feat: add top-artists report

src/reports/reports.service.ts

@@ -17,7 +17,10 @@ import {
 } from "date-fns";
 import { ListensService } from "../listens/listens.service";
 import { GetListenReportDto } from "./dto/get-listen-report.dto";
+import { GetTopArtistsReportDto } from "./dto/get-top-artists-report.dto";
 import { ListenReportDto } from "./dto/listen-report.dto";
+import { TopArtistsReportDto } from "./dto/top-artists-report.dto";
+import { Interval } from "./interval";
 import { Timeframe } from "./timeframe.enum";
 import { TimePreset } from "./timePreset.enum";
 
@@ -55,6 +58,8 @@ const timePresetToDays: { [x in TimePreset]: number } = {
   [TimePreset.CUSTOM]: 0, // Not used for this
 };
 
+const PAGINATION_LIMIT_UNLIMITED = 10000000;
+
 @Injectable()
 export class ReportsService {
   constructor(private readonly listensService: ListensService) {}
@@ -73,7 +78,7 @@ export class ReportsService {
       user,
       filter: { time: interval },
       page: 1,
-      limit: 10000000,
+      limit: PAGINATION_LIMIT_UNLIMITED,
     });
 
     const reportInterval: Interval = {
@@ -91,6 +96,54 @@ export class ReportsService {
 
     return { items: reportItems, timeStart, timeEnd, timeFrame };
   }
+
+  async getTopArtists(
+    options: GetTopArtistsReportDto
+  ): Promise<TopArtistsReportDto> {
+    const { user, timePreset, customTimeStart, customTimeEnd } = options;
+
+    const interval = this.getIntervalFromPreset({
+      timePreset,
+      customTimeStart,
+      customTimeEnd,
+    });
+
+    const { items: listens } = await this.listensService.getListens({
+      user,
+      filter: { time: interval },
+      page: 1,
+      limit: PAGINATION_LIMIT_UNLIMITED,
+    });
+
+    // Declare types for metrics calculation
+    type Item = TopArtistsReportDto["items"][0];
+    type Accumulator = {
+      [x: string]: Item;
+    };
+
+    const items: TopArtistsReportDto["items"] = Object.values<Item>(
+      listens
+        .flatMap((listen) => listen.track.artists)
+        .reduce<Accumulator>((counters, artist) => {
+          if (!counters[artist.id]) {
+            counters[artist.id] = {
+              artist,
+              count: 0,
+            };
+          }
+
+          counters[artist.id].count += 1;
+
+          return counters;
+        }, {})
+    )
+      .sort((a, b) => a.count - b.count)
+      .reverse() // sort descending
+      .slice(0, 20); // TODO: Make configurable
+
+    return { items };
+  }
+
   private getIntervalFromPreset(options: {
     timePreset: TimePreset;
     customTimeStart?: string;