Related:

Fixes SRT subtitle parsing issues where comma-separated milliseconds (e.g.,00:00:01,000) fail to parse when content contains indented template literals.
Closes#1671

Description:

This PR adds whitespace normalization to the#parseContent method inTextTrack to handle indented template literal content before passing it to themedia-captions parser.

Changes:

• Core Fix: Addedcontent.split('\n').map(line => line.trim()).join('\n').trim() to normalize whitespace while preserving line structure
• Test Coverage: Added comprehensive unit tests (16 test cases) covering whitespace normalization scenarios
• Edge Cases: Handles mixed indentation, Windows line endings, tabs, and extremely large indentation
• Backward Compatibility: Preserves empty lines between subtitle blocks and doesn't affect JSON content parsing

Problem Solved:
Themedia-captions library expects clean content without leading/trailing whitespace. When using template literals with indentation for inline SRT content, the parser would fail with errors like"cue start timestamp \'00:00:00,000\' is invalid" even though the SRT format itself was correct.

Ready?

✅Yes - All tests passing, edge cases covered, and backward compatibility maintained.

Anything Else?

Before (Failed):

consttrack=newTextTrack({kind:'subtitles',type:'srt',content:`    1    00:00:01,000 --> 00:00:05,000    First subtitle`});// ❌ Error: cue start timestamp `00:00:01,000` is invalid

After (Works)

consttrack=newTextTrack({kind:'subtitles',type:'srt',content:`    1    00:00:01,000 --> 00:00:05,000    First subtitle`});// ✅ Parses successfully - whitespace normalized automatically

Test Results: ✅16/16 tests passing

Detailed Coverage:

• ✅ Template literal indentation scenarios
• ✅ Mixed whitespace handling
• ✅ Empty line preservation between subtitle blocks
• ✅ JSON content bypass (no normalization applied)
• ✅ Windows line endings (\r\n) compatibility
• ✅ Tab characters and extreme indentation handling
• ✅ SRT comma timestamps (00:00:01,000) parsing
• ✅ VTT period timestamps (00:00:01.000) parsing
• ✅ Complex content with HTML formatting and special characters
• ✅ Single line content normalization
• ✅ Whitespace-only content handling

Manual Test Scenarios:

Template Literal Testing

// Test 1: Basic indented SRT contentconsttrack1=newTextTrack({kind:'subtitles',type:'srt',content:`    1    00:00:01,000 --> 00:00:05,000    First subtitle    2    00:00:06,000 --> 00:00:10,000    Second subtitle`});// Expected: ✅ Parses successfully

Cross-platform Line Endings

// Test 2: Windows line endings (\r\n)constwindowsContent="1\r\n00:00:01,000 --> 00:00:05,000\r\nSubtitle text";consttrack2=newTextTrack({kind:'subtitles',type:'srt',content:`${windowsContent}`});// Expected: ✅ Handles \r\n correctly

JSON Content Bypass

// Test 3: JSON content should skip normalizationconsttrack3=newTextTrack({kind:'subtitles',type:'json',content:{cues:[{startTime:1,endTime:5,text:"Test"}]}});// Expected: ✅ No normalization applied to JSON

VTT Format Testing

// Test 4: VTT with period timestampsconsttrack4=newTextTrack({kind:'subtitles',type:'vtt',content:`    WEBVTT    1    00:00:01.000 --> 00:00:05.000    VTT subtitle`});// Expected: ✅ VTT format works with periods

Edge Case Validation

// Test 5: Mixed whitespace (tabs + spaces)constmixedContent="\t  1\n\t00:00:01,000 --> 00:00:05,000\n\t  Mixed whitespace";consttrack5=newTextTrack({kind:'subtitles',type:'srt',content:mixedContent});// Expected: ✅ Handles mixed tab/space indentation