feat(subtitles): add no-jump subtitle-delay shift commands

src/core/services/subtitle-delay-shift.test.ts

@@ -0,0 +1,122 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { createShiftSubtitleDelayToAdjacentCueHandler } from './subtitle-delay-shift';
+
+function createMpvClient(props: Record<string, unknown>) {
+  return {
+    connected: true,
+    requestProperty: async (name: string) => props[name],
+  };
+}
+
+test('shift subtitle delay to next cue using active external srt track', async () => {
+  const commands: Array<Array<string | number>> = [];
+  const osd: string[] = [];
+  let loadCount = 0;
+  const handler = createShiftSubtitleDelayToAdjacentCueHandler({
+    getMpvClient: () =>
+      createMpvClient({
+        'track-list': [
+          {
+            type: 'sub',
+            id: 2,
+            external: true,
+            'external-filename': '/tmp/subs.srt',
+          },
+        ],
+        sid: 2,
+        'sub-start': 3.0,
+      }),
+    loadSubtitleSourceText: async () => {
+      loadCount += 1;
+      return `1
+00:00:01,000 --> 00:00:02,000
+line-1
+
+2
+00:00:03,000 --> 00:00:04,000
+line-2
+
+3
+00:00:05,000 --> 00:00:06,000
+line-3`;
+    },
+    sendMpvCommand: (command) => commands.push(command),
+    showMpvOsd: (text) => osd.push(text),
+  });
+
+  await handler('next');
+  await handler('next');
+
+  assert.equal(loadCount, 1);
+  assert.equal(commands.length, 2);
+  const delta = commands[0]?.[2];
+  assert.equal(commands[0]?.[0], 'add');
+  assert.equal(commands[0]?.[1], 'sub-delay');
+  assert.equal(typeof delta, 'number');
+  assert.equal(Math.abs((delta as number) - 2) < 0.0001, true);
+  assert.deepEqual(osd, ['Subtitle delay: ${sub-delay}', 'Subtitle delay: ${sub-delay}']);
+});
+
+test('shift subtitle delay to previous cue using active external ass track', async () => {
+  const commands: Array<Array<string | number>> = [];
+  const handler = createShiftSubtitleDelayToAdjacentCueHandler({
+    getMpvClient: () =>
+      createMpvClient({
+        'track-list': [
+          {
+            type: 'sub',
+            id: 4,
+            external: true,
+            'external-filename': '/tmp/subs.ass',
+          },
+        ],
+        sid: 4,
+        'sub-start': 2.0,
+      }),
+    loadSubtitleSourceText: async () => `[Events]
+Dialogue: 0,0:00:00.50,0:00:01.50,Default,,0,0,0,,line-1
+Dialogue: 0,0:00:02.00,0:00:03.00,Default,,0,0,0,,line-2
+Dialogue: 0,0:00:04.00,0:00:05.00,Default,,0,0,0,,line-3`,
+    sendMpvCommand: (command) => commands.push(command),
+    showMpvOsd: () => {},
+  });
+
+  await handler('previous');
+
+  const delta = commands[0]?.[2];
+  assert.equal(typeof delta, 'number');
+  assert.equal(Math.abs((delta as number) + 1.5) < 0.0001, true);
+});
+
+test('shift subtitle delay throws when no next cue exists', async () => {
+  const handler = createShiftSubtitleDelayToAdjacentCueHandler({
+    getMpvClient: () =>
+      createMpvClient({
+        'track-list': [
+          {
+            type: 'sub',
+            id: 1,
+            external: true,
+            'external-filename': '/tmp/subs.vtt',
+          },
+        ],
+        sid: 1,
+        'sub-start': 5.0,
+      }),
+    loadSubtitleSourceText: async () => `WEBVTT
+
+00:00:01.000 --> 00:00:02.000
+line-1
+
+00:00:03.000 --> 00:00:04.000
+line-2
+
+00:00:05.000 --> 00:00:06.000
+line-3`,
+    sendMpvCommand: () => {},
+    showMpvOsd: () => {},
+  });
+
+  await assert.rejects(() => handler('next'), /No next subtitle cue found/);
+});