NewRunnableMethod(&TranslateHelper::CheckTranslateStatus),
      DontDelayTasks() ? 0 : kTranslateStatusCheckDelayMs);
}

void TranslateHelper::NotifyBrowserTranslationFailed(
    TranslateErrors::Type error) {
  translation_pending_ = false;
  // Notify the browser there was an error.
  render_view()->Send(new ViewHostMsg_PageTranslated(
      render_view()->routing_id(), page_id_, source_lang_, target_lang_, error));
}

WebFrame* TranslateHelper::GetMainFrame() {
  WebView* web_view = render_view()->webview();
  if (!web_view) {
    // When the WebView is going away, the render view should have called
    // CancelPendingTranslation() which should have stopped any pending work, so
    // that case should not happen.
    NOTREACHED();
    return NULL;
  }
  return web_view->mainFrame();
}