balena-cli/src/utils/lazy.ts

The official balena Command Line Interface

/* eslint-disable no-restricted-imports */
/** the import blacklist is to enforce lazy loading so exempt this file  */
/*
Copyright 2020 Balena

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import type * as BalenaSdk from 'balena-sdk';
import type * as visuals from 'resin-cli-visuals';
import type * as CliForm from 'resin-cli-form';
import type { ux } from '@oclif/core';
const { version } =
	require('../../package.json') as typeof import('../../package.json');

// Equivalent of _.once but avoiding the need to import lodash for lazy deps
const once = <T>(fn: () => T) => {
	let cached: T;
	return (): T => {
		if (!cached) {
			cached = fn();
		}
		return cached;
	};
};

export const onceAsync = <T>(fn: () => Promise<T>) => {
	let cached: T;
	return async (): Promise<T> => {
		if (!cached) {
			cached = await fn();
		}
		return cached;
	};
};

const cliXBalenaClientHeaderInterceptor: BalenaSdk.Interceptor = {
	request($request) {
		if ($request.headers['X-Balena-Client']) {
			// We intentionally overwrite the sdk version string from the header
			// to conserve bandwidth. We only do that when the SDK already has specified
			// the X-Balena-Client header, since that signals that this is a safe url to
			// include the extra header and will not cause CORS errors.
			$request.headers['X-Balena-Client'] = `balena-cli/${version}`;
		}
		return $request;
	},
};

export const getBalenaSdk = once(() => {
	const sdk = (require('balena-sdk') as typeof BalenaSdk).fromSharedOptions();
	if (!sdk.interceptors.includes(cliXBalenaClientHeaderInterceptor)) {
		sdk.interceptors.push(cliXBalenaClientHeaderInterceptor);
	}
	return sdk;
});

export const getVisuals = once(
	() => require('resin-cli-visuals') as typeof visuals,
);

export const getCliForm = once(
	() => require('resin-cli-form') as typeof CliForm,
);

export const getCliUx = once(() => require('@oclif/core/ux').ux as typeof ux);

// Directly export stripIndent as we always use it immediately, but importing just `stripIndent` reduces startup time
export const stripIndent =
	// tslint:disable-next-line:no-var-requires
	require('common-tags/lib/stripIndent') as typeof import('common-tags/lib/stripIndent');