module Sessions
  # Sceglie il preset più alto supportato dall'upload misurato (test rete).
  class SelectQuality
    UPLOAD_HEADROOM = 0.8
    UPLOAD_HEADROOM_1080P = 1.0

    PRESETS = [
      { id: "1080p_30_4.5mbps", target_bitrate: 4_500_000, target_fps: 30 },
      { id: "720p_30_4mbps", target_bitrate: 4_000_000, target_fps: 30 },
      { id: "720p_30_2.5mbps", target_bitrate: 2_500_000, target_fps: 30 },
      { id: "720p_30_1.5mbps", target_bitrate: 1_500_000, target_fps: 30 }
    ].freeze

    def self.call(upload_mbps:)
      new(upload_mbps: upload_mbps).call
    end

    def initialize(upload_mbps:)
      @upload_mbps = upload_mbps.to_f
    end

    def call
      PRESETS.find { |preset| upload_sufficient?(preset) } || PRESETS.last
    end

    def upload_sufficient?(preset)
      headroom = preset[:id].start_with?("1080p") ? UPLOAD_HEADROOM_1080P : UPLOAD_HEADROOM
      @upload_mbps >= (preset[:target_bitrate] / 1_000_000.0 * headroom)
    end
  end
end