import ComposableArchitecture
import DependenciesAdditions
import InfoViewFeature
import SharedModels
import Styleguide
import SwiftUI

@Reducer
public struct EquipmentMeasurementForm {
  
  public init() { }
  
  @Reducer(state: .equatable, .sendable, action: .sendable)
  public enum Destination {
    case flaggedMeasurementsList(FlaggedMeasurementsList)
    case infoView(InfoViewFeature)
  }
  
  @ObservableState
  public struct State: Equatable, Sendable {
    @Presents public var destination: Destination.State?
    @Shared public var sharedSettings: SharedPressureEstimationState
    public var allowEquipmentTypeSelection: Bool
    public var equipmentType: EquipmentMeasurement.EquipmentType
    public var focusedField: Field?
    public var measurements: Measurements
    
    public init(
      allowEquipmentTypeSelection: Bool = true,
      destination: Destination.State? = nil,
      sharedSettings: Shared<SharedPressureEstimationState>,
      equipmentType: EquipmentMeasurement.EquipmentType = .airHandler,
      focusedField: Field? = nil,
      measurements: Measurements = .init()
    ) {
      self.allowEquipmentTypeSelection = allowEquipmentTypeSelection
      self.destination = destination
      self._sharedSettings = sharedSettings
      self.equipmentType = equipmentType
      self.focusedField = focusedField
      self.measurements = measurements
    }
    
    public var equipmentMeasurement: EquipmentMeasurement {
      measurements.equipmentMeasurement(type: equipmentType)
    }

    private var baseValidations: Bool {
      return measurements.airflow != nil
      && measurements.returnPlenumPressure != nil
      && measurements.supplyPlenumPressure != nil
    }

    private var furnaceAndCoilValidations: Bool {
      return measurements.postFilterPressure != nil
      && measurements.coilPressure != nil
      && baseValidations
    }

    public var isValid: Bool {
      switch equipmentType {
      case .airHandler:
        return baseValidations
      case .furnaceAndCoil:
        return furnaceAndCoilValidations
      }
    }
    
    public struct Measurements: Equatable, Sendable {
      public var airflow: Double?
      public var returnPlenumPressure: Double?
      public var postFilterPressure: Double?
      public var coilPressure: Double?
      public var supplyPlenumPressure: Double?
      
      public init(
        airflow: Double? = nil,
        returnPlenumPressure: Double? = nil,
        postFilterPressure: Double? = nil,
        coilPressure: Double? = nil,
        supplyPlenumPressure: Double? = nil
      ) {
        self.airflow = airflow
        self.returnPlenumPressure = returnPlenumPressure
        self.postFilterPressure = postFilterPressure
        self.coilPressure = coilPressure
        self.supplyPlenumPressure = supplyPlenumPressure
      }
      
      public init(
        equipmentMeasurement: EquipmentMeasurement
      ) {
        switch equipmentMeasurement {
        case let .airHandler(equipment):
          self.init(
            airflow: equipment.airflow,
            returnPlenumPressure: equipment.returnPlenumPressure,
            postFilterPressure: equipment.postFilterPressure,
            coilPressure: equipment.postCoilPressure,
            supplyPlenumPressure: equipment.supplyPlenumPressure
          )
        case let .furnaceAndCoil(equipment):
          self.init(
            airflow: equipment.airflow,
            returnPlenumPressure: equipment.returnPlenumPressure,
            postFilterPressure: equipment.postFilterPressure,
            coilPressure: equipment.preCoilPressure,
            supplyPlenumPressure: equipment.supplyPlenumPressure
          )
        }
      }
      
      public func equipmentMeasurement(
        type: EquipmentMeasurement.EquipmentType
      ) -> EquipmentMeasurement {
        switch type {
        case .airHandler:
          return .airHandler(.init(
            airflow: airflow ?? 0,
            manufacturersIncludedFilterPressureDrop: 0.1,
            returnPlenumPressure: returnPlenumPressure ?? 0,
            postFilterPressure: postFilterPressure ?? 0,
            postCoilPressure: coilPressure ?? 0,
            supplyPlenumPressure: supplyPlenumPressure ?? 0
          ))
          
