import Models
import Services
import SwiftUI
import Views

@MainActor
struct ApplyLabelsView: View {
  enum Mode {
    case item(LinkedItem)
    case highlight(Highlight)
    case list([LinkedItemLabel])

    var navTitle: String {
      switch self {
      case .item, .highlight:
        return "Set Labels"
      case .list:
        return "Set Labels"
      }
    }

    var confirmButtonText: String {
      switch self {
      case .item, .highlight:
        return LocalText.genericSave
      case .list:
        return LocalText.doneGeneric
      }
    }
  }

  let mode: Mode
  let onSave: (([LinkedItemLabel]) -> Void)?

  @EnvironmentObject var dataService: DataService
  @Environment(\.presentationMode) private var presentationMode
  @StateObject var viewModel = LabelsViewModel()
  @State var isLabelsEntryFocused = false

  enum ViewState {
    case mainView
    case editingTitle
    case editingLabels
    case viewingHighlight
  }

  func isSelected(_ label: LinkedItemLabel) -> Bool {
    viewModel.selectedLabels.contains(where: { $0.id == label.id })
  }

  var innerBody: some View {
    VStack {
      LabelsEntryView(
        searchTerm: $viewModel.labelSearchFilter,
        isFocused: $isLabelsEntryFocused,
        viewModel: viewModel
      )
      .padding(.horizontal, 10)
      .padding(.vertical, 20)

      if viewModel.labelSearchFilter.count >= 63 {
        Text("The maximum length of a label is 64 chars.").foregroundColor(Color.red).font(.footnote)
      }

      List {
        ForEach(viewModel.labels.applySearchFilter(viewModel.labelSearchFilter), id: \.self) { label in
          Button(
            action: {
              if isSelected(label) {
                if let idx = viewModel.selectedLabels.firstIndex(of: label) {
                  viewModel.selectedLabels.remove(at: idx)
                }
              } else {
                viewModel.labelSearchFilter = ZWSP
                viewModel.selectedLabels.append(label)
              }
            },
            label: {
              HStack {
                TextChip(feedItemLabel: label).allowsHitTesting(false)
                Spacer()
                if isSelected(label) {
                  Image(systemName: "checkmark")
                }
              }
              .contentShape(Rectangle())
            }
          )
          .padding(.vertical, 5)
          .frame(maxWidth: .infinity, alignment: .leading)
          #if os(macOS)
            .buttonStyle(PlainButtonStyle())
          #endif
        }
        if !viewModel.labelSearchFilter.isEmpty, viewModel.labelSearchFilter != ZWSP {
          createLabelButton
        }
      }
      .listStyle(.plain)
      .background(Color.extensionBackground)
      .frame(maxHeight: .infinity)
    }
    .navigationTitle(mode.navTitle)
    .background(Color.extensionBackground)
    .sheet(isPresented: $viewModel.showCreateLabelModal) {
      CreateLabelView(viewModel: viewModel, newLabelName: viewModel.labelSearchFilter)
    }
    .onAppear {
      Task {
        switch mode {
        case let .item(feedItem):
          await viewModel.loadLabels(dataService: dataService, item: feedItem)
        case let .highlight(highlight):
          await viewModel.loadLabels(dataService: dataService, highlight: highlight)
        case let .list(labels):
          await viewModel.loadLabels(dataService: dataService, initiallySelectedLabels: labels)
        }
      }
    }
  }

  var createLabelButton: some View {
    Button(
      action: { viewModel.showCreateLabelModal = true },
      label: {
        HStack {
          let trimmedLabelName = viewModel.labelSearchFilter.trimmingCharacters(in: .whitespacesAndNewlines)
          Image(systemName: "tag").foregroundColor(.blue)
          Text(
            viewModel.labelSearchFilter.count > 0 ?
              "Create: \"\(trimmedLabelName)\" label" :
              LocalText.createLabelMessage
          ).foregroundColor(.blue)
            .font(Font.system(size: 14))
          Spacer()
        }
      }
    )
    .buttonStyle(PlainButtonStyle())
    .disabled(viewModel.isLoading)
    #if os(iOS)
      .listRowSeparator(.hidden, edges: .bottom)
    #endif
    .padding(.vertical, 10)
  }

  var saveItemChangesButton: some View {
    Button(
      action: {
        switch mode {
        case let .item(feedItem):
          viewModel.saveItemLabelChanges(itemID: feedItem.unwrappedID, dataService: dataService)
          onSave?(Array(viewModel.selectedLabels))
        case .highlight:
          onSave?(Array(viewModel.selectedLabels))
        case .list:
          onSave?(Array(viewModel.selectedLabels))
        }
        presentationMode.wrappedValue.dismiss()
      },
      label: { Text(mode.confirmButtonText).foregroundColor(.appGrayTextContrast) }
    )
  }

  var cancelButton: some View {
    Button(
      action: { presentationMode.wrappedValue.dismiss() },
      label: { Text(LocalText.cancelGeneric).foregroundColor(.appGrayTextContrast) }
    )
  }

  var body: some View {
    #if os(iOS)
      NavigationView {
        innerBody
          .navigationBarTitleDisplayMode(.inline)
          .toolbar {
            ToolbarItem(placement: .navigationBarLeading) {
              cancelButton
            }
            ToolbarItem(placement: .navigationBarTrailing) {
              saveItemChangesButton
            }
          }
      }
    #elseif os(macOS)
      innerBody
        .toolbar {
          ToolbarItemGroup {
            cancelButton
            saveItemChangesButton
          }
        }
        .frame(minWidth: 400, minHeight: 600)
    #endif
  }
}

extension Sequence where Element == LinkedItemLabel {
  func applySearchFilter(_ searchFilter: String) -> [LinkedItemLabel] {
    if searchFilter.isEmpty || searchFilter == ZWSP {
      return map { $0 } // return the identity of the sequence
    }
    if searchFilter.starts(with: ZWSP) {
      let index = searchFilter.index(searchFilter.startIndex, offsetBy: 1)
      let trimmed = searchFilter.suffix(from: index).lowercased()
      return filter { ($0.name ?? "").lowercased().contains(trimmed) }
    }
    return filter { ($0.name ?? "").lowercased().contains(searchFilter.lowercased()) }
  }
}