import type { RandomSource } from './random-source';
import { rollInclusive } from './roll-range';

function fixed(...values: number[]): RandomSource {
  let index = 0;
  return { next: () => values[index++] };
}

describe('rollInclusive', () => {
  it('maps the bottom of the random range to min and the top to max', () => {
    expect(rollInclusive(fixed(0), 4, 7)).toBe(4);
    expect(rollInclusive(fixed(0.999), 4, 7)).toBe(7);
  });

  it('spreads the random range evenly across every value in between', () => {
    expect(rollInclusive(fixed(0.25), 4, 7)).toBe(5);
    expect(rollInclusive(fixed(0.5), 4, 7)).toBe(6);
    expect(rollInclusive(fixed(0.5), 9, 15)).toBe(12);
  });

  it('never exceeds max even if the source yields exactly 1', () => {
    expect(rollInclusive(fixed(1), 9, 15)).toBe(15);
  });

  it('returns the single value when min equals max', () => {
    expect(rollInclusive(fixed(0.7), 1, 1)).toBe(1);
  });
});