cli.js

#!/usr/bin/env node
"use strict";

const meow = require("meow");
const chalk = require("chalk");
const _ = require("lodash");

const cli = meow({
	help: ["Usage", "  $ convert [commands] [options]"]
});

let command_string = cli.input[1];
let input_string = cli.input[2];

// ===========================================================

const keyboard = [
	"1",
	"2",
	"3",
	"4",
	"5",
	"6",
	"7",
	"8",
	"9",
	"0",
	"Q",
	"W",
	"E",
	"R",
	"T",
	"Y",
	"U",
	"I",
	"O",
	"P",
	"A",
	"S",
	"D",
	"F",
	"G",
	"H",
	"J",
	"K",
	"L",
	";",
	"Z",
	"X",
	"C",
	"V",
	"B",
	"N",
	"M",
	",",
	".",
	"/"
];
const keyboardMap = {};

keyboard.forEach(function(val, idx) {
	keyboardMap[val] = idx;
});

function coordinateToIndex(x, y) {
	return 10 * x + y;
}

function indexToCoordinate(i) {
	let x = Math.floor(i / 10);
	let y = i % 10;
	return [x, y];
}

function horizontalFlip(i) {
	const [x, y] = indexToCoordinate(i);
	const newY = 9 - y;
	const result = coordinateToIndex(x, newY);
	return result;
}
function verticalFlip(i) {
	const [x, y] = indexToCoordinate(i);
	const newX = 3 - x;
	return coordinateToIndex(newX, y);
}

function shift(n, i) {
	const newIdx = i - n;
	return newIdx < 0 ? shift(40, newIdx) : newIdx % 40;
}

const re = /(H|V|S(-?\d+))/g;
function getMutator(rule) {
	let m;
	const result = [];

	while ((m = re.exec(rule))) {
		if (m[1] === "H") {
			result.push(horizontalFlip);
			continue;
		}
		if (m[1] === "V") {
			result.push(verticalFlip);
			continue;
		}

		if (m[1].indexOf("S") === 0) {
			result.push(shift.bind(null, parseInt(m[2])));
			continue;
		}
	}
	return _.flow(result);
}

function translateString(rule, text) {
	const mutator = getMutator(rule);

	const result = text.split("").map(function(char) {
		const charIdx = keyboardMap[char.toUpperCase()];
		const newIdx = mutator(charIdx);
		return keyboard[newIdx];
	});
	return result.join("");
}

console.log(translateString(command_string, input_string));