import CoreFoundation
import Models
import Validations

extension BalancePoint.Request {

  func respond() async throws -> BalancePoint.Response {
    try await validate()
    let balancePoint = await thermalBalancePoint(
      heatLoss: Double(heatLoss),
      at47: Double(heatPumpCapacity.at47),
      at17: Double(heatPumpCapacity.at17),
      designTemperature: Double(winterDesignTemperature)
    )
    return .init(balancePointTemperature: balancePoint)
  }
}

extension BalancePoint.Request: AsyncValidatable {

  @inlinable
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.greaterThan(\.heatLoss, 0)
      AsyncValidator.validate(\.heatPumpCapacity)
    }
  }
}

private func thermalBalancePoint(
  heatLoss: Double,
  at47: Double,
  at17: Double,
  designTemperature: Double
) async -> Double {
  (30.0 * (((designTemperature - 65.0) * at47) + (65.0 * heatLoss))
    - ((designTemperature - 65.0) * (at47 - at17) * 47.0))
    / ((30.0 * heatLoss) - ((designTemperature - 65.0) * (at47 - at17)))
}