public enum RoomPressure {

  public static let description = """
  Calculate return grille and duct sizing for room pressure balancing.
  """

  public enum Mode: String, CaseIterable, Codable, Equatable, Sendable, Hashable {
    case knownAirflow
    case measuredPressure

    public var label: String {
      switch self {
      case .knownAirflow: return "Known Airflow"
      case .measuredPressure: return "Measured Pressure"
      }
    }
  }

  public enum Request: Codable, Equatable, Sendable, Hashable {
    case knownAirflow(KnownAirflow)
    case measuredPressure(MeasuredPressure)

    public struct KnownAirflow: Codable, Equatable, Sendable, Hashable {

      public let targetRoomPressure: Double
      public let doorWidth: Double
      public let doorHeight: Double
      public let doorUndercut: Double
      public let supplyAirflow: Double
      public let preferredGrilleHeight: CommonReturnGrilleHeight

      public init(
        targetRoomPressure: Double,
        doorWidth: Double,
        doorHeight: Double,
        doorUndercut: Double,
        supplyAirflow: Double,
        preferredGrilleHeight: RoomPressure.CommonReturnGrilleHeight
      ) {
        self.targetRoomPressure = targetRoomPressure
        self.doorWidth = doorWidth
        self.doorHeight = doorHeight
        self.doorUndercut = doorUndercut
        self.supplyAirflow = supplyAirflow
        self.preferredGrilleHeight = preferredGrilleHeight
      }
    }

    public struct MeasuredPressure: Codable, Equatable, Sendable, Hashable {

      public let measuredRoomPressure: Double // pascals.
      public let doorWidth: Double
      public let doorHeight: Double
      public let doorUndercut: Double
      public let preferredGrilleHeight: CommonReturnGrilleHeight

      public init(
        measuredRoomPressure: Double,
        doorWidth: Double,
        doorHeight: Double,
        doorUndercut: Double,
        preferredGrilleHeight: RoomPressure.CommonReturnGrilleHeight
      ) {
        self.measuredRoomPressure = measuredRoomPressure
        self.doorWidth = doorWidth
        self.doorHeight = doorHeight
        self.doorUndercut = doorUndercut
        self.preferredGrilleHeight = preferredGrilleHeight
      }
    }
  }

  public struct Response: Codable, Equatable, Sendable {

    public let mode: Mode
    public let grilleSize: GrilleSize
    public let ductSize: DuctSize
    public let calculatedAirflow: Double?
    public let warnings: [String]

    public init(
      mode: Mode,
      grilleSize: RoomPressure.Response.GrilleSize,
      ductSize: RoomPressure.Response.DuctSize,
      calculatedAirflow: Double? = nil,
      warnings: [String]
    ) {
      self.mode = mode
      self.grilleSize = grilleSize
      self.ductSize = ductSize
      self.calculatedAirflow = calculatedAirflow
      self.warnings = warnings
    }

    public struct DuctSize: Codable, Equatable, Sendable {

      public let diameter: Int
      public let velocity: Double

      public init(diameter: Int, velocity: Double) {
        self.diameter = diameter
        self.velocity = velocity
      }

    }

    public struct GrilleSize: Codable, Equatable, Sendable {

      public let width: Int
      public let height: Int
      public let area: Double

      public init(width: Int, height: Int, area: Double) {
        self.width = width
        self.height = height
        self.area = area
      }
    }

  }

  public enum CommonReturnGrilleHeight: Int, CaseIterable, Codable, Equatable, Sendable {
    case four = 4
    case six = 6
    case eight = 8
    case ten = 10
    case twelve = 12
    case fourteen = 14
    // case twenty = 20

    public var label: String { "\(rawValue)\"" }
  }
}

#if DEBUG
  public extension RoomPressure.Response {
    static let mock = Self(
      mode: .knownAirflow,
      grilleSize: .init(width: 14, height: 8, area: 72),
      ductSize: .init(diameter: 10, velocity: 367),
      warnings: [
        "Duct leakage area is significant - consider reducing gaps or increasing grille size."
      ]
    )
  }
#endif