import ComposableArchitecture
import FlaggedViews
import InfoViewFeature
import SharedModels
import Styleguide
import SwiftUI

@Reducer
public struct EquipmentSettingsForm {

  @CasePathable
  public enum InfoView {
    case capacities
    case manufacturersIncludedFilterPressureDrop
    case ratedStaticPressures
  }

  @Reducer(state: .equatable)
  public enum Destination {
    case infoView(InfoViewFeature)
  }

  @ObservableState
  public struct State: Equatable {
    @Presents public var destination: Destination.State?
    public var includesFilterDrop: Bool
    public var equipmentType: EquipmentMeasurement.EquipmentType
    public var focusedField: Field? = nil
    @Shared public var sharedSettings: SharedPressureEstimationState

    public init(
      destination: Destination.State? = nil,
      includesFilterDrop: Bool = false,
      equipmentType: EquipmentMeasurement.EquipmentType = .airHandler,
      sharedSettings: Shared<SharedPressureEstimationState>
    ) {
      self.destination = destination
      self.includesFilterDrop = includesFilterDrop
      self.equipmentType = equipmentType
      self._sharedSettings = sharedSettings
    }

    public var isValid: Bool {
      guard equipmentType == .furnaceAndCoil else { return true }
      return sharedSettings.heatingCapacity != nil
    }

    // Note: These need to be in display order.
    public enum Field: Hashable, CaseIterable, FocusableField, Identifiable  {
      case heatingCapacity
      case minimumStaticPressure
      case maximumStaticPressure
      case ratedStaticPressure
      case manufacturersIncludedFilterPressureDrop

      public var id: Self { self }
    }
  }

  public enum Action: BindableAction, ViewAction {
    case binding(BindingAction<State>)
    case destination(PresentationAction<Destination.Action>)
    case view(View)

    @CasePathable
    public enum View {
      case infoButtonTapped(InfoView)
      case resetButtonTapped
      case submitField
    }
  }

  public var body: some Reducer<State, Action> {
    BindingReducer()
    Reduce<State, Action> { state, action in
      switch action {

      case .binding(\.includesFilterDrop):
        guard state.includesFilterDrop else {
          state.sharedSettings.manufacturersIncludedFilterPressureDrop = nil
          return .none
        }
        guard state.sharedSettings.manufacturersIncludedFilterPressureDrop != nil else {
          return .none
        }
        state.sharedSettings.manufacturersIncludedFilterPressureDrop = 0.1
        return .none

      case .binding:
        return .none

      case .destination(.dismiss):
        state.destination = nil
        return .none

      case .destination:
        return .none

      case let .view(action):
        switch action {

        case let .infoButtonTapped(infoView):
          state.destination = .infoView(.init(view: infoView))
          return .none

        case .resetButtonTapped:
          state.sharedSettings.heatingCapacity = nil
          return .none

        case .submitField:
          state.focusedField = state.focusedField?.next
          return .none

        }
      }
    }
    .ifLet(\.$destination, action: \.destination)
  }
}

@ViewAction(for: EquipmentSettingsForm.self)
public struct EquipmentSettingsFormView: View {

  @FocusState private var focusedField: EquipmentSettingsForm.State.Field?
  @Bindable public var store: StoreOf<EquipmentSettingsForm>

  public init(store: StoreOf<EquipmentSettingsForm>) {
    self.store = store
    self.focusedField = store.focusedField
  }

  public var body: some View {
    Form {
      Section {
        EquipmentTypePicker(selection: $store.equipmentType)
          .pickerStyle(.segmented)
        EmptyView()
      } header: {
        Text("Equipment Type")
      }
      .listRowBackground(Color.clear)
      
      Section {
        FanTypePicker(selection: $store.sharedSettings.fanType)
          .pickerStyle(.segmented)
      } header: {
        Text("Fan Type")
      }
      .listRowBackground(Color.clear)
      
      Section {
        Grid(alignment: .leading, horizontalSpacing: 40) {
          GridRow {
            TextLabel(
              store.equipmentType == .furnaceAndCoil
              ? "Cooling"
              : "Capacity"
            )
            Spacer()
            CoolingCapacityPicker(
              selection: $store.sharedSettings.coolingCapacity
            )
          }
          if store.equipmentType == .furnaceAndCoil {
            GridRow {
              TextLabel("Heating")
              textField(
                "Heating Capacity",
                value: $store.sharedSettings.heatingCapacity,
                fractionLength: 0
              )
              .focused($focusedField, equals: .heatingCapacity)
              .numberPad()
              .gridCellColumns(2)
            }
          }
        }
      } header: {
        if store.equipmentType == .airHandler {
          EmptyView()
        } else {
          Text("Capacities")
        }
      }

      Section {
        Grid(alignment: .leading, horizontalSpacing: 40) {
          ForEach(RatingsField.allCases, content: ratingsRow(for:))
        }
        .labeledContentStyle(.gridRow)
      } header: {
        header("Rated Static Pressure", infoView: .ratedStaticPressures)
      }

