import Dependencies
import DependenciesMacros
import Foundation
@_exported import SharedModels

extension DependencyValues {

  public var estimatedPressuresClient: EstimatedPressureDependency {
    get { self[EstimatedPressureDependency.self] }
    set { self[EstimatedPressureDependency.self] = newValue }
  }
}

@DependencyClient
public struct EstimatedPressureDependency {

  public var estimatedAirflow: (EstimatedAirflowRequest) async throws -> Positive<Double>
  public var estimatedPressure: (EstimatedPressureRequest) async throws -> Positive<Double>

  public struct EstimatedPressureRequest: Equatable {
    public let existingPressure: Positive<Double>
    public let existingAirflow: Positive<Double>
    public let targetAirflow: Positive<Double>

    public init(
      existingPressure: Double,
      existingAirflow: Double,
      targetAirflow: Double
    ) {
      self.existingPressure = .init(wrappedValue: existingPressure)
      self.existingAirflow = .init(wrappedValue: existingAirflow)
      self.targetAirflow = .init(wrappedValue: targetAirflow)
    }
  }

  public struct EstimatedAirflowRequest: Equatable {
    public let existingAirflow: Positive<Double>
    public let existingPressure: Positive<Double>
    public let targetPressure: Positive<Double>

    public init(
      existingAirflow: Double,
      existingPressure: Double,
      targetPressure: Double
    ) {
      self.existingPressure = .init(wrappedValue: existingPressure)
      self.existingAirflow = .init(wrappedValue: existingAirflow)
      self.targetPressure = .init(wrappedValue: targetPressure)
    }
  }

  public func estimatedPressure(
    existingPressure: Double,
    existingAirflow: Double,
    targetAirflow: Double
  ) async throws -> Positive<Double> {
    try await self.estimatedPressure(
      .init(
        existingPressure: existingPressure,
        existingAirflow: existingAirflow,
        targetAirflow: targetAirflow
      )
    )
  }
}

extension EstimatedPressureDependency {
  private func estimatedPressure(
    existingPressure: Positive<Double?>,
    existingAirflow: Double,
    targetAirflow: Double
  ) async throws -> Positive<Double> {
    try await self.estimatedPressure(
      .init(
        existingPressure: existingPressure.positiveValue ?? 0,
        existingAirflow: existingAirflow,
        targetAirflow: targetAirflow
      )
    )
  }

  public func estimatedPressure(
    equipmentMeasurement: EquipmentMeasurement,
    airflow updatedAirflow: Double
  ) async throws -> EquipmentMeasurement {
    switch equipmentMeasurement {
    case let .airHandler(airHandler):
      guard let existingAirflow = airHandler.airflow else {
        throw InvalidAirflow()
      }
      return try await .airHandler(
        .init(
          airflow: updatedAirflow,
          returnPlenumPressure: self.estimatedPressure(
            existingPressure: airHandler.$returnPlenumPressure,
            existingAirflow: existingAirflow,
            targetAirflow: updatedAirflow
          ),
          postFilterPressure: self.estimatedPressure(
            existingPressure: airHandler.$postFilterPressure,
            existingAirflow: existingAirflow,
            targetAirflow: updatedAirflow
          ),
          postCoilPressure: self.estimatedPressure(
            existingPressure: airHandler.$postCoilPressure,
            existingAirflow: existingAirflow,
            targetAirflow: updatedAirflow
          ),
          supplyPlenumPressure: self.estimatedPressure(
            existingPressure: airHandler.$supplyPlenumPressure,
            existingAirflow: existingAirflow,
            targetAirflow: updatedAirflow
          )
        )
      )

    case let .furnaceAndCoil(furnaceAndCoil):
      guard let existingAirflow = furnaceAndCoil.airflow else {
        throw InvalidAirflow()
      }
      return try await .furnaceAndCoil(
        .init(
          airflow: updatedAirflow,
          returnPlenumPressure: self.estimatedPressure(
            existingPressure: furnaceAndCoil.$returnPlenumPressure,
            existingAirflow: existingAirflow,
            targetAirflow: updatedAirflow
          ),
          postFilterPressure: self.estimatedPressure(
            existingPressure: furnaceAndCoil.$postFilterPressure,
            existingAirflow: existingAirflow,
            targetAirflow: updatedAirflow
          ),
          preCoilPressure: self.estimatedPressure(
            existingPressure: furnaceAndCoil.$preCoilPressure,
            existingAirflow: existingAirflow,
            targetAirflow: updatedAirflow
          ),
          supplyPlenumPressure: self.estimatedPressure(
            existingPressure: furnaceAndCoil.$supplyPlenumPressure,
            existingAirflow: existingAirflow,
            targetAirflow: updatedAirflow
          )
        )
      )

