Add JWT decoding utilities to API

1 files changed, 101 insertions, 0 deletions

diff --git a/thallium-frontend/src/api/jwt.ts b/thallium-frontend/src/api/jwt.ts
new file mode 100644
index 0000000..be58d1d
--- /dev/null
+++ b/thallium-frontend/src/api/jwt.ts
@@ -0,0 +1,101 @@
+import { jwtDecode } from "jwt-decode";
+
+import store from "../store";
+import { setRefreshTask, setVoucherToken } from "../slices/authorization";
+
+import { refreshToken } from "./login";
+
+const EXPIRY_PRE_BUFFER = 120;
+
+enum JWTType {
+    VOUCHER,
+    USER,
+}
+
+interface ThalliumJWT {
+    sub: string;
+    iss: JWTType;
+    exp: number;
+    nbf: number;
+    iat: number;
+}
+
+interface RawJWT {
+    sub: string;
+    iss: string;
+    exp: number;
+    nbf: number;
+    iat: number;
+}
+
+const expectedKeys = ["sub", "iss", "exp", "nbf", "iat"];
+
+const decodeJWT = (jwt: string): ThalliumJWT => {
+    const decoded = jwtDecode<RawJWT>(jwt);
+
+    const issType = decoded.iss == "thallium:voucher" ? JWTType.VOUCHER : JWTType.USER;
+
+    if (expectedKeys.every((key) => key in Object.keys(decoded))) {
+        throw new Error(`Invalid JWT format, found keys: ${Object.keys(decoded).join(", ")}`);
+    }
+
+    return {
+        sub: decoded.sub,
+        iss: issType,
+        exp: decoded.exp,
+        nbf: decoded.nbf,
+        iat: decoded.iat,
+    };
+};
+
+const isJWTExpired = (jwt: ThalliumJWT): boolean => {
+    return jwt.exp < (Date.now() / 1000);
+};
+
+const secondsToExpiry = (jwt: ThalliumJWT): number => {
+    return jwt.exp - (Date.now() / 1000);
+};
+
+const maybeRefreshTask = () => {
+    const state = store.getState().authorization;
+
+    if (state.refreshTask) {
+        clearInterval(state.refreshTask);
+        console.log("Cleared existing refresh task");
+    }
+
+    const foundToken = state.voucherToken;
+
+    if (!foundToken) {
+        console.log("No token found, not setting refresh task");
+        return;
+    }
+
+    const parsed = decodeJWT(foundToken);
+
+    if (isJWTExpired(parsed)) {
+        console.log("Token is expired, not setting refresh task");
+        return;
+    }
+
+    const task = setTimeout(() => {
+        console.log("Refreshing token");
+        refreshToken(foundToken)
+            .then((newToken) => {
+                store.dispatch(setVoucherToken(newToken.jwt));
+
+                console.log("Refreshed token");
+
+                maybeRefreshTask();
+            })
+            .catch((e: unknown) => {
+                console.error("Failed to refresh token", e);
+            });
+    }, (secondsToExpiry(parsed) - EXPIRY_PRE_BUFFER) * 1000);
+
+    store.dispatch(setRefreshTask(task));
+
+    console.log("Set refresh task");
+};
+
+export { decodeJWT, isJWTExpired, secondsToExpiry, maybeRefreshTask };