Add function calling sample (#127)

Examples/GenerativeAISample/FunctionCallingSample/Screens/FunctionCallingScreen.swift

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+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import GenerativeAIUIComponents
+import GoogleGenerativeAI
+import SwiftUI
+
+struct FunctionCallingScreen: View {
+  @EnvironmentObject
+  var viewModel: FunctionCallingViewModel
+
+  @State
+  private var userPrompt = "What is 100 Euros in U.S. Dollars?"
+
+  enum FocusedField: Hashable {
+    case message
+  }
+
+  @FocusState
+  var focusedField: FocusedField?
+
+  var body: some View {
+    VStack {
+      ScrollViewReader { scrollViewProxy in
+        List {
+          Text("Interact with a currency conversion API using function calling in Gemini.")
+          ForEach(viewModel.messages) { message in
+            MessageView(message: message)
+          }
+          if let error = viewModel.error {
+            ErrorView(error: error)
+              .tag("errorView")
+          }
+        }
+        .listStyle(.plain)
+        .onChange(of: viewModel.messages, perform: { newValue in
+          if viewModel.hasError {
+            // Wait for a short moment to make sure we can actually scroll to the bottom.
+            DispatchQueue.main.asyncAfter(deadline: .now() + 0.05) {
+              withAnimation {
+                scrollViewProxy.scrollTo("errorView", anchor: .bottom)
+              }
+              focusedField = .message
+            }
+          } else {
+            guard let lastMessage = viewModel.messages.last else { return }
+
+            // Wait for a short moment to make sure we can actually scroll to the bottom.
+            DispatchQueue.main.asyncAfter(deadline: .now() + 0.05) {
+              withAnimation {
+                scrollViewProxy.scrollTo(lastMessage.id, anchor: .bottom)
+              }
+              focusedField = .message
+            }
+          }
+        })
+      }
+      InputField("Message...", text: $userPrompt) {
+        Image(systemName: viewModel.busy ? "stop.circle.fill" : "arrow.up.circle.fill")
+          .font(.title)
+      }
+      .focused($focusedField, equals: .message)
+      .onSubmit { sendOrStop() }
+    }
+    .toolbar {
+      ToolbarItem(placement: .primaryAction) {
+        Button(action: newChat) {
+          Image(systemName: "square.and.pencil")
+        }
+      }
+    }
+    .navigationTitle("Function Calling")
+    .onAppear {
+      focusedField = .message
+    }
+  }
+
+  private func sendMessage() {
+    Task {
+      let prompt = userPrompt
+      userPrompt = ""
+      await viewModel.sendMessage(prompt, streaming: true)
+    }
+  }
+
+  private func sendOrStop() {
+    if viewModel.busy {
+      viewModel.stop()
+    } else {
+      sendMessage()
+    }
+  }
+
+  private func newChat() {
+    viewModel.startNewChat()
+  }
+}
+
+struct FunctionCallingScreen_Previews: PreviewProvider {
+  struct ContainerView: View {
+    @EnvironmentObject
+    var viewModel: FunctionCallingViewModel
+
+    var body: some View {
+      FunctionCallingScreen()
+        .onAppear {
+          viewModel.messages = ChatMessage.samples
+        }
+    }
+  }
+
+  static var previews: some View {
+    NavigationStack {
+      FunctionCallingScreen().environmentObject(FunctionCallingViewModel())
+    }
+  }
+}

Examples/GenerativeAISample/FunctionCallingSample/ViewModels/FunctionCallingViewModel.swift

@@ -0,0 +1,266 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import Foundation
+import GoogleGenerativeAI
+import UIKit
+
+@MainActor
+class FunctionCallingViewModel: ObservableObject {
+  /// This array holds both the user's and the system's chat messages
+  @Published var messages = [ChatMessage]()
+
+  /// Indicates we're waiting for the model to finish
+  @Published var busy = false
+
+  @Published var error: Error?
+  var hasError: Bool {
+    return error != nil
+  }
+
+  /// Function calls pending processing
+  private var functionCalls = [FunctionCall]()
+
+  private var model: GenerativeModel
+  private var chat: Chat
+
+  private var chatTask: Task<Void, Never>?
