import { test } from 'node:test';
import assert from 'node:assert/strict';
import { createRng } from '../src/engine/rng.js';

test('the same seed produces the same sequence', () => {
  const a = createRng('seed-one');
  const b = createRng('seed-one');
  const draws = Array.from({ length: 20 }, () => [a.next(), b.next()]);
  for (const [x, y] of draws) assert.equal(x, y);
});

test('different seeds diverge', () => {
  const a = Array.from({ length: 10 }, (_, i) => createRng('one').next());
  const b = Array.from({ length: 10 }, (_, i) => createRng('two').next());
  assert.notDeepEqual(a, b);
});

test('a generator resumes exactly from a saved position', () => {
  const original = createRng('resume-me');
  for (let i = 0; i < 7; i++) original.next();
  const position = original.getPosition();

  const resumed = createRng('resume-me', position);
  const expected = Array.from({ length: 5 }, () => original.next());
  const actual = Array.from({ length: 5 }, () => resumed.next());
  assert.deepEqual(actual, expected);
});

test('a saved position survives a JSON round trip', () => {
  const rng = createRng('json');
  rng.next();
  const revived = createRng('json', JSON.parse(JSON.stringify(rng.getPosition())));
  assert.equal(revived.next(), createRng('json', rng.getPosition()).next());
});

test('draws stay in range', () => {
  const rng = createRng('range');
  for (let i = 0; i < 500; i++) {
    const value = rng.next();
    assert.ok(value >= 0 && value < 1);
    assert.ok(rng.int(10) >= 0 && rng.int(10) < 10);
  }
});

test('weighted picks respect weight and skip zero-weight entries', () => {
  const rng = createRng('weighted');
  const items = [{ id: 'common', w: 99 }, { id: 'rare', w: 1 }, { id: 'never', w: 0 }];
  const counts = { common: 0, rare: 0, never: 0 };
  for (let i = 0; i < 2000; i++) counts[rng.weighted(items, (i2) => i2.w).id]++;
  assert.equal(counts.never, 0, 'zero weight must never be drawn');
  assert.ok(counts.common > counts.rare * 10, `expected common to dominate, got ${JSON.stringify(counts)}`);
  assert.ok(counts.rare > 0, 'a weight of 1 in 100 should still appear over 2000 draws');
});

test('weighted returns undefined when nothing has weight', () => {
  const rng = createRng('empty');
  assert.equal(rng.weighted([{ w: 0 }], (i) => i.w), undefined);
  assert.equal(rng.weighted([], () => 1), undefined);
});