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astro-mermaid

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Mermaid integration using pattern from cloudflare-docs

// repository documentation

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# astro-mermaid

An Astro integration for rendering Mermaid diagrams with automatic theme switching, client-side rendering, and universal compatibility. Works seamlessly with both standalone Astro projects and documentation frameworks like Starlight.

## Live Demos

| Demo Type | URL | Description |
|-----------|-----|-------------|
| **Starlight Integration** | [starlight-mermaid-demo.netlify.app](https://starlight-mermaid-demo.netlify.app/) | Full documentation site with Starlight |
| **Standalone Template** | [astro-mermaid-demo.netlify.app](https://astro-mermaid-demo.netlify.app/) | Pure Astro project template |

Both demos showcase:
- ✅ All diagram types with live examples
- ✅ Theme switching (light/dark modes)  
- ✅ Icon pack integration
- ✅ Responsive design
- ✅ Content collections and direct `.astro` usage

## Features

- 🎨 **Universal Theme Detection** - Works with both `html[data-theme]` and `body[data-theme]` attributes
- 🚀 **Dual Plugin System** - Remark + Rehype plugins for comprehensive markdown processing  
- 📝 **Universal File Support** - Works with `.md`, `.mdx`, and `.astro` files
- ⚡ **Performance Optimized** - Conditional loading and client-side rendering
- 🔧 **Highly Configurable** - Full mermaid.js configuration support
- 🎯 **TypeScript Ready** - Complete type definitions included
- 🔒 **Privacy-Focused** - No external dependencies, fully offline-capable
- 📦 **Zero Configuration** - Works out of the box with sensible defaults
- 🎭 **Smooth UX** - Loading animations and layout shift prevention
- 🦌 **ELK Support** - Optionally works with the `elk` layout ([The Eclipse Layout Kernel](https://eclipse.dev/elk/))

## Quick Start

### 1. Installation

```bash
npm install astro-mermaid mermaid
```

### 2. Add to Astro Config

```js
// astro.config.mjs
import { defineConfig } from 'astro/config';
import mermaid from 'astro-mermaid';

export default defineConfig({
  integrations: [
    mermaid({
      theme: 'forest',
      autoTheme: true
    })
  ]
});
```

### 3. Use in Markdown

````markdown
```mermaid
graph TD
    A[Start] --> B[Process]
    B --> C[End]
```
````

### 4. (Optional) Use ELK layout

To enable the `elk` layout in Mermaid diagrams, install the `@mermaid-js/layout-elk` package.

```bash
npm install @mermaid-js/layout-elk
```

Learn more about [Mermaid layouts](https://mermaid.js.org/config/layouts.html) or [The Eclipse Layout Kernel](https://eclipse.dev/elk/).

## Astro Compatibility

`astro-mermaid` works across Astro 4, 5, 6, and 7 — no configuration needed. It
detects the active markdown engine at build time and registers its transform the
right way for each:

| Astro version | Markdown engine | How mermaid hooks in |
|---------------|-----------------|----------------------|
| 7+ | Sätteri (`@astrojs/markdown-satteri`, the new default) | a Sätteri **mdast plugin** |
| 6.4 – 6.x | `unified()` processor | remark + rehype plugins via `markdown.processor` |
| < 6.4 | legacy pipeline | `markdown.remarkPlugins` / `markdown.rehypePlugins` |

If you previously pinned `markdown.processor` to `unified()` purely to keep
mermaid working on Astro 7, you can now drop that workaround and let Astro use
its default Sätteri processor.

## Integration Order (Important!)

When using with Starlight or other markdown-processing integrations, place mermaid **first**:

```js
import { defineConfig } from 'astro/config';
import starlight from '@astrojs/starlight';
import mermaid from 'astro-mermaid';

export default defineConfig({
  integrations: [
    mermaid(), // ⚠️ Must come BEFORE starlight
    starlight({
      title: 'My Docs'
    })
  ]
});
```

