Merge pull request #425 from StroepWafel/cloud-settings-backup

Cloud settings backup

src/seqta/utils/cloudSettingsSync.ts

@@ -0,0 +1,131 @@
+import browser from "webextension-polyfill";
+
+/** Matches the contract in docs/CLOUD_SETTINGS_SYNC_SERVER.md */
+export const CLOUD_SETTINGS_SYNC_SCHEMA_VERSION = 1;
+
+/**
+ * Never uploaded to the cloud backup (OAuth and legacy keys).
+ * IndexedDB (e.g. Global Search’s `betterseqta-index` database) is not part of
+ * `chrome.storage.local` and is never included in this payload.
+ */
+export const KEYS_OMITTED_FROM_CLOUD_UPLOAD = [
+  "bsplus_token",
+  "bsplus_refresh_token",
+  "bsplus_client_id",
+  "bsplus_user",
+  "cloudAccessToken",
+  "cloudUsername",
+] as const;
+
+/**
+ * Device-only caches / school-related data: never uploaded, never applied from a
+ * cloud snapshot (local values are kept on restore).
+ */
+export const SENSITIVE_DEVICE_STORAGE_KEYS_EXACT = [
+  "plugin.assessments-average.storage.assessments",
+  "plugin.assessments-average.storage.weightings",
+] as const;
+
+/** e.g. any future `plugin.global-search.storage.*` keys in chrome.storage */
+export const SENSITIVE_DEVICE_STORAGE_KEY_PREFIXES = ["plugin.global-search.storage."] as const;
+
+/** After restoring from cloud, keep local session so the user stays signed in. */
+const AUTH_KEYS_TO_PRESERVE = [
+  "bsplus_token",
+  "bsplus_refresh_token",
+  "bsplus_client_id",
+  "bsplus_user",
+] as const;
+
+const OMIT_FROM_UPLOAD_EXACT = new Set<string>([
+  ...KEYS_OMITTED_FROM_CLOUD_UPLOAD,
+  ...SENSITIVE_DEVICE_STORAGE_KEYS_EXACT,
+]);
+
+function shouldOmitKeyFromCloudPayload(key: string): boolean {
+  if (OMIT_FROM_UPLOAD_EXACT.has(key)) return true;
+  for (const prefix of SENSITIVE_DEVICE_STORAGE_KEY_PREFIXES) {
+    if (key.startsWith(prefix)) return true;
+  }
+  return false;
+}
+
+function isSensitiveDeviceKey(key: string): boolean {
+  if ((SENSITIVE_DEVICE_STORAGE_KEYS_EXACT as readonly string[]).includes(key)) return true;
+  for (const prefix of SENSITIVE_DEVICE_STORAGE_KEY_PREFIXES) {
+    if (key.startsWith(prefix)) return true;
+  }
+  return false;
+}
+
+/** Auth + device-only caches to keep when merging a downloaded snapshot. */
+function collectLocalKeysToPreserve(local: Record<string, unknown>): Record<string, unknown> {
+  const out: Record<string, unknown> = {};
+  for (const k of AUTH_KEYS_TO_PRESERVE) {
+    if (local[k] !== undefined) out[k] = local[k];
+  }
+  for (const [k, v] of Object.entries(local)) {
+    if (isSensitiveDeviceKey(k)) out[k] = v;
+  }
+  return out;
+}
+
+/** Remove keys that must never come from the server blob (defense in depth). */
+function stripExcludedKeysFromRemoteData(remote: Record<string, unknown>): Record<string, unknown> {
+  const out: Record<string, unknown> = {};
+  for (const [k, v] of Object.entries(remote)) {
+    if (shouldOmitKeyFromCloudPayload(k)) continue;
+    out[k] = v;
+  }
+  return out;
+}
+
+export function buildUploadPayload(all: Record<string, unknown>): {
+  schemaVersion: number;
+  data: Record<string, unknown>;
+} {
+  const data: Record<string, unknown> = {};
+  for (const [k, v] of Object.entries(all)) {
+    if (shouldOmitKeyFromCloudPayload(k)) continue;
+    data[k] = v;
+  }
+  return { schemaVersion: CLOUD_SETTINGS_SYNC_SCHEMA_VERSION, data };
+}
+
+export async function getSnapshotForUpload(): Promise<{
+  schemaVersion: number;
+  data: Record<string, unknown>;
+}> {
+  const all = await browser.storage.local.get();
+  return buildUploadPayload(all as Record<string, unknown>);
+}
+
+/**
+ * Replace local extension storage with the downloaded snapshot, except auth keys
+ * and device-only sensitive caches, which are preserved from the current device.
+ */
+export async function applyDownloadedEnvelope(envelope: unknown): Promise<void> {
+  let remoteFlat: Record<string, unknown>;
+  if (
+    envelope &&
+    typeof envelope === "object" &&
+    "data" in envelope &&
+    (envelope as { data?: unknown }).data !== undefined &&
+    typeof (envelope as { data?: unknown }).data === "object" &&
+    (envelope as { data?: unknown }).data !== null &&
+    !Array.isArray((envelope as { data?: unknown }).data)
+  ) {
+    remoteFlat = (envelope as { data: Record<string, unknown> }).data;
+  } else if (envelope && typeof envelope === "object" && !Array.isArray(envelope)) {
+    remoteFlat = envelope as Record<string, unknown>;
+  } else {
+    throw new Error("Invalid cloud settings payload");
+  }
+
+  const local = await browser.storage.local.get();
+  const preserved = collectLocalKeysToPreserve(local);
+  const remoteSanitized = stripExcludedKeysFromRemoteData(remoteFlat);
+
+  await browser.storage.local.clear();
+  await browser.storage.local.set({ ...remoteSanitized, ...preserved });
+}