feat: Add a monitoring store.

src/storage/MonitoringStore.ts

@@ -0,0 +1,49 @@
+import { EventEmitter } from 'events';
+import type { Patch } from '../ldp/http/Patch';
+import type { Representation } from '../ldp/representation/Representation';
+import type { RepresentationPreferences } from '../ldp/representation/RepresentationPreferences';
+import type { ResourceIdentifier } from '../ldp/representation/ResourceIdentifier';
+import type { Conditions } from './Conditions';
+import type { ResourceStore } from './ResourceStore';
+
+/**
+ * Store that notifies listeners of changes to its source
+ * by emitting a `changed` event.
+ */
+export class MonitoringStore<T extends ResourceStore = ResourceStore>
+  extends EventEmitter implements ResourceStore {
+  private readonly source: T;
+
+  public constructor(source: T) {
+    super();
+    this.source = source;
+  }
+
+  public async addResource(container: ResourceIdentifier, representation: Representation,
+    conditions?: Conditions): Promise<ResourceIdentifier> {
+    const identifier = await this.source.addResource(container, representation, conditions);
+    this.emit('changed', identifier);
+    return identifier;
+  }
+
+  public async deleteResource(identifier: ResourceIdentifier, conditions?: Conditions): Promise<void> {
+    await this.source.deleteResource(identifier, conditions);
+    this.emit('changed', identifier);
+  }
+
+  public async getRepresentation(identifier: ResourceIdentifier, preferences: RepresentationPreferences,
+    conditions?: Conditions): Promise<Representation> {
+    return this.source.getRepresentation(identifier, preferences, conditions);
+  }
+
+  public async modifyResource(identifier: ResourceIdentifier, patch: Patch, conditions?: Conditions): Promise<void> {
+    await this.source.modifyResource(identifier, patch, conditions);
+    this.emit('changed', identifier);
+  }
+
+  public async setRepresentation(identifier: ResourceIdentifier, representation: Representation,
+    conditions?: Conditions): Promise<void> {
+    await this.source.setRepresentation(identifier, representation, conditions);
+    this.emit('changed', identifier);
+  }
+}