---
model: mimo-v2-pro
---

# Plan: HTML-to-Markdown Transformations for Ingestion

## Summary

Add configurable HTML-to-markdown transformations to `formatHTMLForIngestion.ts` to improve the quality of text stored in the vector index. Transformations convert ecmarkup/HTML elements (code blocks, cross-reference links, lists, inline code) to markdown syntax before the `HTMLTextSplitter` extracts plain text.

## Config Interface

```typescript
interface FormatConfig {
  codeBlocks: {
    block: string[];    // fenced code (pre>code, emu-eqn block)
    inline: string[];   // inline backticks (var, emu-val, emu-const, emu-eqn inline, code)
    grammar: string[];  // fenced bnf (emu-grammar)
  };
  links: string[];      // [text](#hash) (emu-xref a)
  lists: {
    ordered: string[];  // 1. 2. 3. (ol)
    unordered: string[];// - item (ul)
  };
  tables: string[];     // markdown tables (table, emu-table)
}
```

Default config:
```typescript
const DEFAULT_CONFIG: FormatConfig = {
  codeBlocks: {
    block: ["pre>code", "emu-eqn:not([class*='inline'])"],
    inline: ["var", "emu-val", "emu-const", "emu-eqn.inline"],
    // Note: standalone <code> (outside <pre>) is rare; handle with :not(pre > *) check in converter
    grammar: ["emu-grammar"],
  },
  links: ["emu-xref a"],
  lists: {
    ordered: ["ol"],
    unordered: ["ul"],
  },
  tables: ["table", "emu-table"],
};
```

## Transformation Order

0. **`addNewlinesAfterBlocks($)`** — global newline injection (existing function, runs first)
1. **Inline leaves**: `emu-xref a[href]` → links, `var`/`emu-val`/`emu-const` → inline code
2. **Block leaves**: `pre>code` → fenced code, `emu-eqn` → fenced code
3. **Structural parents**: `emu-grammar` → fenced bnf (uses `.text()` with pre-injected newlines), `ol/ul` → markdown lists, `table` → markdown tables

## Implementation Details

### Approach: Cheerio only

All conversions use cheerio DOM manipulation (already in codebase). No external HTML-to-markdown library. Each conversion replaces DOM elements with text/markdown nodes. The existing `HTMLTextSplitter` processes the modified DOM unchanged.

### New functions in `setup/utils/formatHTMLForIngestion.ts`

Each function receives `cheerio.CheerioAPI` and modifies the DOM in-place.

1. **`convertLinksToMarkdown($, selector: string)`** — selector default: `emu-xref a[href]`
   - `$(selector).each(...)`: get href, strip filename, get text, replaceWith `<span>` containing `[text](#hash)`
   - Safety: skip if href starts with `http`

2. **`convertInlineCodeToMarkdown($, tags: string[])`**
   - `$(tag).each(...)`: get `.text()`, replaceWith `<span>` containing `` `text` ``
   - For `code` tags: skip if parent is `pre`

3. **`convertBlockCodeToMarkdown($, tags: string[])`**
   - For `pre>code`: get language from `class`, get `.text()` from code, replaceWith `<pre>` containing `` ```lang\ntext\n``` ``
   - For `emu-eqn` block: get `.text()`, replaceWith `<pre>` containing `` ```\ntext\n``` ``

4. **`convertGrammarToMarkdown($, selector: string)`**
   - Walk inner tags (emu-nt, emu-t, emu-rhs, emu-geq), build text representation
   - ReplaceWith `<pre>` containing `` ```bnf\ntext\n``` ``

5. **`convertListsToMarkdown($, ordered: string[], unordered: string[])`**
   - For each `ol`/`ul`: recursive function `listToMarkdown(elem, depth, isOrdered)`
   - Process `li` children, add `1. ` / `- ` prefix with indentation
   - ReplaceWith `<pre>` containing markdown text

