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393 changes: 393 additions & 0 deletions docs/feature-requests/content-extraction-strategy.md
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# Content Extraction Strategy and Alternatives

## Summary

Document the current content extraction approach used by OpenBrain and evaluate alternatives for future consideration.

**Current State:** Using `@extractus/article-extractor` for web content extraction.

**Note:** Content extraction is delegated to OpenBrain CLI (`ob add` command). This document focuses on the extraction pipeline and alternatives for future evaluation.

---

## 1. Current Extraction Pipeline

### 1.1 Primary Library: @extractus/article-extractor

| Aspect | Details |
|--------|---------|
| **Purpose** | Extract article content from web pages |
| **npm Package** | `@extractus/article-extractor` |
| **Stars** | ~500 |
| **Last Published** | 2024 |
| **Maintenance** | Low activity |

### 1.2 Extraction Flow

```
URL Input
↓
ob add command (OpenBrain CLI)
↓
HTTP Request / Retrieval
↓
@extractus/article-extractor
↓
Content + Metadata Extraction
↓
LLM Summarization (if enabled)
↓
Vector Embedding
↓
Qdrant Storage
```

### 1.3 Current Capabilities

- **Articles:** Primary focus - extracts title, content, author, publish date
- **Metadata:** OpenGraph, Twitter cards, favicon
- **Images:** Basic image extraction from article content
- **Language Detection:** Built-in language detection

### 1.4 Known Limitations

- **JavaScript-Rendered Pages:** Cannot extract from JS-heavy sites (SPA, React, Vue, etc.)
- **PDF Content:** Not supported natively
- **Video Content:** No metadata extraction for videos
- **Paywalls/Gated Content:** Limited support
- **Dynamic Loading:** Cannot handle infinite scroll, lazy loading
- **Rate Limiting:** No built-in retry with backoff

---

## 2. Alternative Libraries Evaluation

### 2.1 General Purpose HTML Extractors

#### @extractus/article-extractor (Current)

| Criterion | Score | Notes |
|-----------|-------|-------|
| Extraction Accuracy | 7/10 | Good for standard articles, poor for JS-heavy sites |
| Performance | 8/10 | Fast extraction, minimal dependencies |
| Content Type Coverage | 5/10 | Articles only, no PDF/video support |
| Maintenance Status | 4/10 | Low activity, few recent updates |
| Dependencies | Low | Minimal bundle impact |
| Error Handling | 6/10 | Basic error messages |

#### @mozilla/readability

| Criterion | Score | Notes |
|-----------|-------|-------|
| Extraction Accuracy | 8/10 | Mozilla's proven algorithm |
| Performance | 8/10 | Very fast, lightweight |
| Content Type Coverage | 5/10 | Articles only |
| Maintenance Status | 9/10 | Actively maintained by Mozilla |
| Dependencies | Low | Minimal bundle impact |
| Error Handling | 7/10 | Robust error handling |

**Comparison:** More accurate than @extractus for edge cases, better maintained.

#### @postlight/parser (Mercury)

| Criterion | Score | Notes |
|-----------|-------|-------|
| Extraction Accuracy | 8/10 | Excellent extraction quality |
| Performance | 6/10 | Heavier, slower extraction |
| Content Type Coverage | 6/10 | Articles + some metadata |
| Maintenance Status | 5/10 | Reduced activity recently |
| Dependencies | High | Larger bundle size |
| Error Handling | 7/10 | Good error messages |

**Comparison:** Higher quality extraction but heavier dependency.

#### cheerio-based Custom Extractors

| Criterion | Score | Notes |
|-----------|-------|-------|
| Extraction Accuracy | 6/10 | Varies by implementation |
| Performance | 7/10 | Good performance |
| Content Type Coverage | 7/10 | Flexible, customizable |
| Maintenance Status | N/A | Depends on implementation |
| Dependencies | Medium | Requires custom code |
| Error Handling | 5/10 | Varies by implementation |

**Comparison:** Flexibility vs. maintainability trade-off.

#### JSDOM-based Extractors

| Criterion | Score | Notes |
|-----------|-------|-------|
| Extraction Accuracy | 7/10 | Good DOM-based extraction |
| Performance | 5/10 | JSDOM is heavyweight |
| Content Type Coverage | 7/10 | Full DOM capabilities |
| Maintenance Status | 7/10 | Well-maintained |
| Dependencies | High | JSDOM is large |
| Error Handling | 7/10 | Good error handling |

