Add MMKV interface (#5169)

src/storage/index.ts

@@ -0,0 +1,72 @@
+import {MMKV} from 'react-native-mmkv'
+
+import {Device} from '#/storage/schema'
+
+/**
+ * Generic storage class. DO NOT use this directly. Instead, use the exported
+ * storage instances below.
+ */
+export class Storage<Scopes extends unknown[], Schema> {
+  protected sep = ':'
+  protected store: MMKV
+
+  constructor({id}: {id: string}) {
+    this.store = new MMKV({id})
+  }
+
+  /**
+   * Store a value in storage based on scopes and/or keys
+   *
+   *   `set([key], value)`
+   *   `set([scope, key], value)`
+   */
+  set<Key extends keyof Schema>(
+    scopes: [...Scopes, Key],
+    data: Schema[Key],
+  ): void {
+    // stored as `{ data: <value> }` structure to ease stringification
+    this.store.set(scopes.join(this.sep), JSON.stringify({data}))
+  }
+
+  /**
+   * Get a value from storage based on scopes and/or keys
+   *
+   *   `get([key])`
+   *   `get([scope, key])`
+   */
+  get<Key extends keyof Schema>(
+    scopes: [...Scopes, Key],
+  ): Schema[Key] | undefined {
+    const res = this.store.getString(scopes.join(this.sep))
+    if (!res) return undefined
+    // parsed from storage structure `{ data: <value> }`
+    return JSON.parse(res).data
+  }
+
+  /**
+   * Remove a value from storage based on scopes and/or keys
+   *
+   *   `remove([key])`
+   *   `remove([scope, key])`
+   */
+  remove<Key extends keyof Schema>(scopes: [...Scopes, Key]) {
+    this.store.delete(scopes.join(this.sep))
+  }
+
+  /**
+   * Remove many values from the same storage scope by keys
+   *
+   *   `removeMany([], [key])`
+   *   `removeMany([scope], [key])`
+   */
+  removeMany<Key extends keyof Schema>(scopes: [...Scopes], keys: Key[]) {
+    keys.forEach(key => this.remove([...scopes, key]))
+  }
+}
+
+/**
+ * Device data that's specific to the device and does not vary based on account
+ *
+ *   `device.set([key], true)`
+ */
+export const device = new Storage<[], Device>({id: 'device'})