mirror of
https://github.com/Psychotoxical/psysonic.git
synced 2026-07-21 23:05:46 +00:00
Frank Stellmacher
d3a8160b37
Moves four self-contained helpers into src/utils/, each with co-located characterization tests. playerStore re-exports them for the ~30 existing call sites; Phase E will migrate those imports. - shuffleArray (Fisher-Yates, generic) - resolveReplayGainDb (track/album/auto mode resolution) - songToTrack (Subsonic -> Track shape) - buildInfiniteQueueCandidates (Instant-Mix top-up source) playerStore.ts: 3732 -> 3618 LOC (-114).
52 lines
1.7 KiB
TypeScript
52 lines
1.7 KiB
TypeScript
/**
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* Pure-helper characterization for `shuffleArray` (Fisher-Yates).
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*
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* Originally lived in `playerStore.ts`; extracted in M0 of the frontend
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* refactor (2026-05-12).
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*/
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import { afterEach, describe, expect, it, vi } from 'vitest';
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import { shuffleArray } from './shuffleArray';
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describe('shuffleArray', () => {
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afterEach(() => {
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vi.restoreAllMocks();
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});
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it('does not mutate the input array', () => {
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const input = [1, 2, 3, 4, 5];
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const snapshot = [...input];
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shuffleArray(input);
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expect(input).toEqual(snapshot);
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});
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it('preserves the multiset of elements (same length, same members)', () => {
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const input = ['a', 'b', 'c', 'd', 'e'];
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const out = shuffleArray(input);
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expect(out).toHaveLength(input.length);
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expect([...out].sort()).toEqual([...input].sort());
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});
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it('returns a copy (not the same reference)', () => {
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const input = [1, 2, 3];
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expect(shuffleArray(input)).not.toBe(input);
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});
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it('returns an empty array when called with an empty array', () => {
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expect(shuffleArray([])).toEqual([]);
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});
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it('returns the single-element input unchanged', () => {
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expect(shuffleArray(['only'])).toEqual(['only']);
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});
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it('produces a deterministic order under a mocked RNG (Math.random=0 picks j=0 each iteration)', () => {
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vi.spyOn(Math, 'random').mockReturnValue(0);
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// With Math.random()=0, j=floor(0 * (i+1))=0 for every i. The Fisher-Yates
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// step swaps arr[i] with arr[0]. Walk it through for [1,2,3,4]:
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// i=3: swap(3,0) → [4,2,3,1]
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// i=2: swap(2,0) → [3,2,4,1]
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// i=1: swap(1,0) → [2,3,4,1]
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expect(shuffleArray([1, 2, 3, 4])).toEqual([2, 3, 4, 1]);
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});
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});
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