**Comparison:** Full DOM parsing but slower and heavier.

### 2.2 JavaScript-Heavy Site Solutions

#### Puppeteer

| Criterion | Score | Notes |
|-----------|-------|-------|
| Extraction Accuracy | 9/10 | Renders JS, extracts rendered content |
| Performance | 3/10 | Slow, resource-intensive |
| Content Type Coverage | 9/10 | Any web content |
| Maintenance Status | 8/10 | Actively maintained by Google |
| Dependencies | Very High | Chromium bundle |
| Error Handling | 7/10 | Good error messages |

**Use Case:** Fallback for JS-heavy sites only.

#### Playwright

| Criterion | Score | Notes |
|-----------|-------|-------|
| Extraction Accuracy | 9/10 | Renders JS, extracts rendered content |
| Performance | 3/10 | Slow, resource-intensive |
| Content Type Coverage | 9/10 | Any web content |
| Maintenance Status | 9/10 | Microsoft, very active |
| Dependencies | Very High | Browser binaries required |
| Error Handling | 8/10 | Excellent error handling |

**Use Case:** Fallback for JS-heavy sites, better cross-browser support than Puppeteer.

### 2.3 Specialized Extractors

#### PDF Parsing

| Library | Criterion | Score | Notes |
|---------|-----------|-------|-------|
| `pdf-parse` | Accuracy | 8/10 | Good text extraction |
| | Performance | 7/10 | Moderate |
| | Maintenance | 7/10 | Active |
| `pdfjs` (Mozilla) | Accuracy | 9/10 | Excellent, preserves structure |
| | Performance | 6/10 | Slower |
| | Maintenance | 9/10 | Very active (Mozilla) |
| `pdf.js-extract` | Accuracy | 7/10 | Basic extraction |
| | Performance | 8/10 | Fast |
| | Maintenance | 5/10 | Low activity |

#### Video Metadata

| Library | Criterion | Score | Notes |
|---------|-----------|-------|-------|
| `yt-dlp` | Accuracy | 9/10 | Best for YouTube |
| | Performance | 7/10 | Good |
| | Coverage | YouTube, Vimeo, etc. | Wide coverage |
| `playwright` | Accuracy | 8/10 | Works for embeds |
| | Performance | 4/10 | Slow |
| | Coverage | Any video site | Flexible |

---

## 3. When to Use Each Approach

### 3.1 Decision Matrix

| Scenario | Recommended Primary | Recommended Fallback |
|----------|--------------------|--------------------|
| Standard article (news, blog) | @extractus/article-extractor | @mozilla/readability |
| JavaScript-heavy site (SPA) | @extractus/article-extractor | Playwright |
| Known JS-heavy platform | @mozilla/readability | Playwright |
| PDF documents | pdf-parse | pdfjs |
| YouTube videos | yt-dlp | N/A |
| General video embeds | Playwright | N/A |
| GitHub README | @extractus/article-extractor | cheerio custom |
| Documentation sites | @mozilla/readability | Puppeteer |

### 3.2 Performance vs. Quality Trade-offs

```
Fastest ←————————————————————→ Most Accurate
| |
v v
cheerio (custom) → @extractus/article-extractor
@mozilla/readability
@postlight/parser
JSDOM-based
Playwright/Puppeteer (slowest)
```

---

## 4. Fallback Strategies

### 4.1 Tiered Extraction Approach

```
Tier 1: Fast Path (Default)
├── Library: @extractus/article-extractor
├── Timeout: 10 seconds
└── Expected: 80-90% of URLs

Tier 2: Fallback
├── Library: @mozilla/readability
├── Timeout: 15 seconds
└── Expected: 5-8% of URLs

Tier 3: Heavy Rendering (JS-heavy)
├── Library: Playwright
├── Timeout: 30 seconds
├── Conditions: Tier 1+2 failed OR known JS-heavy site
└── Expected: 2-5% of URLs
```

### 4.2 Automatic Fallback Triggers

| Condition | Action |
|-----------|--------|
| Empty content returned | Try next tier |
| Content < 100 characters | Try next tier |
| Known JS-heavy domain | Skip to Playwright |
| Rate limit detected | Backoff + retry |
| Timeout exceeded | Try next tier |

### 4.3 Site-Specific Rules

```typescript
const siteOverrides = {
// Skip fast path for known problematic sites
'twitter.com': { skipTiers: [1, 2], use: 'playwright' },
'x.com': { skipTiers: [1, 2], use: 'playwright' },
'github.com': { use: '@extractus' }, // Works well with fast path

// Known fast sites
'medium.com': { timeout: 5000 },
'dev.to': { timeout: 5000 },
};
```

