# pdftract-2bs4j — PDF/A Conformance Detection

## Summary

The PDF/A conformance detection module (`crates/pdftract-core/src/conformance.rs`) implements complete XMP metadata parsing for PDF/A identification. All acceptance criteria pass.

## Implementation Verified

### Public API
- `detect_conformance(metadata_stream: Option<&[u8]>) -> Option<String>` — lines 64-111
- `detect_conformance_from_ref(metadata_ref, resolver, source) -> Option<String>` — lines 128-145

### Key Features Verified
- **XMP parsing via quick-xml** — line 65-66: uses `quick_xml::events::Event` and `Reader`
- **Namespace-agnostic matching** — lines 80-82: matches local name (after colon) for any prefix (pdfaid, x, foo, etc.)
- **Graceful failure** — line 100: malformed XML returns `None` instead of propagating errors (INV-8 compliant)
- **Combined format** — lines 106-110: returns "PDF/A-{part}{conformance}" or "PDF/A-{part}" if conformance missing

### Test Results
```
15 tests run: 15 passed
- test_detect_conformance_pdf_a_1b: PASS
- test_detect_conformance_pdf_a_2u: PASS
- test_detect_conformance_pdf_a_3a: PASS
- test_detect_conformance_pdf_a_4e: PASS
- test_detect_conformance_pdf_a_4f: PASS
- test_detect_conformance_part_only: PASS
- test_detect_conformance_no_metadata: PASS
- test_detect_conformance_empty_xml: PASS
- test_detect_conformance_malformed_xml: PASS
- test_detect_conformance_no_pdfaid_elements: PASS
- test_detect_conformance_different_namespace_prefix: PASS
- test_detect_conformance_minimal_xmp: PASS
- test_detect_conformance_nested_elements: PASS
- test_detect_conformance_unicode_in_namespace: PASS
- test_detect_conformance_whitespace_handling: PASS
```

## Acceptance Criteria Status

| Criterion | Status | Test |
|-----------|--------|------|
| pdfaid:part=1, pdfaid:conformance=b → "PDF/A-1b" | PASS | test_detect_conformance_pdf_a_1b |
| pdfaid:part=2, pdfaid:conformance=u → "PDF/A-2u" | PASS | test_detect_conformance_pdf_a_2u |
| pdfaid:part=3 only → "PDF/A-3" | PASS | test_detect_conformance_part_only |
| No XMP metadata → None | PASS | test_detect_conformance_no_metadata |
| Malformed XMP → None | PASS | test_detect_conformance_malformed_xml |
| quick-xml in default feature | PASS | Cargo.toml line 46: no feature gate |

## Code Quality

- **Documentation**: Comprehensive module-level docs explaining PDF/A levels (1a/b, 2a/b/u/f, 3a/b/u/f, 4e/f)
- **Error handling**: Never panics; all parse errors return `None`
- **XMP namespace handling**: Correctly matches on local name regardless of prefix
- **Performance**: Single-pass XML parsing with bounded buffer

## Dependency Status

- `quick-xml = "0.36"` is in default dependencies (Cargo.toml line 46)
- No feature gate — available for all default builds
- Binary size impact: ~30 KB (acceptable for metadata detection capability)

## Retrospective

### What worked
- Implementation was already complete with comprehensive test coverage
- XMP namespace-agnostic matching handles all prefix variations correctly
- quick-xml was already moved to default features

### What didn't
- No issues encountered; implementation is complete

### Surprise
- The module includes a convenience function `detect_conformance_from_ref` that handles catalog metadata resolution, which wasn't explicitly requested but is useful for callers

### Reusable pattern
- The local-name matching pattern (`split(|&b| b == b':').last()`) is reusable for any XML namespace parsing where the prefix may vary
- The graceful failure pattern (return `None` on any error) is appropriate for metadata detection where missing data is not exceptional