// some templates you might use
var home = "<h1>homepage</h1>";
var about = "<h1>about page</h1>";

// maybe you get a string from the URL like
// site.com?page=home
// but how can you use 'home' to get the variable home ?

// Object to map keys to values
var pages = {
	home: home,
	about: "<h1>about page</h1>",
}; // you can use an object and [] notation, right?

// dynamic key lookup
var currentPage = "home";

document.body.innerHTML = pages[currentPage];

// example standalone functions of some sort
function goToBed() {
	console.log("The monster snuggles into bed and dreams of snacks!");
}

function chaseTheCat() { ... }

function chowDown() { ... }


// "factory" to dynamically select a function
function MonsterActionFactory(actionName) {
	const actions = {
		"go-to-bed": goToBed,
		"chaseTheCat": chaseTheCat,
		chowDown,
	}; // ^ rememember this is short-hand (you choose how to compose these)

	if (!actions[actionName]) {
		throw new Error(`No action found with name: ${actionName}`);
	}

	return actions[actionName];
}

// Example Usage
const bedtime = MonsterActionFactory('go-to-bed');
bedtime(); // The monster snuggles into bed and dreams of snacks!

// or

MonsterActionFactory('chowDown')(); // would just run itself

const MonsterRegistry = ( function() {
  // private variable to hold the single instance
  let instance;

  // Function to create the instance
  function createInstance() {
    return {
      monsters: [],
      addMonster(name) {
        this.monsters.push(name);
        console.log(`${name} has been added to the registry.`);
      },
      getMonsters() {
        return this.monsters;
      },
    };
  }

  // Public method to get the single instance
  return {
    getInstance() {
      if (!instance) {
        instance = createInstance();
      }
      return instance;
    },
  };
})();
// note IIFE

// example usage
const registry1 = MonsterRegistry.getInstance();
registry1.addMonster("Chunky"); // Output: "Chunky has been added to the registry."

const registry2 = MonsterRegistry.getInstance();
registry2.addMonster("Munchy"); // Output: "Munchy has been added to the registry."

console.log(registry1.getMonsters()); // Output: ["Chunky", "Munchy"]
console.log(registry1 === registry2); // Output: true (both are the same instance)

// module to manage monster inventory
const MonsterInventory = ( function() {
  // 'private' variables and methods (often denoted with an _underscore)
  let inventory = [];

  function logInventory() {
    console.log("Current inventory:", inventory.join(", "));
  }

  // Public API
  return {
    addMonster(name) {
      inventory.push(name);
      console.log(`${name} has been added to the inventory.`);
      logInventory();
    },
    removeMonster(name) {
      const index = inventory.indexOf(name);
      if (index > -1) {
        inventory.splice(index, 1);
        console.log(`${name} has been removed from the inventory.`);
      } else {
        console.log(`${name} is not in the inventory.`);
      }
      logInventory();
    },
    getInventory() {
      return [...inventory]; // Return a copy to prevent direct modification
    },
  };
})();

MonsterInventory.addMonster("Chunky"); // Output: Chunky has been added to the inventory.
MonsterInventory.addMonster("Munchy"); // Output: Munchy has been added to the inventory.
MonsterInventory.removeMonster("Chunky"); // Output: Chunky has been removed from the inventory.
console.log(MonsterInventory.getInventory()); // Output: ["Munchy"]

// Monster Observer for health monitoring
const MonsterHealth = (function () {
  let observers = []; // Private list of observers (functions)

  function notifyObservers(monster) {
    observers.forEach((observer) => observer(monster));
  }

  // Public API
  return {
    subscribe(observer) {
      observers.push(observer);
      console.log("A new observer has subscribed.");
    },
    unsubscribe(observer) {
      observers = observers.filter((obs) => obs !== observer);
      console.log("An observer has unsubscribed.");
    },
    updateHealth(monster, health) {
      monster.health = health;
      console.log(`${monster.name} now has ${health} health.`);
      notifyObservers(monster);
    },
  };
})();

// example Usage
const chunky = { name: "Chunky", health: 100 };
const munchy = { name: "Munchy", health: 80 };

// Define observers
function alertLowHealth(monster) {
  if (monster.health < 50) {
    console.log(`Warning! ${monster.name} has low health: ${monster.health}`);
  }
}

function logHealth(monster) {
  console.log(`Logging health: ${monster.name} is now at ${monster.health}.`);
}

// Subscribe observers
MonsterHealth.subscribe(alertLowHealth);
MonsterHealth.subscribe(logHealth);

// Update health
MonsterHealth.updateHealth(chunky, 40); 
// Logs: Warning! Chunky has low health: 40
// Logs: Logging health: Chunky is now at 40

MonsterHealth.updateHealth(munchy, 70); 
// Logs: Logging health: Munchy is now at 70