# Story 3.3: Content Interlinking Injection

## Status
✅ **COMPLETE** - Implemented, Integrated, and Tested

## Summary
This story injects three types of links into article HTML:
1. **Tiered Links** - T1 articles link to money site, T2+ link to lower-tier articles
2. **Homepage Links** - Link to the site's homepage (base domain)
3. **"See Also" Section** - Links to all other articles in the batch

Uses existing `anchor_text_generator.py` for tier-based anchor text with support for job config overrides (default/override/append modes).

## Story
**As a developer**, I want to inject all required links (batch "wheel", home page, and tiered/money site) into each new article's HTML content, so that the articles are fully interlinked and ready for deployment.

## Context
- Story 3.1 generates final URLs for all articles in the batch
- Story 3.2 finds the required tiered links (money site or lower-tier URLs)
- Articles have raw HTML content from Epic 2 (h2, h3, p tags)
- Project contains anchor text lists for each tier
- Articles need wheel links (next/previous), homepage links, and tiered links

## Acceptance Criteria

### Core Functionality
- A function takes raw HTML content, URL list, tiered links, and project data
- **Wheel Links:** Each article gets "next" and "previous" links to other articles in the batch
  - Last article's "next" links to first article (circular)
  - First article's "previous" links to last article (circular)
- **Homepage Links:** Each article gets a link to its site's homepage
- **Tiered Links:** Articles get links based on their tier
  - Tier 1: Links to money site using T1 anchor text
  - Tier 2+: Links to lower-tier articles using appropriate tier anchor text

### Input Requirements
- Raw HTML content (from Epic 2)
- List of article URLs with titles (from Story 3.1)
- Tiered links object (from Story 3.2)
- Project data (for anchor text lists)
- Batch tier information

### Output Requirements
- Final HTML content with all links injected
- Updated content stored in database
- Link relationships recorded in `article_links` table

## Implementation Details

### Anchor Text Generation
**RESOLVED:** Use existing `src/interlinking/anchor_text_generator.py` with job config overrides
- **Default tier-based anchor text:**
  - Tier 1: Uses main keyword variations
  - Tier 2: Uses related searches
  - Tier 3: Uses main keyword variations
  - Tier 4+: Uses entities
- **Job config overrides via `anchor_text_config`:**
  - `mode: "default"` - Use tier-based defaults
  - `mode: "override"` - Replace defaults with `custom_text` list
  - `mode: "append"` - Add `custom_text` to tier-based defaults
- Import and use `get_anchor_text_for_tier()` function

### Homepage URL Generation
**RESOLVED:** Remove the slug after `/` from the article URL
- Example: `https://site.com/article-slug.html` → `https://site.com/`
- Use base domain as homepage URL

### Link Placement Strategy

#### Tiered Links (Money Site / Lower Tier)
1. **First Priority:** Find anchor text already in the document
   - Search for anchor text in HTML content
   - Add link to FIRST match only (prevent duplicate links)
   - Case-insensitive matching
2. **Fallback:** If anchor text not found in document
   - Insert anchor text into a sentence in the article
   - Make it a link to the target URL

#### Wheel Links (See Also Section)
- Add a "See Also" section after the last paragraph
- Format as heading + unordered list
- Include ALL other articles in the batch (excluding current article)
- Each list item is an article title as a link
- Example:
  ```html
  <h3>See Also</h3>
  <ul>
    <li><a href="url1">Article Title 1</a></li>
    <li><a href="url2">Article Title 2</a></li>
    <li><a href="url3">Article Title 3</a></li>
  </ul>
  ```

#### Homepage Links
- Same as tiered links: find anchor text in content or insert it
- Link to site homepage (base domain)

## Implementation Approach

### Function Signature
```python
def inject_interlinks(
    content_records: List[GeneratedContent],
    article_urls: List[Dict],  # [{content_id, title, url}, ...]
    tiered_links: Dict,       # From Story 3.2
    project: Project,
    content_repo: GeneratedContentRepository,
    link_repo: ArticleLinkRepository
) -> None:  # Updates content in database
```

