add comments in the server

server.ts

@@ -1,4 +1,4 @@
-import { blue } from "std/fmt/colors.ts";
+import { blue, red } from "std/fmt/colors.ts";
 import {
   type Order,
   orderDecider,
@@ -24,21 +24,31 @@ import {
 } from "./lib/api_schema.ts";
 import type { Command, Event } from "./lib/api.ts";
 
+// Open the key-value store: running in-memory
 const kv = await Deno.openKv(":memory:");
+
+// Listen to events from kv queue and apply them to the materialized view
+// retry policy can specified on kv.enqueue method (optionally enabled in the DenoEventRepository)
 kv.listenQueue(async (raw) => {
   try {
+    // Parse the event and metadata from the raw data / Zod validation/parsing
     const event: Event & EventMetadata = eventAndMetadataSchema.parse(raw);
     console.log(blue("Handling event: "), event);
-    const readRepository = new DenoViewStateRepository(kv);
+    // Combine views to create a new view that can handle both restaurant and order events
     const view = restaurantView.combine(orderView);
+    // Create a repository for the view state / a Deno implementation of the IViewStateRepository
+    const readRepository = new DenoViewStateRepository(kv);
+    // Create a materialized view to handle the events of all types / MaterializedView is composed of a view and a read repository
     const materializedView: ApplicationMaterializedView = new MaterializedView(
       view,
       readRepository,
     );
+    // Handle the events of all types
     const result = await materializedView.handle(event);
     console.log(blue("Result of event handling: "), result);
   } catch (error) {
-    console.error("Error of event handling: ", error);
+    // Catch & no throw to prevent queue retries
+    console.log(red("Error of event handling: "), error);
   }
 });
 
@@ -52,11 +62,10 @@ Deno.serve(async (request: Request) => {
 
     console.log(blue("Handling command: "), command);
 
-    // Open the key-value store
     // Combine deciders to create a new decider that can handle both restaurant and order commands
     const decider: Decider<Command, (Order & Restaurant) | null, Event> =
       restaurantDecider.combine(orderDecider);
-    // Create a repository for the events / a Deno implementation of the IEventRepository
+    // Create a repository for the events / a Deno implementation of the IEventRepository and optionally enable event enqueueing
     const eventRepository = new DenoEventRepository(kv, true);
     // Create an aggregate to handle the commands of all types / Aggregate is composed of a decider and an event repository
     const aggregate: ApplicationAggregate = new EventSourcingAggregate(
@@ -72,7 +81,7 @@ Deno.serve(async (request: Request) => {
     });
   } catch (error) {
     console.error("Error of command handling: ", error);
-    return new Response(error?.message ?? error, {
+    return new Response((error as Error)?.message ?? error, {
       headers: { "Content-Type": "application/json" },
       status: 500,
     });