static/js/history.js

class History {
  constructor(maxStates = 50) {
    this.states = [];
    this.currentIndex = -1;
    this.maxStates = maxStates;
  }

  push(state) {
    // Remove any states after current index
    this.states = this.states.slice(0, this.currentIndex + 1);
    
    // Add new state
    this.states.push(state);
    
    // Remove oldest state if exceeding maxStates
    if (this.states.length > this.maxStates) {
      this.states.shift();
    }
    
    this.currentIndex = this.states.length - 1;
  }

  undo() {
    if (this.currentIndex > 0) {
      this.currentIndex--;
      return this.states[this.currentIndex];
    }
    return null;
  }

  redo() {
    if (this.currentIndex < this.states.length - 1) {
      this.currentIndex++;
      return this.states[this.currentIndex];
    }
    return null;
  }

  canUndo() {
    return this.currentIndex > 0;
  }

  canRedo() {
    return this.currentIndex < this.states.length - 1;
  }
}