+
+  init() {
+    model = GenerativeModel(
+      name: "gemini-1.0-pro",
+      apiKey: APIKey.default,
+      tools: [Tool(functionDeclarations: [
+        FunctionDeclaration(
+          name: "get_exchange_rate",
+          description: "Get the exchange rate for currencies between countries",
+          parameters: [
+            "currency_from": Schema(
+              type: .string,
+              format: "enum",
+              description: "The currency to convert from in ISO 4217 format",
+              enumValues: ["USD", "EUR", "JPY", "GBP", "AUD", "CAD"]
+            ),
+            "currency_to": Schema(
+              type: .string,
+              format: "enum",
+              description: "The currency to convert to in ISO 4217 format",
+              enumValues: ["USD", "EUR", "JPY", "GBP", "AUD", "CAD"]
+            ),
+          ],
+          requiredParameters: ["currency_from", "currency_to"]
+        ),
+      ])],
+      requestOptions: RequestOptions(apiVersion: "v1beta")
+    )
+    chat = model.startChat()
+  }
+
+  func sendMessage(_ text: String, streaming: Bool = true) async {
+    error = nil
+    chatTask?.cancel()
+
+    chatTask = Task {
+      busy = true
+      defer {
+        busy = false
+      }
+
+      // first, add the user's message to the chat
+      let userMessage = ChatMessage(message: text, participant: .user)
+      messages.append(userMessage)
+
+      // add a pending message while we're waiting for a response from the backend
+      let systemMessage = ChatMessage.pending(participant: .system)
+      messages.append(systemMessage)
+
+      print(messages)
+      do {
+        repeat {
+          if streaming {
+            try await internalSendMessageStreaming(text)
+          } else {
+            try await internalSendMessage(text)
+          }
+        } while !functionCalls.isEmpty
+      } catch {
+        self.error = error
+        print(error.localizedDescription)
+        messages.removeLast()
+      }
+    }
+  }
+
+  func startNewChat() {
+    stop()
+    error = nil
+    chat = model.startChat()
+    messages.removeAll()
+  }
+
+  func stop() {
+    chatTask?.cancel()
+    error = nil
+  }
+
+  private func internalSendMessageStreaming(_ text: String) async throws {
+    let functionResponses = try await processFunctionCalls()
+    let responseStream: AsyncThrowingStream<GenerateContentResponse, Error>
+    if functionResponses.isEmpty {
+      responseStream = chat.sendMessageStream(text)
+    } else {
+      for functionResponse in functionResponses {
+        messages.insert(functionResponse.chatMessage(), at: messages.count - 1)
+      }
+      responseStream = chat.sendMessageStream(functionResponses.modelContent())
+    }
+    for try await chunk in responseStream {
+      processResponseContent(content: chunk)
+    }
+  }
+
+  private func internalSendMessage(_ text: String) async throws {
+    let functionResponses = try await processFunctionCalls()
+    let response: GenerateContentResponse
+    if functionResponses.isEmpty {
+      response = try await chat.sendMessage(text)
+    } else {
+      for functionResponse in functionResponses {
+        messages.insert(functionResponse.chatMessage(), at: messages.count - 1)
+      }
+      response = try await chat.sendMessage(functionResponses.modelContent())
+    }
+    processResponseContent(content: response)
+  }
+
+  func processResponseContent(content: GenerateContentResponse) {
+    guard let candidate = content.candidates.first else {
+      fatalError("No candidate.")
+    }
+
+    for part in candidate.content.parts {
+      switch part {
+      case let .text(text):
+        // replace pending message with backend response
+        messages[messages.count - 1].message += text
+        messages[messages.count - 1].pending = false
+      case let .functionCall(functionCall):
+        messages.insert(functionCall.chatMessage(), at: messages.count - 1)
+        functionCalls.append(functionCall)
+      case .data, .functionResponse:
+        fatalError("Unsupported response content.")