### Processing Flow
1. For each article in the batch:
   a. Load its raw HTML content
   b. Generate tier-appropriate anchor text using `get_anchor_text_for_tier()`
   c. Inject tiered links (money site or lower tier)
   d. Inject homepage link
   e. Inject wheel links ("See Also" section)
   f. Update content in database
   g. Record all links in `article_links` table

### Link Injection Details

#### Tiered Link Injection
```python
# Get anchor text for this tier
from src.interlinking.anchor_text_generator import get_anchor_text_for_tier

# Get default tier-based anchor text
default_anchors = get_anchor_text_for_tier(tier, project, count=5)

# Apply job config overrides if present
if job_config.anchor_text_config:
    if job_config.anchor_text_config.mode == "override":
        anchor_texts = job_config.anchor_text_config.custom_text or default_anchors
    elif job_config.anchor_text_config.mode == "append":
        anchor_texts = default_anchors + (job_config.anchor_text_config.custom_text or [])
    else:  # "default"
        anchor_texts = default_anchors
else:
    anchor_texts = default_anchors

# For each anchor text:
for anchor_text in anchor_texts:
    if anchor_text in html_content (case-insensitive):
        # Wrap FIRST occurrence with link
        html_content = wrap_first_occurrence(html_content, anchor_text, target_url)
        break
    else:
        # Insert anchor text + link into a paragraph
        html_content = insert_link_into_content(html_content, anchor_text, target_url)
```

#### Homepage Link Injection
```python
# Derive homepage URL
homepage_url = extract_base_url(article_url)  # https://site.com/article.html → https://site.com/

# Use main keyword as anchor text
anchor_text = project.main_keyword
# Find or insert link (same strategy as tiered links)
```

#### Wheel Link Injection
```python
# Build "See Also" section with ALL other articles in batch
other_articles = [a for a in article_urls if a['content_id'] != current_article.id]

see_also_html = "<h3>See Also</h3>\n<ul>\n"
for article in other_articles:
    see_also_html += f'  <li><a href="{article["url"]}">{article["title"]}</a></li>\n'
see_also_html += "</ul>\n"

# Append after last paragraph (before closing tags)
html_content = insert_before_closing_tags(html_content, see_also_html)
```

### Database Updates
- Update `GeneratedContent.content` with final HTML
- Create `ArticleLink` records for all injected links:
  - `link_type="tiered"` for money site / lower tier links
  - `link_type="homepage"` for homepage links
  - `link_type="wheel_see_also"` for "See Also" section links
- Track both internal (`to_content_id`) and external (`to_url`) links

**Note:** The "See Also" section replaces the previous wheel_next/wheel_prev concept. Each article links to all other articles in the batch via the "See Also" section.

## Tasks / Subtasks

### 1. Create Content Injection Module
**Effort:** 3 story points

- [ ] Create `src/interlinking/content_injection.py`
- [ ] Implement `inject_interlinks()` main function
- [ ] Implement "See Also" section builder (all batch articles)
- [ ] Implement homepage URL extraction (base domain)
- [ ] Implement tiered link injection with anchor text matching

### 2. Anchor Text Processing
**Effort:** 2 story points

- [ ] Import `get_anchor_text_for_tier()` from existing module
- [ ] Apply job config `anchor_text_config` overrides (default/override/append)
- [ ] Implement case-insensitive anchor text search in HTML
- [ ] Wrap first occurrence of anchor text with link
- [ ] Implement fallback: insert anchor text + link if not found in content

### 3. HTML Link Injection
**Effort:** 2 story points

- [ ] Implement safe HTML parsing (avoid breaking existing tags)
- [ ] Implement link insertion before closing article/body tags
- [ ] Ensure proper link formatting (`<a href="...">text</a>`)
- [ ] Handle edge cases (empty content, malformed HTML)
- [ ] Preserve HTML structure and formatting

### 4. Database Integration
**Effort:** 2 story points

- [ ] Update `GeneratedContent.content` with final HTML
- [ ] Create `ArticleLink` records for all links
- [ ] Handle both internal (content_id) and external (URL) links
- [ ] Ensure proper link type categorization

