StarPunk/docs/reports/2025-11-26-v1.1.2-phase2-complete.md

StarPunk v1.1.2 Phase 2 Feed Formats - Implementation Report (COMPLETE)

Date: 2025-11-26 Developer: StarPunk Fullstack Developer (AI) Phase: v1.1.2 "Syndicate" - Phase 2 (All Phases 2.0-2.4 Complete) Status: COMPLETE

Executive Summary

Successfully completed all phases of Phase 2 feed formats implementation, adding multi-format feed support (RSS 2.0, ATOM 1.0, JSON Feed 1.1) with HTTP content negotiation. This marks the complete implementation of the "Syndicate" feed generation system.

Phases Completed

• ✅ Phase 2.0: RSS Feed Ordering Fix (CRITICAL bug fix)
• ✅ Phase 2.1: Feed Module Restructuring
• ✅ Phase 2.2: ATOM 1.0 Feed Implementation
• ✅ Phase 2.3: JSON Feed 1.1 Implementation
• ✅ Phase 2.4: Content Negotiation (COMPLETE)

Key Achievements

1. Fixed Critical RSS Bug: Streaming RSS was showing oldest-first instead of newest-first
2. Added ATOM Support: Full RFC 4287 compliance with 11 passing tests
3. Added JSON Feed Support: JSON Feed 1.1 spec with 13 passing tests
4. Content Negotiation: Smart format selection via HTTP Accept headers
5. Dual Endpoint Strategy: Both content negotiation and explicit format endpoints
6. Restructured Code: Clean module organization in starpunk/feeds/
7. Business Metrics: Integrated feed generation tracking
8. Test Coverage: 132 total feed tests, all passing

Phase 2.4: Content Negotiation Implementation

Overview (Completed 2025-11-26)

Implemented HTTP content negotiation for feed formats, allowing clients to request their preferred format via Accept headers while maintaining backward compatibility and providing explicit format endpoints.

Time Invested: 1 hour (as estimated)

Implementation Details

Content Negotiation Module

Created starpunk/feeds/negotiation.py with three main functions:

1. Accept Header Parsing

def _parse_accept_header(accept_header: str) -> List[tuple]:
    """
    Parse Accept header into (mime_type, quality) tuples

    Features:
    - Parses quality factors (q=0.9)
    - Sorts by quality (highest first)
    - Handles wildcards (*/* and application/*)
    - Simple implementation (StarPunk philosophy)
    """

2. Format Scoring

def _score_format(format_name: str, media_types: List[tuple]) -> float:
    """
    Score a format based on Accept header

    Matching:
    - Exact MIME type match (e.g., application/rss+xml)
    - Alternative MIME types (e.g., application/json for JSON Feed)
    - Wildcard matches (*/* and application/*)
    - Returns highest quality score
    """

3. Format Negotiation

def negotiate_feed_format(accept_header: str, available_formats: List[str]) -> str:
    """
    Determine best feed format from Accept header

    Returns:
    - Best matching format name ('rss', 'atom', or 'json')

    Raises:
    - ValueError if no acceptable format (caller returns 406)

    Default behavior:
    - Wildcards (*/*) default to RSS
    - Quality ties default to RSS, then ATOM, then JSON
    """

4. MIME Type Helper

def get_mime_type(format_name: str) -> str:
    """Get MIME type string for format name"""

MIME Type Mappings

MIME_TYPES = {
    'rss': 'application/rss+xml',
    'atom': 'application/atom+xml',
    'json': 'application/feed+json',
}

MIME_TO_FORMAT = {
    'application/rss+xml': 'rss',
    'application/atom+xml': 'atom',
    'application/feed+json': 'json',
    'application/json': 'json',  # Also accept generic JSON
}

Route Implementation

Content Negotiation Endpoint

Added /feed endpoint to starpunk/routes/public.py:

@bp.route("/feed")
def feed():
    """
    Content negotiation endpoint for feeds

    Behavior:
    - Parse Accept header
    - Negotiate format (RSS, ATOM, or JSON)
    - Route to appropriate generator
    - Return 406 if no acceptable format
    """

Example requests:

# Request ATOM feed
curl -H "Accept: application/atom+xml" https://example.com/feed

# Request JSON Feed with fallback
curl -H "Accept: application/json, */*;q=0.8" https://example.com/feed

# Browser (defaults to RSS)
curl -H "Accept: text/html,application/xml;q=0.9,*/*;q=0.8" https://example.com/feed

Explicit Format Endpoints

Added four explicit endpoints:

@bp.route("/feed.rss")
def feed_rss():
    """Explicit RSS 2.0 feed"""

@bp.route("/feed.atom")
def feed_atom():
    """Explicit ATOM 1.0 feed"""

@bp.route("/feed.json")
def feed_json():
    """Explicit JSON Feed 1.1"""

@bp.route("/feed.xml")
def feed_xml_legacy():
    """Backward compatibility - redirects to /feed.rss"""

Cache Helper Function

Added shared note caching function:

def _get_cached_notes():
    """
    Get cached note list or fetch fresh notes

    Benefits:
    - Single cache for all formats
    - Reduces repeated DB queries
    - Respects FEED_CACHE_SECONDS config
    """

All endpoints use this shared cache, ensuring consistent behavior.

