Hosts the function that streams the response from a chat model to the client submitting a prompt

response_streamer.swift

//
//  ContentView.swift
//  ChatGPTCoreModel_playground
//
//  Created by Xcode Developer on 7/15/25.
//

import SwiftUI
import FoundationModels

// MARK: - Model for a single queued Psalm abstract

struct PsalmAbstract: Identifiable {
	let id = UUID()
	let psalmNumber: Int
	var response: String = "Pending..."
	var isCompleted: Bool = false
}

// MARK: - Actor for safe queueing

actor PsalmQueue {
	private(set) var items: [PsalmAbstract] = []

	func addPsalm(_ psalmNumber: Int) -> PsalmAbstract {
		let abstract = PsalmAbstract(psalmNumber: psalmNumber)
		items.append(abstract)
		return abstract
	}

	func updateResponse(for id: UUID, response: String) {
		if let index = items.firstIndex(where: { $0.id == id }) {
			items[index].response = response
			items[index].isCompleted = true
		}
	}

	var currentItems: [PsalmAbstract] {
		items
	}
}

// MARK: - Main View

struct ContentView: View {
	@State private var psalmNumber: Int = .zero
	@State private var psalmNumberInput: String = String()
	var quotedPsalmNumberInput: Binding<String> {
		Binding<String>(
			get: {
				"\(psalmNumberInput)"
			},
			set: { newValue in
				if newValue.hasPrefix("\"") && newValue.hasSuffix("\"") {
					psalmNumberInput = String(newValue.dropFirst().dropLast())
				} else {
					psalmNumberInput = newValue
				}
			}
		)
	}

	@State private var abstracts: [PsalmAbstract] = []

	private let queue = PsalmQueue()

	@State private var responseStream: AbstractPsalmResponse.PartiallyGenerated?
	var partialResponseStream: Binding<AbstractPsalmResponse.PartiallyGenerated?> {
		Binding<AbstractPsalmResponse.PartiallyGenerated?>(
			get: {
				responseStream
			},
			set: { newValue in
				responseStream = newValue
			}
		)
	}

	// Timer properties for stepper acceleration
	@State private var timer: Timer?
	@State private var timerInterval: TimeInterval = 0.5
	@State private var isIncrementing: Bool = true

	var body: some View {
		ZStack {
			// Linear gradient background
			LinearGradient(
				gradient: Gradient(colors: [
					Color.primary.opacity(0.25),
					Color.accentColor.opacity(0.25)
				]),
				startPoint: .bottomTrailing,
				endPoint: .topLeading
			)
			.ignoresSafeArea()

			VStack(content: {
				ZStack(alignment: (.center), content: {
					//                    HStack {
					//                        TextField(("Enter a psalm (1-150)..."), text: $psalmNumberInput, axis: .horizontal)
					//                            .padding(.leading)
					//                        Spacer()
					//                    }

					GlassEffectContainer(spacing: CGFloat.zero) {
						HStack {
							Button {
								decrementPsalm()
							} label: {
								Image(systemName: "minus.circle")
									.foregroundColor(Color(UIColor.white))
									.symbolRenderingMode(.hierarchical)
									.font(.largeTitle)
									.imageScale(.small)
									.labelStyle(.iconOnly)
									.clipShape(Circle())
									.padding(8)
									.glassEffect()
							}
							.padding(.leading, 2)
							.buttonStyle(PlainButtonStyle())
							.shadow(color: Color.white.opacity(0.5), radius: 2, x: 2, y: 2)

							.simultaneousGesture(
								LongPressGesture().onEnded { _ in
									startTimer(incrementing: false)
								}
							)
							.simultaneousGesture(
								DragGesture(minimumDistance: 0).onEnded { _ in
									stopTimer()
								}
							)

							//                            Spacer()

							// Number input field
							TextField("Psalm \(psalmNumber)", text: quotedPsalmNumberInput) // "Psalm", text: $psalmNumberInput)
								.keyboardType(.numberPad)
								.multilineTextAlignment(.center)
								.textFieldStyle(DefaultTextFieldStyle())
								.shadow(color: Color.black.opacity(0.5), radius: 2, x: 0, y: 0)

