Removal of localStorage dependency v1

packages/store/src/synced.ts

@@ -1,11 +1,37 @@
 import {writable} from "svelte/store"
 import {getJson, setJson} from "@welshman/lib"
 
-export const synced = <T>(key: string, defaultValue: T) => {
-  const init = getJson(key)
-  const store = writable<T>(init === undefined ? defaultValue : init)
+export interface StorageProvider {
+  get: (key: string) => Promise<any>
+  set: (key: string, value: any) => Promise<void>
+}
 
-  store.subscribe((value: T) => setJson(key, value))
+export interface SyncedConfig {
+  key: string
+  storage: StorageProvider
+  defaultValue: any
+}
+
+export const localStorageProvider: StorageProvider = {
+  get: async (key: string) => getJson(key),
+  set: async (key: string, value: any) => setJson(key, value),
+}
+
+export const synced = <T>(config: SyncedConfig) => {
+  const {key, storage, defaultValue} = config
+  const store = writable<T>(defaultValue)
+
+  // Async initialization
+  storage.get(key).then((value: any) => {
+    if (value !== undefined) {
+      store.set(value)
+    }
+  })
+
+  // Subscribe to changes
+  store.subscribe(async (value: T) => {
+    await storage.set(key, value)
+  })
 
   return store
 }