feat: add yt-dlp argument builder

src/lib/__tests__/ytdlp.test.ts

@@ -0,0 +1,63 @@
+import { buildYtdlpArgs } from '../ytdlp'
+
+const base = {
+  url: 'https://www.youtube.com/watch?v=dQw4w9WgXcQ',
+  uuid: 'abc-123',
+  format: 'mp4',
+  quality: 'best',
+  subtitles: false,
+  extraArgs: null,
+}
+
+describe('buildYtdlpArgs', () => {
+  it('always includes --no-playlist', () => {
+    expect(buildYtdlpArgs(base)).toContain('--no-playlist')
+  })
+
+  it('sets output path with uuid and %(ext)s template', () => {
+    const args = buildYtdlpArgs(base)
+    const idx = args.indexOf('-o')
+    expect(idx).toBeGreaterThan(-1)
+    expect(args[idx + 1]).toContain('abc-123')
+    expect(args[idx + 1]).toContain('%(ext)s')
+  })
+
+  it('adds format filter when quality is not "best"', () => {
+    const args = buildYtdlpArgs({ ...base, quality: '1080p' })
+    expect(args).toContain('-f')
+  })
+
+  it('does not add -f flag when quality is "best"', () => {
+    expect(buildYtdlpArgs(base)).not.toContain('-f')
+  })
+
+  it('adds subtitle flags when subtitles is true', () => {
+    const args = buildYtdlpArgs({ ...base, subtitles: true })
+    expect(args).toContain('--write-sub')
+    expect(args).toContain('--sub-lang')
+  })
+
+  it('does not add subtitle flags when subtitles is false', () => {
+    expect(buildYtdlpArgs(base)).not.toContain('--write-sub')
+  })
+
+  it('appends extra args from a JSON array string', () => {
+    const args = buildYtdlpArgs({
+      ...base,
+      extraArgs: '["--sponsorblock-remove","all"]',
+    })
+    expect(args).toContain('--sponsorblock-remove')
+    expect(args).toContain('all')
+  })
+
+  it('ignores malformed extraArgs JSON', () => {
+    expect(() =>
+      buildYtdlpArgs({ ...base, extraArgs: 'not-json' })
+    ).not.toThrow()
+  })
+
+  it('url is the last argument', () => {
+    const args = buildYtdlpArgs(base)
+    expect(args[args.length - 1]).toBe(base.url)
+  })
+})