        case .furnaceAndCoil:
          return .furnaceAndCoil(.init(
            airflow: airflow ?? 0,
            manufacturersIncludedFilterPressureDrop: 0,
            returnPlenumPressure: returnPlenumPressure ?? 0,
            postFilterPressure: postFilterPressure ?? 0,
            preCoilPressure: coilPressure ?? 0,
            supplyPlenumPressure: supplyPlenumPressure ?? 0
          ))
        }
      }
    }
    
    public enum Field: CaseIterable, FocusableField, Hashable, Identifiable, Sendable {
      case returnPlenumPressure
      case postFilterPressure
      case coilPressure
      case supplyPlenumPressure
      case airflow
      
      public var id: Self { self }

    }
  }
  
  public enum Action: BindableAction, ViewAction, Sendable {
    case binding(BindingAction<State>)
    case destination(PresentationAction<Destination.Action>)
    case view(View)
    
    @CasePathable
    public enum View: Sendable {
      case infoButtonTapped
      case nextButtonTapped
      case onAppear
      case resetButtonTapped
      case submitField
    }
  }

  @Dependency(\.logger["\(Self.self)"]) var logger

  public var body: some Reducer<State, Action> {
    BindingReducer()
    Reduce<State, Action> { state, action in
      switch action {
        
      case .binding:
        return .none
        
      case .destination:
        return .none
       
      case let .view(action):
        switch action {
          
        case .infoButtonTapped:
          state.destination = .infoView(.init())
          return .none

        case .nextButtonTapped:
          guard state.isValid else {
            return .fail(
              """
              Received next button tapped action, but the state is not valid.

              This is considered an application logic error.
              """,
              logger: logger
            )
          }
          state.sharedSettings.equipmentMeasurement = state.equipmentMeasurement
          state.destination = .flaggedMeasurementsList(.init(sharedSettings: state.$sharedSettings))
          return .none

        case .onAppear:
          guard let measurement = state.sharedSettings.equipmentMeasurement else {
            return .none
          }
          state.measurements = .init(equipmentMeasurement: measurement)
          return .none

        case .resetButtonTapped:
          state.measurements = .init()
          return .none

        case .submitField:
          if state.focusedField == .airflow {
            return .send(.view(.nextButtonTapped))
          }
          state.focusedField = state.focusedField?.next
          return .none
          
        }
      }
    }
    .ifLet(\.$destination, action: \.destination)
  }
}

fileprivate extension Store where State == EquipmentMeasurementForm.State {

  func prompt(
    field: EquipmentMeasurementForm.State.Field
  ) -> String {
    let label = label(field: field)
    guard field != .airflow else { return label }
    if field == .coilPressure && state.equipmentType == .airHandler {
      return "\(label) (Optional)"
    }
    if field == .postFilterPressure && state.equipmentType == .airHandler {
      return "\(label) (Optional)"
    }
    return "\(label) Pressure"
  }
  
  func label(
    field: EquipmentMeasurementForm.State.Field
  ) -> String {
    switch field {
    case .returnPlenumPressure:
      return "Return"
    case .postFilterPressure:
      return "Post-Filter"
    case .coilPressure:
      switch state.equipmentType {
      case .airHandler:
        return "Post-Coil"
      case .furnaceAndCoil:
        return "Pre-Coil"
      }
    case .supplyPlenumPressure:
      return "Supply"
    case .airflow:
      return "CFM"
    }
  }
  
  var pressureFields: [EquipmentMeasurementForm.State.Field] {
    EquipmentMeasurementForm.State.Field.allCases.filter {
      $0 != .airflow
    }
  }
}

@ViewAction(for: EquipmentMeasurementForm.self)
public struct EquipmentMeasurementFormView: View {
  
