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// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/language/core/browser/url_language_histogram.h"
#include <algorithm>
#include <map>
#include <set>
#include "components/prefs/pref_registry.h"
#include "components/prefs/pref_registry_simple.h"
#include "components/prefs/pref_service.h"
#include "components/prefs/scoped_user_pref_update.h"
namespace language {
namespace {
const char kUrlLanguageHistogramCounters[] = "language_model_counters";
const int kMaxCountersSum = 1000;
const int kMinCountersSum = 10;
const float kCutoffRatio = 0.005f;
const float kDiscountFactor = 0.75f;
// Gets the sum of the counter for all languages in the histogram.
int GetCountersSum(const base::Value::Dict& dict) {
int sum = 0;
for (const auto itr : dict) {
if (itr.second.is_int())
sum += itr.second.GetInt();
}
return sum;
}
// Removes languages with small counter values and discount remaining counters.
void DiscountAndCleanCounters(base::Value::Dict& dict) {
std::set<std::string> remove_keys;
for (const auto itr : dict) {
// Remove languages with invalid or small values.
if (!itr.second.is_int() ||
itr.second.GetInt() < (kCutoffRatio * kMaxCountersSum)) {
remove_keys.insert(itr.first);
continue;
}
// Discount the value.
dict.Set(itr.first, int(itr.second.GetInt() * kDiscountFactor));
}
for (const std::string& lang_to_remove : remove_keys)
dict.Remove(lang_to_remove);
}
// Transforms the counters from prefs into a list of LanguageInfo structs.
std::vector<UrlLanguageHistogram::LanguageInfo> GetAllLanguages(
const base::Value::Dict& dict) {
int counters_sum = GetCountersSum(dict);
// If the sample is not large enough yet, pretend there are no top languages.
if (counters_sum < kMinCountersSum)
return std::vector<UrlLanguageHistogram::LanguageInfo>();
std::vector<UrlLanguageHistogram::LanguageInfo> top_languages;
for (const auto itr : dict) {
if (!itr.second.is_int())
continue;
top_languages.emplace_back(
itr.first, static_cast<float>(itr.second.GetInt()) / counters_sum);
}
return top_languages;
}
} // namespace
UrlLanguageHistogram::UrlLanguageHistogram(PrefService* pref_service)
: pref_service_(pref_service) {}
UrlLanguageHistogram::~UrlLanguageHistogram() = default;
// static
void UrlLanguageHistogram::RegisterProfilePrefs(PrefRegistrySimple* registry) {
registry->RegisterDictionaryPref(kUrlLanguageHistogramCounters,
PrefRegistry::LOSSY_PREF);
}
std::vector<UrlLanguageHistogram::LanguageInfo>
UrlLanguageHistogram::GetTopLanguages() const {
std::vector<UrlLanguageHistogram::LanguageInfo> top_languages =
GetAllLanguages(pref_service_->GetDict(kUrlLanguageHistogramCounters));
std::sort(top_languages.begin(), top_languages.end(),
[](const UrlLanguageHistogram::LanguageInfo& a,
const UrlLanguageHistogram::LanguageInfo& b) {
return a.frequency > b.frequency;
});
return top_languages;
}
float UrlLanguageHistogram::GetLanguageFrequency(
const std::string& language_code) const {
const base::Value::Dict& dict =
pref_service_->GetDict(kUrlLanguageHistogramCounters);
int counters_sum = GetCountersSum(dict);
// If the sample is not large enough yet, pretend there are no top languages.
if (counters_sum < kMinCountersSum)
return 0;
// If the key |language_code| does not exist, |counter_value| stays 0.
int counter_value = dict.FindInt(language_code).value_or(0);
return static_cast<float>(counter_value) / counters_sum;
}
void UrlLanguageHistogram::OnPageVisited(const std::string& language_code) {
ScopedDictPrefUpdate update(pref_service_, kUrlLanguageHistogramCounters);
base::Value::Dict& dict = update.Get();
// If the key |language_code| does not exist, |counter_value| stays 0.
int counter_value = dict.FindInt(language_code).value_or(0);
dict.Set(language_code, counter_value + 1);
if (GetCountersSum(dict) > kMaxCountersSum)
DiscountAndCleanCounters(dict);
}
void UrlLanguageHistogram::ClearHistory(base::Time begin, base::Time end) {
// Ignore all partial removals and react only to "entire" history removal.
bool is_entire_history = (begin == base::Time() && end == base::Time::Max());
if (!is_entire_history) {
return;
}
pref_service_->ClearPref(kUrlLanguageHistogramCounters);
}
} // namespace language
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