# DESIGN: Notes Rich Text Editor + Obsidian-Style Linking

**Version:** v0.17.3
**Status:** Draft
**Scope:** Upgrade the notes editor from a plain `<textarea>` to a CM6-powered
markdown editor with live preview, `[[wikilink]]` resolution, and a backlinks
system.

**Depends on:** v0.17.2 (CodeMirror 6 bundle provides `CM.codeEditor()` and
the markdown language mode).

---

## Motivation

The notes system (v0.9.3 side panel, CRUD, folders, search) stores markdown
but edits it as raw text in a `<textarea>`. Now that CM6 is bundled, we can
give notes the same live-preview markdown experience that the chat input gets
— plus something the chat input doesn't need: **inter-note linking**.

The Obsidian model is the right reference: markdown files with `[[wikilinks]]`
resolved at render time, bidirectional backlinks, and create-on-reference.
Our advantage over Obsidian: we already have **semantic search via embeddings**
(v0.14.0 KB infrastructure), so link autocomplete can be smarter than
filename matching.

---

## Architecture

### New CM6 Factory: `CM.noteEditor()`

A third factory alongside `chatInput()` and `codeEditor()`, tailored for
long-form markdown editing in the notes panel.

```javascript
CM.noteEditor(target, {
    value: '',                    // initial markdown content
    darkMode: true,
    onChange: (text) => {},        // live content callback
    onLink: (title) => {},        // [[link]] activated callback
    linkCompleter: async (query) => [], // fuzzy note search for [[ autocomplete
});
```

**Behavior:**

- Full markdown syntax highlighting (headings, bold, italic, code, lists, links)
- Live inline preview: headings render at size, bold/italic styled, code blocks
  highlighted — the document is still markdown but *looks* formatted
- `[[` triggers autocomplete dropdown of existing notes (fuzzy search)
- `[[Note Title]]` tokens rendered as clickable chips (CM6 `Decoration.widget`)
- Line numbers off (it's a note, not code)
- Spell check enabled (`EditorView.contentAttributes: { spellcheck: 'true' }`)
- Vim/Emacs keybindings respected (user preference from v0.17.2)

### Wikilink Syntax

Standard double-bracket syntax with optional display text:

```
[[Note Title]]              → links to note titled "Note Title"
[[Note Title|display text]] → shows "display text", links to "Note Title"
```

Resolution order:
1. Exact title match (case-insensitive)
2. Fuzzy title match (for autocomplete, not for rendering)
3. Unresolved → rendered as red chip with "create" affordance

### Bundle Addition

The note editor factory lives in a new file in `src/editor/`:

```
src/editor/
  index.mjs           # existing — adds noteEditor to window.CM
  chat-input.mjs      # existing
  code-editor.mjs     # existing
  note-editor.mjs     # NEW — noteEditor() factory
  wikilink.mjs        # NEW — CM6 extension: parse, decorate, autocomplete [[links]]
  theme.mjs           # existing
```

The wikilink extension is CM6-native: a `ViewPlugin` that scans for `[[...]]`
patterns and replaces them with `Decoration.widget` nodes (clickable chips).
The autocomplete uses CM6's `autocompletion` with a custom `completeFromList`
source triggered by `[[`.

No bundle size concern — the wikilink plugin is tiny custom code, not an
external dependency.

---

## Data Model

### `note_links` Table

Tracks directed links between notes, extracted on save.

```sql
-- Postgres
CREATE TABLE IF NOT EXISTS note_links (
    source_note_id  UUID NOT NULL REFERENCES notes(id) ON DELETE CASCADE,
    target_note_id  UUID REFERENCES notes(id) ON DELETE CASCADE,
    target_title    TEXT NOT NULL,           -- raw [[title]] text, for unresolved links
    display_text    TEXT,                    -- optional |alias
    created_at      TIMESTAMPTZ DEFAULT now(),
    PRIMARY KEY (source_note_id, target_title)
);

CREATE INDEX idx_note_links_target ON note_links(target_note_id)
    WHERE target_note_id IS NOT NULL;

-- SQLite
CREATE TABLE IF NOT EXISTS note_links (
    source_note_id  TEXT NOT NULL REFERENCES notes(id) ON DELETE CASCADE,
    target_note_id  TEXT REFERENCES notes(id) ON DELETE CASCADE,
    target_title    TEXT NOT NULL,
    display_text    TEXT,
    created_at      TEXT DEFAULT (datetime('now')),
    PRIMARY KEY (source_note_id, target_title)
);

CREATE INDEX IF NOT EXISTS idx_note_links_target ON note_links(target_note_id)
    WHERE target_note_id IS NOT NULL;
```

**Key design decisions:**

- `target_note_id` is **nullable** — an unresolved link (target note doesn't
  exist yet) stores the title but has `NULL` for the FK. When a note with that
  title is created, a background pass resolves dangling links.
- Primary key is `(source_note_id, target_title)` — a note can only link to
  the same title once (last one wins if duplicated).
- `target_title` is always stored for human readability and re-resolution
  after renames.

