feat: improve initial load performance on mobile (#2126)

packages/mobile/src/Lib/Database/DatabaseMetadata.ts

@@ -0,0 +1,39 @@
+import { DatabaseItemMetadata, isNotUndefined, TransferPayload } from '@standardnotes/snjs'
+import { FlashKeyValueStore } from './FlashKeyValueStore'
+
+export class DatabaseMetadata {
+  constructor(private identifier: string, private flashStorage: FlashKeyValueStore) {}
+
+  runMigration(payloads: TransferPayload[]) {
+    const metadataItems = this.setMetadataForPayloads(payloads)
+    return metadataItems
+  }
+
+  setMetadataForPayloads(payloads: TransferPayload[]) {
+    const metadataItems = []
+    for (const payload of payloads) {
+      const { uuid, content_type, updated_at } = payload
+      const key = this.keyForUuid(uuid)
+      const metadata: DatabaseItemMetadata = { uuid, content_type, updated_at }
+      this.flashStorage.set(key, metadata)
+      metadataItems.push(metadata)
+    }
+    return metadataItems
+  }
+
+  deleteMetadataItem(itemUuid: string) {
+    const key = this.keyForUuid(itemUuid)
+    this.flashStorage.delete(key)
+  }
+
+  getAllMetadataItems(): DatabaseItemMetadata[] {
+    const keys = this.flashStorage.getAllKeys()
+    const metadataKeys = keys.filter((key) => key.endsWith('-Metadata'))
+    const metadataItems = this.flashStorage.multiGet<DatabaseItemMetadata>(metadataKeys).filter(isNotUndefined)
+    return metadataItems
+  }
+
+  private keyForUuid(uuid: string) {
+    return `${this.identifier}-Item-${uuid}-Metadata`
+  }
+}