# frozen_string_literal: true

class Stats::CalculateMonth
  def initialize(user_id, year, month)
    @user = User.find(user_id)
    @year = year.to_i
    @month = month.to_i
  end

  def call
    if points.empty?
      destroy_month_stats(year, month)

      return
    end

    update_month_stats(year, month)
  rescue StandardError => e
    create_stats_update_failed_notification(user, e)
  end

  private

  attr_reader :user, :year, :month

  def start_timestamp = DateTime.new(year, month, 1).to_i

  def end_timestamp
    DateTime.new(year, month, -1).to_i # -1 returns last day of month
  end

  def update_month_stats(year, month)
    Stat.transaction do
      stat = Stat.find_or_initialize_by(year:, month:, user:)
      distance_by_day = stat.distance_by_day

      stat.assign_attributes(
        daily_distance: distance_by_day,
        distance: distance(distance_by_day),
        toponyms: toponyms,
        hexagon_centers: calculate_hexagon_centers
      )
      stat.save
    end
  end

  def points
    return @points if defined?(@points)

    @points = user
              .points
              .without_raw_data
              .where(timestamp: start_timestamp..end_timestamp)
              .select(:lonlat, :timestamp)
              .order(timestamp: :asc)
  end

  def distance(distance_by_day)
    distance_by_day.sum { |day| day[1] }
  end

  def toponyms
    toponym_points =
      user
      .points
      .without_raw_data
      .where(timestamp: start_timestamp..end_timestamp)
      .select(:city, :country_name)
      .distinct

    CountriesAndCities.new(toponym_points).call
  end

  def create_stats_update_failed_notification(user, error)
    Notifications::Create.new(
      user:,
      kind: :error,
      title: 'Stats update failed',
      content: "#{error.message}, stacktrace: #{error.backtrace.join("\n")}"
    ).call
  end

  def destroy_month_stats(year, month)
    Stat.where(year:, month:, user:).destroy_all
  end

  def calculate_hexagon_centers
    return nil if points.empty?

    begin
      service = Maps::H3HexagonCenters.new(
        user_id: user.id,
        start_date: start_date_iso8601,
        end_date: end_date_iso8601
      )

      result = service.call

      if result.empty?
        Rails.logger.info "No H3 hexagon centers calculated for user #{user.id}, #{year}-#{month} (no data)"
        return nil
      end

      Rails.logger.info "Pre-calculated #{result.size} H3 hexagon centers for user #{user.id}, #{year}-#{month}"
      result
    rescue Maps::H3HexagonCenters::PostGISError => e
      Rails.logger.warn "H3 hexagon centers calculation failed for user #{user.id}, #{year}-#{month}: #{e.message}"
      nil
    end
  end

  def start_date_iso8601
    DateTime.new(year, month, 1).beginning_of_day.iso8601
  end

  def end_date_iso8601
    DateTime.new(year, month, -1).end_of_day.iso8601
  end
end