+      }
+    }
+  }
+
+  func processFunctionCalls() async throws -> [FunctionResponse] {
+    var functionResponses = [FunctionResponse]()
+    for functionCall in functionCalls {
+      switch functionCall.name {
+      case "get_exchange_rate":
+        let exchangeRates = getExchangeRate(args: functionCall.args)
+        functionResponses.append(FunctionResponse(
+          name: "get_exchange_rate",
+          response: exchangeRates
+        ))
+      default:
+        fatalError("Unknown function named \"\(functionCall.name)\".")
+      }
+    }
+    functionCalls = []
+
+    return functionResponses
+  }
+
+  // MARK: - Callable Functions
+
+  func getExchangeRate(args: JSONObject) -> JSONObject {
+    // 1. Validate and extract the parameters provided by the model (from a `FunctionCall`)
+    guard case let .string(from) = args["currency_from"] else {
+      fatalError("Missing `currency_from` parameter.")
+    }
+    guard case let .string(to) = args["currency_to"] else {
+      fatalError("Missing `currency_to` parameter.")
+    }
+
+    // 2. Get the exchange rate
+    let allRates: [String: [String: Double]] = [
+      "AUD": ["CAD": 0.89265, "EUR": 0.6072, "GBP": 0.51714, "JPY": 97.75, "USD": 0.66379],
+      "CAD": ["AUD": 1.1203, "EUR": 0.68023, "GBP": 0.57933, "JPY": 109.51, "USD": 0.74362],
+      "EUR": ["AUD": 1.6469, "CAD": 1.4701, "GBP": 0.85168, "JPY": 160.99, "USD": 1.0932],
+      "GBP": ["AUD": 1.9337, "CAD": 1.7261, "EUR": 1.1741, "JPY": 189.03, "USD": 1.2836],
+      "JPY": ["AUD": 0.01023, "CAD": 0.00913, "EUR": 0.00621, "GBP": 0.00529, "USD": 0.00679],
+      "USD": ["AUD": 1.5065, "CAD": 1.3448, "EUR": 0.91475, "GBP": 0.77907, "JPY": 147.26],
+    ]
+    guard let fromRates = allRates[from] else {
+      return ["error": .string("No data for currency \(from).")]
+    }
+    guard let toRate = fromRates[to] else {
+      return ["error": .string("No data for currency \(to).")]
+    }
+
+    // 3. Return the exchange rates as a JSON object (returned to the model in a `FunctionResponse`)
+    return ["rates": .number(toRate)]
+  }
+}
+
+private extension FunctionCall {
+  func chatMessage() -> ChatMessage {
+    let encoder = JSONEncoder()
+    encoder.outputFormatting = .prettyPrinted
+
+    let jsonData: Data
+    do {
+      jsonData = try encoder.encode(self)
+    } catch {
+      fatalError("JSON Encoding Failed: \(error.localizedDescription)")
+    }
+    guard let json = String(data: jsonData, encoding: .utf8) else {
+      fatalError("Failed to convert JSON data to a String.")
+    }
+    let messageText = "Function call requested by model:\n```\n\(json)\n```"
+
+    return ChatMessage(message: messageText, participant: .system)
+  }
+}
+
+private extension FunctionResponse {
+  func chatMessage() -> ChatMessage {
+    let encoder = JSONEncoder()
+    encoder.outputFormatting = .prettyPrinted
+
+    let jsonData: Data
+    do {
+      jsonData = try encoder.encode(self)
+    } catch {
+      fatalError("JSON Encoding Failed: \(error.localizedDescription)")
+    }
+    guard let json = String(data: jsonData, encoding: .utf8) else {
+      fatalError("Failed to convert JSON data to a String.")
+    }
+    let messageText = "Function response returned by app:\n```\n\(json)\n```"
+
+    return ChatMessage(message: messageText, participant: .user)
+  }
+}
+
+private extension [FunctionResponse] {
+  func modelContent() -> [ModelContent] {
+    return self.map { ModelContent(
+      role: "function",
+      parts: [ModelContent.Part.functionResponse($0)]
+    )
+    }
+  }
+}