/**
 * @license
 * Copyright 2019 Balena Ltd.
 *
 * 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 * as Bluebird from 'bluebird';
import { spawn, StdioOptions } from 'child_process';
import * as _ from 'lodash';
import { TypedError } from 'typed-error';

export class ExecError extends TypedError {
	public cmd: string;
	public exitCode: number;

	constructor(cmd: string, exitCode: number) {
		super(`Command '${cmd}' failed with error: ${exitCode}`);
		this.cmd = cmd;
		this.exitCode = exitCode;
	}
}

export async function exec(
	deviceIp: string,
	cmd: string,
	stdout?: NodeJS.WritableStream,
): Promise<void> {
	const { which } = await import('./helpers');
	const program = await which('ssh');
	const args = [
		'-n',
		'-t',
		'-p',
		'22222',
		'-o',
		'LogLevel=ERROR',
		'-o',
		'StrictHostKeyChecking=no',
		'-o',
		'UserKnownHostsFile=/dev/null',
		`root@${deviceIp}`,
		cmd,
	];
	if (process.env.DEBUG) {
		const logger = (await import('./logger')).getLogger();
		logger.logDebug(`Executing [${program},${args}]`);
	}

	// Note: stdin must be 'inherit' to workaround a bug in older versions of
	// the built-in Windows 10 ssh client that otherwise prints the following
	// to stderr and hangs: "GetConsoleMode on STD_INPUT_HANDLE failed with 6"
	// They fixed the bug in newer versions of the ssh client:
	// https://github.com/PowerShell/Win32-OpenSSH/issues/856
	// but users whould have to manually download and install a new client.
	// Note that "ssh -n" does not solve the problem, but should in theory
	// prevent the ssh client from using the CLI process stdin, even if it
	// is connected with 'inherit'.
	const stdio: StdioOptions = [
		'inherit',
		stdout ? 'pipe' : 'inherit',
		'inherit',
	];

	const exitCode = await new Bluebird<number>((resolve, reject) => {
		const ps = spawn(program, args, { stdio })
			.on('error', reject)
			.on('close', resolve);

		if (stdout) {
			ps.stdout.pipe(stdout);
		}
	});
	if (exitCode !== 0) {
		throw new ExecError(cmd, exitCode);
	}
}

export async function execBuffered(
	deviceIp: string,
	cmd: string,
	enc?: string,
): Promise<string> {
	const through = await import('through2');
	const buffer: string[] = [];
	await exec(
		deviceIp,
		cmd,
		through(function(data, _enc, cb) {
			buffer.push(data.toString(enc));
			cb();
		}),
	);
	return buffer.join('');
}

/**
 * Return a device's balenaOS release by executing 'cat /etc/os-release'
 * over ssh to the given deviceIp address.  The result is cached with
 * lodash's memoize.
 */
export const getDeviceOsRelease = _.memoize(async (deviceIp: string) =>
	execBuffered(deviceIp, 'cat /etc/os-release'),
);