enhance(backend): improve chart engine

packages/backend/src/services/chart/charts/federation.ts

@@ -0,0 +1,66 @@
+import autobind from 'autobind-decorator';
+import Chart, { Obj, DeepPartial } from '../core';
+import { SchemaType } from '@/misc/schema';
+import { Instances } from '@/models/index';
+import { name, schema } from './entities/federation';
+
+type FederationLog = SchemaType<typeof schema>;
+
+/**
+ * フェデレーションに関するチャート
+ */
+// eslint-disable-next-line import/no-default-export
+export default class FederationChart extends Chart<FederationLog> {
+	constructor() {
+		super(name, schema);
+	}
+
+	@autobind
+	protected genNewLog(latest: FederationLog): DeepPartial<FederationLog> {
+		return {
+			instance: {
+				total: latest.instance.total,
+			},
+		};
+	}
+
+	@autobind
+	protected aggregate(logs: FederationLog[]): FederationLog {
+		return {
+			instance: {
+				total: logs[0].instance.total,
+				inc: logs.reduce((a, b) => a + b.instance.inc, 0),
+				dec: logs.reduce((a, b) => a + b.instance.dec, 0),
+			},
+		};
+	}
+
+	@autobind
+	protected async fetchActual(): Promise<DeepPartial<FederationLog>> {
+		const [total] = await Promise.all([
+			Instances.count({}),
+		]);
+
+		return {
+			instance: {
+				total: total,
+			},
+		};
+	}
+
+	@autobind
+	public async update(isAdditional: boolean): Promise<void> {
+		const update: Obj = {};
+
+		update.total = isAdditional ? 1 : -1;
+		if (isAdditional) {
+			update.inc = 1;
+		} else {
+			update.dec = 1;
+		}
+
+		await this.inc({
+			instance: update,
+		});
+	}
+}