import React from 'dom-chef';
import select from 'select-dom';
import pushForm from 'push-form';
import * as pageDetect from 'github-url-detection';
import delegate, {DelegateEvent} from 'delegate-it';

import features from '../feature-manager';
import * as api from '../github-helpers/api';
import fetchDom from '../helpers/fetch-dom';
import showToast from '../github-helpers/toast';
import {getConversationNumber} from '../github-helpers';

/**
Get the current base commit of this PR. It should change after rebases and merges in this PR.
This value is not consistently available on the page (appears in `/files` but not when only 1 commit is selected)
*/
// TODO: Replace this with `get-pr-info` when GHE supports it
async function getBaseReference(): Promise<string> {
	const {repository} = await api.v4(`
		repository() {
			pullRequest(number: ${getConversationNumber()!}) {
				baseRefOid
			}
		}
	`);
	return repository.pullRequest.baseRefOid;
}

async function getFile(filePath: string): Promise<{isTruncated: boolean; text: string} | undefined> {
	const {repository} = await api.v4(`
		repository() {
			file: object(expression: "${await getBaseReference()}:${filePath}") {
				... on Blob {
					isTruncated
					text
				}
			}
		}
	`);
	return repository.file;
}

async function restoreFile(progress: (message: string) => void, menuItem: Element, filePath: string): Promise<void> {
	const file = await getFile(filePath);

	if (!file) {
		// The file was created by this PR.
		// This code won’t be reached if `highlight-deleted-and-added-files-in-diffs` works.
		throw new Error('Nothing to restore. Delete file instead');
	}

	if (file.isTruncated) {
		throw new Error('Restore failed: File too big');
	}

	let {pathname} = menuItem.previousElementSibling as HTMLAnchorElement;
	// Check if file was deleted by PR
	if (menuItem.closest('[data-file-deleted="true"]')) {
		progress('Undeleting…');
		const [nameWithOwner, headBranch] = select('.head-ref')!.title.split(':');
		pathname = `/${nameWithOwner}/new/${headBranch}?filename=${filePath}`;
	} else {
		progress('Committing…');
	}

	const content = file.text;
	// This is either an `edit` or `create` form
	const form = (await fetchDom(pathname, 'form.js-blob-form'))!;
	form.elements.value.value = content; // Restore content (`value` is the name of the file content field)
	form.elements.message.value = (form.elements.message as HTMLInputElement).placeholder
		.replace(/^Create|^Update/, 'Restore');

	const response = await pushForm(form);
	if (!response.ok) {
		throw new Error(response.statusText);
	}
}

async function handleRestoreFileClick(event: DelegateEvent<MouseEvent, HTMLButtonElement>): Promise<void> {
	const menuItem = event.delegateTarget;

	await showToast(async progress => {
		const filePath = menuItem.closest<HTMLDivElement>('[data-path]')!.dataset.path!;
		return restoreFile(progress!, menuItem, filePath);
	}, {
		message: 'Restoring…',
		doneMessage: 'Restored!',
	});

	// Hide file from view
	menuItem.closest('.file')!.remove();
}

function handleMenuOpening({delegateTarget: dropdown}: DelegateEvent): void {
	const editFile = select('a[aria-label^="Change this"]', dropdown);
	if (!editFile || select.exists('.rgh-restore-file', dropdown)) {
		return;
	}

	if (editFile.closest('.file-header')!.querySelector('[aria-label="File added"]')) {
		// The file is new. "Restoring" it means deleting it, which is already possible.
		// Depends on `highlight-deleted-and-added-files-in-diffs`.
		return;
	}

	editFile.after(
		<button
			className="pl-5 dropdown-item btn-link rgh-restore-file"
			style={{whiteSpace: 'pre-wrap'}}
			role="menuitem"
			type="button"
		>
			Restore file
		</button>,
	);
}

function init(signal: AbortSignal): void {
	// `capture: true` required to be fired before GitHub's handlers
	delegate(document, '.file-header .js-file-header-dropdown', 'toggle', handleMenuOpening, {capture: true, signal});
	delegate(document, '.rgh-restore-file', 'click', handleRestoreFileClick, {capture: true, signal});
}

void features.add(import.meta.url, {
	include: [
		pageDetect.isPRFiles,
		pageDetect.isPRCommit,
	],
	init,
});
