chore: add pre-commit configuration and CI

.codespellignore

@@ -0,0 +1,4 @@
+mor
+tok
+fpan
+dpan

.github/workflows/linter.yml

@@ -0,0 +1,31 @@
+#   Copyright 2026 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.
+
+name: Lint
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  pre-commit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.x"
+      - uses: pre-commit/action@v3.0.1

.pre-commit-config.yaml

@@ -0,0 +1,45 @@
+#   Copyright 2026 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.
+
+exclude: '^(\.github/|\.vscode/|node_modules/).*|CODE_OF_CONDUCT\.md|CHANGELOG\.md'
+
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v6.0.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-yaml
+        args: [--unsafe]
+      - id: check-json
+      - id: check-added-large-files
+      - id: detect-private-key
+      - id: check-shebang-scripts-are-executable
+      - id: check-executables-have-shebangs
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.14.13
+    hooks:
+      - id: ruff
+        args: [--fix, --exit-non-zero-on-fix]
+      - id: ruff-format
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: v4.0.0-alpha.8
+    hooks:
+      - id: prettier
+        files: \.(ts|tsx|js|jsx|json|md|yaml|yml|css|html)$
+  - repo: https://github.com/codespell-project/codespell
+    rev: v2.4.1
+    hooks:
+      - id: codespell
+        args: ["--skip", "*.lock,package-lock.json", "-I", ".codespellignore"]

.prettierrc

@@ -0,0 +1,8 @@
+{
+  "tabWidth": 2,
+  "useTabs": false,
+  "singleQuote": false,
+  "trailingComma": "es5",
+  "bracketSameLine": false,
+  "printWidth": 80
+}

a2a/chat-client/App.tsx

@@ -36,7 +36,7 @@ type RequestPart =
 function createChatMessage(
   sender: Sender,
   text: string,
-  props: Partial<ChatMessage> = {},
+  props: Partial<ChatMessage> = {}
 ): ChatMessage {
   return {
     id: crypto.randomUUID(),
@@ -49,7 +49,7 @@ function createChatMessage(
 const initialMessage: ChatMessage = createChatMessage(
   Sender.MODEL,
   appConfig.defaultMessage,
-  { id: "initial" },
+  { id: "initial" }
 );
 
 /**
@@ -58,7 +58,7 @@ const initialMessage: ChatMessage = createChatMessage(
  */
 function App() {
   const [user_email, _setUserEmail] = useState<string | null>(
-    "foo@example.com",
+    "foo@example.com"
   );
   const [messages, setMessages] = useState<ChatMessage[]>([initialMessage]);
   const [isLoading, setIsLoading] = useState(false);
@@ -96,20 +96,20 @@ function App() {
     if (!checkout || !checkout.payment || !checkout.payment.handlers) {
       const errorMessage = createChatMessage(
         Sender.MODEL,
-        "Sorry, I couldn't retrieve payment methods.",
+        "Sorry, I couldn't retrieve payment methods."
       );
       setMessages((prev) => [...prev, errorMessage]);
       return;
     }
 
     //find the handler with id "example_payment_provider"
     const handler = checkout.payment.handlers.find(
-      (handler: PaymentHandler) => handler.id === "example_payment_provider",
+      (handler: PaymentHandler) => handler.id === "example_payment_provider"
     );
     if (!handler) {
       const errorMessage = createChatMessage(
         Sender.MODEL,
-        "Sorry, I couldn't find the supported payment handler.",
+        "Sorry, I couldn't find the supported payment handler."
       );
       setMessages((prev) => [...prev, errorMessage]);
       return;
@@ -119,7 +119,7 @@ function App() {
       const paymentResponse =
         await credentialProvider.current.getSupportedPaymentMethods(
           user_email,
-          handler.config,
+          handler.config
         );
       const paymentMethods = paymentResponse.payment_method_aliases;
 
@@ -131,7 +131,7 @@ function App() {
       console.error("Failed to resolve mandate:", error);
       const errorMessage = createChatMessage(
         Sender.MODEL,
-        "Sorry, I couldn't retrieve payment methods.",
+        "Sorry, I couldn't retrieve payment methods."
       );
       setMessages((prev) => [...prev, errorMessage]);
     }
@@ -145,7 +145,7 @@ function App() {
     const userActionMessage = createChatMessage(
       Sender.USER,
       `User selected payment method: ${selectedMethod}`,
-      { isUserAction: true },
+      { isUserAction: true }
     );
     setMessages((prev) => [...prev, userActionMessage]);
 
