Add function calling sample

Examples/GenerativeAISample/FunctionCallingSample/Screens/FunctionCallingScreen.swift

@@ -0,0 +1,128 @@
+// 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())
+    }
+  }
+}