feat(game): play confetti for finished games

src/utils/confetti.js

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+const FINISHED = ['FINISHED', 'COMPLETED'];
+
+/**
+ * Every achievement unlocked. Only while the stats are visible: Core can still send the old unlock count after they turn private.
+ */
+export const allAchievementsUnlocked = (game) => game.hasAchievements && game.statsVisible
+    && game.achievementsTotal > 0 && game.achievementsUnlocked >= game.achievementsTotal;
+
+/**
+ * 0: not finished, 1: finished, 2: finished and every achievement unlocked.
+ */
+export const celebrationLevel = (game) => {
+    if (!FINISHED.includes(game.status)) return 0;
+    return allAchievementsUnlocked(game) ? 2 : 1;
+};
+
+/**
+ * The confetti to play when the page shows this game: on opening a finished game, and when the level rises on the
+ * same page (e.g. the user sets FINISHED). A reload of the same game plays nothing.
+ *
+ * @param before {appid, level} of the game shown before, null on opening the page
+ * @returns 'small', 'big' or null
+ */
+export const celebrationFor = (before, game) => {
+    const level = celebrationLevel(game);
+    const from = before?.appid === game.appid ? before.level : 0;
+    if (level <= from) return null;
+    return level === 2 ? 'big' : 'small';
+};

src/utils/confetti.test.js

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+import {describe, expect, it} from 'vitest';
+import {celebrationFor, celebrationLevel} from './confetti.js';
+
+const game = (status, unlocked = 0, total = 0, appid = 620) =>
+    ({appid, status, hasAchievements: total > 0, statsVisible: true, achievementsUnlocked: unlocked, achievementsTotal: total});
+
+describe('celebrationLevel', () => {
+    it('is 0 for a game not finished, 1 for finished, 2 for finished with every achievement', () => {
+        expect(celebrationLevel(game('PLAYING', 4, 4))).toBe(0);
+        expect(celebrationLevel(game('FINISHED'))).toBe(1);
+        expect(celebrationLevel(game('COMPLETED', 3, 4))).toBe(1);
+        expect(celebrationLevel(game('FINISHED', 4, 4))).toBe(2);
+        expect(celebrationLevel(game('COMPLETED', 4, 4))).toBe(2);
+    });
+
+    it('counts no achievements while the stats are hidden', () => {
+        expect(celebrationLevel({...game('FINISHED', 4, 4), statsVisible: false})).toBe(1);
+    });
+});
+
+describe('celebrationFor', () => {
+    it('plays on opening a finished game', () => {
+        expect(celebrationFor(null, game('FINISHED'))).toBe('small');
+        expect(celebrationFor(null, game('COMPLETED', 4, 4))).toBe('big');
+        expect(celebrationFor(null, game('BACKLOG'))).toBeNull();
+    });
+
+    it('plays when the status rises on the same page, not when the game loads again', () => {
+        expect(celebrationFor({appid: 620, level: 0}, game('FINISHED'))).toBe('small');
+        expect(celebrationFor({appid: 620, level: 1}, game('FINISHED', 4, 4))).toBe('big');
+        expect(celebrationFor({appid: 620, level: 1}, game('FINISHED'))).toBeNull();
+        expect(celebrationFor({appid: 620, level: 2}, game('PLAYING'))).toBeNull();
+    });
+
+    it('plays for another game opened from the page', () => {
+        expect(celebrationFor({appid: 620, level: 1}, game('FINISHED', 0, 0, 220))).toBe('small');
+    });
+});