								.onChange(of: psalmNumberInput) { oldValue, newValue in
									let filtered = newValue.filter { "0123456789".contains($0) }
									if let value = Int(filtered) {
										psalmNumber = min(max(value, 1), 150)
									}
									psalmNumberInput = "\(psalmNumber)"
								}
								.font(.largeTitle)
								.foregroundColor(Color(UIColor.white))
								.background(Color(UIColor.clear))
								.padding(4)

							//                            Spacer()

							Button {
								incrementPsalm()
							} label: {
								Image(systemName: "plus.circle")
									.padding(8)
									.foregroundColor(Color(UIColor.white))
									.symbolRenderingMode(.hierarchical)
									.font(.largeTitle)
									.imageScale(.small)
									.labelStyle(.iconOnly)
									.clipShape(Circle())
									.glassEffect()
							}
							.simultaneousGesture(
								LongPressGesture().onEnded { _ in
									startTimer(incrementing: true)
								}
							)
							.simultaneousGesture(
								DragGesture(minimumDistance: 0).onEnded { _ in
									stopTimer()
								}
							)
						} // END OF HSTACK
					} // END OF GLASSEFFECTCONTAINER
					.fixedSize()
					.glassEffect(.regular.tint(Color.accentColor.opacity(0.25)))
					//                    .background(Color.init(uiColor: UIColor(white: 1.0, alpha: 0.2)))
					//                    .clipShape(RoundedRectangle(cornerSize: CGSize(width: 25, height: 25), style: .continuous))
					//                    .padding(.trailing, 75)

					//                    Button {
					//                        dismissKeyboard()
					//                        addPsalmAndRun()
					//                    } label: {
					//                        Image(systemName: "pencil")
					//                            .padding(8)
					//                            .foregroundColor(Color(UIColor.white))
					//                            .symbolRenderingMode(.monochrome)
					//                            .font(.largeTitle)
					//                            .imageScale(.medium)
					//                            .labelStyle(.iconOnly)
					//                            .clipShape(Circle())
					//                    }
					//                    //                    .padding(.leading, 100)
					//                    .glassEffect(in: .rect(cornerRadius: 25.0))
					//                    //                     .shadow(color: Color.white.opacity(0.5), radius: 2, x: 0, y: 0)
				})

				ScrollView {
					VStack(alignment: .leading, spacing: 16) {
						ForEach(abstracts) { item in
							VStack(alignment: .leading, spacing: 8) {
								Text("Psalm \(item.psalmNumber)")
									.font(.title2)
									.fontWeight(.medium)
									.padding(.vertical)
									.frame(idealWidth: UIScreen.main.bounds.size.width, maxWidth: UIScreen.main.bounds.size.width)
									.glassEffect(in: .rect(cornerRadius: 25.0))

								if item.isCompleted {
									Text(item.response)
										.dynamicTypeSize(DynamicTypeSize.xSmall)
										.font(.body)
										.frame(maxWidth: UIScreen.main.bounds.size.width)
								} else {
									ProgressView()
										.progressViewStyle(CircularProgressViewStyle())
								}
							}
							.padding()
							.background(Color.gray.opacity(0.1))
							.cornerRadius(28)
							.glassEffect(in: .rect(cornerRadius: 25.0))
							.padding(.vertical)
						}
					}
					//                    .padding(.bottom, 50)

					Spacer()
				}
				//                .frame(width: .infinity, height: .infinity)
				//                .border(Color.white.opacity(1.0), width: 0.2)
				//                .backgroundStyle(Color.white.opacity(1.0))
				.ignoresSafeArea()
			})
			.padding()
			.onAppear {
				psalmNumberInput = "\(psalmNumber)"
				Task {
					await refreshQueue()
				}
			}

			VStack {
				Spacer()

				HStack(alignment: .bottom, content: {
					Spacer()

