implement demo mode

server/demo/demo-sessions.js

@@ -0,0 +1,126 @@
+// In-memory session map keyed by cookie value.
+//
+// Each entry tracks the user's vault names, last-activity timestamp, and bytes used.
+// On disk, vaults are stored under a session-prefixed name so two sessions can both have a vault called "Notes".
+
+const crypto = require("crypto");
+const config = require("../config");
+
+const COOKIE_NAME = "ignis-demo";
+const PREFIX_SEPARATOR = "__";
+
+// sessionId -> { lastActivity, vaults: Set<userVaultName>, bytesUsed }
+const sessions = new Map();
+
+function newSessionId() {
+  return crypto.randomBytes(12).toString("hex");
+}
+
+function prefixFor(sessionId) {
+  return "demo-" + sessionId + PREFIX_SEPARATOR;
+}
+
+function makeStorageName(sessionId, userVaultName) {
+  return prefixFor(sessionId) + userVaultName;
+}
+
+function tryParseUserVaultName(sessionId, storageName) {
+  const prefix = prefixFor(sessionId);
+
+  if (storageName && storageName.startsWith(prefix)) {
+    return storageName.slice(prefix.length);
+  }
+
+  return null;
+}
+
+function parseCookies(req) {
+  const header = req.headers.cookie;
+
+  if (!header) {
+    return {};
+  }
+
+  const out = {};
+
+  for (const part of header.split(/;\s*/)) {
+    const eq = part.indexOf("=");
+
+    if (eq < 0) {
+      continue;
+    }
+
+    out[part.slice(0, eq)] = decodeURIComponent(part.slice(eq + 1));
+  }
+
+  return out;
+}
+
+function setSessionCookie(res, sessionId) {
+  const maxAgeSeconds = Math.floor(config.demoTimeoutMs / 1000);
+
+  res.setHeader(
+    "Set-Cookie",
+    `${COOKIE_NAME}=${sessionId}; Path=/; HttpOnly; SameSite=Lax; Max-Age=${maxAgeSeconds}`,
+  );
+}
+
+// Resolve the session for a request. If none exists, create one (unless options.peek is true).
+function getOrCreateSession(req, res, options = {}) {
+  const cookies = parseCookies(req);
+  const existing = cookies[COOKIE_NAME];
+
+  if (existing && sessions.has(existing)) {
+    return existing;
+  }
+
+  if (existing && !sessions.has(existing)) {
+    // Cookie outlived in-memory session. reuse the id to keep the prefix.
+    sessions.set(existing, {
+      lastActivity: Date.now(),
+      vaults: new Set(),
+      bytesUsed: 0,
+    });
+    return existing;
+  }
+
+  if (options.peek) {
+    return null;
+  }
+
+  if (sessions.size >= config.demoMaxSessions) {
+    return null;
+  }
+
+  const sessionId = newSessionId();
+
+  sessions.set(sessionId, {
+    lastActivity: Date.now(),
+    vaults: new Set(),
+    bytesUsed: 0,
+  });
+
+  setSessionCookie(res, sessionId);
+  return sessionId;
+}
+
+function touchSession(sessionId) {
+  const s = sessions.get(sessionId);
+
+  if (s) {
+    s.lastActivity = Date.now();
+  }
+}
+
+module.exports = {
+  COOKIE_NAME,
+  PREFIX_SEPARATOR,
+  sessions,
+  prefixFor,
+  makeStorageName,
+  tryParseUserVaultName,
+  parseCookies,
+  setSessionCookie,
+  getOrCreateSession,
+  touchSession,
+};