    }
  }

  public func estimatedPressure(
    equipmentMeasurement: EquipmentMeasurement,
    airflow updatedAirflow: Double,
    filterPressureDrop: Positive<Double>
  ) async throws -> EquipmentMeasurement {
    let estimate = try await estimatedPressure(
      equipmentMeasurement: equipmentMeasurement,
      airflow: updatedAirflow
    )

    switch estimate {

    case var .airHandler(airHandler):
      airHandler.postFilterPressure = airHandler.returnPlenumPressure + filterPressureDrop.positiveValue
      return .airHandler(airHandler)

    case var .furnaceAndCoil(furnaceAndCoil):
      furnaceAndCoil.postFilterPressure = furnaceAndCoil.returnPlenumPressure + filterPressureDrop.positiveValue
      return .furnaceAndCoil(furnaceAndCoil)
    }
  }
  
  public func estimatedPressure(
    equipmentMeasurement: EquipmentMeasurement,
    airflow updatedAirflow: Double,
    filterPressureDrop: Positive<Double>?
  ) async throws -> EquipmentMeasurement {
    guard let filterPressureDrop else {
      return try await estimatedPressure(
        equipmentMeasurement: equipmentMeasurement,
        airflow: updatedAirflow
      )
    }
    return try await estimatedPressure(
      equipmentMeasurement: equipmentMeasurement,
      airflow: updatedAirflow,
      filterPressureDrop: filterPressureDrop
    )
  }
}

extension EstimatedPressureDependency: DependencyKey {

  public static var testValue: EstimatedPressureDependency { Self() }

  public static var liveValue: EstimatedPressureDependency {
    .init(
      estimatedAirflow: { request in
        guard request.existingPressure.positiveValue > 0 else {
          throw LessThanZeroError.existingPressure
        }
        let value = request.existingAirflow.positiveValue * sqrt(
          request.targetPressure.positiveValue / request.existingPressure.positiveValue
        )
        return .init(wrappedValue: value)
      },
      estimatedPressure: { request in
        guard request.existingAirflow.positiveValue > 0 else {
          throw LessThanZeroError.existingAirflow
        }

        let value = pow(
          request.targetAirflow.positiveValue / request.existingAirflow.positiveValue,
          2
        ) * request.existingPressure.positiveValue

        return .init(wrappedValue: value)
      }
    )
  }
}

fileprivate extension EquipmentMeasurement.AirHandler {
  init(
    airflow: Double? = nil,
    returnPlenumPressure: Positive<Double>,
    postFilterPressure: Positive<Double>,
    postCoilPressure: Positive<Double>,
    supplyPlenumPressure: Positive<Double>
  ) {
    self.init(
      airflow: airflow,
      returnPlenumPressure: returnPlenumPressure.positiveValue,
      postFilterPressure: postFilterPressure.positiveValue,
      postCoilPressure: postCoilPressure.positiveValue,
      supplyPlenumPressure: supplyPlenumPressure.positiveValue
    )
  }
}

fileprivate extension EquipmentMeasurement.FurnaceAndCoil {
  init(
    airflow: Double? = nil,
    returnPlenumPressure: Positive<Double>,
    postFilterPressure: Positive<Double>,
    preCoilPressure: Positive<Double>,
    supplyPlenumPressure: Positive<Double>
  ) {
    self.init(
      airflow: airflow,
      returnPlenumPressure: returnPlenumPressure.positiveValue,
      postFilterPressure: postFilterPressure.positiveValue,
      preCoilPressure: preCoilPressure.positiveValue,
      supplyPlenumPressure: supplyPlenumPressure.positiveValue
    )
  }
}

struct InvalidAirflow: Error { }

enum LessThanZeroError: Error {
  case existingAirflow
  case existingPressure
}