// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_TRANSLATE_CORE_LANGUAGE_DETECTION_LANGUAGE_DETECTION_MODEL_H_
#define COMPONENTS_TRANSLATE_CORE_LANGUAGE_DETECTION_LANGUAGE_DETECTION_MODEL_H_

#include <memory>
#include <string>
#include <string_view>

#include "base/files/file.h"
#include "build/build_config.h"
#include "components/language_detection/core/language_detection_model.h"
#include "partition_alloc/pointers/raw_ref.h"

namespace translate {

// Exposed for testing.

// The number of characters to sample and provide as a buffer to the model
// for determining its language.
inline constexpr size_t kTextSampleLength = 256;

// The number of samples of |kTextSampleLength| to evaluate the model when
// determining the language of the page content.
inline constexpr int kNumTextSamples = 3;

// A language detection model that will use a TFLite model to determine the
// language of the content of the web page.
class LanguageDetectionModel {
 public:
  explicit LanguageDetectionModel(
      language_detection::LanguageDetectionModel& shared_tflite_model);
  explicit LanguageDetectionModel(
      std::unique_ptr<language_detection::LanguageDetectionModel>
          owned_tflite_model);
  ~LanguageDetectionModel();

  // Updates the language detection model for use by memory-mapping
  // |model_file| used to detect the language of the page.
  //
  // This method is blocking and should only be called in context where
  // it is valid to block the current thread. If this is not the case,
  // use UpdateWithFileAsync(...) instead.
  void UpdateWithFile(base::File model_file);

  // Asynchronously updates the language detection model for use by
  // memory-mapping |model_file| used to detect the language of the
  // page and invokes |callback| when the update is done.
  void UpdateWithFileAsync(base::File model_file, base::OnceClosure callback);

  // Returns whether |this| is initialized and is available to handle requests
  // to determine the language of the page.
  bool IsAvailable() const;

  // Determines content page language from Content-Language code and contents.
  // Returns the contents language results in |predicted_language|,
  // |is_prediction_reliable|, and |prediction_reliability_score|.
  std::string DeterminePageLanguage(std::string_view code,
                                    std::string_view html_lang,
                                    const std::u16string& contents,
                                    std::string* predicted_language,
                                    bool* is_prediction_reliable,
                                    float& prediction_reliability_score) const;

  language_detection::Prediction DetectLanguage(
      const std::u16string& contents) const;

  std::string GetModelVersion() const;

  language_detection::LanguageDetectionModel& tflite_model() {
    return *tflite_model_;
  }

 private:
  // The tflite classifier that can determine the language of text.
  std::unique_ptr<language_detection::LanguageDetectionModel>
      owned_tflite_model_;
  const raw_ref<language_detection::LanguageDetectionModel> tflite_model_;
};

}  // namespace translate
#endif  // COMPONENTS_TRANSLATE_CORE_LANGUAGE_DETECTION_LANGUAGE_DETECTION_MODEL_H_