feat: initial mini simple event sourcing for pending application updates

infrastructure/FileEventStore.ts

@@ -0,0 +1,60 @@
+import { appendFile } from "node:fs/promises";
+import EventStore from "../domain/EventStore";
+import { ApplicationUpdateStarted } from "../domain/events/ApplicationUpdateStarted";
+
+export default class FileEventStore implements EventStore {
+  private handlers: DomainProjection[] = [];
+  constructor(private readonly filePath: string) {}
+
+  append(event: DomainEvent<any>): void {
+    appendFile(this.filePath, this.serialize(event) + "\n");
+    this.emit(event);
+  }
+
+  subscribe(projection: DomainProjection) {
+    this.handlers.push(projection);
+  }
+
+  async replay() {
+    // TODO Improve this with streaming
+    console.log("Replaying events from", this.filePath);
+    const file = Bun.file(this.filePath);
+    const content = await file.text();
+    const lines = content.split("\n");
+    for (const line of lines) {
+      if (!line) {
+        continue;
+      }
+      console.log("Deserializing", line);
+      const event = this.deserialize(line);
+      this.emit(event);
+    }
+    console.log("Replaying done");
+  }
+
+  private emit(event: DomainEvent<any>) {
+    for (const handler of this.handlers) {
+      handler.handle(event);
+    }
+  }
+
+  private serialize(event: DomainEvent<any>) {
+    return JSON.stringify(event);
+  }
+
+  private deserialize(line: string) {
+    const event = JSON.parse(line);
+    switch (event.type) {
+      case "ApplicationUpdateStarted":
+        return new ApplicationUpdateStarted(
+          {
+            id: event.payload.id,
+            newVersion: event.payload.newVersion,
+          },
+          new Date(event.createdAt)
+        );
+      default:
+        throw new Error("Unknown event type" + event.type);
+    }
+  }
+}