import { describe, it, expect } from 'vitest';
import { History } from '../src/state/history';

describe('History', () => {
  it('starts with nothing to undo or redo', () => {
    const h = new History('initial');
    expect(h.canUndo).toBe(false);
    expect(h.canRedo).toBe(false);
    expect(h.undo()).toBeUndefined();
    expect(h.redo()).toBeUndefined();
  });

  it('undoes and redoes pushed states in order', () => {
    const h = new History('s0');
    h.push('s1');
    h.push('s2');
    expect(h.undo()).toBe('s1');
    expect(h.undo()).toBe('s0');
    expect(h.canUndo).toBe(false);
    expect(h.redo()).toBe('s1');
    expect(h.redo()).toBe('s2');
    expect(h.canRedo).toBe(false);
  });

  it('clears the redo stack on a new push after undo', () => {
    const h = new History('s0');
    h.push('s1');
    h.push('s2');
    h.undo(); // back to s1
    h.push('s3');
    expect(h.canRedo).toBe(false);
    expect(h.undo()).toBe('s1');
    expect(h.redo()).toBe('s3');
  });

  it('honors the depth limit by dropping oldest entries', () => {
    const h = new History(0, 3);
    for (let i = 1; i <= 10; i += 1) h.push(i);
    let undos = 0;
    while (h.canUndo) {
      h.undo();
      undos += 1;
    }
    expect(undos).toBe(3);
    expect(h.peek()).toBe(7);
  });

  it('reset replaces state and clears both stacks', () => {
    const h = new History('a');
    h.push('b');
    h.undo();
    h.reset('fresh');
    expect(h.canUndo).toBe(false);
    expect(h.canRedo).toBe(false);
    expect(h.peek()).toBe('fresh');
  });
});