Extraction Pipeline Patterns

Xberg's format detection -> extraction -> fallback orchestration for 75+ file formats

Core Pipeline Architecture

The extraction pipeline (crates/xberg/src/core/pipeline.rs, crates/xberg/src/extraction/) orchestrates:

1. Format Detection - MIME type inference + extension validation -> select appropriate extractor
2. Intelligent Extraction - Route to format-specific extractors (PDF, DOCX, Excel, HTML, images, archives, etc.)
3. Fallback Strategies - Password-protected PDFs, OCR for images, nested archive handling, corrupted file recovery
4. Post-Processing Pipeline - Validators, quality processing, chunking, custom hooks (see core/pipeline.rs)

Format Detection Strategy

Location: crates/xberg/src/core/mime.rs, crates/xberg/src/core/formats.rs

Pattern: detect via magic bytes, validate extension alignment (prevent spoofing), route to extractor. Multiple extractors for same format -> choose highest confidence/specificity.

rust
// Pseudocode: core/mime.rs
match (magic_bytes(content), extension) {
    (Some(fmt), Some(ext)) if aligned -> Ok(fmt),
    (Some(fmt), Some(ext)) if misaligned -> Err(FormatMismatch),
    (Some(fmt), None) -> Ok(fmt),  // magic bytes only
    (None, Some(ext)) -> Ok(from_extension(ext)),
    _ -> Err(UnknownFormat),
}

Extraction Modules (75 Formats)

| Category | Extractors | Key Modules | | ------------ | ------------------------------------------------ | ---------------------------------------------------- | | Office | DOCX, XLSX, XLSM, XLSB, XLS, PPTX, ODP, ODS | extraction/{docx,excel,pptx}.rs | | PDF | Standard + encrypted, password attempts | pdf/ subdirectory (13 files) | | Images | PNG, JPG, TIFF, WebP, JP2, SVG (OCR-enabled) | extraction/image.rs + ocr/ | | Web | HTML, XHTML, XML, SVG (DOM parsing) | extraction/html.rs (67KB - complex table handling) | | Email | EML, MSG (headers, body, attachments, threading) | extraction/email.rs | | Archives | ZIP, TAR, GZ, 7Z (recursive extraction) | extraction/archive.rs (31KB) | | Markdown | MD, TXT, RST, Org Mode, RTF | extraction/markdown.rs | | Academic | LaTeX, BibTeX, JATS, Jupyter, DocBook | extraction/{structured,xml}.rs |

Extraction Dispatcher

rust
// Pseudocode: extraction/mod.rs
let format = detect_format(source.bytes, source.extension);
let result = match format {
    Pdf -> extract_pdf(source, config),
    Docx -> extract_docx(source, config),
    Image -> extract_image_with_ocr_fallback(source, config),
    Archive -> extract_archive_recursive(source, config),
    _ -> extract_with_plugin(format, source, config),
};
run_pipeline(result, config)  // post-processing always runs

Fallback Strategies

• Password-Protected PDFs: Try primary password -> secondary password list -> return is_encrypted=true in metadata on failure
• OCR Fallback: If image text extraction confidence < threshold, trigger OCR backend; return both results with scores
• Nested Archives: Recursive extraction with configurable depth limit; flatten or preserve hierarchy
• Corrupted File Recovery: Stream-based parsing, emit content up to error point, include error location in metadata

Configuration Integration

Location: crates/xberg/src/core/config.rs, crates/xberg/src/core/config_validation.rs

ExtractionConfig holds format-specific configs (pdf, image, html, office), fallback orchestration (fallback), and post-processing (postprocessor, chunking, keywords). See struct definition in config.rs.

Plugin System Integration

Location: crates/xberg/src/plugins/

• CustomExtractor: Override built-in format extractors
• PostProcessor: Modify results after extraction (Early/Middle/Late stages)
• Validator: Fail-fast validation (e.g., minimum text length)
• OCRBackend: Swap OCR engine

Plugin registry loaded at startup, cached for zero-cost lookup.

Feature Flag Strategy

Location: Cargo.toml (workspace), crates/xberg/Cargo.toml, FEATURE_MATRIX.md

20+ features across 9 language bindings. Key feature groups:

| Group | Features | Notes | | -------- | ------------------------------------------------------------------------------------ | --------------------------------- | | OCR | tesseract (default), tesseract-static, ocr-minimal | Mutually exclusive recommendation | | Formats | pdf, pdf-minimal, office, office-minimal | | | AI/ML | embeddings (requires ONNX), keywords-yake, keywords-rake, language-detection | | | Server | api (Axum), mcp, tokio-runtime, lite-runtime | | | Bindings | python-bindings, ruby-bindings, php-bindings, node-bindings, wasm | |

Conditional compilation: modules gated with #[cfg(feature = "...")]. Runtime validate_config() warns if requested feature not compiled in.

Feature Flag Critical Rules

1. Never mix conflicting features - e.g., ocr-minimal + tesseract should error at compile time
2. Always provide feature diagnostics - Config validation must warn if feature unavailable
3. Default to maximum feature set - Unless embedded/minimal specifically requested
4. Test all feature combinations - Matrix testing in CI catches regressions
5. WASM incompatible with embeddings, keywords, OCR

Critical Rules

1. Always use format detection before routing to extractors (prevent confusion attacks)
2. Stream-based parsing for PDFs/archives to handle multi-GB files
3. Post-pipeline is mandatory: All extraction results flow through run_pipeline() for validators/hooks
4. Plugin overrides are order-dependent: Plugins registered first take priority
5. Fallback timeouts: Set reasonable OCR/archive extraction timeouts (config-driven)
6. Metadata preservation: Include format detection confidence, extraction method used, any fallbacks applied

Related Skills

• ocr-backend-management - OCR engine selection and image preprocessing
• chunking-embeddings - Post-extraction text splitting with FastEmbed
• api-server-mcp - Axum endpoint for extraction pipeline exposure and MCP server