fix(app): keep quick switcher focus when results are recomputed (#1746)

fluxer_app/src/features/search/state/QuickSwitcherSelection.test.ts

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {resolveRecomputedSelectedIndex} from '@app/features/search/state/QuickSwitcherSelection';
+import type {QuickSwitcherResult} from '@app/features/search/state/QuickSwitcherTypes';
+import {QuickSwitcherResultTypes} from '@fluxer/constants/src/QuickSwitcherConstants';
+import {describe, expect, it} from 'vitest';
+
+const result = (type: QuickSwitcherResult['type'], id: string) => ({type, id}) as QuickSwitcherResult;
+
+describe('resolveRecomputedSelectedIndex', () => {
+	it('follows the focused result when the list is reordered', () => {
+		const previous = result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c3');
+		const results = [
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c3'),
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c1'),
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c2'),
+		];
+		expect(resolveRecomputedSelectedIndex(previous, results, 0)).toBe(0);
+	});
+
+	it('keeps the focused result when entries are inserted above it', () => {
+		const previous = result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c2');
+		const results = [
+			result(QuickSwitcherResultTypes.HEADER, 'h1'),
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c9'),
+			result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c2'),
+		];
+		expect(resolveRecomputedSelectedIndex(previous, results, 1)).toBe(2);
+	});
+
+	it('falls back when the focused result disappears', () => {
+		const previous = result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'gone');
+		const results = [result(QuickSwitcherResultTypes.TEXT_CHANNEL, 'c1')];
+		expect(resolveRecomputedSelectedIndex(previous, results, 0)).toBe(0);
+	});
+
+	it('does not confuse ids that repeat across result types', () => {
+		const previous = result(QuickSwitcherResultTypes.GUILD, '42');
+		const results = [result(QuickSwitcherResultTypes.TEXT_CHANNEL, '42'), result(QuickSwitcherResultTypes.GUILD, '42')];
+		expect(resolveRecomputedSelectedIndex(previous, results, 0)).toBe(1);
+	});
+
+	it('uses the fallback when nothing was focused', () => {
+		expect(resolveRecomputedSelectedIndex(undefined, [result(QuickSwitcherResultTypes.GUILD, 'g')], 0)).toBe(0);
+	});
+});