components/webapps/isolated_web_apps/error/uma_logging.h

// Copyright 2023 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_WEBAPPS_ISOLATED_WEB_APPS_ERROR_UMA_LOGGING_H_
#define COMPONENTS_WEBAPPS_ISOLATED_WEB_APPS_ERROR_UMA_LOGGING_H_

#include <string_view>

#include "base/metrics/histogram_functions.h"
#include "base/strings/strcat.h"
#include "base/types/expected.h"

namespace web_app {

// Every error type that is logged by the UmaLogExpectedStatus function should
// be converted to a UMA-friendly enumeration. This function is an
// implementation for the case when the error type is enumeration.
template <class E>
E ToErrorEnum(E e) {
  static_assert(std::is_enum<E>::value, "E is not an enum.");
  return e;
}

// These functions return the names of the histograms where the
// wrapped in base::expected<> error are logged.
std::string ToSuccessHistogramName(std::string_view base_name);
std::string ToErrorHistogramName(std::string_view base_name);

// UMA-logs an error wrapped in base::expected<SuccessType, ErrorType>. It
// creates 2 histograms by appending corresponding suffixes to `base_name`. One
// histogram logs the success/failure rate. The other histogram logs the error
// type if any. Any custom error type should provide a specialized template
// function that converts the custom error type to error enum.
// `SuccessType` is not actually used, it is added for convenience of calling
// this function.
template <class T, class E>
void UmaLogExpectedStatus(std::string_view base_name,
                          const base::expected<T, E>& status) {
  base::UmaHistogramBoolean(ToSuccessHistogramName(base_name),
                            status.has_value());

  if (!status.has_value()) {
    base::UmaHistogramEnumeration(ToErrorHistogramName(base_name),
                                  ToErrorEnum(status.error()));
  }
}

// Similar to UmaLogExpectedStatus<T, E>, but it supports
// base::expected<void, ErrorType>.
template <class E>
void UmaLogExpectedStatus(std::string_view base_name,
                          const base::expected<void, E>& status) {
  UmaLogExpectedStatus<void, E>(base_name, status);
}

}  // namespace web_app
#endif  // COMPONENTS_WEBAPPS_ISOLATED_WEB_APPS_ERROR_UMA_LOGGING_H_