feat: initial mini simple event sourcing for pending application updates

.gitignore

@@ -1,3 +1,4 @@
 node_modules
 
 .env.local
+data/

Makefile

@@ -7,3 +7,6 @@ test:
 
 tdd:
 	bun test --watch
+
+lint:
+	bun lint

domain/AppProjections.ts

@@ -0,0 +1,9 @@
+import ApplicationUpdates from "./projections/ApplicationUpdates";
+
+export default class AppProjections {
+  public readonly ApplicationUpdates = new ApplicationUpdates();
+
+  getAll(): DomainProjection[] {
+    return [this.ApplicationUpdates];
+  }
+}

domain/AppQueries.ts

@@ -0,0 +1,11 @@
+import AppProjections from "./AppProjections";
+import { UpdateDefinition } from "./projections/ApplicationUpdates";
+
+export default class AppQueries {
+  constructor(private readonly projections: AppProjections) {}
+
+  pendingApplicationUpdates(appName?: string): UpdateDefinition[] {
+    // TODO: Implement filtering by appName
+    return this.projections.ApplicationUpdates.getPendingUpdates();
+  }
+}

domain/DomainEvent.ts

@@ -0,0 +1,5 @@
+interface DomainEvent<T> {
+  readonly type: string;
+  readonly createdAt: Date;
+  readonly payload: T;
+}

domain/DomainProjection.ts

@@ -0,0 +1,3 @@
+interface DomainProjection {
+  handle(event: DomainEvent<any>): void;
+}

domain/EventStore.ts

@@ -0,0 +1,5 @@
+export default interface EventStore {
+  append(event: DomainEvent<any>): void;
+  subscribe(projection: DomainProjection): void;
+  replay(): Promise<void>;
+}

domain/events/ApplicationUpdateStarted.ts

@@ -0,0 +1,14 @@
+type ApplicationUpdateStartedPayload = {
+  id: string;
+  newVersion: string;
+};
+
+export class ApplicationUpdateStarted
+  implements DomainEvent<ApplicationUpdateStartedPayload>
+{
+  readonly type = "ApplicationUpdateStarted" as const;
+  constructor(
+    public readonly payload: ApplicationUpdateStartedPayload,
+    public readonly createdAt: Date
+  ) {}
+}

domain/projections/ApplicationUpdates.ts

@@ -0,0 +1,18 @@
+export type UpdateDefinition = {
+  id: string;
+  newVersion: string;
+};
+
+export default class ApplicationUpdates implements DomainProjection {
+  private readonly pendingUpdates: UpdateDefinition[] = [];
+  handle(event: DomainEvent<any>): void {
+    if (event.type === "ApplicationUpdateStarted") {
+      console.log("ApplicationUpdateStarted", event.payload);
+      this.pendingUpdates.push(event.payload);
+    }
+  }
+
+  getPendingUpdates(): UpdateDefinition[] {
+    return this.pendingUpdates;
+  }
+}

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);
+    }
+  }
+}

joe.ts

@@ -3,14 +3,26 @@ import applications from "./routes/applications";
 import applicationsUpdate from "./routes/applications.update";
 import Layout, { html } from "./ui/Layout";
 import DockerHub from "./services/DockerHub";
+import FileEventStore from "./infrastructure/FileEventStore";
+import AppQueries from "./domain/AppQueries";
+import AppProjections from "./domain/AppProjections";
 
-console.log("Hello Pierrot!");
+// Domain
+const eventStore = new FileEventStore("./data/events.jsonl");
+const projections = new AppProjections();
+const queries = new AppQueries(projections);
 
+projections.getAll().forEach((projection) => {
+  eventStore.subscribe(projection);
+});
+await eventStore.replay();
+
+// External services
 const caprover = new Caprover(
+  eventStore,
   process.env.CAPTAIN_DOMAIN,
   process.env.CAPTAIN_PASSWORD
 );
-
 const dockerHub = new DockerHub();
 
 const server = Bun.serve({
@@ -29,7 +41,7 @@ const server = Bun.serve({
       case "/applications":
         return applications(req, caprover);
       case "/applications/update":
-        return applicationsUpdate(req, caprover, dockerHub);
+        return applicationsUpdate(req, caprover, dockerHub, queries);
       default:
         return new Response("Not Found", { status: 404 });
     }

routes/applications.update.ts

@@ -1,3 +1,5 @@
+import AppQueries from "../domain/AppQueries";
+import { UpdateDefinition } from "../domain/projections/ApplicationUpdates";
 import Caprover, { Application } from "../services/Caprover";
 import DockerHub from "../services/DockerHub";
 import Layout, { html } from "../ui/Layout";
@@ -19,10 +21,33 @@ const UpdateForm = (application: Application, latestVersions: string[]) => {
   </form>`;
 };
 
