import { describe, it, expect } from 'vitest';
import { generateTask, TARGETS, type Target } from './tasks';

describe('generateTask', () => {
  it.each(TARGETS)('produces a valid decomposition for target %i', (target) => {
    for (let i = 0; i < 50; i++) {
      const task = generateTask(target);
      expect(task.target).toBe(target);
      expect(task.given).toBeGreaterThanOrEqual(1);
      expect(task.given).toBeLessThanOrEqual(target - 1);
      expect(task.given + task.answer).toBe(target);
    }
  });

  it('always includes the correct answer in choices', () => {
    for (const target of TARGETS) {
      for (let i = 0; i < 30; i++) {
        const task = generateTask(target);
        expect(task.choices).toContain(task.answer);
      }
    }
  });

  it('produces choices without duplicates', () => {
    for (const target of TARGETS) {
      for (let i = 0; i < 30; i++) {
        const task = generateTask(target);
        const unique = new Set(task.choices);
        expect(unique.size).toBe(task.choices.length);
      }
    }
  });

  it('returns 3 choices for targets >= 5', () => {
    for (const target of [5, 6, 7, 8, 9, 10] as Target[]) {
      const task = generateTask(target);
      expect(task.choices.length).toBe(3);
    }
  });

  it('returns 3 choices for target 4 (3 possible answers total)', () => {
    const task = generateTask(4);
    expect(task.choices.length).toBe(3);
  });

  it('avoids reusing the same given when possible', () => {
    const target: Target = 7;
    const prev = generateTask(target);
    let differed = 0;
    for (let i = 0; i < 50; i++) {
      const t = generateTask(target, prev);
      if (t.given !== prev.given) differed++;
    }
    expect(differed).toBe(50);
  });
});