feat(core): add Electron runtime, services, and app composition

src/core/services/mpv-state.test.ts

@@ -0,0 +1,33 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { resolveCurrentAudioStreamIndex } from './mpv';
+
+test('resolveCurrentAudioStreamIndex returns selected ff-index when no current track id', () => {
+  assert.equal(
+    resolveCurrentAudioStreamIndex(
+      [
+        { type: 'audio', id: 1, selected: false, 'ff-index': 1 },
+        { type: 'audio', id: 2, selected: true, 'ff-index': 3 },
+      ],
+      null,
+    ),
+    3,
+  );
+});
+
+test('resolveCurrentAudioStreamIndex prefers matching current audio track id', () => {
+  assert.equal(
+    resolveCurrentAudioStreamIndex(
+      [
+        { type: 'audio', id: 1, selected: true, 'ff-index': 3 },
+        { type: 'audio', id: 2, selected: false, 'ff-index': 6 },
+      ],
+      2,
+    ),
+    6,
+  );
+});
+
+test('resolveCurrentAudioStreamIndex returns null when tracks are not an array', () => {
+  assert.equal(resolveCurrentAudioStreamIndex(null, null), null);
+});