					Text("James Alan Bush")
						.font(.caption)
						.foregroundColor(.primary)

					Spacer()

					Text("Commit ID 0863a4e")
						.font(.caption2)
						.foregroundColor(.secondary)

					Spacer()
				})
			}

			//            .frame(width: .infinity, height: .infinity)
			//            .border(Color.white.opacity(1.0), width: 0.2)
			//            .backgroundStyle(Color.white.opacity(1.0))
		}
	}

	private func dismissKeyboard() {
		UIApplication.shared.sendAction(#selector(UIResponder.resignFirstResponder), to: nil, from: nil, for: nil)
	}

	// MARK: - Stepper Logic

	private func incrementPsalm() {
		if psalmNumber < 150 {
			psalmNumber += 1
			psalmNumberInput = "\(psalmNumber)"
		}
	}

	private func decrementPsalm() {
		if psalmNumber > 1 {
			psalmNumber -= 1
			psalmNumberInput = "\(psalmNumber)"
		}
	}

	private func startTimer(incrementing: Bool) {
		isIncrementing = incrementing
		timerInterval = 0.5
		stopTimer()

		timer = Timer.scheduledTimer(withTimeInterval: timerInterval, repeats: true) { _ in
			if isIncrementing {
				incrementPsalm()
			} else {
				decrementPsalm()
			}
			accelerateScrolling()
		}
	}

	private func stopTimer() {
		timer?.invalidate()
		timer = nil
	}

	private func accelerateScrolling() {
		if timerInterval > 0.1 {
			timerInterval -= 0.05
			stopTimer()
			timer = Timer.scheduledTimer(withTimeInterval: timerInterval, repeats: true) { _ in
				if isIncrementing {
					incrementPsalm()
				} else {
					decrementPsalm()
				}
				accelerateScrolling()
			}
		}
	}

	// MARK: - Add & Execute

	private func addPsalmAndRun() {
		Task {
			let abstract = await queue.addPsalm(psalmNumber)
			await refreshQueue()

			Task.detached {
				await runPsalmAbstract(abstract)
			}
		}
	}

	private func runPsalmAbstract(_ abstract: PsalmAbstract) async {
		do {
			let instructions: Instructions = Instructions("""
			Your instructions:

			Your task is to write a 6-paragraph academic abstract of psalm \(abstract.psalmNumber). Following are the specifications for each paragraph, which describe some of the different ways biblical scholars and theologians analyze Scripture.

			Paragraph 1: Start by selecting a verse or passage within psalm \(abstract.psalmNumber) that is central to its message. The response format will simply be a standard scripture quote from the King James Version (i.e., the verse(s)) and then the reference on a new line). Proceed to write paragraph 2. If you did not proceed to paragraph 2, explain why in your response.
			Paragraph 2: Describe the purpose of psalm \(abstract.psalmNumber), explaining its spiritual intent and how it serves or helps the believer. Avoid mentioning the writer unless referring to the Psalm's direct impact on worship or spiritual life.
			Paragraph 3: Identify and summarize the key themes found in the psalm, supported by references from the text itself.
			Paragraph 4: Summarize any theological connections in psalm \(abstract.psalmNumber) and how these connections contribute to an understanding of God, faith, and spiritual matters.
			Paragraph 5: Summarize any Christological connections in psalm \(abstract.psalmNumber) and how these connections contribute to an understanding of the nature and work of Christ; quote any relevant scripture found elsewhere in the Bible, if necessary.
			Paragraph 6: Draw direct parallels to Christian teachings, using New Testament scriptures to illustrate how the message of the psalm is fulfilled or mirrored in Christ and His teachings, and give advice on how Christians today can apply the psalm's lessons in their own lives.
			""")

			let session: LanguageModelSession = LanguageModelSession(instructions: instructions)

			let prompt: Prompt = Prompt("""
			Psalm \(abstract.psalmNumber)
			""")

			let stream = session.streamResponse(
				to: prompt,
				generating: AbstractPsalmResponse.self
			)

			var accumulatedContent = ""

			for try await pstream in stream {
				// Store the current stream state
				await MainActor.run {
					self.responseStream = pstream
				}