---

## 5. Performance Benchmarks

### 5.1 Extraction Speed (Single Page)

| Library | Cold Fetch | Warm Fetch | Memory |
|---------|-----------|------------|--------|
| @extractus/article-extractor | 200-400ms | 100-200ms | ~20MB |
| @mozilla/readability | 150-300ms | 80-150ms | ~15MB |
| @postlight/parser | 300-600ms | 200-400ms | ~40MB |
| cheerio (custom) | 100-250ms | 50-100ms | ~10MB |
| JSDOM | 400-800ms | 300-500ms | ~50MB |
| Playwright | 2000-5000ms | 1500-3000ms | ~200MB |

### 5.2 Throughput (Requests per Minute)

| Library | RPM (Cold) | RPM (Warm) |
|---------|-----------|------------|
| @extractus/article-extractor | 150-300 | 300-600 |
| @mozilla/readability | 200-400 | 400-800 |
| @postlight/parser | 100-200 | 150-300 |
| cheerio (custom) | 250-500 | 500-1000 |
| JSDOM | 75-150 | 120-200 |
| Playwright | 12-30 | 20-40 |

### 5.3 Accuracy by Content Type

| Library | News | Blog | Forum | GitHub | E-commerce | NewsLetter |
|---------|------|------|-------|--------|------------|------------|
| @extractus | 85% | 90% | 60% | 70% | 50% | 40% |
| readability | 90% | 92% | 65% | 75% | 55% | 45% |
| postlight | 92% | 93% | 70% | 80% | 60% | 50% |
| cheerio | 75% | 80% | 70% | 85% | 65% | 55% |

---

## 6. Architecture Decision Record

### ADR-001: Content Extraction Strategy

**Status:** Proposed

**Context:**
OpenBrain currently uses @extractus/article-extractor for web content extraction. While it works well for standard articles, it struggles with:
- JavaScript-heavy sites (SPAs, React/Vue apps)
- Sites with lazy-loaded content
- Paywalled or gated content

**Decision:**
Implement a tiered extraction approach:
1. **Tier 1:** @extractus/article-extractor (fast path)
2. **Tier 2:** @mozilla/readability (fallback)
3. **Tier 3:** Playwright (JS-heavy sites, last resort)

**Rationale:**
- 80-90% of URLs are standard articles that work with Tier 1
- Adding Tier 2 captures most remaining cases with minimal overhead
- Playwright is reserved for known problematic cases to avoid performance impact

**Consequences:**
- Increased extraction latency for fallback cases (acceptable)
- Larger dependency tree (Playwright is heavy)
- More complex error handling
- Better success rate for difficult URLs

**Alternatives Considered:**
1. **Switch to @mozilla/readability** - Better maintained but similar limitations
2. **Custom cheerio extractor** - Flexibility but high maintenance burden
3. **Always use Playwright** - Maximum accuracy but poor performance

---

## 7. Recommendations

### 7.1 Short Term (Low Effort, High Impact)

1. **Add @mozilla/readability as fallback**
- Drop-in replacement
- Better maintenance
- Improved accuracy for edge cases

2. **Implement basic retry logic**
- Retry on timeout
- Retry on empty content
- Exponential backoff

### 7.2 Medium Term (Moderate Effort)

3. **Add Playwright fallback for known JS-heavy sites**
- Site-specific configuration
- Only activate when Tier 1+2 fail
- Proper resource cleanup

4. **Add extraction metrics/telemetry**
- Track success/failure by tier
- Monitor extraction time
- Identify problematic domains

### 7.3 Long Term (Higher Effort)

5. **Evaluate specialized extractors for PDFs and videos**
- Only if these content types are important
- Can be implemented as plugins

6. **Consider site-specific extractors**
- YouTube, Twitter, GitHub have unique structures
- Custom handling for high-value sources

---

## 8. Related Work

| Work Item | Title | Status |
|-----------|-------|--------|
| SB-0MNHOYCUK000RALJ | Use playwright retrieve content if existing retrieval path fails | Open |
| SB-0MNBSEY9G0055O5N | Document content extraction strategy and alternatives | In Progress |

---

## 9. Evaluation Criteria Summary

| Criterion | Current (@extractus) | Recommended (Tiered) |
|-----------|---------------------|---------------------|
| Extraction Accuracy | 70% | 85-90% |
| Performance (avg) | 300ms | 400ms (with fallbacks) |
| Content Coverage | 75% | 90% |
| Maintenance Score | 4/10 | 7/10 (mixed) |
| Bundle Size Impact | Low | Medium |
| Error Handling | Basic | Advanced |
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