@@ -157,7 +157,7 @@ function App() {
       const paymentInstrument =
         await credentialProvider.current.getPaymentToken(
           user_email,
-          selectedMethod,
+          selectedMethod
         );
 
       if (!paymentInstrument || !paymentInstrument.credential) {
@@ -172,7 +172,7 @@ function App() {
       console.error("Failed to process payment mandate:", error);
       const errorMessage = createChatMessage(
         Sender.MODEL,
-        "Sorry, I couldn't process the payment. Please try again.",
+        "Sorry, I couldn't process the payment. Please try again."
       );
       setMessages((prev) => [...prev, errorMessage]);
     }
@@ -183,7 +183,7 @@ function App() {
     const userActionMessage = createChatMessage(
       Sender.USER,
       `User confirmed payment.`,
-      { isUserAction: true },
+      { isUserAction: true }
     );
     // Let handleSendMessage manage the loading indicator
     setMessages((prev) => [
@@ -210,7 +210,7 @@ function App() {
       console.error("Error confirming payment:", error);
       const errorMessage = createChatMessage(
         Sender.MODEL,
-        "Sorry, there was an issue confirming your payment.",
+        "Sorry, there was an issue confirming your payment."
       );
       // If handleSendMessage wasn't called, we might need to manually update state
       // In this case, we remove the loading indicator that handleSendMessage would have added
@@ -221,7 +221,7 @@ function App() {
 
   const handleSendMessage = async (
     messageContent: string | RequestPart[],
-    options?: { isUserAction?: boolean; headers?: Record<string, string> },
+    options?: { isUserAction?: boolean; headers?: Record<string, string> }
   ) => {
     if (isLoading) return;
 
@@ -231,7 +231,7 @@ function App() {
         ? "<User Action>"
         : typeof messageContent === "string"
           ? messageContent
-          : "Sent complex data",
+          : "Sent complex data"
     );
     if (userMessage.text) {
       // Only add if there's text
@@ -366,7 +366,7 @@ function App() {
       console.error("Error sending message:", error);
       const errorMessage = createChatMessage(
         Sender.MODEL,
-        "Sorry, something went wrong. Please try again.",
+        "Sorry, something went wrong. Please try again."
       );
       // Replace the placeholder with the error message
       setMessages((prev) => [...prev.slice(0, -1), errorMessage]);

a2a/chat-client/components/Checkout.tsx

@@ -95,7 +95,7 @@ const CheckoutComponent: React.FC<CheckoutProps> = ({
               <p className="text-gray-800 font-medium pl-2">
                 {formatCurrency(
                   getItemTotal(lineItem).amount,
-                  checkout.currency,
+                  checkout.currency
                 )}
               </p>
             </div>

a2a/chat-client/config.ts

@@ -25,7 +25,7 @@ export class AppProperties {
     description: string,
     logoUrl: string,
     defaultMessage: string,
-    titleText: string,
+    titleText: string
   ) {
     this.name = name;
     this.description = description;
@@ -40,5 +40,5 @@ export const appConfig = new AppProperties(
   "Your personal shopping assistant.",
   "/images/logo.jpg",
   "Hello, I am your Business Agent. How can I help you?",
-  "Shop with Business Agent",
+  "Shop with Business Agent"
 );

a2a/chat-client/index.tsx

@@ -26,5 +26,5 @@ const root = ReactDOM.createRoot(rootElement);
 root.render(
   <React.StrictMode>
     <App />
-  </React.StrictMode>,
+  </React.StrictMode>
 );

a2a/chat-client/mocks/credentialProviderProxy.ts

@@ -61,11 +61,11 @@ export class CredentialProviderProxy {
   async getSupportedPaymentMethods(
     user_email: string,
     // biome-ignore lint/suspicious/noExplicitAny: no specific type for config
-    config: any,
+    config: any
   ): Promise<{ payment_method_aliases: PaymentMethod[] }> {
     console.log(
       `CredentialProviderProxy: Simulating fetch for ${user_email} supported payment methods with config:`,
-      config,
+      config
     );
     // Simulate network latency
     await new Promise((resolve) => setTimeout(resolve, 500));
@@ -80,17 +80,17 @@ export class CredentialProviderProxy {
    */
   async getPaymentToken(
     user_email: string,
-    payment_method_id: string,
+    payment_method_id: string
   ): Promise<PaymentInstrument | undefined> {
     console.log(
-      `CredentialProviderProxy: Simulating fetch for payment token for user ${user_email} and method ${payment_method_id}`,
+      `CredentialProviderProxy: Simulating fetch for payment token for user ${user_email} and method ${payment_method_id}`
     );
     // Simulate network latency
     await new Promise((resolve) => setTimeout(resolve, 500));
     const randomId = crypto.randomUUID();
     const payment_method =
       this._getMockPaymentMethods().payment_method_aliases.find(
-        (method) => method.id === payment_method_id,
+        (method) => method.id === payment_method_id
       );
 
     if (!payment_method) {

a2a/docs/05-frontend.md

@@ -179,7 +179,7 @@ class CredentialProviderProxy {
   // Returns mock payment methods (wrapped in object)
   async getSupportedPaymentMethods(
     user_email: string,
-    config: any,
+    config: any
   ): Promise<{ payment_method_aliases: PaymentMethod[] }> {
     return {
       payment_method_aliases: [
@@ -206,7 +206,7 @@ class CredentialProviderProxy {
   // Converts method to PaymentInstrument with token
   async getPaymentToken(
     user_email: string,
-    payment_method_id: string,
+    payment_method_id: string
   ): Promise<PaymentInstrument | undefined> {
     return {
       ...payment_method,
@@ -243,6 +243,6 @@ export const appConfig = new AppProperties(
   "Your personal shopping assistant.",
   "/images/logo.jpg",
   "Hello, I am your Business Agent...",
-  "Shop with Business Agent",
+  "Shop with Business Agent"
 );
 ```