Test Coverage

Unit Tests (41 tests)

Created tests/test_feeds_negotiation.py:

Accept Header Parsing (12 tests):

• Single and multiple media types
• Quality factor parsing and sorting
• Wildcard handling (*/* and application/*)
• Whitespace handling
• Invalid quality factor handling
• Quality clamping (0-1 range)

Format Scoring (6 tests):

• Exact MIME type matching
• Wildcard matching
• Type wildcard matching
• No match scenarios
• Best quality selection
• Invalid format handling

Format Negotiation (17 tests):

• Exact format matches (RSS, ATOM, JSON)
• Generic application/json matching JSON Feed
• Wildcard defaults to RSS
• Quality factor selection
• Tie-breaking (prefers RSS > ATOM > JSON)
• No acceptable format raises ValueError
• Complex Accept headers
• Browser-like Accept headers
• Feed reader Accept headers
• JSON API client Accept headers

Helper Functions (6 tests):

• get_mime_type() for all formats
• MIME type constant validation
• Error handling for unknown formats

Integration Tests (22 tests)

Created tests/test_routes_feeds.py:

Explicit Endpoints (4 tests):

• /feed.rss returns RSS with correct MIME type
• /feed.atom returns ATOM with correct MIME type
• /feed.json returns JSON Feed with correct MIME type
• /feed.xml backward compatibility

Content Negotiation (10 tests):

• Accept: application/rss+xml → RSS
• Accept: application/atom+xml → ATOM
• Accept: application/feed+json → JSON Feed
• Accept: application/json → JSON Feed
• Accept: / → RSS (default)
• No Accept header → RSS
• Quality factors work correctly
• Browser Accept headers → RSS
• Returns 406 for unsupported formats

Cache Headers (3 tests):

• All formats include Cache-Control header
• Respects FEED_CACHE_SECONDS config

Feed Content (3 tests):

• All formats contain test notes
• Content is correct for each format

Backward Compatibility (2 tests):

• /feed.xml returns same content as /feed.rss
• /feed.xml contains valid RSS

Design Decisions

Simplicity Over RFC Compliance

Per StarPunk philosophy, implemented simple content negotiation rather than full RFC 7231 compliance:

What We Implemented:

• Basic quality factor parsing (split on ;, parse q=)
• Exact MIME type matching
• Wildcard matching (*/* and type wildcards)
• Default to RSS on ties

What We Skipped:

• Complex media type parameters
• Character set negotiation
• Language negotiation
• Partial matches on parameters

This covers 99% of real-world use cases with 1% of the complexity.

Default Format Selection

Chose RSS as default for several reasons:

1. Universal Support: Every feed reader supports RSS
2. Backward Compatibility: Existing tools expect RSS
3. Wildcard Behavior: */* should return most compatible format
4. User Expectation: RSS is synonymous with "feed"

On quality ties, preference order is RSS > ATOM > JSON Feed.

Dual Endpoint Strategy

Implemented both content negotiation AND explicit endpoints:

Benefits:

• Content negotiation for smart clients
• Explicit endpoints for simple cases
• Clear URLs for users (/feed.atom vs /feed?format=atom)
• No query string pollution
• Easy to bookmark specific formats

Backward Compatibility:

• /feed.xml continues to work (maps to /feed.rss)
• No breaking changes to existing feed consumers

Files Created/Modified

New Files

starpunk/feeds/negotiation.py              # Content negotiation logic (~200 lines)
tests/test_feeds_negotiation.py            # Unit tests (~350 lines)
tests/test_routes_feeds.py                 # Integration tests (~280 lines)
docs/reports/2025-11-26-v1.1.2-phase2-complete.md  # This report

Modified Files

starpunk/feeds/__init__.py                 # Export negotiation functions
starpunk/routes/public.py                  # Add feed endpoints
CHANGELOG.md                               # Document Phase 2.4

Complete Phase 2 Summary

Testing Results

Total Tests: 132 (all passing)

Breakdown:

• RSS Tests: 24 tests (existing + ordering fix)
• ATOM Tests: 11 tests (Phase 2.2)
• JSON Feed Tests: 13 tests (Phase 2.3)
• Negotiation Unit Tests: 41 tests (Phase 2.4)
• Negotiation Integration Tests: 22 tests (Phase 2.4)
• Legacy Feed Route Tests: 21 tests (existing)

Test run results:

$ uv run pytest tests/test_feed*.py tests/test_routes_feed*.py -q
132 passed in 11.42s

Code Quality Metrics

Lines of Code Added (across all phases):

• starpunk/feeds/: ~1,210 lines (rss, atom, json_feed, negotiation)
• Test files: ~1,330 lines (6 test files + helpers)
• Total new code: ~2,540 lines
• Total with documentation: ~3,000+ lines

Test Coverage:

• All feed generation code tested
• All negotiation logic tested
• All route endpoints tested
• Edge cases covered
• Error cases covered

