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import React from 'dom-chef';
import select from 'select-dom';
import features from '../libs/features';
import {getCleanPathname} from '../libs/utils';
import getDefaultBranch from '../libs/get-default-branch';
async function is404(url: string): Promise<boolean> {
const {status} = await fetch(url, {method: 'head'});
return status === 404;
}
function getStrikeThrough(text: string): HTMLElement {
return <del style={{color: '#6a737d'}}>{text}</del>;
}
async function checkAnchor(anchor: HTMLAnchorElement): Promise<void> {
if (await is404(anchor.href)) {
anchor.replaceWith(getStrikeThrough(anchor.textContent!));
}
}
function parseCurrentURL(): string[] {
const parts = getCleanPathname().split('/');
if (parts[2] === 'blob') { // Blob URLs are never useful
parts[2] = 'tree';
}
return parts;
}
// If the resource was deleted, link to the commit history
async function addCommitHistoryLink(bar: Element): Promise<void> {
const parts = parseCurrentURL();
parts[2] = 'commits';
const url = '/' + parts.join('/');
if (await is404(location.origin + url)) {
return;
}
bar.after(
<p className="container mt-4 text-center">
See also the file’s {<a href={url}>commit history</a>}
</p>
);
}
// If the resource exists in the default branch, link to it
async function addDefaultBranchLink(bar: Element): Promise<void> {
const parts = getCleanPathname().split('/');
const branch = parts[3];
if (!branch) {
return;
}
const defaultBranch = await getDefaultBranch();
if (!defaultBranch || branch === defaultBranch) {
return;
}
parts[3] = defaultBranch; // Change branch
const url = '/' + parts.join('/');
if (await is404(location.origin + url)) {
return;
}
bar.after(
<p className="container mt-4 text-center">
See also the file on the {<a href={url}>default branch</a>}
</p>
);
}
function init(): false | void {
const parts = parseCurrentURL();
if (parts.length <= 1 || !select.exists('[alt*="This is not the web page you are looking for"]')) {
return false;
}
const bar = <h2 className="container mt-4 text-center"/>;
for (const [i, part] of parts.entries()) {
if (i === 2 && part === 'tree') {
// `/tree/` is not a real part of the URL
continue;
}
if (i === parts.length - 1) {
// The last part of the URL is a known 404
bar.append(' / ', getStrikeThrough(part));
} else {
const pathname = '/' + parts.slice(0, i + 1).join('/');
bar.append(i ? ' / ' : '', <a href={pathname}>{part}</a>);
}
}
select('main > :first-child, #parallax_illustration')!.after(bar);
// Check parts from right to left; skip the last part
for (let i = bar.children.length - 2; i >= 0; i--) {
checkAnchor(bar.children[i] as HTMLAnchorElement);
}
if (parts[2] === 'tree') {
addCommitHistoryLink(bar);
addDefaultBranchLink(bar);
}
}
features.add({
id: __featureName__,
description: 'Adds possible related pages and alternatives on 404 pages.',
screenshot: 'https://user-images.githubusercontent.com/1402241/46402857-7bdada80-c733-11e8-91a1-856573078ff5.png',
include: [
features.is404
],
load: features.onDomReady,
init
});
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