-const Page = (application: Application, latestVersions: string[]) => {
+const PendingUpdates = (pendingUpdates: UpdateDefinition[]) => {
+  if (pendingUpdates.length === 0) {
+    return "";
+  }
+
+  return html`<div>
+    <h2>Pending updates</h2>
+    <ul>
+      ${pendingUpdates
+        .map((update) => {
+          return html`<li>${update.newVersion}</li>`;
+        })
+        .join("")}
+    </ul>
+  </div>`;
+};
+
+const Page = (
+  application: Application,
+  latestVersions: string[],
+  pendingUpdates: UpdateDefinition[]
+) => {
   return html`<div>
     <h1>Updating ${application.name}</h1>
 
+    ${PendingUpdates(pendingUpdates)}
+
     <dl>
       <dt>Last deployment</dt>
       <dd>${application.lastDeployedAt.toLocaleString("fr-FR")}</dd>
@@ -49,12 +74,15 @@ const Page = (application: Application, latestVersions: string[]) => {
 export default async (
   req: Request,
   caprover: Caprover,
-  dockerHub: DockerHub
+  dockerHub: DockerHub,
+  queries: AppQueries
 ): Promise<Response> => {
   if (req.method === "POST") {
     const body = await req.formData();
-    console.log("TODO Implement application update", [...body.entries()]);
+    caprover.updateApplication(
-    throw new Error("Not implemented");
+      body.get("appName") as string,
+      body.get("version") as string
+    );
   }
 
   const applications = await caprover.getApps();
@@ -76,7 +104,12 @@ export default async (
     appToUpdate.dockerImage!.name
   );
 
-  return new Response(Layout(Page(appToUpdate, latestVersions)), {
+  const pendingUpdates = queries.pendingApplicationUpdates(appToUpdate.name);
+
+  return new Response(
+    Layout(Page(appToUpdate, latestVersions, pendingUpdates)),
+    {
       headers: { "Content-Type": "text/html" },
-  });
+    }
+  );
 };

services/Caprover.ts

@@ -1,3 +1,6 @@
+import EventStore from "../domain/EventStore";
+import { ApplicationUpdateStarted } from "../domain/events/ApplicationUpdateStarted";
+
 type TODO_TypeDefinition = any;
 
 class Application {
@@ -52,12 +55,18 @@ class Application {
 class Caprover {
   private authToken: string = "";
   private readonly apiUrl: string;
+  private readonly eventStore: EventStore;
 
-  constructor(readonly domain?: string, private readonly password?: string) {
+  constructor(
+    eventStore: EventStore,
+    readonly domain?: string,
+    private readonly password?: string
+  ) {
     if (!domain || !password) {
       throw new Error("Missing domain or password");
     }
     this.apiUrl = `https://${domain}/api/v2`;
+    this.eventStore = eventStore;
   }
 
   async getApps(): Promise<Application[]> {
@@ -70,6 +79,16 @@ class Caprover {
     );
   }
 
+  async updateApplication(appName: string, version: string) {
+    console.log("TODO: Implement remote call", appName, version); // TODO
+    this.eventStore.append(
+      new ApplicationUpdateStarted(
+        { id: appName, newVersion: version },
+        new Date()
+      )
+    );
+  }
+
   private async authenticate() {
     if (this.authToken) {
       return;

tsconfig.json

@@ -1,7 +1,7 @@
 {
   "compilerOptions": {
-    "target": "es2017",
+    "target": "ES2022",
-    "module": "commonjs",
+    "module": "ES2022",
     "forceConsistentCasingInFileNames": true,
     "strict": true,
     "types": ["bun-types"]