### 5. Unit Tests
**Effort:** 3 story points

- [ ] Test "See Also" section generation (all batch articles)
- [ ] Test homepage URL extraction (remove slug after `/`)
- [ ] Test tiered link injection for T1 (money site) and T2+ (lower tier)
- [ ] Test anchor text config modes: default, override, append
- [ ] Test case-insensitive anchor text matching (first occurrence only)
- [ ] Test fallback anchor text insertion when not found in content
- [ ] Test HTML structure preservation after link injection
- [ ] Test database record creation (ArticleLink for all link types)
- [ ] Test with different tier configurations (T1, T2, T3, T4+)

### 6. Integration Tests
**Effort:** 2 story points

- [ ] Test full flow: Story 3.1 URLs → Story 3.2 tiered links → Story 3.3 injection
- [ ] Test with different batch sizes (5, 10, 20 articles)
- [ ] Test with various HTML content structures
- [ ] Verify link relationships in `article_links` table
- [ ] Test with different tiers and project configurations
- [ ] Verify final HTML is deployable (well-formed)

## Dependencies
- Story 3.1: URL generation must be complete
- Story 3.2: Tiered link finding must be complete
- Story 2.3: Generated content must exist
- Story 1.x: Project and database models must exist

## Future Considerations
- Story 4.x will use the final HTML content for deployment
- Analytics dashboard will use `article_links` data
- Future: Advanced link placement strategies
- Future: Link density optimization

## Total Effort
14 story points

## Technical Notes

### Existing Code to Use
```python
# Use existing anchor text generator
from src.interlinking.anchor_text_generator import get_anchor_text_for_tier

# Example usage - Default tier-based
anchor_texts = get_anchor_text_for_tier("tier1", project, count=5)
# Returns: ["shaft machining", "learn about shaft machining", "shaft machining guide", ...]

# Example usage - With job config override
if job_config.anchor_text_config:
    if job_config.anchor_text_config.mode == "override":
        anchor_texts = job_config.anchor_text_config.custom_text
        # Returns: ["click here for more info", "learn more about this topic", ...]
    elif job_config.anchor_text_config.mode == "append":
        anchor_texts = default_anchors + job_config.anchor_text_config.custom_text
        # Returns: ["shaft machining", "learn about...", "click here...", ...]
```

### Anchor Text Configuration (Job Config)
Job configuration supports three modes for anchor text:

```json
{
  "anchor_text_config": {
    "mode": "default|override|append",
    "custom_text": ["anchor 1", "anchor 2", ...]
  }
}
```

**Modes:**
- `default`: Use tier-based anchor text from `anchor_text_generator.py`
- `override`: Replace tier-based anchors with `custom_text` list
- `append`: Add `custom_text` to tier-based anchors

**Example - Override Mode:**
```json
{
  "anchor_text_config": {
    "mode": "override",
    "custom_text": [
      "click here for more info",
      "learn more about this topic",
      "discover the best practices"
    ]
  }
}
```

### Link Injection Rules
1. **One link per anchor text** - Only link the FIRST occurrence
2. **Case-insensitive search** - Match "Shaft Machining" with "shaft machining"
3. **Preserve HTML structure** - Don't break existing tags
4. **Fallback insertion** - If anchor text not in content, insert it naturally
5. **Config overrides** - Job config can override/append to tier-based defaults

### "See Also" Section Format
```html
<!-- Appended after last paragraph -->
<h3>See Also</h3>
<ul>
  <li><a href="https://site1.com/article1.html">Article Title 1</a></li>
  <li><a href="https://site2.com/article2.html">Article Title 2</a></li>
  <li><a href="https://site3.com/article3.html">Article Title 3</a></li>
</ul>
```

### Homepage URL Examples
```
https://example.com/article-slug.html → https://example.com/
https://site.b-cdn.net/my-article.html → https://site.b-cdn.net/
https://www.custom.com/path/to/article.html → https://www.custom.com/
```

## Notes
This story uses existing tier-based anchor text generation. No need to implement anchor text logic from scratch - just import and use the existing functions that handle all edge cases automatically.