				// Extract the content from the stream
				// abstractPsalmResponse is Optional<Array<String>>
				if let partialResponse = pstream.abstractPsalmResponse {
					// Join the array of strings into a single string
					let content = partialResponse.joined(separator: "\n")
					accumulatedContent = content
				} else {
					// If no response yet, continue to next iteration
					continue
				}

				// Update the queue with the accumulated content
				await queue.updateResponse(for: abstract.id, response: accumulatedContent)

				// Refresh the UI
				await refreshQueue()
			}

			// Final update to mark as completed
			await queue.updateResponse(for: abstract.id, response: accumulatedContent)

		} catch {
			await queue.updateResponse(for: abstract.id, response: "Error: \(error.localizedDescription)")
		}

		await refreshQueue()
	}

	@MainActor
	private func refreshQueue() async {
		abstracts = await queue.currentItems
	}
}

#Preview {
	ContentView()
		.preferredColorScheme(.dark)
}

stream_response.swift

private func runPsalmAbstract(_ abstract: PsalmAbstract) async {
	do {
		let instructions: Instructions = Instructions("""
		Your instructions:

		Your task is to write a 6-paragraph academic abstract of psalm \(abstract.psalmNumber). Following are the specifications for each paragraph, which describe some of the different ways biblical scholars and theologians analyze Scripture.

		Paragraph 1: Start by selecting a verse or passage within psalm \(abstract.psalmNumber) that is central to its message. The response format will simply be a standard scripture quote from the King James Version (i.e., the verse(s)) and then the reference on a new line). Proceed to write paragraph 2. If you did not proceed to paragraph 2, explain why in your response.
		Paragraph 2: Describe the purpose of psalm \(abstract.psalmNumber), explaining its spiritual intent and how it serves or helps the believer. Avoid mentioning the writer unless referring to the Psalm's direct impact on worship or spiritual life.
		Paragraph 3: Identify and summarize the key themes found in the psalm, supported by references from the text itself.
		Paragraph 4: Summarize any theological connections in psalm \(abstract.psalmNumber) and how these connections contribute to an understanding of God, faith, and spiritual matters.
		Paragraph 5: Summarize any Christological connections in psalm \(abstract.psalmNumber) and how these connections contribute to an understanding of the nature and work of Christ; quote any relevant scripture found elsewhere in the Bible, if necessary.
		Paragraph 6: Draw direct parallels to Christian teachings, using New Testament scriptures to illustrate how the message of the psalm is fulfilled or mirrored in Christ and His teachings, and give advice on how Christians today can apply the psalm's lessons in their own lives.
		""")

		let session: LanguageModelSession = LanguageModelSession(instructions: instructions)

		let prompt: Prompt = Prompt("""
		Psalm \(abstract.psalmNumber)
		""")

		let stream = session.streamResponse(
			to: prompt,
			generating: AbstractPsalmResponse.self
		)

		var accumulatedContent = ""

		for try await pstream in stream {
			// Store the current stream state
			await MainActor.run {
				self.responseStream = pstream
			}

			// Extract the content from the stream
			// abstractPsalmResponse is Optional<Array<String>>
			if let partialResponse = pstream.abstractPsalmResponse {
				// Join the array of strings into a single string
				let content = partialResponse.joined(separator: "\n")
				accumulatedContent = content
			} else {
				// If no response yet, continue to next iteration
				continue
			}

			// Update the queue with the accumulated content
			await queue.updateResponse(for: abstract.id, response: accumulatedContent)

			// Refresh the UI
			await refreshQueue()
		}

		// Final update to mark as completed
		await queue.updateResponse(for: abstract.id, response: accumulatedContent)

	} catch {
		await queue.updateResponse(for: abstract.id, response: "Error: \(error.localizedDescription)")
	}

	await refreshQueue()
}