6. **`formatForIngestion($, config?)`** — orchestrator, calls all in order

## Critical Implementation Code

### Config interface

```typescript
export interface FormatConfig {
  codeBlocks: {
    block: string[];
    inline: string[];
    grammar: string[];
  };
  links: string[];
  lists: {
    ordered: string[];
    unordered: string[];
  };
  tables: string[];
}

export const DEFAULT_CONFIG: FormatConfig = {
  codeBlocks: {
    block: ["pre>code", "emu-eqn:not([class*='inline'])"],
    inline: ["var", "emu-val", "emu-const", "emu-eqn.inline"],
    grammar: ["emu-grammar"],
  },
  links: ["emu-xref a"],
  lists: {
    ordered: ["ol"],
    unordered: ["ul"],
  },
  tables: ["table", "emu-table"],
};
```

### `convertLinksToMarkdown` — filename stripping

```typescript
export function convertLinksToMarkdown(
  $: cheerio.CheerioAPI,
  selector: string = "emu-xref a[href]",
): void {
  $(selector).each((_, elem) => {
    const $a = $(elem);
    const href = $a.attr("href") ?? "";

    // Skip external links
    if (href.startsWith("http")) return;

    // Strip filename prefix: "abstract-operations.html#sec-tonumber" → "#sec-tonumber"
    const hash = href.includes("#") ? `#${href.split("#")[1]}` : href;
    const text = $a.text().trim();

    if (!text || !hash) return;

    $a.replaceWith(`<span class="link-markdown">[${text}](${hash})</span>`);
  });
}
```

### `convertInlineCodeToMarkdown` — backtick wrapping

```typescript
export function convertInlineCodeToMarkdown(
  $: cheerio.CheerioAPI,
  tags: string[],
): void {
  for (const tag of tags) {
    $(tag).each((_, elem) => {
      // Skip <code> inside <pre> (handled by block converter)
      if (elem.name === "code" && $(elem).parent("pre").length > 0) return;

      const text = $(elem).text().trim();
      if (!text) return;
      $(elem).replaceWith(`<span class="inline-code">\`${text}\`</span>`);
    });
  }
}
```

### `convertBlockCodeToMarkdown` — fenced code blocks

```typescript
function extractLanguage(codeClass: string | undefined): string {
  // "javascript hljs" → "javascript", "python hljs" → "python"
  if (!codeClass) return "";
  const match = codeClass.match(/^(\w+)/);
  return match?.[1] ?? "";
}

export function convertBlockCodeToMarkdown(
  $: cheerio.CheerioAPI,
  tags: string[],
): void {
  // Handle pre>code (JS code examples)
  $("pre > code").each((_, code) => {
    const lang = extractLanguage($(code).attr("class"));
    const text = $(code).text().trim();
    const pre = $(code).parent("pre");
    pre.replaceWith(
      $(`<pre class="code-markdown">\`\`\`${lang}\n${text}\n\`\`\`</pre>`),
    );
  });

  // Handle standalone emu-eqn (block-level equations)
  $("emu-eqn:not([class*='inline'])").each((_, eqn) => {
    const text = $(eqn).text().trim();
    $(eqn).replaceWith(
      $(`<pre class="code-markdown">\`\`\`\n${text}\n\`\`\`</pre>`),
    );
  });
}
```

### `convertListsToMarkdown` — recursive list processing

```typescript
function listToMarkdown(
  $: cheerio.CheerioAPI,
  elem: cheerio.Element,
  depth: number = 0,
): string {
  const $elem = $(elem);
  const isOrdered = elem.name === "ol";
  const indent = "  ".repeat(depth);
  const lines: string[] = [];

  $elem.children("li").each((i, li) => {
    const prefix = isOrdered ? `${i + 1}. ` : "- ";
    const $li = $(li);

    // Recurse into nested lists first (depth-first)
    $li.children("ol, ul").each((_, nested) => {
      const nestedMarkdown = listToMarkdown($, nested, depth + 1);
      $(nested).replaceWith($(`<pre class="list-processed">${nestedMarkdown}</pre>`));
    });

    // Now get full text (nested lists are replaced with <pre> containing markdown)
    const itemText = $li.text().trim().replace(/\s+/g, " ");
    lines.push(`${indent}${prefix}${itemText}`);
  });

  return lines.join("\n");
}

export function convertListsToMarkdown(
  $: cheerio.CheerioAPI,
  ordered: string[] = ["ol"],
  unordered: string[] = ["ul"],
): void {
  const selectors = [...ordered, ...unordered].join(", ");
  // Process from outermost — recursion handles depth-first nesting
  $(selectors).each((_, elem) => {
    // Skip if already processed (parent already handled this)
    if ($(elem).hasClass("list-markdown")) return;
    const markdown = listToMarkdown($, elem, 0);
    $(elem).replaceWith($(`<pre class="list-markdown">${markdown}</pre>`));
  });
}
```