### Link Extraction (on save)

When a note is saved, the backend:

1. Parses content for `[[...]]` patterns (simple regex: `\[\[([^\]|]+)(?:\|([^\]]+))?\]\]`)
2. Resolves each title to a note ID: `SELECT id FROM notes WHERE LOWER(title) = LOWER($1) AND user_id = $2`
3. Deletes existing links for this source note: `DELETE FROM note_links WHERE source_note_id = $1`
4. Inserts fresh links with resolved (or NULL) target IDs

This full-replace approach is simple and correct — notes don't have thousands
of links, so the cost is negligible.

### Backlinks Query

```sql
SELECT n.id, n.title, n.folder_path, n.updated_at, nl.display_text
FROM note_links nl
JOIN notes n ON n.id = nl.source_note_id
WHERE nl.target_note_id = $1
ORDER BY n.updated_at DESC;
```

### Dangling Link Resolution

When a new note is created, resolve any dangling links pointing at its title:

```sql
UPDATE note_links
SET target_note_id = $1
WHERE target_note_id IS NULL
AND LOWER(target_title) = LOWER($2)
AND source_note_id IN (SELECT id FROM notes WHERE user_id = $3);
```

This runs once on note creation — cheap and ensures links "light up"
retroactively.

---

## API Changes

### Existing Endpoints (modified)

**`PUT /api/v1/notes/:id`** — after updating note content, re-extract links.
No API signature change; link extraction is a server-side side effect.

**`POST /api/v1/notes`** — after creating a note, extract links AND resolve
dangling links from other notes that reference this title.

### New Endpoints

**`GET /api/v1/notes/:id/backlinks`**

Returns notes that link to this note.

```json
{
    "data": [
        {
            "id": "uuid",
            "title": "Meeting Notes 2026-02-28",
            "folder_path": "/work",
            "updated_at": "2026-02-28T10:00:00Z",
            "display_text": null
        }
    ]
}
```

**`GET /api/v1/notes/search-titles?q=<query>&limit=10`**

Lightweight fuzzy title search for the `[[` autocomplete. Returns titles
and IDs only — no content, no embeddings. Fast path.

```json
{
    "data": [
        { "id": "uuid", "title": "Project Kickoff Notes" },
        { "id": "uuid", "title": "Project Architecture" }
    ]
}
```

Uses `ILIKE` on Postgres, `LIKE` on SQLite (case-insensitive via COLLATE).
The semantic search endpoint (`GET /api/v1/notes/search`) remains available
for deeper searches but is overkill for autocomplete.

---

## Frontend Integration

### Note Editor Swap

In `notes.js`, `openNoteEditor()` currently sets `.value` on the
`#noteEditorContent` textarea. After v0.17.3:

```javascript
// Replace textarea with CM6 note editor
const container = document.getElementById('noteEditorContentContainer');
const editor = CM.noteEditor(container, {
    value: note.content || '',
    darkMode: document.body.classList.contains('dark-theme'),
    onChange: (text) => {
        // Could auto-save or mark dirty
    },
    onLink: (title) => {
        // Navigate to linked note
        const linked = _findNoteByTitle(title);
        if (linked) {
            openNoteEditor(linked.id);
        } else {
            // Offer to create
            _createNoteFromLink(title);
        }
    },
    linkCompleter: async (query) => {
        const resp = await API.searchNoteTitles(query, 10);
        return (resp.data || []).map(n => ({ label: n.title, id: n.id }));
    },
});
```

The HTML changes from:
```html
<textarea id="noteEditorContent" rows="12" ...></textarea>
```
To:
```html
<div id="noteEditorContentContainer" class="notes-content-input"></div>
```

With graceful fallback: if `window.CM?.noteEditor` is undefined, create a
`<textarea>` inside the container (same behavior as today).

### Backlinks Panel

Below the note editor, a collapsible "Backlinks" section:

```html
<div id="noteBacklinks" class="note-backlinks" style="display:none">
    <div class="note-backlinks-header" onclick="toggleBacklinks()">
        <span>Linked mentions</span>
        <span id="noteBacklinksCount" class="badge">0</span>
    </div>
    <div id="noteBacklinksList" class="note-backlinks-list"></div>
</div>
```

Loaded on `openNoteEditor()` for existing notes:
```javascript
async function loadBacklinks(noteId) {
    const resp = await API.getNoteBacklinks(noteId);
    const links = resp.data || [];
    const el = document.getElementById('noteBacklinksList');
    const count = document.getElementById('noteBacklinksCount');
    count.textContent = links.length;
    document.getElementById('noteBacklinks').style.display =
        links.length > 0 ? '' : 'none';
    el.innerHTML = links.map(n => `
        <div class="note-backlink-item" onclick="openNoteEditor('${n.id}')">
            <span class="note-backlink-title">${esc(n.title)}</span>
            <span class="note-backlink-folder text-muted">${esc(n.folder_path)}</span>
        </div>
    `).join('');
}
```

### Note Preview (read mode)

The existing note list view shows raw markdown. After this release,
`[[Note Title]]` patterns in rendered markdown (via marked.js) become
clickable links. A small marked.js extension or post-render pass
converts `[[...]]` to `<a>` tags with `onclick` handlers.

