// Copyright 2020 The Fuchsia 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 "src/local_aggregation_1_1/backfill_manager.h"

#include <chrono>

#include "src/lib/util/datetime_util.h"
#include "src/local_aggregation_1_1/local_aggregation.pb.h"
#include "src/registry/metric_definition.pb.h"

namespace cobalt::local_aggregation {

using TimeInfo = util::TimeInfo;

BackfillManager::BackfillManager(uint32_t total_backfill_window)
    : backstop_days_(total_backfill_window > 0 ? total_backfill_window - 1 : 0) {}

std::vector<TimeInfo> BackfillManager::CalculateBackfill(TimeInfo start_time, TimeInfo end_time,
                                                         MetricDefinition::TimeZonePolicy time_zone,
                                                         bool is_daily) const {
  uint32_t backstop_day = end_time.day_index - backstop_days_;
  if (end_time.day_index < backstop_days_) {
    backstop_day = 0;
  }
  uint32_t backstop_hour = util::DayIndexToHourId(backstop_day);

  std::vector<TimeInfo> backfill;
  if (is_daily) {
    uint32_t start_day_index = std::max(start_time.day_index + 1, backstop_day);

    for (uint32_t day_index = start_day_index; day_index <= end_time.day_index; day_index++) {
      backfill.push_back(TimeInfo::FromDayIndex(day_index));
    }
  } else {
    uint32_t start_hour_id = std::max(start_time.hour_id + 1, backstop_hour);
    int64_t start_epoch = util::DayIndexToUnixSeconds(backstop_day);
    int64_t end_epoch = util::DayIndexToUnixSeconds(end_time.day_index + 2);
    for (int64_t epoch = start_epoch; epoch < end_epoch; epoch += util::kNumUnixSecondsPerHour) {
      uint32_t current_hour_id = util::TimeToHourId(
          std::chrono::system_clock::to_time_t(util::FromUnixSeconds(epoch)), time_zone);

      if (current_hour_id >= start_hour_id && current_hour_id <= end_time.hour_id) {
        backfill.push_back(TimeInfo::FromHourId(current_hour_id));
      }
    }
  }

  return backfill;
}

}  // namespace cobalt::local_aggregation