import { describe, expect, it } from "vitest";

import {
  generateProblem,
  generateSession,
  gradeAnswer,
} from "./parenthesis-sign";

describe("parenthesis sign problem engine", () => {
  it("generates a problem within the configured ranges", () => {
    for (let index = 0; index < 100; index += 1) {
      const problem = generateProblem();

      expect(Number.isInteger(problem.multiplier)).toBe(true);
      expect(problem.multiplier).toBeGreaterThanOrEqual(-9);
      expect(problem.multiplier).toBeLessThanOrEqual(-1);
      expect(problem.a).toBeGreaterThanOrEqual(1);
      expect(problem.a).toBeLessThanOrEqual(9);
      expect(problem.b).toBeGreaterThanOrEqual(1);
      expect(problem.b).toBeLessThanOrEqual(9);
      expect(problem.a).not.toBe(problem.b);
      expect(["+", "-"]).toContain(problem.operator);
    }
  });

  it("distributes the multiplier correctly for both operators", () => {
    for (let index = 0; index < 100; index += 1) {
      const problem = generateProblem();
      const signedB = problem.operator === "-" ? -problem.b : problem.b;

      expect(problem.distributedA).toBe(problem.multiplier * problem.a);
      expect(problem.distributedB).toBe(problem.multiplier * signedB);
    }
  });

  it("grades correct and incorrect answers", () => {
    const problem = generateProblem();

    const correctResult = gradeAnswer(problem, {
      a: problem.distributedA,
      b: problem.distributedB,
    });

    expect(correctResult.correct).toBe(true);
    expect(correctResult.userAnswer).toEqual([
      problem.distributedA,
      problem.distributedB,
    ]);

    expect(
      gradeAnswer(problem, {
        a: problem.distributedB,
        b: problem.distributedA,
      }).correct,
    ).toBe(false);
  });

  it("generates a session with unique problem keys", () => {
    const problems = generateSession(10);
    const keys = new Set(problems.map((problem) => problem.key));

    expect(problems).toHaveLength(10);
    expect(keys.size).toBe(10);
  });

  it("rejects impossible session sizes", () => {
    expect(() => generateSession(0)).toThrow();
    expect(() => generateSession(145)).toThrow();
  });
});