# `@aegisjsproject/markdown`

Markdown parser for [`@aegisjsproject/core`](https://github.com/AegisJSProject/core)

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- - -

- [Code of Conduct](./.github/CODE_OF_CONDUCT.md)
- [Contributing](./.github/CONTRIBUTING.md)
<!-- - [Security Policy](./.github/SECURITY.md) -->

## Adding language support

In order to reduce bundle size, only plaintext is available/supported by default.
However, you can easily add support for additional languages in a variety of ways:

### Registering from Static Imports

**Note**: All languages provided by `highlight.js` may be found at [`/es/languages/${lang}.min.js`](https://unpkg.com/browse/@highlightjs/cdn-assets/es/languages/).

```js
import { registerLanguage } from '@aegisjsproject/markdown';
import javascript from 'highlight.js/lanuages/javascript.min.js';
import xml from 'highlight.js/languages/xml.min.js';
import css from 'highlight.js/languages/css.min.js';

registerLanguage('javascript', javascript);
registerLanguage('xml', xml);
registerLanguage('css',css);

// Or
import { registerLanguages } from '@aegisjsproject/markdown';
import javascript from 'highlight.js/lanuages/javascript.min.js';
import xml from 'highlight.js/languages/xml.min.js';
import css from 'highlight.js/languages/css.min.js';

registerLanguages({ javascript, xml, css });
```

### Dynamically Loading and Registering using Dynamic Imports

This uses `import()` for dynamic loading of language modules from `unpkg.com`.

**Note**: These are case-sensitive and **MUST** be the correct filename (without extension).

```js
import { loadLanguages } from '@aegisjsproject/markdown';

await loadLanguages('javascript', 'css', 'xml', 'typescript');
```

## Example

```js
import { md, createStyleSheet, getMarkdown, registerLanguages } from '@aegisjsproject/markdown';
import javascript from 'highlight.js/languages/javascript.min.js';
import css from 'highlight.js/languages/css.min.js';
import xml from 'highlight.js/languages/xml.min.js';

registerLanguages({ javascript, css, xml });

document.head.append(
  createStyleSheet('github', { media: '(prefers-color-scheme: light)' }),
  createStyleSheet('github-dark', { media: '(prefers-color-scheme: dark)' }),
);

document.getElementById('header').append(md`
  # Hello, World!

  ## It is currently ${new Date()}.
`);

customElements.define('md-preview', class HTMLMDPreviewElement extends HTMLElement {
  #shadow;

  constructor() {
    super();

    this.#shadow = this.attachShadow({ mode: 'closed' });
    const container = document.createElement('div');
    container.id = 'container';
    container.part.add('container');

    this.#shadow.append(
      createStyleSheet('github', { media: '(prefers-color-scheme: light)' }),
      createStyleSheet('github-dark', { media: '(prefers-color-scheme: dark)' }),
      container,
    );
  }

  async attributeChangedCallback(name, oldVal, newVal) {
    switch(name) {
      case 'src':
        if (typeof newVal === 'string') {
          this.#shadow.getElementById('container').replaceChildren(await getMarkdown(this.src));
        } else {
          this.#shadow.getElementById('container').replaceChildren();
        }
        break;

      default:
        throw new Error(`Unhandled attribute change: ${name}.`);
    }
  }

  set content(val) {
    if (typeof val === 'string' && val.length !== 0) {
      this.#shadow.getElementById('container').replaceChildren(md`${val}`);
      this.scrollIntoView({ behavior: 'smooth', block: 'start' });
    } else {
      this.#shadow.getElementById('container').replaceChildren();
    }
  }

  get src() {
    return this.getAttribute('src');
  }

  set src(val) {
    if (typeof val === 'string' || val instanceof URL) {
      this.setAttribute('src', val);
    } else {
      this.removeAttribute('src');
    }
  }

  clear() {
    this.content = null;
  }

  static get observedAttributes() {
    return ['src'];
  }
});

document.forms.test.addEventListener('submit', event => {
  event.preventDefault();
  const data = new FormData(event.target);
  document.getElementById('preview').content = data.get('md');
});

document.forms.test.addEventListener('reset', () => document.getElementById('preview').clear());
```