import React from 'dom-chef';
import elementReady from 'element-ready';
import * as pageDetect from 'github-url-detection';
import {ChevronLeftIcon} from '@primer/octicons-react';

import features from '.';
import GitHubURL from '../github-helpers/github-url';
import {groupButtons} from '../github-helpers/group-buttons';
import getDefaultBranch from '../github-helpers/get-default-branch';
import {getCurrentCommittish} from '../github-helpers';

async function init(): Promise<false | void> {
	const defaultBranch = await getDefaultBranch();
	const branchSelector = await elementReady('[data-hotkey="w"]');
	// The branch selector is missing from History pages of files and folders (it only appears on the root)
	if (!branchSelector) {
		return false;
	}

	const currentBranch = getCurrentCommittish();

	// Don't show the button if we’re already on the default branch
	if (defaultBranch === currentBranch) {
		return false;
	}

	const url = new GitHubURL(location.href);
	if (pageDetect.isRepoRoot()) {
		// The default branch of the root directory is just /user/repo/
		url.route = '';
		url.branch = '';
	} else {
		url.branch = defaultBranch;
	}

	const defaultLink = (
		<a
			className="btn tooltipped tooltipped-ne rgh-default-branch-button"
			href={String(url)}
			data-pjax="#repo-content-pjax-container"
			aria-label="See this view on the default branch"
		>
			<ChevronLeftIcon/>
		</a>
	);

	branchSelector.parentElement!.before(defaultLink);
	branchSelector.parentElement!.style.zIndex = 'auto'; // For #4240
	groupButtons([defaultLink, branchSelector.parentElement!]).classList.add('d-flex');
}

void features.add(__filebasename, {
	include: [
		pageDetect.isRepoTree,
		pageDetect.isSingleFile,
		pageDetect.isRepoCommitList,
	],
	exclude: [
		pageDetect.isRepoHome,
	],
	awaitDomReady: false,
	deduplicate: '.rgh-default-branch-button', // #3945
	init,
});
