module Sessions
  # Sceglie il preset più alto supportato dall'upload misurato (test rete).
  class SelectQuality
    UPLOAD_HEADROOM = 0.8
    UPLOAD_HEADROOM_1080P = 1.0
    AUTO_ID = "auto"
    AUTO_FLOOR_BITRATE = 800_000

    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

    MIN_QUALITY_IDS = ([AUTO_ID] + PRESETS.map { |preset| preset[:id] }).freeze

    def self.floor_bitrate(preset_id)
      return AUTO_FLOOR_BITRATE if preset_id.blank? || preset_id == AUTO_ID

      PRESETS.find { |preset| preset[:id] == preset_id }&.fetch(:target_bitrate) || AUTO_FLOOR_BITRATE
    end

    def self.allowed_min_ids(session_preset)
      ids = [AUTO_ID] + PRESETS.reject { |preset| preset[:id].start_with?("1080p") }.reverse.map { |preset| preset[:id] }
      ids << "1080p_30_4.5mbps" if session_preset.to_s.start_with?("1080p")
      ids
    end

    def self.display_name(preset_id)
      return AUTO_ID if preset_id.blank? || preset_id == AUTO_ID

      preset = PRESETS.find { |item| item[:id] == preset_id }
      return preset_id unless preset

      resolution = preset[:id].start_with?("1080p") ? "1080p" : "720p"
      mbps = preset[:target_bitrate] / 1_000_000.0
      mbps_text = (mbps == mbps.to_i) ? mbps.to_i.to_s : format("%.1f", mbps)
      "#{resolution} · #{mbps_text} Mbps"
    end

    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