      Section {
        VStack(alignment: .leading) {
          HStack {
            TextLabel("Includes Filter Drop")
            Spacer()
            Toggle("Includes Filter Drop", isOn: $store.includesFilterDrop)
          }
          if store.includesFilterDrop {
            HStack {
              TextLabel("Filter Drop")
              Spacer()
              textField(
                "Filter Drop",
                value: $store.sharedSettings.manufacturersIncludedFilterPressureDrop
              )
              .focused($focusedField, equals: .manufacturersIncludedFilterPressureDrop)
              .decimalPad()
              .padding(.leading, 40)
            }
          }
        }
      } header: {
        header(infoView: .manufacturersIncludedFilterPressureDrop) {
          VStack(alignment: .leading) {
            Text("Manufacturer's")
            Text("Filter Pressure Drop")
          }
        }
      }
    }
    .labelsHidden()
    .bind($focusedField, to: $store.focusedField)
    .textLabelStyle(.boldSecondary)
    .textFieldStyle(.roundedBorder)
    .sheet(
      item: $store.scope(
        state: \.destination?.infoView,
        action: \.destination.infoView
      )
    ) { store in
      NavigationStack {
        InfoView(store: store)
      }
    }
  }

  private func ratingsRow(for ratingsField: RatingsField) -> some View {

    func binding(for ratingsField: RatingsField) -> Binding<Double> {
      switch ratingsField {
      case .maximum:
        return $store.sharedSettings.ratedStaticPressures.maximum
      case .minimum:
        return $store.sharedSettings.ratedStaticPressures.minimum
      case .rated:
        return $store.sharedSettings.ratedStaticPressures.rated
      }
    }

    return TextLabeledContent(ratingsField.label) {
      TextField(ratingsField.prompt, value: binding(for: ratingsField), fractionLength: 2)
        .decimalPad()
        .focused($focusedField, equals: ratingsField.field)
        .onSubmit { send(.submitField) }
    }
  }

  private func header<Label: View>(
    infoView: EquipmentSettingsForm.InfoView,
    label: @escaping () -> Label
  ) -> some View {
    HStack {
      label()
      Spacer()
      InfoButton { send(.infoButtonTapped(infoView)) }
    }
  }

  private func header(
    _ title: String,
    infoView: EquipmentSettingsForm.InfoView
  ) -> some View {
    header(infoView: infoView) { Text(title) }
  }

  private func textField(
    _ title: String,
    value: Binding<Double?>,
    fractionLength: Int = 2
  ) -> some View {
    TextField(title, value: value, fractionLength: fractionLength, prompt: Text(title))
      .onSubmit { send(.submitField) }
  }
}

fileprivate struct BudgetFlagViewStyle: FlaggedViewStyle {

  func makeBody(configuration: Configuration) -> some View {
    HStack {
      configuration.flagged.flagImage
      Spacer()
      configuration.flagged.messageView
    }
  }
}

fileprivate extension InfoViewFeature.State {
  init(view: EquipmentSettingsForm.InfoView) {
    switch view {
    case .capacities:
      self.init(
        title: "Capacities",
        body: """
        Record the cooling and heating capacities of the system.
        """
      )
    case .manufacturersIncludedFilterPressureDrop:
      self.init(
        title: "Filter Pressure Drop",
        body: """
        Record the filter pressure drop that the manufacturer includes in their blower performance table, if applicable.

        Sometimes this information is not listed, therefore it may be reasonable to use a sensible default value of '0.1'.

        Note: The value that is set get's deducted from the filter pressure drop when determining the external static pressure of a system.
        """
      )
    case .ratedStaticPressures:
      self.init(
        title: "Rated Static",
        body: """
        Record the rated static pressures of the system.

        These are generally found on the nameplate of the equipment or in the installation manual.

        The defaults are generally acceptable for most unitary equipment.
        """
      )

    }
  }
}

fileprivate enum RatingsField: String, Hashable, CaseIterable, Identifiable {
  case maximum
  case minimum
  case rated

  var id: Self { self }

  var field: EquipmentSettingsForm.State.Field {
    switch self {
    case .maximum: return .maximumStaticPressure
    case .minimum: return .minimumStaticPressure
    case .rated: return .ratedStaticPressure
    }
  }

  var label: String { rawValue.capitalized }

  var prompt: String { "\(label) Pressure" }
}

#Preview {
  NavigationStack {
    EquipmentSettingsFormView(
      store: Store(
        initialState: EquipmentSettingsForm.State(
          sharedSettings: Shared(SharedPressureEstimationState())
        )
      ) {
        EquipmentSettingsForm()._printChanges()
      }
    )
    #if os(macOS)
    .frame(width: 400, height: 600)
    .padding()
    #endif
  }
}