mime-detection-routing

name

mime-detection-routing

description

MIME type detection and extractor routing in core/mime.rs and core/extractor/bytes.rs — the extension→EXT_TO_MIME→validate→registry→extractor flow, key detection functions, the 115 case-insensitive extension map, priority-based registry selection, wildcard MIME families, and how to add a new MIME type. Load when adding a format, wiring an extractor to a MIME type, or debugging why a file routes to the wrong (or no) extractor.

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

115 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(|| XbergError::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