Add function to retrieve and refresh access token

Author: rickkoh

frontend/src/lib/auth.ts

@@ -0,0 +1,53 @@
+"use server";
+
+import { cookies } from "next/headers";
+import {
+  AccessToken,
+  AccessTokenPayload,
+  AccessTokenPayloadSchema,
+  AccessTokenResponse,
+  AccessTokenSchema,
+} from "@/types/Token";
+import { refreshAccessToken } from "@/services/authService";
+
+/**
+ * This function retrieves the access token from the cookie store.
+ * If the access token is expired, it will refresh the token and store the new token in the cookie store.
+ *
+ * @returns {Promise<AccessToken>}
+ */
+export async function getAccessToken(): Promise<AccessToken> {
+  const cookieStore = cookies();
+  const access_token = AccessTokenSchema.parse(
+    cookieStore.get("access_token")?.value
+  );
+
+  if (!access_token || isTokenExpired(access_token)) {
+    const accessTokenResponse: AccessTokenResponse = await refreshAccessToken();
+    if (accessTokenResponse.statusCode === 200 && accessTokenResponse.data) {
+      return accessTokenResponse.data.access_token;
+    }
+  }
+
+  return access_token;
+}
+
+function isTokenExpired(token: AccessToken): boolean {
+  const decoded = parseJwt(token);
+  const currentTime = Math.floor(Date.now() / 1000);
+  return decoded.exp < currentTime;
+}
+
+function parseJwt(token: AccessToken): AccessTokenPayload {
+  const base64Url = token.split(".")[1];
+  const base64 = base64Url.replace(/-/g, "+").replace(/_/g, "/");
+  const jsonPayload = decodeURIComponent(
+    atob(base64)
+      .split("")
+      .map((c) => {
+        return "%" + ("00" + c.charCodeAt(0).toString(16)).slice(-2);
+      })
+      .join("")
+  );
+  return AccessTokenPayloadSchema.parse(JSON.parse(jsonPayload));
+}