LLM Search Using Core Spotlight (SpotlightSearchTool)

import SwiftUI
import CoreSpotlight
import FoundationModels

// MARK: - Spotlight Index Delegate
final class TrailIndexDelegate: NSObject, CSSearchableIndexDelegate {
    func searchableIndex(_ searchableIndex: CSSearchableIndex, reindexAllSearchableItemsWithAcknowledgementHandler acknowledgementHandler: @escaping () -> Void) {
        acknowledgementHandler()
    }

    func searchableIndex(_ searchableIndex: CSSearchableIndex, reindexSearchableItemsWithIdentifiers identifiers: [String], acknowledgementHandler: @escaping () -> Void) {
        acknowledgementHandler()
    }

    // New in iOS 27: called by SpotlightSearchTool to recover full item metadata
    func searchableItems(forIdentifiers identifiers: [String]) async -> [CSSearchableItem] {
        return identifiers.compactMap { id in
            let attrs = CSSearchableItemAttributeSet(contentType: .text)
            attrs.title = "Example Trail"
            attrs.contentDescription = "A scenic trail with river views, completed on 2025-06-10."
            attrs.namedLocation = "Marin County, CA"
            return CSSearchableItem(uniqueIdentifier: id, domainIdentifier: "trails", attributeSet: attrs)
        }
    }
}

// MARK: - View Model
@Observable
final class TrailSearchViewModel {
    var messages: [(role: String, text: String)] = []
    var isLoading = false

    private let indexDelegate = TrailIndexDelegate()

    func ask(_ question: String) async {
        messages.append((role: "user", text: question))
        isLoading = true
        defer { isLoading = false }

        // 1. Configure SpotlightSearchTool for app bundle index
        let searchTool = SpotlightSearchTool()

        // 2. Set the delegate so the tool can recover full item metadata
        let index = CSSearchableIndex.default()
        index.indexDelegate = indexDelegate

        // 3. Create a session with the on-device model + tool
        let session = LanguageModelSession(
            model: SystemLanguageModel.default,
            tools: [searchTool]
        )

        do {
            let response = try await session.respond(to: question)
            messages.append((role: "assistant", text: response.content))
        } catch {
            messages.append((role: "assistant", text: "Error: \(error.localizedDescription)"))
        }
    }
}

// MARK: - SwiftUI View
struct TrailSearchView: View {
    @State private var viewModel = TrailSearchViewModel()
    @State private var input = ""

    var body: some View {
        NavigationStack {
            VStack {
                ScrollView {
                    LazyVStack(alignment: .leading, spacing: 12) {
                        ForEach(viewModel.messages.indices, id: \.self) { i in
                            let msg = viewModel.messages[i]
                            HStack {
                                if msg.role == "user" { Spacer() }
                                Text(msg.text)
                                    .padding(10)
                                    .background(msg.role == "user" ? Color.blue.opacity(0.2) : Color.gray.opacity(0.15))
                                    .clipShape(RoundedRectangle(cornerRadius: 12))
                                if msg.role == "assistant" { Spacer() }
                            }
                        }
                    }
                    .padding()
                }
                if viewModel.isLoading {
                    ProgressView("Searching trails…").padding(.bottom, 4)
                }
                HStack {
                    TextField("Ask about your hikes…", text: $input)
                        .textFieldStyle(.roundedBorder)
                    Button("Send") {
                        let q = input
                        input = ""
                        Task { await viewModel.ask(q) }
                    }
                    .disabled(input.isEmpty || viewModel.isLoading)
                }
                .padding()
            }
            .navigationTitle("Trail Journal")
        }
    }
}