feat(ap1): add vanilla SPA PKCE login

frontend/src/app.js

@@ -0,0 +1,138 @@
+import {
+  InMemoryWebStorage,
+  UserManager,
+  WebStorageStateStore,
+} from "oidc-client-ts";
+
+import { createPkcePair } from "./pkce.js";
+
+const authority = "http://localhost:8080/realms/keycloak-patterns";
+const backendBaseUrl = "http://localhost:8081";
+
+const userManager = new UserManager({
+  authority,
+  client_id: "spa-public",
+  redirect_uri: "http://localhost:8088/callback.html",
+  post_logout_redirect_uri: "http://localhost:8088/",
+  response_type: "code",
+  scope: "openid profile email",
+  automaticSilentRenew: true,
+  monitorSession: false,
+  loadUserInfo: false,
+  userStore: new WebStorageStateStore({
+    store: new InMemoryWebStorage(),
+  }),
+  stateStore: new WebStorageStateStore({
+    store: window.sessionStorage,
+  }),
+});
+
+const loginButton = document.querySelector("#login");
+const logoutButton = document.querySelector("#logout");
+const apiButton = document.querySelector("#call-api");
+const pkceButton = document.querySelector("#pkce-demo");
+const sessionState = document.querySelector("#session-state");
+const result = document.querySelector("#result");
+
+let currentUser = null;
+
+function renderJson(value) {
+  result.textContent = JSON.stringify(value, null, 2);
+}
+
+function tokenMetadata(user) {
+  return {
+    subject: user.profile.sub,
+    username: user.profile.preferred_username,
+    expiresAt: new Date(user.expires_at * 1000).toISOString(),
+    accessTokenHeldBy: "browser memory",
+    refreshTokenHeldBy: user.refresh_token ? "browser memory" : "not issued",
+  };
+}
+
+function renderSession(user) {
+  currentUser = user;
+  const authenticated = Boolean(user && !user.expired);
+  sessionState.dataset.authenticated = String(authenticated);
+  sessionState.textContent = authenticated
+    ? `${user.profile.preferred_username} 로그인됨 · token은 메모리에만 보관`
+    : "로그인되지 않음 · 브라우저 저장소에 token 없음";
+  loginButton.disabled = authenticated;
+  logoutButton.disabled = !authenticated;
+  apiButton.disabled = !authenticated;
+
+  if (authenticated) {
+    renderJson(tokenMetadata(user));
+  }
+}
+
+async function finishSigninCallback() {
+  const params = new URLSearchParams(window.location.search);
+  const isCallback = window.location.pathname === "/callback.html"
+    && (params.has("code") || params.has("error"));
+
+  if (!isCallback) {
+    return null;
+  }
+
+  const user = await userManager.signinRedirectCallback();
+  window.history.replaceState({}, document.title, "/");
+  return user;
+}
+
+async function callProtectedApi() {
+  if (!currentUser || currentUser.expired) {
+    throw new Error("로그인이 필요합니다.");
+  }
+
+  const response = await fetch(`${backendBaseUrl}/api/me`, {
+    headers: {
+      Authorization: `Bearer ${currentUser.access_token}`,
+    },
+  });
+  const body = await response.json();
+  renderJson({
+    httpStatus: response.status,
+    resourceServerResponse: body,
+    tokenBoundary: tokenMetadata(currentUser),
+  });
+
+  if (!response.ok) {
+    throw new Error(`보호 API가 ${response.status}를 반환했습니다.`);
+  }
+}
+
+loginButton.addEventListener("click", () => userManager.signinRedirect());
+logoutButton.addEventListener("click", () => userManager.signoutRedirect());
+apiButton.addEventListener("click", () => {
+  callProtectedApi().catch((error) => renderJson({ error: error.message }));
+});
+pkceButton.addEventListener("click", () => {
+  createPkcePair()
+    .then(({ verifier, challenge, method }) => renderJson({
+      method,
+      verifierLength: verifier.length,
+      challengeLength: challenge.length,
+      note: "실제 로그인에서는 oidc-client-ts가 같은 S256 단계를 수행합니다.",
+    }))
+    .catch((error) => renderJson({ error: error.message }));
+});
+
+userManager.events.addUserLoaded(renderSession);
+userManager.events.addUserUnloaded(() => renderSession(null));
+userManager.events.addAccessTokenExpired(() => renderSession(null));
+
+window.__pattern1 = {
+  getAccessToken: () => currentUser?.access_token ?? null,
+  getRefreshToken: () => currentUser?.refresh_token ?? null,
+  getIdToken: () => currentUser?.id_token ?? null,
+  callProtectedApi,
+};
+
+try {
+  const callbackUser = await finishSigninCallback();
+  renderSession(callbackUser ?? await userManager.getUser());
+} catch (error) {
+  renderSession(null);
+  renderJson({ error: error.message });
+}