index.js

#!/usr/bin/env node

const { spawn } = require("child_process");
const util = require("util");
const exec = util.promisify(require("child_process").exec);
const { writeFileSync } = require("fs");
const chalk = require("chalk");

const COMMAND_PREFIX = ";;";
const COMMANDS = {
  help: () => {
    console.log("This is the help info");
  },
  macro: () => {
    console.log("Recording... (Press Escape to End)");
  },
  hello_world: () => {
      console.log("Hi Eric!");
  }
};

//https://en.wikipedia.org/wiki/Modifier_key
const modifiers = {
    SHIFT: {
        names: ["Shift_R", "Shift_L"],
        active: false
    },
    CTRL: {
        names: ["Control_R", "Control_L"],
        active: false
    }
};

let human_readable_history = [];
const max_human_readable_history_length =
  Math.max(...Object.keys(COMMANDS).map((cmd) => cmd.length)) +
  COMMAND_PREFIX.length;

function setModifier(name, value) {
    for (modifierName in modifiers) {
        const modifier = modifiers[modifierName];
        if (modifier.names.indexOf(name) >= 0) {
            modifier.active = value;
            return true;
        }
    }
}

function onLiteralKeyEvent(keyboard_map, key_bundle) {
  switch (key_bundle.action) {
    case "press":
      if (!setModifier(key_bundle.name, true)) {
          const mapping = keyboard_map[key_bundle.code];
          human_readable_history.push(modifiers.SHIFT.active ? mapping.shift : mapping.default)
      }

        const input = toUTF8(human_readable_history);

        for (commandName of Object.keys(COMMANDS)) {
            if (input.endsWith(COMMAND_PREFIX + commandName)) {
                COMMANDS[commandName]();
                break;
            }
        }
      break;
    case "release":
        setModifier(key_bundle.name, false);
  }

  human_readable_history = human_readable_history.slice(-max_human_readable_history_length);
}

function toUTF8(arr) {
    return Buffer.from(arr).toString("utf8");
}

(async () => {
  writeFileSync(
    "/tmp/xinput_capture",
    `#!/usr/bin/env bash
xinput list |
  grep -Po 'id=\\K\\d+(?=.*slave\\s*keyboard)' |
  xargs -P0 -n1 xinput test |
  awk 'BEGIN{while (("xmodmap -pke" | getline) > 0) k[$2]=$4}
     {print $0 k[$NF]; fflush("/dev/stdout")}'`
  );

  //http://wiki.linuxquestions.org/wiki/List_of_Keysyms_Recognised_by_Xmodmap
  // https://www.cl.cam.ac.uk/~mgk25/ucs/keysymdef.h
  const keyboard_map = (await exec("xmodmap -pk")).stdout
    .split("\n")
    .map((row) => row.split(/[\W]/).filter((c) => c))
      .reduce((map, row) => {
          row = [...row, "", "", "", "", "", "", ""];
          map[row[0]] = {default: row[1], shift: row[3]};
          return map;
      }, {});

  console.log(`${chalk.green('✓')} Loaded ${Object.keys(keyboard_map).length} key map`);

  const xinput_capture = spawn("bash", ["/tmp/xinput_capture"]);

  xinput_capture.stdout.on("data", (data) =>
    data
      .toString()
      .trim()
      .split(/\W/)
      .filter((d) => d && d !== "key")
      .join(",")
      .match(/([^,]+,[^,]+,[^,]+),?/g)
      .map((match) => {
        const [action, code, name] = match.split(",");
        return { action, code, name };
      })
      .forEach(onLiteralKeyEvent.bind(null, keyboard_map))
  );

    console.log(`${chalk.green('✓')} Listening for keystrokes...`);
})();

package.json

{
  "name": "keyro",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "bin": "./index.js",
  "dependencies": {
    "chalk": "^4.1.0"
  }
}