// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "services/screen_ai/public/cpp/metrics.h"

#include <map>
#include <string>
#include <vector>

#include "base/i18n/language_tag.h"
#include "base/i18n/tag_converters.h"
#include "base/metrics/histogram_functions.h"
#include "base/metrics/metrics_hashes.h"
#include "base/strings/string_split.h"
#include "base/strings/string_util.h"

namespace screen_ai {

using ::base::i18n::GetKnownLanguageTag;
using ::base::i18n::LanguageTag;
using ::base::i18n::LanguageTagConverter;

std::optional<uint64_t> GetMostDetectedLanguageInOcrData(
    const chrome_screen_ai::VisualAnnotation& ocr_data) {
  if (ocr_data.lines().empty()) {
    return std::nullopt;
  }

  // Count each detected language.
  std::map<std::string, size_t> detected_language_count_map;
  for (const auto& line : ocr_data.lines()) {
    for (const auto& word : line.words()) {
      if (word.language().size()) {
        detected_language_count_map[word.language()]++;
      }
    }
  }

  // Get the most detected language.
  std::string most_detected_language;
  size_t most_detected_language_count = 0u;
  for (const auto& elem : detected_language_count_map) {
    if (elem.second > most_detected_language_count) {
      most_detected_language = elem.first;
      most_detected_language_count = elem.second;
    }
  }

  if (most_detected_language_count == 0u) {
    return std::nullopt;
  }

  // Convert to a Chrome language code synonym. Then pass it to
  // `base::HashMetricName()` that maps this code to a `LocaleCodeBCP47` enum
  // value expected by this histogram. See tools/metrics/histograms/enums.xml
  // enum LocaleCodeBCP47. The enum there doesn't always have locales where
  // the base lang and the locale are the same (e.g. they don't have id-id, but
  // do have id). So if the base lang and the locale are the same, just use the
  // base lang.
  std::string language_to_log = most_detected_language;
  std::vector<std::string> lang_split =
      base::SplitString(base::ToLowerASCII(language_to_log), "-",
                        base::KEEP_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
  if (lang_split.size() == 2 && lang_split[0] == lang_split[1]) {
    language_to_log = lang_split[0];
  }
  std::optional<LanguageTag> parsed_tag =
      LanguageTagConverter::GetInstance().FromString(language_to_log);
  if (parsed_tag) {
    language_to_log = std::string(parsed_tag->tag_string());
  }
  return base::HashMetricName(language_to_log);
}

}  // namespace screen_ai