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import $ from 'jquery';
import { once } from 'lodash';
import { deprecatedCreateFlash as flash } from '~/flash';
import { __, sprintf } from '~/locale';
// Renders diagrams and flowcharts from text using Mermaid in any element with the
// `js-render-mermaid` class.
//
// Example markup:
//
// <pre class="js-render-mermaid">
// graph TD;
// A-- > B;
// A-- > C;
// B-- > D;
// C-- > D;
// </pre>
//
// This is an arbitrary number; Can be iterated upon when suitable.
const MAX_CHAR_LIMIT = 2000;
// Max # of mermaid blocks that can be rendered in a page.
const MAX_MERMAID_BLOCK_LIMIT = 50;
// Keep a map of mermaid blocks we've already rendered.
const elsProcessingMap = new WeakMap();
let renderedMermaidBlocks = 0;
let mermaidModule = {};
function importMermaidModule() {
return import(/* webpackChunkName: 'mermaid' */ 'mermaid')
.then(mermaid => {
let theme = 'neutral';
const ideDarkThemes = ['dark', 'solarized-dark', 'monokai'];
if (
ideDarkThemes.includes(window.gon?.user_color_scheme) &&
// if on the Web IDE page
document.querySelector('.ide')
) {
theme = 'dark';
}
mermaid.initialize({
// mermaid core options
mermaid: {
startOnLoad: false,
},
// mermaidAPI options
theme,
flowchart: {
useMaxWidth: true,
htmlLabels: false,
},
securityLevel: 'strict',
});
mermaidModule = mermaid;
return mermaid;
})
.catch(err => {
flash(sprintf(__("Can't load mermaid module: %{err}"), { err }));
// eslint-disable-next-line no-console
console.error(err);
});
}
function fixElementSource(el) {
// Mermaid doesn't like `<br />` tags, so collapse all like tags into `<br>`, which is parsed correctly.
const source = el.textContent.replace(/<br\s*\/>/g, '<br>');
// Remove any extra spans added by the backend syntax highlighting.
Object.assign(el, { textContent: source });
return { source };
}
function renderMermaidEl(el) {
mermaidModule.init(undefined, el, id => {
const source = el.textContent;
const svg = document.getElementById(id);
// As of https://github.com/knsv/mermaid/commit/57b780a0d,
// Mermaid will make two init callbacks:one to initialize the
// flow charts, and another to initialize the Gannt charts.
// Guard against an error caused by double initialization.
if (svg.classList.contains('mermaid')) {
return;
}
svg.classList.add('mermaid');
// pre > code > svg
svg.closest('pre').replaceWith(svg);
// We need to add the original source into the DOM to allow Copy-as-GFM
// to access it.
const sourceEl = document.createElement('text');
sourceEl.classList.add('source');
sourceEl.setAttribute('display', 'none');
sourceEl.textContent = source;
svg.appendChild(sourceEl);
});
}
function renderMermaids($els) {
if (!$els.length) return;
// A diagram may have been truncated in search results which will cause errors, so abort the render.
if (document.querySelector('body').dataset.page === 'search:show') return;
importMermaidModule()
.then(() => {
let renderedChars = 0;
$els.each((i, el) => {
// Skipping all the elements which we've already queued in requestIdleCallback
if (elsProcessingMap.has(el)) {
return;
}
const { source } = fixElementSource(el);
/**
* Restrict the rendering to a certain amount of character
* and mermaid blocks to prevent mermaidjs from hanging
* up the entire thread and causing a DoS.
*/
if (
(source && source.length > MAX_CHAR_LIMIT) ||
renderedChars > MAX_CHAR_LIMIT ||
renderedMermaidBlocks >= MAX_MERMAID_BLOCK_LIMIT
) {
const html = `
<div class="alert gl-alert gl-alert-warning alert-dismissible lazy-render-mermaid-container js-lazy-render-mermaid-container fade show" role="alert">
<div>
<div class="display-flex">
<div>${__(
'Warning: Displaying this diagram might cause performance issues on this page.',
)}</div>
<div class="gl-alert-actions">
<button class="js-lazy-render-mermaid btn gl-alert-action btn-warning btn-md new-gl-button">Display</button>
</div>
</div>
<button type="button" class="close" data-dismiss="alert" aria-label="Close">
<span aria-hidden="true">×</span>
</button>
</div>
</div>
`;
const $parent = $(el).parent();
if (!$parent.hasClass('lazy-alert-shown')) {
$parent.after(html);
$parent.addClass('lazy-alert-shown');
}
return;
}
renderedChars += source.length;
renderedMermaidBlocks += 1;
const requestId = window.requestIdleCallback(() => {
renderMermaidEl(el);
});
elsProcessingMap.set(el, requestId);
});
})
.catch(err => {
flash(sprintf(__('Encountered an error while rendering: %{err}'), { err }));
// eslint-disable-next-line no-console
console.error(err);
});
}
const hookLazyRenderMermaidEvent = once(() => {
$(document.body).on('click', '.js-lazy-render-mermaid', function eventHandler() {
const parent = $(this).closest('.js-lazy-render-mermaid-container');
const pre = parent.prev();
const el = pre.find('.js-render-mermaid');
parent.remove();
renderMermaidEl(el);
});
});
export default function renderMermaid($els) {
if (!$els.length) return;
const visibleMermaids = $els.filter(function filter() {
return $(this).closest('details').length === 0 && $(this).is(':visible');
});
renderMermaids(visibleMermaids);
$els.closest('details').one('toggle', function toggle() {
if (this.open) {
renderMermaids($(this).find('.js-render-mermaid'));
}
});
hookLazyRenderMermaidEvent();
}
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