Key insight: recursion goes depth-first. When processing an `li`, nested `ol`/`ul` children are first replaced with `<pre class="list-processed">` containing their markdown. Then `$li.text()` includes that markdown. Outer `$(selectors).each(...)` skips already-processed elements.

### `convertGrammarToMarkdown` — grammar production text

`addNewlinesAfterBlocks` runs first globally, injecting `\n` after `emu-production` and `emu-rhs` (added to `BLOCK_ELEMENTS`). Then `.text()` on `emu-grammar` naturally preserves production/alternative boundaries.

```typescript
export function convertGrammarToMarkdown(
  $: cheerio.CheerioAPI,
  selector: string = "emu-grammar",
): void {
  $(selector).each((_, grammar) => {
    const text = $(grammar).text().trim();
    $(grammar).replaceWith(
      $(`<pre class="code-markdown">\`\`\`bnf\n${text}\n\`\`\`</pre>`),
    );
  });
}
```

Add `"emu-production"` and `"emu-rhs"` to `BLOCK_ELEMENTS` array.

### `formatForIngestion` — orchestrator

```typescript
export function formatForIngestion(
  $: cheerio.CheerioAPI,
  config: Partial<FormatConfig> = {},
): void {
  const cfg = { ...DEFAULT_CONFIG, ...config };

  // 1. Inject newlines globally (affects li, p, pre, emu-production, emu-rhs, etc.)
  addNewlinesAfterBlocks($);

  // 2. Inline leaves (links first — must be before lists/code destroy DOM)
  convertLinksToMarkdown($, cfg.links.join(", "));

  // 3. Inline code
  convertInlineCodeToMarkdown($, cfg.codeBlocks.inline);

  // 4. Block leaves (fenced code)
  convertBlockCodeToMarkdown($, cfg.codeBlocks.block);

  // 5. Structural parents (grammar, lists, tables)
  convertGrammarToMarkdown($, cfg.codeBlocks.grammar.join(", "));
  convertListsToMarkdown($, cfg.lists.ordered, cfg.lists.unordered);
  convertTablesToMarkdown($);
}
```

### Modify existing functions

- **`convertTablesToMarkdown($)`**: No changes needed. `.text()` already extracts markdown text from pre-processed `<span>` elements.

### Modify `setup/ingest.ts`

- Replace individual calls to `convertTablesToMarkdown($)` and `addNewlinesAfterBlocks($)` with single call to `formatForIngestion($)`.
- The child `emu-clause` replacement and deep nesting cleanup remain as-is (before `formatForIngestion`).

Updated call order in `buildSpecDocuments()`:
```typescript
// 1. Child clause replacement (existing)
$section.children("emu-clause").each(...);
$section.find("emu-clause").remove();

// 2. All formatting transformations (single call)
formatForIngestion($);
```

## Files to Modify

1. **`setup/utils/formatHTMLForIngestion.ts`** — add config interface, 5 new functions, orchestrating function
2. **`setup/ingest.ts`** — replace individual calls with `formatForIngestion($)` call
3. **New test file: `setup/utils/formatHTMLForIngestion.test.ts`** — unit tests for each transformation

No new dependencies. Cheerio only.

## Verification

1. **Unit tests**: Write tests for each transformation with sample HTML snippets from the spec:
   - `emu-xref a` → markdown link
   - `var`/`emu-val`/`emu-const` → inline code
   - `pre>code` → fenced code
   - `emu-grammar` → fenced bnf
   - `ol`/`ul` with nesting → markdown lists
   - `table` → markdown table (with links inside cells preserved)
   - Full pipeline via `formatForIngestion`
2. **Manual verification**: Run `bun run setup/ingest.ts` and inspect output chunks for correct markdown syntax
3. **Run lint/typecheck**: `bun run lint` and `bun run typecheck` (if available)
