Portable Text Conversion

# Portable Text Conversion

Convert external content (HTML, Markdown) into Portable Text for Sanity. Three main approaches:

1. **`markdownToPortableText`** — Convert Markdown directly using `@portabletext/markdown` (recommended for Markdown)
2. **`htmlToBlocks`** — Parse HTML into PT blocks using `@portabletext/block-tools` (for HTML migration)
3. **Manual construction** — Build PT blocks directly from any source (APIs, databases, etc.)

## Portable Text Specification

Understand the target format before converting. PT is an array of blocks:

```json
[
  {
    "_type": "block",
    "_key": "abc123",
    "style": "normal",
    "children": [
      {"_type": "span", "_key": "def456", "text": "Hello ", "marks": []},
      {"_type": "span", "_key": "ghi789", "text": "world", "marks": ["strong"]}
    ],
    "markDefs": []
  },
  {
    "_type": "block",
    "_key": "jkl012",
    "style": "h2",
    "children": [
      {"_type": "span", "_key": "mno345", "text": "A heading", "marks": []}
    ],
    "markDefs": []
  },
  {
    "_type": "image",
    "_key": "pqr678",
    "asset": {"_type": "reference", "_ref": "image-abc-200x200-png"}
  }
]
```

**Key rules:**
- Every block and span needs `_key` (unique within the array)
- `_type: "block"` is for text blocks; custom types use their own `_type`
- `markDefs` holds annotation data; `marks` on spans reference `markDefs[*]._key` or are decorator strings
- Lists use `listItem` ("bullet" | "number") and `level` (1, 2, 3...) on regular blocks

## Conversion Rules

Read the rule file matching your source format:

- **Markdown → Portable Text**: `rules/markdown-to-pt.md` — `@portabletext/markdown` with `markdownToPortableText` (recommended)
- **HTML → Portable Text**: `rules/html-to-pt.md` — `@portabletext/block-tools` with `htmlToBlocks`
- **Manual PT Construction**: `rules/manual-construction.md` — build blocks programmatically from any source

> **Note:** `@sanity/block-tools` is the legacy package name. Always use `@portabletext/block-tools` for new projects. The API is the same.