---

## Access Control

**Links respect existing note ownership.** A user can only:
- Create links to notes they own (their own notes)
- See backlinks from notes they own
- Autocomplete searches their own notes

Team-scoped notes (via `team_id` on the notes table) follow the same
grant model as other team resources. When team notes ship (potentially
v0.23.0 channel-scoped notes), the link resolution query adds
`AND (user_id = $1 OR team_id IN (...))`.

For v0.17.3, the scope is **personal notes only** — which is the
current notes model.

---

## Store Layer

### `NoteLinkStore` Interface

```go
type NoteLinkStore interface {
    // ReplaceLinks deletes existing links for sourceNoteID and inserts new ones.
    // Each link has TargetTitle (always set) and TargetNoteID (nullable, resolved).
    ReplaceLinks(ctx context.Context, sourceNoteID string, links []NoteLink) error

    // ResolveByTitle sets target_note_id on dangling links matching the title.
    ResolveByTitle(ctx context.Context, userID, targetNoteID, title string) error

    // Backlinks returns notes that link to the given note.
    Backlinks(ctx context.Context, noteID string) ([]NoteLinkResult, error)
}

type NoteLink struct {
    TargetNoteID *string // nil for unresolved
    TargetTitle  string
    DisplayText  string
}

type NoteLinkResult struct {
    SourceNoteID string
    Title        string
    FolderPath   string
    UpdatedAt    time.Time
    DisplayText  string
}
```

Implementations in both `store/postgres/note_link.go` and
`store/sqlite/note_link.go`.

### Link Extraction Helper

```go
// ExtractWikilinks parses [[Title]] and [[Title|Display]] from markdown content.
func ExtractWikilinks(content string) []NoteLink {
    re := regexp.MustCompile(`\[\[([^\]|]+?)(?:\|([^\]]+?))?\]\]`)
    matches := re.FindAllStringSubmatch(content, -1)
    seen := make(map[string]bool)
    var links []NoteLink
    for _, m := range matches {
        title := strings.TrimSpace(m[1])
        if seen[strings.ToLower(title)] { continue }
        seen[strings.ToLower(title)] = true
        link := NoteLink{TargetTitle: title}
        if len(m) > 2 && m[2] != "" {
            link.DisplayText = strings.TrimSpace(m[2])
        }
        links = append(links, link)
    }
    return links
}
```

This lives in a shared `notes/` package (or in the handler) — it's pure
string parsing with no DB dependency.

---

## Migration

**Migration 002** (both Postgres and SQLite):

```sql
-- 002_note_links.sql
CREATE TABLE IF NOT EXISTS note_links ( ... );
CREATE INDEX ...;
```

No backfill needed — existing notes have no `[[links]]` in their content,
so the table starts empty. Links populate organically as users edit notes
with the new editor.

---

## Implementation Checklist

### Phase 1: Backend (links infrastructure)
- [ ] Migration 002: `note_links` table (Postgres + SQLite)
- [ ] `NoteLinkStore` interface + Postgres/SQLite implementations
- [ ] `ExtractWikilinks()` helper with tests
- [ ] Link extraction on note create/update in handlers
- [ ] Dangling link resolution on note create
- [ ] `GET /api/v1/notes/:id/backlinks` endpoint
- [ ] `GET /api/v1/notes/search-titles?q=` endpoint
- [ ] API client additions in `api.js`

### Phase 2: Frontend (CM6 note editor)
- [ ] `src/editor/note-editor.mjs` — `CM.noteEditor()` factory
- [ ] `src/editor/wikilink.mjs` — CM6 extension (parse, decorate, autocomplete)
- [ ] Rebuild CM6 bundle (add new modules to `index.mjs`)
- [ ] Replace `<textarea>` with CM6 note editor in `notes.js`
- [ ] `saveNote()` reads from CM6 `.getValue()`
- [ ] Graceful fallback if CM6 unavailable
- [ ] Backlinks panel UI below editor
- [ ] `[[link]]` rendering in note list preview (marked.js extension)

### Phase 3: Polish
- [ ] Wikilink chips styled to match app theme (accent color, hover state)
- [ ] Unresolved links styled distinctly (red/dashed, "click to create")
- [ ] Autocomplete dropdown styled (note title + folder path hint)
- [ ] Keyboard navigation in autocomplete (↑/↓, Enter to select, Esc to dismiss)
- [ ] Mobile/touch testing for link taps
- [ ] Update ARCHITECTURE.md

---

## Future (not in v0.17.3)

- **Graph view**: visual node graph of note connections (d3 force layout)
- **Orphan detection**: notes with no inbound or outbound links
- **Link suggestions**: "notes that might be related" via embedding similarity
  (reuse KB infrastructure)
- **Transclusion**: `![[Note Title]]` embeds the target note's content inline
- **Tag linking**: `#tag` syntax as an alternative navigation path
- **Team note links**: cross-user linking when team/channel-scoped notes ship