import Models
import Validations

extension CoolingInterpolation.Request {

  func respond() async throws -> CoolingInterpolation.Response {
    try await validate()
    let interpolatedCapacity = await interpolatedCapacity()
    let excessLatent = excessLatent(interpolatedCapacity.latent)
    let elevationDeratings = try await elevationDeratings()
    let sizingLimits = try await sizingLimits()

    let finalCapacity = calculateFinalCapacity(
      interpolated: interpolatedCapacity,
      excessLatent: excessLatent,
      adjustmentMultipliers: interpolation.adjustmentMultipliers,
      elevationDeratings: elevationDeratings
    )

    let capacityAsPercentOfLoad = Capacity.Cooling(
      total: normalizePercentage(finalCapacity.total, coolingLoad.total),
      sensible: normalizePercentage(finalCapacity.sensible, coolingLoad.sensible),
      latent: normalizePercentage(finalCapacity.latent, coolingLoad.latent)
    )

    return .init(
      failures: sizingLimits.validate(capacityAsPercentOfLoad: capacityAsPercentOfLoad),
      interpolatedCapacity: interpolatedCapacity,
      excessLatent: excessLatent,
      finalCapacityAtDesign: finalCapacity,
      altitudeDerating: elevationDeratings,
      capacityAsPercentOfLoad: capacityAsPercentOfLoad,
      sizingLimits: sizingLimits
    )
  }

  private func interpolatedCapacity() async -> Capacity.Cooling {
    await interpolation.interpolatedCapacity(
      outdoorDesignTemperature: summerDesignInfo.outdoorTemperature
    )
  }

  private func elevationDeratings() async throws -> AdjustmentMultiplier? {
    guard let elevation else { return nil }

    return try await Derating.Request(elevation: elevation, systemType: systemType)
      .respond()
  }

  private func sizingLimits() async throws -> SizingLimits.Response {
    try await SizingLimits.Request(systemType: systemType, coolingLoad: coolingLoad)
      .respond()
  }

  private func excessLatent(_ interpolatedLatent: Int) -> Int {
    (interpolatedLatent - coolingLoad.latent) / 2
  }

}

private func calculateFinalCapacity(
  interpolated: Capacity.Cooling,
  excessLatent: Int,
  adjustmentMultipliers: AdjustmentMultiplier?,
  elevationDeratings: AdjustmentMultiplier?
) -> Capacity.Cooling {
  var total = interpolated.total
  var sensible = interpolated.sensible + excessLatent
  if let adjustmentMultipliers {
    adjustmentMultipliers.apply(total: &total, sensible: &sensible)
  }
  if let elevationDeratings {
    elevationDeratings.apply(total: &total, sensible: &sensible)
  }
  return .init(total: total, sensible: sensible)
}

private extension AdjustmentMultiplier {
  func apply(total: inout Int, sensible: inout Int) {
    if let coolingTotal {
      total = Int(Double(total) * coolingTotal)
    }
    if let coolingSensible {
      sensible = Int(Double(sensible) * coolingSensible)
    }
  }
}

private extension SizingLimits.Response {

  func validate(capacityAsPercentOfLoad: Capacity.Cooling) -> [String]? {
    var failures = [String]()

    // Check oversizing limits.
    if capacityAsPercentOfLoad.total > oversizing.coolingTotal {
      failures.append(
        "Oversizing total failure."
      )
    }
    if let coolingLatent = oversizing.coolingLatent,
       capacityAsPercentOfLoad.latent > coolingLatent
    {
      failures.append(
        "Oversizing latent failure."
      )
    }

    if capacityAsPercentOfLoad.total < undersizing.coolingTotal {
      failures.append(
        "Undersizing total failure."
      )
    }
    if let coolingSensible = undersizing.coolingSensible,
       capacityAsPercentOfLoad.sensible < coolingSensible
    {
      failures.append(
        "Undersizing sensible failure."
      )
    }
    if let coolingLatent = undersizing.coolingLatent,
       capacityAsPercentOfLoad.latent < coolingLatent
    {
      failures.append(
        "Undersizing latent failure."
      )
    }

    return failures.isEmpty ? nil : failures
  }
}

private func normalizePercentage(
  _ lhs: Int,
  _ rhs: Int
) -> Int {
  let value = Double(lhs) / Double(rhs)
  return Int((value * 1000).rounded() / 10.0)
}