Standards Compliance:

• RSS 2.0: Full spec compliance
• ATOM 1.0: RFC 4287 compliance
• JSON Feed 1.1: Spec compliance
• HTTP: Practical content negotiation (simplified RFC 7231)

Performance Characteristics

Memory Usage:

• Streaming generation: O(1) memory (chunks yielded)
• Non-streaming generation: O(n) for feed size
• Note cache: O(n) for FEED_MAX_ITEMS (default 50)

Response Times (estimated):

• Content negotiation overhead: <1ms
• RSS generation: ~2-5ms for 50 items
• ATOM generation: ~2-5ms for 50 items
• JSON generation: ~1-3ms for 50 items (faster, no XML)

Business Metrics:

• All formats tracked with track_feed_generated()
• Metrics include format, item count, duration
• Minimal overhead (<1ms per generation)

Available Endpoints

After Phase 2 completion:

GET /feed              # Content negotiation (RSS/ATOM/JSON)
GET /feed.rss          # Explicit RSS 2.0
GET /feed.atom         # Explicit ATOM 1.0
GET /feed.json         # Explicit JSON Feed 1.1
GET /feed.xml          # Backward compat (→ /feed.rss)

All endpoints:

• Support streaming generation
• Include Cache-Control headers
• Respect FEED_CACHE_SECONDS config
• Respect FEED_MAX_ITEMS config
• Include business metrics
• Return newest-first ordering

Feed Format Comparison

Feature	RSS 2.0	ATOM 1.0	JSON Feed 1.1
Spec	RSS 2.0	RFC 4287	JSON Feed 1.1
MIME Type	application/rss+xml	application/atom+xml	application/feed+json
Date Format	RFC 822	RFC 3339	RFC 3339
Encoding	UTF-8 XML	UTF-8 XML	UTF-8 JSON
Content	HTML (escaped)	HTML (escaped)	HTML or text
Support	Universal	Widespread	Growing
Extension	No	No	Yes (_starpunk)

Remaining Work

None for Phase 2 - all phases complete!

Future Enhancements (Post v1.1.2)

From the architect's design:

1. Feed Caching (v1.1.2 Phase 3):

   • Checksum-based feed caching
   • ETag support
   • Conditional GET (304 responses)

2. Feed Discovery (Future):

   • Add <link> tags to HTML for auto-discovery
   • Support for podcast RSS extensions
   • Media enclosures

3. Enhanced JSON Feed (Future):

   • Author objects (when Note model supports)
   • Attachments for media
   • Tags/categories

4. Analytics (Future):

   • Feed subscriber tracking
   • Format popularity metrics
   • Reader app identification

Questions for Architect

None. All implementation followed the design specifications exactly. Phase 2 is complete and ready for review.

Recommendations

Immediate Next Steps

1. Architect Review: Review Phase 2 implementation for approval
2. Manual Testing: Test feeds in actual feed readers
3. Move to Phase 3: Begin feed caching implementation

Testing in Feed Readers

Recommended feed readers for manual testing:

• RSS: NetNewsWire, Feedly, The Old Reader
• ATOM: Thunderbird, NewsBlur
• JSON Feed: NetNewsWire (has JSON Feed support)

Documentation Updates

Consider adding user-facing documentation:

• /docs/user/ - How to subscribe to feeds
• README.md - Mention multi-format feed support
• Example feed reader configurations

Future Monitoring

With business metrics in place, track:

• Feed format popularity (RSS vs ATOM vs JSON)
• Feed generation times by format
• Cache hit rates (once caching implemented)
• Feed reader user agents

Conclusion

Phase 2 "Feed Formats" is COMPLETE:

✅ Critical RSS ordering bug fixed (Phase 2.0) ✅ Clean feed module architecture (Phase 2.1) ✅ ATOM 1.0 feed support (Phase 2.2) ✅ JSON Feed 1.1 support (Phase 2.3) ✅ HTTP content negotiation (Phase 2.4) ✅ Dual endpoint strategy ✅ Business metrics integration ✅ Comprehensive test coverage (132 tests, all passing) ✅ Backward compatibility maintained

StarPunk now offers a complete multi-format feed syndication system with:

• Three feed formats (RSS, ATOM, JSON)
• Smart content negotiation
• Explicit format endpoints
• Streaming generation for memory efficiency
• Proper caching support
• Full standards compliance
• Excellent test coverage

The implementation follows StarPunk's core principles:

• Simple: Clean code, standard library usage, no unnecessary complexity
• Standard: Full compliance with RSS 2.0, ATOM 1.0, and JSON Feed 1.1
• Tested: 132 passing tests covering all functionality
• Documented: Clear code, comprehensive docstrings, this report

Phase 2 Status: COMPLETE - Ready for architect review and production deployment.

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Implementation Date: 2025-11-26 Developer: StarPunk Fullstack Developer (AI) Total Time: ~8 hours (7 hours for 2.0-2.3 + 1 hour for 2.4) Total Tests: 132 passing Next Phase: Phase 3 - Feed Caching (per architect's design)