kreuzberg-dev/.ai-rulez/skills/mime-detection-routing

priority: high

MIME Detection & Routing

Detection Flow

Extension → EXT_TO_MIME map → validate → Registry lookup → Extractor

Key Functions

| Function | Location | Purpose | |----------|----------|---------| | detect_mime_type(path, inspect) | core/mime.rs | Extension + optional content inspection | | detect_mime_type_from_bytes(bytes) | core/mime.rs | Magic number detection (infer crate) | | validate_mime_type(mime) | core/mime.rs | Check if any extractor supports it |

Extension Mapping

118+ extensions mapped in EXT_TO_MIME (core/mime.rs). Case-insensitive.

Key mappings: .pdf → application/pdf, .docx → application/vnd.openxmlformats-officedocument.wordprocessingml.document, .xlsx → spreadsheet variant, .png/.jpg → image/*

Registry Selection

// In core/extractor/bytes.rs
fn select_extractor_for_mime(mime_type: &str) -> Result<Arc<dyn DocumentExtractor>> {
    let registry = get_document_extractor_registry();
    let registry_guard = registry.read()?;
    registry_guard.get_for_mime_type(mime_type)
        .ok_or_else(|| KreuzbergError::UnsupportedFormat(mime_type.into()))
}

Selects highest-priority extractor registered for that MIME type.

Adding New MIME Types

1. Add extension mapping: m.insert("ext", "application/x-new"); in core/mime.rs
2. Implement DocumentExtractor with supported_mime_types() returning the MIME
3. Register in register_default_extractors()

Wildcard Support

Extractors can register for MIME type families: "image/*" matches image/png, image/jpeg, etc.

Critical Rules

1. Always validate_mime_type() before extraction
2. Extension mapping is case-insensitive
3. Content inspection (infer crate) is fallback for extension-less files
4. Registry validation is final authority on supported types