import SwiftUI

struct InstanceGroupEditorView: View {
  @Environment(\.dismiss) private var dismiss
  @ObservedObject var model: FleetViewModel
  let targetIDs: [UUID]
  let onSaved: () -> Void

  @State private var selectedGroupID: UUID?
  @State private var isCreatingGroup = false
  @State private var newGroupName = ""
  @State private var isWorking = false
  @State private var errorMessage: String?

  private var selectedCount: Int { targetIDs.count }

  var body: some View {
    NavigationStack {
      ScrollView {
        LazyVStack(spacing: 12) {
          if let errorMessage {
            AIStatusBanner(
              errorMessage,
              tint: AITheme.danger,
              systemImage: "exclamationmark.triangle"
            )
          }

          AICard(padding: 16) {
            VStack(alignment: .leading, spacing: 12) {
              AISectionTitle(
                "批量归类",
                systemImage: "folder.badge.gearshape",
                detail: selectedCount == 0 ? "全部实例" : "\(selectedCount) 个实例"
              )
              Text("选择一个分组后保存，所选实例会立即移入该分组。")
                .font(.footnote)
                .foregroundStyle(AITheme.muted)
                .frame(maxWidth: .infinity, alignment: .leading)
            }
          }

          if isCreatingGroup {
            AICard(padding: 16) {
              VStack(alignment: .leading, spacing: 10) {
                AIFieldLabel("新分组名称")
                TextField("例如：家里、外场、测试机", text: $newGroupName)
                  .textFieldStyle(AIFieldStyle())
                  .submitLabel(.done)
              }
            }
          } else {
            AICard(padding: 8) {
              VStack(spacing: 2) {
                groupRow(
                  title: "未分组",
                  subtitle: "移出当前分组",
                  systemImage: "square.dashed",
                  value: nil,
                  isSelected: selectedGroupID == nil,
                  selectionTrait: selectedGroupID == nil
                )

                ForEach(model.groups) { group in
                  Divider()
                    .overlay(AITheme.line.opacity(0.55))
                  groupRow(
                    title: group.name,
                    subtitle: "\(instanceCount(group.id)) 个实例",
                    systemImage: "folder",
                    value: group.id,
                    isSelected: selectedGroupID == group.id,
                    selectionTrait: selectedGroupID == group.id
                  )
                }
              }
            }
          }
        }
        .padding(16)
      }
      .background(AITheme.canvas.ignoresSafeArea())
      .navigationTitle("实例分组")
      #if os(iOS)
        .navigationBarTitleDisplayMode(.inline)
      #endif
      .toolbar {
        ToolbarItem(placement: .cancellationAction) {
          Button("取消") { dismiss() }
        }
        ToolbarItem(placement: .primaryAction) {
          Button("新建") {
            selectedGroupID = nil
            isCreatingGroup = true
            errorMessage = nil
          }
          .disabled(isWorking)
        }
      }
      .aiBottomActionBar {
        AIActionRow {
          Button {
            Task { await save() }
          } label: {
            Label(
              selectedGroupID == nil ? "移出分组" : "移入分组",
              systemImage: "tray.and.arrow.down"
            )
          }
          .buttonStyle(AIButtonStyle(kind: .primary, size: .regular, fillsWidth: true))
          .disabled(isWorking || (selectedGroupID == nil && !isCreatingGroup))
        }
      }
    }
  }

  private func groupRow(
    title: String,
    subtitle: String,
    systemImage: String,
    value: UUID?,
    isSelected: Bool,
    selectionTrait: Bool
  ) -> some View {
    Button {
      selectedGroupID = value
      isCreatingGroup = false
      newGroupName = ""
      errorMessage = nil
    } label: {
      HStack(spacing: 12) {
        Image(systemName: systemImage)
          .font(.subheadline.weight(.semibold))
          .foregroundStyle(isSelected ? AITheme.primary : AITheme.muted)
          .frame(width: 32, height: 32)
          .background((isSelected ? AITheme.primary : AITheme.muted).opacity(0.10))
          .clipShape(RoundedRectangle(cornerRadius: 10, style: .continuous))
          .accessibilityHidden(true)

        VStack(alignment: .leading, spacing: 2) {
          Text(title)
            .font(.subheadline.weight(.semibold))
            .foregroundStyle(AITheme.ink)
            .lineLimit(1)
          Text(subtitle)
            .font(.caption)
            .foregroundStyle(AITheme.muted)
            .lineLimit(1)
        }

        Spacer(minLength: 8)

        Image(
          systemName: isSelected
            ? "checkmark.circle.fill"
            : "circle.dashed"
        )
        .font(.system(size: 18))
        .foregroundStyle(isSelected ? AITheme.primary : AITheme.muted)
      }
      .padding(.horizontal, 12)
      .padding(.vertical, 8)
      .frame(minHeight: 54)
      .background(isSelected ? AITheme.primary.opacity(0.08) : Color.clear)
      .clipShape(RoundedRectangle(cornerRadius: 12, style: .continuous))
      .contentShape(Rectangle())
      .accessibilityElement(children: .combine)
      .accessibilityLabel("\(title)，\(subtitle)")
      .accessibilityAddTraits(isSelected ? [.isSelected, .isButton] : [.isButton])
    }
    .buttonStyle(.plain)
  }

  private func instanceCount(_ id: UUID) -> Int {
    model.rows.filter { $0.instance.groupId == id }.count
  }

  private func save() async {
    guard !isWorking else { return }
    isWorking = true
    errorMessage = nil

    do {
      if isCreatingGroup {
        let name = newGroupName.trimmingCharacters(in: .whitespacesAndNewlines)
        let group = try await model.createGroup(named: name)
        selectedGroupID = group.id
        isCreatingGroup = false
        newGroupName = ""
      }

      try await model.assign(
        groupID: selectedGroupID,
        to: targetIDs.isEmpty ? model.visibleRows.map(\.id) : targetIDs
      )
      onSaved()
      dismiss()
    } catch {
      errorMessage = isCreatingGroup
        ? "创建分组失败，名称不能为空且不能重复。"
        : "保存分组失败，请检查节点后重试。"
    }
    isWorking = false
  }
}