module BlameHelper
  def age_map_duration(blame_groups, project)
    now = Time.zone.now
    start_date = blame_groups.map { |blame_group| blame_group[:commit].committed_date }
      .append(project.created_at).min

    {
      now: now,
      started_days_ago: (now - start_date).to_i / 1.day
    }
  end

  def age_map_class(commit_date, duration)
    commit_date_days_ago = (duration[:now] - commit_date).to_i / 1.day
    # Numbers 0 to 10 come from this calculation, but only commits on the oldest
    # day get number 10 (all other numbers can be multiple days), so the range
    # is normalized to 0-9
    age_group = [(10 * commit_date_days_ago) / duration[:started_days_ago], 9].min
    "blame-commit-age-#{age_group}"
  end
end