import { describe, it, expect } from 'vitest';
import { createHistory } from './history';

describe('createHistory', () => {
  it('starts empty; undo/redo are no-ops', () => {
    const h = createHistory<number>();
    expect(h.canUndo()).toBe(false);
    expect(h.canRedo()).toBe(false);
    expect(h.undo(1)).toBeUndefined();
    expect(h.redo(1)).toBeUndefined();
  });

  it('records pre-edit snapshots, then undoes and redoes through them', () => {
    const h = createHistory<string>();
    // document went a -> b (record a) -> c (record b); current is 'c'
    h.record('a');
    h.record('b');
    expect(h.canUndo()).toBe(true);

    expect(h.undo('c')).toBe('b'); // current 'c' pushed to redo
    expect(h.canRedo()).toBe(true);
    expect(h.undo('b')).toBe('a');
    expect(h.canUndo()).toBe(false);

    expect(h.redo('a')).toBe('b');
    expect(h.redo('b')).toBe('c');
    expect(h.canRedo()).toBe(false);
  });

  it('record() clears the redo stack (no dead redo after a fresh edit)', () => {
    const h = createHistory<string>();
    h.record('a');
    h.undo('b'); // redo now holds 'b'
    expect(h.canRedo()).toBe(true);
    h.record('x');
    expect(h.canRedo()).toBe(false);
  });

  it('caps the stack depth', () => {
    const h = createHistory<number>(3);
    for (let i = 0; i < 5; i++) h.record(i);
    let undos = 0;
    let cur = 99;
    while (h.canUndo()) {
      cur = h.undo(cur)!;
      undos++;
    }
    expect(undos).toBe(3);
  });

  it('clear() empties both stacks', () => {
    const h = createHistory<number>();
    h.record(1);
    h.undo(2);
    h.clear();
    expect(h.canUndo()).toBe(false);
    expect(h.canRedo()).toBe(false);
  });
});