function createUser(
  name,
  role = "viewer",
  permissions = [role],
  metadata = { createdBy: name, level: permissions.length }
) {
  return { name, role, permissions, metadata };
}

const user1 = createUser("Carlos");
const user2 = createUser("Diana", "admin", ["read", "write", "delete"]);
const user3 = createUser("Eve", "editor", undefined, { createdBy: "system", level: 99 });

console.log(user1.role, user1.permissions, user1.metadata.level);
console.log(user2.metadata.createdBy, user2.permissions.length);
console.log(user3.permissions[0], user3.metadata.level);

const name = "Carlos";
const age = 28;
const score = 95;

const player = {
  name,
  age,
  score,
  greet() {
    return `${this.name} (${this.age}) scored ${this.score}`;
  },
  get rank() {
    return this.score >= 90 ? "Gold" : "Silver";
  }
};

const { name: playerName, rank, greet } = player;

console.log(`${playerName} | ${rank} | ${greet.call(player)}`);

const config = {
  host: "localhost",
  port: 3000,
  db: {
    name: "mydb",
    retries: 5
  }
};

Object.freeze(config);

config.port = 9999;
config.newProp = "injected";
config.db.retries = 99;
delete config.host;

console.log(
  config.port,
  config.newProp,
  config.db.retries,
  config.host
);

const memoize = (fn) => {
  const cache = new Map();
  return (...args) => {
    const key = JSON.stringify(args);
    if (cache.has(key)) {
      return cache.get(key);
    }
    const result = fn(...args);
    cache.set(key, result);
    return result;
  };
};

let callCount = 0;

const expensiveMultiply = memoize((a, b) => {
  callCount++;
  return a * b;
});

console.log(expensiveMultiply(3, 4));
console.log(expensiveMultiply(3, 4));
console.log(expensiveMultiply(2, 5));
console.log(expensiveMultiply(3, 4));
console.log(`calls: ${callCount}`);

const config = {
  version: 1,
  settings: { theme: "dark", fontSize: 14 },
  tags: ["beta", "v1"],
};

Object.seal(config);
Object.freeze(config.settings);

config.version = 99;
config.newProp = "ignored";
delete config.tags;

config.settings.theme = "light";
config.settings.newKey = "ignored";

config.tags.push("v2");
config.tags[0] = "stable";

console.log(
  config.version,
  config.newProp,
  config.settings.theme,
  config.tags
);

"use strict";

function createCounter() {
  let count = 0;

  return {
    increment() { count++; },
    get value() { return count; },
    reset: function() { count = 0; }
  };
}

const counter = createCounter();
counter.increment();
counter.increment();
counter.increment();

const { value, reset } = counter;
reset();

console.log(counter.value, value);

const delay = (val) => Promise.resolve(val);

async function pipeline(input) {
  const result = await delay(input)
    .then((v) => v * 2)
    .then((v) => v + 10)
    .then((v) => {
      if (v > 20) throw new Error(`Too large: ${v}`);
      return v;
    })
    .catch((e) => `Caught: ${e.message}`)
    .then((v) => (typeof v === "string" ? v.toUpperCase() : v * 3));

  return result;
}

Promise.all([pipeline(4), pipeline(8)]).then(([a, b]) => {
  console.log(a);
  console.log(b);
});

const handler = {
  get(target, prop, receiver) {
    if (prop in target) {
      return Reflect.get(target, prop, receiver) * 2;
    }
    return `${prop} not found`;
  },
  set(target, prop, value) {
    if (typeof value !== "number") {
      throw new TypeError("Only numbers allowed");
    }
    target[prop] = value + 10;
    return true;
  },
  has(target, prop) {
    return prop.startsWith("x") ? false : prop in target;
  },
};

const obj = new Proxy({ score: 5, xp: 100 }, handler);

obj.level = 3;
console.log(obj.score);
console.log(obj.level);
console.log("xp" in obj);
console.log("score" in obj);
console.log(obj.rank);