private extension CoolingInterpolation.InterpolationRequest {

  func interpolatedCapacity(outdoorDesignTemperature: Int) async -> Capacity.Cooling {
    switch self {
    case let .noInterpolation(request, _):
      return .init(total: request.capacity.totalCapacity, sensible: request.capacity.sensibleCapacity)
    case let .oneWayIndoor(request):
      return await request.interpolatedCapacity()
    case let .oneWayOutdoor(request):
      return await request.interpolatedCapacity(outdoorDesignTemperature: outdoorDesignTemperature)
    case let .twoWay(request):
      return await request.interpolatedCapacity(outdoorDesignTemperature: outdoorDesignTemperature)
    }
  }

  var adjustmentMultipliers: AdjustmentMultiplier? {
    switch self {
    case let .noInterpolation(_, adjustmentMultipliers):
      return adjustmentMultipliers
    case let .oneWayIndoor(request):
      return request.adjustmentMultipliers
    case let .oneWayOutdoor(request):
      return request.adjustmentMultipliers
    case let .twoWay(request):
      return request.adjustmentMultipliers
    }
  }
}

private func interpolateIndoorCapacity(
  above: Capacity.ManufacturersContainer,
  below: Capacity.ManufacturersContainer
) async -> Capacity.Cooling {
  let total = below.totalCapacity
    + ((above.totalCapacity - below.totalCapacity) / (above.wetBulb - below.wetBulb))
    * (63 - below.wetBulb)

  let sensible = Double(below.sensibleCapacity)
    + (Double(above.sensibleCapacity) - Double(below.sensibleCapacity))
    / (Double(below.totalCapacity) - Double(above.totalCapacity))
    * (Double(below.totalCapacity) - Double(total))

  return .init(total: total, sensible: Int(sensible))
}

private func interpolateOutdoorCapacity(
  outdoorDesignTemperature: Int,
  aboveCapacity: Int,
  aboveOutdoorTemperature: Int,
  belowCapacity: Int,
  belowOutdoorTemperature: Int
) async -> Int {
  return belowCapacity
    - (outdoorDesignTemperature - belowOutdoorTemperature)
    * ((belowCapacity - aboveCapacity) / (aboveOutdoorTemperature - belowOutdoorTemperature))
}

private extension CoolingInterpolation.OneWayIndoor {

  func interpolatedCapacity() async -> Capacity.Cooling {
    return await interpolateIndoorCapacity(
      above: capacities.aboveDewpoint,
      below: capacities.belowDewpoint
    )
  }
}

private extension CoolingInterpolation.OneWayOutdoor {
  func interpolatedCapacity(outdoorDesignTemperature: Int) async -> Capacity.Cooling {
    let total = await interpolate(
      outdoorDesignTemperature: outdoorDesignTemperature,
      aboveCapacity: \.totalCapacity,
      belowCapacity: \.totalCapacity
    )
    let sensible = await interpolate(
      outdoorDesignTemperature: outdoorDesignTemperature,
      aboveCapacity: \.sensibleCapacity,
      belowCapacity: \.sensibleCapacity
    )

    return .init(total: total, sensible: sensible)
  }

  private func interpolate(
    outdoorDesignTemperature: Int,
    aboveCapacity: KeyPath<CoolingInterpolation.OneWayOutdoor.Capacities.Capacity, Int>,
    belowCapacity: KeyPath<CoolingInterpolation.OneWayOutdoor.Capacities.Capacity, Int>
  ) async -> Int {
    return await interpolateOutdoorCapacity(
      outdoorDesignTemperature: outdoorDesignTemperature,
      aboveCapacity: capacities.aboveOutdoor[keyPath: aboveCapacity],
      aboveOutdoorTemperature: capacities.aboveOutdoor.outdoorTemperature,
      belowCapacity: capacities.belowOutdoor[keyPath: belowCapacity],
      belowOutdoorTemperature: capacities.belowOutdoor.outdoorTemperature
    )
  }
}

private extension CoolingInterpolation.TwoWay {

  func interpolatedCapacity(outdoorDesignTemperature: Int) async -> Capacity.Cooling {
    let aboveIndoorInterpolation = await self.aboveIndoorInterpolation()
    let belowIndoorInterpolation = await self.belowIndoorInterpolation()
    return await interpolate(
      outdoorDesignTemperature: outdoorDesignTemperature,
      aboveIndoor: aboveIndoorInterpolation,
      belowIndoor: belowIndoorInterpolation
    )
  }

