Reorganise for easier extraction

Summary:
To make the DataSource abstraction reusable for other teams and an upcoming talk, this diff moves all DataSource storage & virtualization logic in one folder.

Will set up a build process and demo project in later diffs.

Reviewed By: nikoant

Differential Revision: D28056700

fbshipit-source-id: 7cfe5b40bbbe387da711f765a604a45029d451c7

desktop/flipper-plugin/src/state/createDataSource.tsx

@@ -0,0 +1,49 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import {DataSource, ExtractKeyType} from '../data-source/DataSource';
+import {registerStorageAtom} from '../plugin/PluginBase';
+
+type CreateDataSourceOptions<T, K extends keyof T> = {
+  /**
+   * If a key is set, the given field of the records is assumed to be unique,
+   * and it's value can be used to perform lookups and upserts.
+   */
+  key?: K;
+  /**
+   * The maximum amount of records that this DataSource will store.
+   * If the limit is exceeded, the oldest records will automatically be dropped to make place for the new ones
+   */
+  limit?: number;
+  /**
+   * Should this state persist when exporting a plugin?
+   * If set, the dataSource will be saved / loaded under the key provided
+   */
+  persist?: string;
+};
+
+export function createDataSource<T, KEY extends keyof T = any>(
+  initialSet: T[],
+  options: CreateDataSourceOptions<T, KEY>,
+): DataSource<T, KEY, ExtractKeyType<T, KEY>>;
+export function createDataSource<T>(
+  initialSet?: T[],
+): DataSource<T, never, never>;
+export function createDataSource<T, KEY extends keyof T>(
+  initialSet: T[] = [],
+  options?: CreateDataSourceOptions<T, KEY>,
+): DataSource<T, any, any> {
+  const ds = new DataSource<T, KEY>(options?.key);
+  if (options?.limit !== undefined) {
+    ds.limit = options.limit;
+  }
+  registerStorageAtom(options?.persist, ds);
+  initialSet.forEach((value) => ds.append(value));
+  return ds;
+}