class SimpleCalculator {
  constructor(containerId) {
    this.container = document.getElementById(containerId);
    if (!this.container) return;
    this.currentInput = "0";
    this.previousInput = "";
    this.operation = null;
    this.init();
  }

  init() {
    this.container.innerHTML = `
      <div class="w-72 bg-slate-800 p-4 rounded-2xl shadow-xl select-none text-slate-100">
        <!-- Écran avec une hauteur fixe (min-h) pour éviter qu'il ne rétrécisse -->
        <div id="calc-screen" class="bg-slate-900 text-right p-4 rounded-xl mb-4 text-2xl font-mono tracking-wider overflow-hidden min-h-[4rem] flex flex-col justify-center">
          <div id="calc-prev" class="text-xs text-slate-400 h-4"></div>
          <div id="calc-current">0</div>
        </div>
        <!-- Clavier -->
        <div class="grid grid-cols-4 gap-2">
          <button data-action="clear" class="col-span-2 bg-red-600 hover:bg-red-500 p-3 rounded-xl font-bold transition">AC</button>
          <button data-action="delete" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">⌫</button>
          <button data-action="operator" data-value="/" class="bg-amber-600 hover:bg-amber-500 p-3 rounded-xl font-bold transition">÷</button>
          
          <button data-action="number" data-value="7" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">7</button>
          <button data-action="number" data-value="8" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">8</button>
          <button data-action="number" data-value="9" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">9</button>
          <button data-action="operator" data-value="*" class="bg-amber-600 hover:bg-amber-500 p-3 rounded-xl font-bold transition">×</button>
          
          <button data-action="number" data-value="4" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">4</button>
          <button data-action="number" data-value="5" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">5</button>
          <button data-action="number" data-value="6" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">6</button>
          <button data-action="operator" data-value="-" class="bg-amber-600 hover:bg-amber-500 p-3 rounded-xl font-bold transition">-</button>
          
          <button data-action="number" data-value="1" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">1</button>
          <button data-action="number" data-value="2" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">2</button>
          <button data-action="number" data-value="3" class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">3</button>
          <button data-action="operator" data-value="+" class="bg-amber-600 hover:bg-amber-500 p-3 rounded-xl font-bold transition">+</button>
          
          <button data-action="number" data-value="0" class="col-span-2 bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">0</button>
          <button data-action="number" data-value="." class="bg-slate-700 hover:bg-slate-600 p-3 rounded-xl font-bold transition">.</button>
          <button data-action="calculate" class="bg-emerald-600 hover:bg-emerald-500 p-3 rounded-xl font-bold transition">=</button>
        </div>
      </div>
    `;

    this.prevScreen = this.container.querySelector("#calc-prev");
    this.currentScreen = this.container.querySelector("#calc-current");
    this.addListeners();
  }

  addListeners() {
    this.container.addEventListener("click", (e) => {
      const button = e.target.closest("button");
      if (!button) return;

      const action = button.getAttribute("data-action");
      const value = button.getAttribute("data-value");

      if (action === "number") {
        this.appendNumber(value);
      } else if (action === "operator") {
        this.chooseOperation(value);
      } else if (action === "calculate") {
        this.compute();
      } else if (action === "clear") {
        this.clear();
      } else if (action === "delete") {
        this.deleteDigit();
      }

      this.updateScreen();
    });
  }

  appendNumber(number) {
    if (number === "." && this.currentInput.includes(".")) return;
    if (this.currentInput === "0" && number !== ".") {
      this.currentInput = number;
    } else {
      this.currentInput += number;
    }
  }

  chooseOperation(op) {
    if (this.currentInput === "") return;
    if (this.previousInput !== "") {
      this.compute();
    }
    this.operation = op;
    this.previousInput = this.currentInput;
    this.currentInput = "";
  }

  compute() {
    let computation;
    const prev = parseFloat(this.previousInput);
    const current = parseFloat(this.currentInput);
    if (isNaN(prev) || isNaN(current)) return;

    switch (this.operation) {
      case "+":
        computation = prev + current;
        break;
      case "-":
        computation = prev - current;
        break;
      case "*":
        computation = prev * current;
        break;
      case "/":
        computation = current === 0 ? "Erreur" : prev / current;
        break;
      default:
        return;
    }

    this.currentInput = computation.toString();
    this.operation = null;
    this.previousInput = "";
  }

  clear() {
    this.currentInput = "0";
    this.previousInput = "";
    this.operation = null;
  }

  deleteDigit() {
    if (this.currentInput.length === 1) {
      this.currentInput = "0";
    } else {
      this.currentInput = this.currentInput.slice(0, -1);
    }
  }

  updateScreen() {
    this.currentScreen.innerText =
      this.currentInput === "" ? "0" : this.currentInput;
    if (this.operation != null) {
      this.prevScreen.innerText = `${this.previousInput} ${this.operation}`;
    } else {
      this.prevScreen.innerText = "";
    }
  }
}