import { describe, it, expect } from 'vitest';
import { hash32, makeRng, rollFor } from '../src/sim/rng.js';

describe('rng', () => {
  it('hash32 is deterministic and spreads', () => {
    expect(hash32('abc')).toBe(hash32('abc'));
    expect(hash32('abc')).not.toBe(hash32('abd'));
  });

  it('makeRng produces a deterministic sequence in [0,1)', () => {
    const a = makeRng(42), b = makeRng(42);
    for (let i = 0; i < 100; i++) {
      const v = a();
      expect(v).toBe(b());
      expect(v).toBeGreaterThanOrEqual(0);
      expect(v).toBeLessThan(1);
    }
  });

  it('rollFor depends on seed and label, independently', () => {
    expect(rollFor('s1', 'x')).toBe(rollFor('s1', 'x'));
    expect(rollFor('s1', 'x')).not.toBe(rollFor('s1', 'y'));
    expect(rollFor('s1', 'x')).not.toBe(rollFor('s2', 'x'));
  });

  it('rollFor is roughly uniform', () => {
    let sum = 0;
    for (let i = 0; i < 2000; i++) sum += rollFor('u', `l${i}`);
    expect(sum / 2000).toBeGreaterThan(0.45);
    expect(sum / 2000).toBeLessThan(0.55);
  });
});