plugin-architecture-patterns

name	plugin-architecture-patterns
description	Plugin architecture, registration, and trait patterns
priority	critical

Plugin Architecture & Registration

Plugin Types

Type	Trait	Location
Document Extractor	DocumentExtractor: Plugin	plugins/extractor/trait.rs
OCR Backend	OcrBackend: Plugin	plugins/ocr/trait.rs
Post Processor	PostProcessor: Plugin	plugins/processor/trait.rs
Validator	Validator: Plugin	plugins/validator/trait.rs

DocumentExtractor Implementation

use crate::plugins::{DocumentExtractor, Plugin};
use async_trait::async_trait;

pub struct MyExtractor;

impl Plugin for MyExtractor {
    fn name(&self) -> &str { "my-extractor" }
    fn version(&self) -> String { env!("CARGO_PKG_VERSION").to_string() }
}

#[async_trait]
impl DocumentExtractor for MyExtractor {
    async fn extract(&self, input: ExtractInput, config: &ExtractionConfig)
        -> Result<ExtractedDocument> { /* ... */ }

    fn supported_mime_types(&self) -> &[&str] { &["application/x-custom"] }
    fn priority(&self) -> i32 { 50 }

    // WASM support (optional)
    fn as_sync_extractor(&self) -> Option<&dyn SyncExtractor> { None }
}

Priority System

Range	Use
0-25	Fallback/low-quality
26-49	Alternative extractors
50	Default (built-in)
51-75	Premium/enhanced
76-100	Specialized/high-priority

Registry selects highest priority extractor for each MIME type. Override built-ins with priority > 50.

Registration

// In extractors/mod.rs → register_default_extractors()
let registry = get_document_extractor_registry();
let mut registry = registry.write()
    .map_err(|e| XbergError::Other(format!("Registry lock poisoned: {}", e)))?;
registry.register(Arc::new(MyExtractor::new()))?;

Feature-Gated Registration

#[cfg(feature = "office")]
{
    registry.register(Arc::new(DocxExtractor::new()))?;
    registry.register(Arc::new(PptxExtractor::new()))?;
}

PostProcessor Pattern

impl PostProcessor for MyProcessor {
    async fn process(&self, result: &mut ExtractionResult, config: &ExtractionConfig)
        -> Result<()> {
        result.content = process_content(&result.content);
        Ok(())
    }
    fn stage(&self) -> ProcessorStage { ProcessorStage::Middle }
}

Stages: Early → Middle → Late. Failures isolated (don't block others).

Critical Rules

1. All plugins MUST be Send + Sync
2. Feature gate with #[cfg(feature = "...")] for optional formats
3. Use #[async_trait] for DocumentExtractor
4. Initialization via ensure_initialized() (lazy, called before first extraction)
5. Plugin names: kebab-case (e.g., "pdf-extractor")