  func interpolate(
    outdoorDesignTemperature: Int,
    aboveIndoor: Capacity.Cooling,
    belowIndoor: Capacity.Cooling
  ) async -> Capacity.Cooling {
    let request = CoolingInterpolation.OneWayOutdoor(
      airflow: 0,
      wetBulb: 63,
      capacities: .init(
        aboveOutdoor: .init(
          outdoorTemperature: capacities.above.outdoorTemperature,
          totalCapacity: aboveIndoor.total,
          sensibleCapacity: aboveIndoor.sensible
        ),
        belowOutdoor: .init(
          outdoorTemperature: capacities.below.outdoorTemperature,
          totalCapacity: belowIndoor.total,
          sensibleCapacity: belowIndoor.sensible
        )
      )
    )

    return await request.interpolatedCapacity(outdoorDesignTemperature: outdoorDesignTemperature)
  }

  func aboveIndoorInterpolation() async -> Capacity.Cooling {
    return await interpolateIndoorCapacity(
      above: capacities.above.aboveDewPoint,
      below: capacities.above.belowDewPoint
    )
  }

  func belowIndoorInterpolation() async -> Capacity.Cooling {
    return await interpolateIndoorCapacity(
      above: capacities.below.aboveDewPoint,
      below: capacities.below.belowDewPoint
    )
  }
}

// MARK: - Validations

// Basic validations of the request.
extension CoolingInterpolation.Request: AsyncValidatable {
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.validate(\.summerDesignInfo)
      AsyncValidator.validate(\.coolingLoad)
      AsyncValidator.validate(\.interpolation)
    }
  }
}

extension CoolingInterpolation.InterpolationRequest: AsyncValidatable {

  public typealias Value = CoolingInterpolation.InterpolationRequest

  public func validate(_ value: Self) async throws {
    switch value {
    case let .noInterpolation(request, _):
      try await request.validate()
    case let .oneWayIndoor(request):
      try await request.validate()
    case let .oneWayOutdoor(request):
      try await request.validate()
    case let .twoWay(request):
      try await request.validate()
    }
  }
}

extension CoolingInterpolation.OneWayIndoor: AsyncValidatable {
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.greaterThan(\.airflow, 0)
      AsyncValidator.greaterThan(\.outdoorTemperature, 0)
      AsyncValidator.validate(\.capacities)
    }
  }
}

extension CoolingInterpolation.OneWayIndoor.Capacities: AsyncValidatable {
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.validate(\.aboveDewpoint)
      AsyncValidator.validate(\.belowDewpoint)
    }
  }
}

extension CoolingInterpolation.OneWayOutdoor: AsyncValidatable {
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.greaterThan(\.airflow, 0)
      AsyncValidator.greaterThan(\.wetBulb, 0)
      AsyncValidator.validate(\.capacities)
    }
  }
}

extension CoolingInterpolation.OneWayOutdoor.Capacities: AsyncValidatable {

  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.validate(\.aboveOutdoor)
      AsyncValidator.validate(\.belowOutdoor)
    }
  }
}

extension CoolingInterpolation.OneWayOutdoor.Capacities.Capacity: AsyncValidatable {
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.greaterThan(\.outdoorTemperature, 0)
      AsyncValidator.greaterThan(\.totalCapacity, 0)
      AsyncValidator.greaterThan(\.sensibleCapacity, 0)
      AsyncValidator.greaterThanOrEquals(\.totalCapacity, \.sensibleCapacity)
    }
  }
}

extension CoolingInterpolation.TwoWay: AsyncValidatable {
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.greaterThan(\.airflow, 0)
      AsyncValidator.validate(\.capacities)
    }
  }
}

extension CoolingInterpolation.TwoWay.Capacities: AsyncValidatable {
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.validate(\.above)
      AsyncValidator.validate(\.below)
    }
  }
}

extension CoolingInterpolation.TwoWay.Capacities.CapacityContainer: AsyncValidatable {
  public var body: some AsyncValidation<Self> {
    AsyncValidator.accumulating {
      AsyncValidator.validate(\.aboveDewPoint)
      AsyncValidator.validate(\.belowDewPoint)
    }
  }
}

private struct CapacityContainer {
  let above: Capacity.ManufacturersCooling.Container
  let below: Capacity.ManufacturersCooling.Container
}

public struct ValidationError: Equatable, Error {
  public let message: String

  public init(message: String) {
    self.message = message
  }
}