import SwiftUI

struct InstanceFormView: View {
  @Environment(\.dismiss) private var dismiss
  @ObservedObject var model: FleetViewModel
  let instance: Instance?
  @State private var name = ""
  @State private var originText = ""
  @State private var tags: [String] = []
  @State private var tagDraft = ""
  @State private var password = ""
  @State private var validationMessage: String?
  @State private var isSaving = false

  init(model: FleetViewModel, instance: Instance? = nil) {
    self.model = model
    self.instance = instance
    _name = State(initialValue: instance?.name ?? "")
    _originText = State(initialValue: instance?.endpoint.displayAddress ?? "")
    _tags = State(initialValue: instance?.tags ?? [])
  }

  /// A relay instance is edited by name and tags only. Its address is not a URL the user typed —
  /// it is a pairing, and letting the form rewrite it would either drop the node's keys or produce
  /// an endpoint that fails validation. Re-pairing is the way to change it.
  private var isRelay: Bool { instance?.endpoint.isRelay == true }

  private var canSave: Bool {
    !name.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty
      && (isRelay || !originText.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
  }

  var body: some View {
    NavigationStack {
      ScrollView {
        VStack(spacing: 12) {
          AICard {
            VStack(alignment: .leading, spacing: 14) {
              field("名称", text: $name, placeholder: "Home Node")
              if isRelay {
                relayChannelRow
              } else {
                field("地址", text: $originText, placeholder: "http://192.168.1.10:3000")
              }
              tagEditor
              if !isRelay {
                field(
                  "实例密码",
                  text: $password,
                  placeholder: instance == nil ? "可选，仅保存在本机" : "留空则不修改密码",
                  secure: true
                )
              }
            }
          }
          if isRelay {
            AIStatusBanner(
              "中继节点的密码保存在节点 agent 上，手机不持有；更换中继需要重新配对。",
              tint: AITheme.muted,
              systemImage: "lock.shield"
            )
          }
          if let validationMessage {
            AIStatusBanner(
              validationMessage, tint: AITheme.danger, systemImage: "exclamationmark.triangle")
          }
        }
        .padding(16)
        .padding(.bottom, 8)
      }
      .aiBottomActionBar {
        AIActionRow {
          Button("取消") { dismiss() }
            .buttonStyle(AIButtonStyle(kind: .secondary, size: .regular, fillsWidth: true))

          Button {
            save()
          } label: {
            HStack(spacing: 8) {
              if isSaving {
                ProgressView()
                  .controlSize(.small)
              }
              Text(isSaving ? "保存中" : "保存实例")
            }
          }
          .buttonStyle(AIButtonStyle(kind: .primary, size: .regular, fillsWidth: true))
          .disabled(!canSave || isSaving)
        }
      }
      .background(AITheme.canvas.ignoresSafeArea())
      .navigationTitle(instance == nil ? "添加实例" : "编辑实例")
      #if os(iOS)
        // 表单表统一用行内标题：大标题会在卡片上方留出一整条空白，
        // 而「批量标签」等其它表已经是行内样式。
        .navigationBarTitleDisplayMode(.inline)
        .scrollDismissesKeyboard(.interactively)
      #endif
    }
  }

  /// The relay channel is read-only here, but it must still be visible: without it the form shows
  /// a node with no address at all, which reads as missing data rather than as a different mode.
  private var relayChannelRow: some View {
    VStack(alignment: .leading, spacing: 6) {
      AIFieldLabel("通道")
      HStack(spacing: 8) {
        Text("中继")
          .font(.caption.weight(.semibold))
          .foregroundStyle(AITheme.muted)
          .padding(.horizontal, 8)
          .padding(.vertical, 3)
          .background(AITheme.canvas, in: Capsule())
        Text(originText.isEmpty ? "已配对节点" : originText)
          .font(.footnote)
          .foregroundStyle(AITheme.ink)
          .lineLimit(1)
          .truncationMode(.middle)
      }
    }
    .accessibilityElement(children: .combine)
  }

  private var tagEditor: some View {
    VStack(alignment: .leading, spacing: 6) {
      AIFieldLabel("标签")
      TagEditorView(tags: $tags, suggestions: model.allTags)
    }
    .accessibilityElement(children: .contain)
  }

  private func field(
    _ title: String,
    text: Binding<String>,
    placeholder: String,
    secure: Bool = false
  ) -> some View {
    VStack(alignment: .leading, spacing: 6) {
      AIFieldLabel(title)
      if secure {
        SecureField(placeholder, text: text)
          .textFieldStyle(AIFieldStyle())
          .textContentType(.password)
          .accessibilityLabel(title)
      } else {
        TextField(placeholder, text: text)
          .textFieldStyle(AIFieldStyle())
          .accessibilityLabel(title)
          .submitLabel(.done)
          #if os(iOS)
            .keyboardType(title == "地址" ? .URL : .default)
            .textInputAutocapitalization(.never)
          #endif
          .autocorrectionDisabled()
      }
    }
  }

  private func save() {
    guard !isSaving else { return }
    isSaving = true
    let normalizedName = name.trimmingCharacters(in: .whitespacesAndNewlines)
    guard let origin = URL(string: originText.trimmingCharacters(in: .whitespacesAndNewlines)),
      origin.scheme == "http" || origin.scheme == "https",
      origin.host != nil
    else {
      validationMessage = "请输入有效的 HTTP 或 HTTPS 根地址。"
      isSaving = false
      return
    }
    // An existing relay instance keeps its endpoint: the address field only edits a direct
    // origin, and rewriting a pairing into a direct one here would silently drop the node's keys.
    let endpoint = instance?.endpoint.isRelay == true ? instance!.endpoint : InstanceEndpoint.direct(origin)
    let input = InstanceInput(
      name: normalizedName,
      endpoint: endpoint,
      tags: tags,
      password: password.isEmpty ? nil : password
    )
    Task {
      do {
        if let instance {
          try await model.update(instance.id, input)
        } else {
          try await model.add(input)
        }
      } catch {
        validationMessage = "保存失败，请检查地址是否重复。"
      }
      isSaving = false
    }
  }
}