import SwiftUI

/// "Join a call as a guest": paste the invite link you were sent, and
/// that meeting's own browser sign-in runs for it, on whatever server the
/// link names. Nothing about it is kept.
///
/// The clipboard is read only through the Paste control, so iPhone never
/// asks whether Calls may paste, and nothing is read that the person did
/// not hand over.
@MainActor public struct GuestJoinView: View {
  @ObservedObject private var model: CallsModel
  private let done: () -> Void
  @State private var link: String
  @State private var problem: String = ""

  /// `problem` shows the link's validation at once — for snapshots of
  /// the inline error.
  public init(
    model: CallsModel, link: String = "", problem: Bool = false, done: @escaping () -> Void
  ) {
    self.model = model
    self.done = done
    _link = State(initialValue: link)
    var message = ""
    if problem, case .failure(let failure) = MeetingLink.validate(link) {
      message = failure.message
    }
    _problem = State(initialValue: message)
  }

  public var body: some View {
    NavigationStack {
      Form {
        Section {
          TextField("Invite link", text: $link, prompt: Text("https://…/j/…"))
            .accessibilityIdentifier("inviteLink")
            #if os(iOS)
              .keyboardType(.URL).textInputAutocapitalization(.never).autocorrectionDisabled()
            #endif
            .onSubmit(join)
            .onChange(of: link) { problem = "" }
          PasteButton(payloadType: String.self) { strings in
            guard let text = strings.first else { return }
            Task { @MainActor in paste(text) }
          }
          .accessibilityIdentifier("pasteInvite")
          if !problem.isEmpty {
            Label(problem, systemImage: "exclamationmark.circle.fill")
              .foregroundStyle(.red).fixedSize(horizontal: false, vertical: true)
              .accessibilityLabel("Error: \(problem)")
          }
        } footer: {
          Text(
            "Paste the link someone sent you. Your browser opens to confirm who you are for this meeting; nothing is saved on this device, and your Calls server stays \(model.serverHost)."
          )
        }
      }
      .formStyle(.grouped)
      #if os(iOS)
        .navigationTitle("Join as a guest")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
          ToolbarItem(placement: .cancellationAction) { Button("Cancel", action: done) }
          ToolbarItem(placement: .confirmationAction) { joinButton }
        }
      #else
        // A Mac sheet has no title bar to carry these, so they sit under
        // the form where a Mac dialog keeps its buttons.
        .safeAreaInset(edge: .top) {
          Text("Join as a guest").font(.title2.bold())
            .frame(maxWidth: .infinity, alignment: .leading).padding([.horizontal, .top], 20)
        }
        .safeAreaInset(edge: .bottom) {
          HStack {
            Spacer()
            Button("Cancel", action: done).keyboardShortcut(.cancelAction)
            joinButton.keyboardShortcut(.defaultAction)
          }.padding([.horizontal, .bottom], 20)
        }
      #endif
    }
    #if os(macOS)
      .frame(width: 460)
      .fixedSize(horizontal: false, vertical: true)
    #endif
    .tint(CallsAppearance.accent)
  }

  private var joinButton: some View {
    Button("Join", action: join).accessibilityIdentifier("guestJoin")
      .disabled(link.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
  }

  /// Fills the field only with a Calls link; anything else on the
  /// clipboard is left there, and said so.
  private func paste(_ text: String) {
    if case .success(let url) = MeetingLink.validate(text) {
      link = url.absoluteString
      problem = ""
    } else {
      problem = "The clipboard doesn’t hold a Calls invite link."
    }
  }

  private func join() {
    if let failure = model.joinAsGuest(link) {
      problem = failure.message
    } else {
      done()
    }
  }
}