first commit

libs/api/shared/infrastructure/src/lib/event-store/deserializers/event.deserializer.ts

@@ -0,0 +1,26 @@
+import { Injectable, Type } from '@nestjs/common';
+import {
+  EventClsRegistry,
+  SerializableEvent,
+} from '@task-stream/api/shared/domain';
+
+@Injectable()
+export class EventDeserializer {
+  deserialize<T>(event: SerializableEvent): SerializableEvent<T> {
+    const eventCls = EventClsRegistry.get(event.type);
+    return {
+      streamId: event.streamId,
+      type: event.type,
+      position: event.position,
+      data: this.instantiateSerializedEvent(eventCls, event.data),
+    };
+  }
+
+  /** Rebuilds the event with its class prototype, without running the constructor. */
+  instantiateSerializedEvent<T extends Type>(
+    eventCls: T,
+    data: Record<string, unknown>,
+  ) {
+    return Object.assign(Object.create(eventCls.prototype), data);
+  }
+}