## Configuration

```js
mermaid({
  // Default theme: 'default', 'dark', 'forest', 'neutral', 'base'
  theme: 'forest',

// Enable automatic theme switching based on data-theme attribute
  autoTheme: true,

// Enable client-side logging (default: true). Set to false to suppress
  // console.log output in the browser. Errors are always logged.
  enableLog: false,

// Additional mermaid configuration
  mermaidConfig: {
    flowchart: {
      curve: 'basis'
    }
  },

// Register icon packs for use in diagrams
  iconPacks: [
    {
      name: 'logos',
      loader: () => fetch('https://unpkg.com/@iconify-json/logos@1/icons.json').then(res => res.json())
    },
    {
      name: 'iconoir',
      loader: () => fetch('https://unpkg.com/@iconify-json/iconoir@1/icons.json').then(res => res.json())
    }
  ]
})
```

## Icon Packs

You can register icon packs to use custom icons in your diagrams. There are three ways to provide a pack:

```js
iconPacks: [
  // 1. url — preferred: a JSON endpoint, fetched safely at runtime
  {
    name: 'logos',
    url: 'https://unpkg.com/@iconify-json/logos@1/icons.json'
  },

// 2. icons — pass icon data directly (e.g. an imported JSON file).
  //    No serialization concerns, so this works with imports and shared data.
  {
    name: 'my-icons',
    icons: myIcons // import myIcons from './my-icons.json'
  },

// 3. loader — legacy. The function source is inspected for a fetch('...')
  //    URL. Prefer `url` or `icons` instead.
  {
    name: 'iconoir',
    loader: () => fetch('https://unpkg.com/@iconify-json/iconoir@1/icons.json').then(res => res.json())
  }
]
```

> The integration never serializes arbitrary function bodies to the client. A `loader` is only used to extract its `fetch(...)` URL; if no URL can be found, the pack is skipped with a warning. Use `url` or `icons` for reliable results.

Then use icons in your diagrams:

````markdown
```mermaid
architecture-beta
  group api(logos:aws-lambda)[API]

service db(logos:postgresql)[Database] in api
  service disk1(logos:aws-s3)[Storage] in api
  service disk2(logos:cloudflare)[CDN] in api
  service server(logos:docker)[Server] in api

db:L -- R:server
  disk1:T -- B:server
  disk2:T -- B:db
```
````

## Theme Switching

If `autoTheme` is enabled (default), the integration will automatically switch between themes based on your site's `data-theme` attribute:

- `data-theme="light"` → uses 'default' mermaid theme
- `data-theme="dark"` → uses 'dark' mermaid theme

## Client-Side Rendering & Security

### 🔒 Privacy & Security Benefits

This integration uses **100% client-side rendering** with zero external dependencies at runtime:

- **No Data Transmission**: Your diagram content never leaves your browser
- **No External Servers**: No calls to mermaid.live or any external services
- **Offline Capable**: Works completely offline after initial page load
- **Zero Network Latency**: Instant diagram rendering without network delays
- **Corporate Firewall Friendly**: No external domains need to be whitelisted

### ⚡ How It Works

1. **Build Time**: Mermaid code blocks are transformed to `<pre class="mermaid">` elements
2. **Runtime**: The bundled Mermaid JavaScript library renders diagrams locally
3. **Output**: Pure SVG generated entirely in your browser

```javascript
// All rendering happens locally - no network calls
import mermaid from 'mermaid';
const { svg } = await mermaid.render(id, diagramDefinition);
```

### 🛡️ Enterprise & Compliance

Perfect for:
- Corporate environments with strict security policies
- GDPR/privacy-compliant applications  
- Air-gapped or restricted network environments
- Applications requiring data sovereignty
- High-security environments where external requests are prohibited

## Supported Diagrams

All mermaid diagram types are supported:

- Flowcharts
- Sequence diagrams
- Gantt charts
- Class diagrams
- State diagrams
- Entity Relationship diagrams
- User Journey diagrams
- Git graphs
- Pie charts
- Requirement diagrams
- C4 diagrams
- Mindmaps
- Timeline diagrams
- Quadrant charts
- And more!

## Version

See [changelog](https://github.com/joesaby/astro-mermaid/releases) for version history.

## Contributing

Contributions welcome! See our [demos](https://astro-mermaid-demo.netlify.app/) for examples.

## License

astro-mermaid

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