Add idb-keyval backed archival storage (#9754)

* Add idb-keyval backed archival storage

* Cleanup

* Remove test

src/storage/archive/db/index.ts

@@ -0,0 +1,22 @@
+import {MMKV} from '@bsky.app/react-native-mmkv'
+
+import {type DB} from '#/storage/archive/db/types'
+
+export function create({id}: {id: string}): DB {
+  const store = new MMKV({id})
+
+  return {
+    async get(key: string): Promise<string | undefined> {
+      return store.getString(key) ?? undefined
+    },
+    async set(key: string, value: string): Promise<void> {
+      store.set(key, value)
+    },
+    async delete(key: string): Promise<void> {
+      store.delete(key)
+    },
+    async clear(): Promise<void> {
+      store.clearAll()
+    },
+  }
+}

src/storage/archive/db/index.web.ts

@@ -0,0 +1,22 @@
+import {clear, createStore, del, get, set} from 'idb-keyval'
+
+import {type DB} from '#/storage/archive/db/types'
+
+export function create({id}: {id: string}): DB {
+  const store = createStore(id, id)
+
+  return {
+    async get(key: string): Promise<string | undefined> {
+      return get(key, store) ?? undefined
+    },
+    async set(key: string, value: string): Promise<void> {
+      await set(key, value, store)
+    },
+    async delete(key: string): Promise<void> {
+      await del(key, store)
+    },
+    async clear(): Promise<void> {
+      await clear(store)
+    },
+  }
+}

src/storage/archive/db/types.ts

@@ -0,0 +1,6 @@
+export type DB = {
+  get(key: string): Promise<string | undefined>
+  set(key: string, value: string): Promise<void>
+  delete(key: string): Promise<void>
+  clear(): Promise<void>
+}

src/storage/archive/index.ts

@@ -0,0 +1,90 @@
+import {create} from '#/storage/archive/db'
+import {type DB} from '#/storage/archive/db/types'
+import {type Device} from '#/storage/archive/schema'
+
+export * from '#/storage/archive/schema'
+
+/**
+ * Generic archival storage class. DO NOT use this directly. Instead, use the
+ * exported `Archive` instances below.
+ */
+export class Archive<Scopes extends unknown[], Schema> {
+  protected sep = ':'
+  protected store: DB
+
+  constructor({id}: {id: string}) {
+    this.store = create({id})
+  }
+
+  /**
+   * Store a value in archival storage based on scopes and/or keys
+   *
+   *   `set([key], value)`
+   *   `set([scope, key], value)`
+   */
+  async set<Key extends keyof Schema>(
+    scopes: [...Scopes, Key],
+    data: Schema[Key],
+  ): Promise<void> {
+    // stored as `{ data: <value> }` structure to ease stringification
+    return this.store.set(scopes.join(this.sep), JSON.stringify({data}))
+  }
+
+  /**
+   * Get a value from archival storage based on scopes and/or keys
+   *
+   *   `get([key])`
+   *   `get([scope, key])`
+   */
+  async get<Key extends keyof Schema>(
+    scopes: [...Scopes, Key],
+  ): Promise<Schema[Key] | undefined> {
+    const res = await this.store.get(scopes.join(this.sep))
+    if (!res) return undefined
+    // parsed from storage structure `{ data: <value> }`
+    return JSON.parse(res).data
+  }
+
+  /**
+   * Remove a value from archival storage based on scopes and/or keys
+   *
+   *   `remove([key])`
+   *   `remove([scope, key])`
+   */
+  async remove<Key extends keyof Schema>(scopes: [...Scopes, Key]) {
+    return this.store.delete(scopes.join(this.sep))
+  }
+
+  /**
+   * Remove many values from the same archival storage scope by keys
+   *
+   *   `removeMany([], [key])`
+   *   `removeMany([scope], [key])`
+   */
+  async removeMany<Key extends keyof Schema>(scopes: [...Scopes], keys: Key[]) {
+    return Promise.all(keys.map(key => this.remove([...scopes, key])))
+  }
+
+  /**
+   * For debugging purposes
+   */
+  async removeAll() {
+    return this.store.clear()
+  }
+}
+
+/**
+ * Device data that's specific to the device and does not vary based on account
+ *
+ *   `device.set([key], true)`
+ */
+export const deviceArchive = new Archive<[], Device>({
+  id: 'bsky_archive_device',
+})
+
+if (__DEV__ && typeof window !== 'undefined') {
+  // @ts-expect-error - dev global
+  window.bsky_archive = {
+    deviceArchive,
+  }
+}

src/storage/archive/schema.ts

@@ -0,0 +1,10 @@
+/**
+ * Data that's specific to the device and does not vary based account.
+ * Values here should be optional (since they may not have been saved
+ * yet), hence the `Partial`.
+ *
+ * See `#/storage/schema.ts` for examples.
+ */
+export type Device = Partial<{
+  // add values here
+}>

src/storage/schema.ts

@@ -2,7 +2,7 @@ import {type ID as PolicyUpdate202508} from '#/components/PolicyUpdateOverlay/up
 import {type Geolocation} from '#/geolocation/types'
 
 /**
- * Device data that's specific to the device and does not vary based account
+ * Data that's specific to the device and does not vary based account
  */
 export type Device = {
   /**