import Foundation

// TODO: Needs updated for when forms are using `minmal` values.
public struct FlaggedEquipmentMeasurement: Equatable {
  public var airflow: Flagged
  public var coilPressureDrop: Flagged
  public var externalStaticPressure: Flagged
  public var filterPressureDrop: Flagged
  public var returnPlenumPressure: Flagged
  public var supplyPlenumPressure: Flagged

  public init(
    airflow: Flagged,
    coilPressureDrop: Flagged,
    externalStaticPressure: Flagged,
    filterPressureDrop: Flagged,
    returnPlenumPressure: Flagged,
    supplyPlenumPressure: Flagged
  ) {
    self.airflow = airflow
    self.coilPressureDrop = coilPressureDrop
    self.externalStaticPressure = externalStaticPressure
    self.filterPressureDrop = filterPressureDrop
    self.returnPlenumPressure = returnPlenumPressure
    self.supplyPlenumPressure = supplyPlenumPressure
  }

  public init(
    budgets: BudgetedPercentEnvelope,
    measurement: EquipmentMeasurement,
    ratedPressures: RatedStaticPressures,
    tons: CoolingCapacity?
  ) {
    switch measurement {
    case let .airHandler(airHandler):
      self = .airHandler(
        budgets: budgets,
        measurement: airHandler,
        ratedPressures: ratedPressures,
        tons: tons
      )
    case let .furnaceAndCoil(furnaceAndCoil):
      self = .furnaceAndCoil(
        budgets: budgets,
        measurement: furnaceAndCoil,
        ratedPressures: ratedPressures,
        tons: tons
      )
    }
  }

  public static func airHandler(
    budgets: BudgetedPercentEnvelope,
    measurement: EquipmentMeasurement.AirHandler,
    ratedPressures: RatedStaticPressures,
    tons: CoolingCapacity?
  ) -> Self {
    .init(
      airflow: checkAirflow(value: measurement.airflow, tons: tons),
      coilPressureDrop: .init(
        wrappedValue: (measurement.$postCoilPressure.positiveValue - measurement.$postFilterPressure.positiveValue) ?? 0,
        .result(.good())
      ),
      externalStaticPressure: checkExternalStaticPressure(
        value: measurement.externalStaticPressure,
        ratedPressures: ratedPressures
      ),
      filterPressureDrop: .init(
        value: measurement.$postFilterPressure.positiveValue - measurement.$returnPlenumPressure.positiveValue,
        budget: budgets.filterBudget,
        ratedPressures: ratedPressures
      ),
      returnPlenumPressure: .init(
        value: measurement.$returnPlenumPressure.positiveValue,
        budget: budgets.returnPlenumBudget,
        ratedPressures: ratedPressures
      ),
      supplyPlenumPressure: .init(
        value: measurement.$supplyPlenumPressure.positiveValue ?? 0,
        budget: budgets.supplyPlenumBudget,
        ratedPressures: ratedPressures
      )
    )
  }

  public static func furnaceAndCoil(
    budgets: BudgetedPercentEnvelope,
    measurement: EquipmentMeasurement.FurnaceAndCoil,
    ratedPressures: RatedStaticPressures,
    tons: CoolingCapacity?
  ) -> Self {
    .init(
      airflow: checkAirflow(value: measurement.airflow, tons: tons),
      coilPressureDrop: .init(
        value: measurement.$preCoilPressure.positiveValue - measurement.$supplyPlenumPressure.positiveValue,
        budget: budgets.coilBudget,
        ratedPressures: ratedPressures
      ),
      externalStaticPressure: checkExternalStaticPressure(
        value: measurement.externalStaticPressure,
        ratedPressures: ratedPressures
      ),
      filterPressureDrop: .init(
        value: measurement.$postFilterPressure.positiveValue - measurement.$returnPlenumPressure.positiveValue,
        budget: budgets.filterBudget,
        ratedPressures: ratedPressures,
        ignoreMinimum: true
      ),
      returnPlenumPressure: .init(
        value: measurement.$returnPlenumPressure.positiveValue,
        budget: budgets.returnPlenumBudget,
        ratedPressures: ratedPressures
      ),
      supplyPlenumPressure: .init(
        value: measurement.$supplyPlenumPressure.positiveValue,
        budget: budgets.supplyPlenumBudget,
        ratedPressures: ratedPressures
      )
    )
  }
}

// MARK: - Helpers
#if DEBUG
extension FlaggedEquipmentMeasurement {
  public static func mock(type equipmentType: EquipmentType) -> Self {
    .init(
      budgets: .init(equipmentType: equipmentType, fanType: .variableSpeed),
      measurement: .mock(type: equipmentType),
      ratedPressures: .init(),
      tons: .default
    )
  }
}
#endif
fileprivate extension Flagged {

  init(
    value: Double,
    budget: Percentage,
    ratedPressures: RatedStaticPressures,
    ignoreMinimum: Bool = false
  ) {
    let minimum = ignoreMinimum ? 0 : ratedPressures.minimum * budget.fraction
    let maximum = ratedPressures.maximum * budget.fraction
    let rated = ratedPressures.rated * budget.fraction
    self.init(
      wrappedValue: value,
      .using(maximum: maximum, minimum: minimum, rated: rated)
    )
  }

  init(
    value: Double?,
    budget: Percentage,
    ratedPressures: RatedStaticPressures,
    ignoreMinimum: Bool = false
  ) {
    guard let value else {
      self = .error(message: "Value is not set.")
      return
    }
    self.init(
      value: value,
      budget: budget,
      ratedPressures: ratedPressures,
      ignoreMinimum: ignoreMinimum
    )
  }
}

fileprivate func checkExternalStaticPressure(
  value: Double,
  ratedPressures: RatedStaticPressures
) -> Flagged {
  .init(
    wrappedValue: value,
    .rated(ratedPressures)
  )
}

fileprivate func checkAirflow(
  value: Double?,
  tons: CoolingCapacity?
) -> Flagged {
  guard let value, let tons else {
    return .init(wrappedValue: value ?? 0, .result(.good()))
  }
  return .init(wrappedValue: value, .airflow(tons: tons))
}