class Statistics
  attr_reader :user

  def initialize(user)
    @user = user
  end

  def total_plays
    Activity.where(user: user).count
  end

  def total_plays_year
    year_start = Date.today.beginning_of_year
    Activity.where(user: user, created_at: year_start..Date.today.end_of_day).count
  end

  def activity_by_day
    start_date = 1.year.ago.to_date
    end_date = Date.today
    activities = Activity.where(user: user, created_at: start_date.beginning_of_day..end_date.end_of_day)
    activities.group("DATE(created_at)").count.transform_keys { |d| d.to_s }
  end

  def top_artists_all_time
    Activity.where(user: user)
      .group(:item_title).order("count_id DESC").limit(5).count(:id)
  end

  def top_artists_year
    year_start = Date.today.beginning_of_year
    Activity.where(user: user, created_at: year_start..Date.today.end_of_day)
      .group(:item_title).order("count_id DESC").limit(5).count(:id)
  end

  def top_artists_upcoming
    upcoming_start = 30.days.ago.to_date
    upcoming_end = Date.today
    Activity.where(user: user, started_at: upcoming_start.beginning_of_day..upcoming_end.end_of_day)
      .group(:item_title).order("count_id DESC").limit(5).count(:id)
  end

  def since_date
    Activity.where(user: user).order(:created_at).limit(1).pick(:created_at)
  end

  # Returns a hash with streak info: :start_date, :end_date, :length, :total_plays, :most_played_song, :most_played_song_count
  def longest_streak
    days = activity_by_day.keys.map { |d| Date.parse(d) }.sort
    return nil if days.empty?
    streaks = []
    current_streak = []
    days.each_with_index do |day, i|
      if i == 0 || day == days[i-1] + 1
        current_streak << day
      else
        streaks << current_streak
        current_streak = [day]
      end
    end
    streaks << current_streak unless current_streak.empty?
    best = streaks.max_by(&:length)
    return nil unless best && best.length > 0
    streak_start = best.first
    streak_end = best.last
    plays = Activity.where(user: user, created_at: streak_start.beginning_of_day..streak_end.end_of_day)
    total_plays = plays.count
    song_counts = plays.group(:item_title).order('count_id DESC').limit(1).count(:id)
    most_played_song, most_played_song_count = song_counts.first || [nil, 0]
    {
      start_date: streak_start,
      end_date: streak_end,
      length: best.length,
      total_plays: total_plays,
      most_played_song: most_played_song,
      most_played_song_count: most_played_song_count
    }
  end
end