  @FocusState private var focusedField: EquipmentMeasurementForm.State.Field?
  @Bindable public var store: StoreOf<EquipmentMeasurementForm>

  public init(store: StoreOf<EquipmentMeasurementForm>) {
    self.store = store
  }
  
  public var body: some View {
    Form {
      if store.allowEquipmentTypeSelection {
        Section {
        } header: {
          Text("Equipment Type")
        } footer: {
          EquipmentTypePicker(selection: $store.equipmentType)
            .pickerStyle(.segmented)
            .labelsHidden()
        }
      }
      Section {
        Grid(alignment: .leading, horizontalSpacing: 40) {
          ForEach(store.pressureFields, content: gridRow(for:)) 
        }
      } header: {
        HStack {
          Text("Static Measurements")
          Spacer()
          InfoButton { send(.infoButtonTapped) }
        }
      }
      
      Section {
        Grid(alignment: .leading, horizontalSpacing: 80) {
          gridRow(for: .airflow)
        }
      } header: {
        HStack {
          Spacer()
          Text(store.sharedSettings.equipmentMetadata.coolingCapacity.description)
        }
      } footer: {
        HStack {
          Spacer()
          ResetButton { send(.resetButtonTapped) }
            .padding(.top)
          Spacer()
        }
      }
    }
    .bind($focusedField, to: $store.focusedField)
    .labeledContentStyle(.gridRow)
    .onAppear { send(.onAppear) }
    .textLabelStyle(.boldSecondary)
    .textFieldStyle(.roundedBorder)
    .toolbar {
      NextButton { send(.nextButtonTapped) }
        .nextButtonStyle(.toolbar)
        .disabled(!store.isValid)
    }
    .sheet(
      item: $store.scope(state: \.destination?.infoView, action: \.destination.infoView)
    ){ store in
      NavigationStack {
        InfoView(store: store)
      }
    }
    .navigationDestination(
      item: $store.scope(
        state: \.destination?.flaggedMeasurementsList,
        action: \.destination.flaggedMeasurementsList
      )
    ) { store in
      FlaggedMeasurementListView(store: store)
    }
  }

  private func gridRow(for field: EquipmentMeasurementForm.State.Field) -> some View {
    TextLabeledContent(store.label(field: field)) {
      textField(for: field)
    }
  }

  private func textField(
    for field: EquipmentMeasurementForm.State.Field
  ) -> some View {
    let value: Binding<Double?>
    var fractionLength: Int = 2
    
    switch field {
    case .returnPlenumPressure:
      value = $store.measurements.returnPlenumPressure
    case .postFilterPressure:
      value = $store.measurements.postFilterPressure
    case .coilPressure:
      value = $store.measurements.coilPressure
    case .supplyPlenumPressure:
      value = $store.measurements.supplyPlenumPressure
    case .airflow:
      value = $store.measurements.airflow
      fractionLength = 0
    }
    
    return textField(
      title: store.prompt(field: field),
      value: value,
      fractionLength: fractionLength,
      numberPad: field == .airflow
    )
    .focused($focusedField, equals: field)
  }
  
  @ViewBuilder
  private func textField(
    title: String,
    value: Binding<Double?>,
    fractionLength: Int,
    numberPad: Bool
  ) -> some View {
    if numberPad {
      TextField(
        title,
        value: value,
        fractionLength: fractionLength,
        prompt: Text(title)
      )
      .numberPad()
      .onSubmit { send(.submitField) }
    } else {
      TextField(
        title,
        value: value,
        fractionLength: fractionLength,
        prompt: Text(title)
      )
      .decimalPad()
      .onSubmit { send(.submitField) }
    }
  }
}

fileprivate extension InfoViewFeature.State {

  init() {
    self.init(
      title: "Existing Measurements",
      body: """
      Record the current static pressure and airflow measurements of the existing system.
      """
    )
  }
}

#Preview {
  NavigationStack {
    EquipmentMeasurementFormView(
      store: Store(initialState: EquipmentMeasurementForm.State(
        sharedSettings: Shared(SharedPressureEstimationState()))
      ) {
        EquipmentMeasurementForm()
      }
    )
  }
}