/**
* Purdue Brightspace MCP Server
* Copyright (c) 2025 Rohan Muppa. All rights reserved.
* Licensed under AGPL-3.0 — see LICENSE file for details.
*/
import type { TokenData } from "../types/index.js";
import { SessionStore } from "./session-store.js";
import { log } from "../utils/logger.js";
/**
* Token refresh buffer - tokens within this time of expiry are considered invalid.
* This prevents using tokens that might expire during a request.
*/
const REFRESH_BUFFER_MS = 5 * 60 * 1000; // 5 minutes
/**
* TokenManager manages token lifecycle with in-memory caching and disk persistence.
* Handles expiry detection with a configurable refresh buffer.
*/
export class TokenManager {
private cachedToken: TokenData | null = null;
private readonly sessionStore: SessionStore;
constructor(sessionDir?: string) {
this.sessionStore = new SessionStore(sessionDir);
}
/**
* Get the current token if valid, otherwise null.
* Checks memory cache first, then loads from disk if needed.
* Returns null if token is expired or within refresh buffer.
*/
async getToken(): Promise<TokenData | null> {
// Check memory cache first
if (this.cachedToken && this.isValid(this.cachedToken)) {
log("DEBUG", "Returning cached token");
return this.cachedToken;
}
// Try loading from disk
const storedToken = await this.sessionStore.load();
if (storedToken && this.isValid(storedToken)) {
log("DEBUG", "Loaded valid token from session store");
this.cachedToken = storedToken;
return storedToken;
}
log("DEBUG", "No valid token available");
return null;
}
/**
* Set a new token, caching in memory and persisting to disk.
*/
async setToken(token: TokenData): Promise<void> {
this.cachedToken = token;
await this.sessionStore.save(token);
log("DEBUG", "Token cached and persisted");
}
/**
* Clear the token from memory and disk.
*/
async clearToken(): Promise<void> {
this.cachedToken = null;
await this.sessionStore.clear();
log("DEBUG", "Token cleared from memory and disk");
}
/**
* Check if a token is valid (not expired and outside refresh buffer).
* A token is valid if it expires more than REFRESH_BUFFER_MS from now.
*/
isValid(token: TokenData): boolean {
const now = Date.now();
const timeUntilExpiry = token.expiresAt - now;
// Token must expire more than REFRESH_BUFFER_MS in the future
const valid = timeUntilExpiry > REFRESH_BUFFER_MS;
if (!valid) {
log(
"DEBUG",
`Token invalid: expires in ${Math.round(timeUntilExpiry / 1000)}s (buffer: ${REFRESH_BUFFER_MS / 1000}s)`
);
}
return valid;
}
/**
* Check if a token refresh is needed.
* Returns true if no valid token is available.
*/
async needsRefresh(): Promise<boolean> {
const token = await this.getToken();
return token === null;
}
}
