'use strict';

/**
 * The proven half of Link 2.
 *
 * Two grains were tested. These lock the one that earned a place and the
 * refusals that keep the other from creeping back in.
 */

const pq = require('../../src/services/model/penQuality');

const games = (n, q) => Array.from({ length: n }, () => ({ quality: q }));

describe('abstains rather than imputing', () => {
  it('an arm below the appearance floor has no readable quality', () => {
    expect(pq.armQuality({ pa: 12, hits: 3 })).toBeNull();
    expect(pq.armQuality({ pa: 60, hits: 12 })).toBeCloseTo(0.2, 6);
  });

  it('a club with too few prior games returns null, not a league-average pen', () => {
    // A league-average stand-in asserts "this is an ordinary bullpen" — a claim,
    // and usually the wrong one for exactly the clubs whose pens just turned over.
    expect(pq.projectPen(games(3, 0.22))).toBeNull();
    expect(pq.projectPen([])).toBeNull();
    expect(pq.projectPen(null)).toBeNull();
    expect(pq.projectPen(games(8, 0.22)).readable).toBe(true);
  });

  it('unreadable quality produces no shift at all', () => {
    expect(pq.hitRateShift(null)).toBeNull();
    expect(pq.hitRateShift(undefined)).toBeNull();
  });
});

describe('the grain that proved, and the two that did not', () => {
  it('reports pen QUALITY and names what it refuses', () => {
    const pen = pq.projectPen(games(10, 0.24));
    expect(pen.grain).toBe('pen_quality');
    expect(pen.individual_arm_refused).toMatch(/17.2%/);
    expect(pen.archetype_refused).toMatch(/did not prove/);
    // The module must not offer an archetype — that grain did not earn one.
    expect(pen.archetype).toBeUndefined();
  });
});

describe('the shift follows the measured direction', () => {
  it('a weaker pen raises the hit rate, a stronger one lowers it', () => {
    expect(pq.hitRateShift(0.26)).toBeGreaterThan(0);
    expect(pq.hitRateShift(0.19)).toBeLessThan(0);
    expect(pq.hitRateShift(pq.LEAGUE_PEN_QUALITY)).toBeCloseTo(0, 6);
  });

  it('is bounded — it was measured over a range, not extrapolated past one', () => {
    expect(pq.hitRateShift(0.9)).toBeLessThanOrEqual(pq.MAX_SHIFT + 1e-9);
    expect(pq.hitRateShift(0.01)).toBeGreaterThanOrEqual(-pq.MAX_SHIFT - 1e-9);
  });

  it('reproduces the measured tercile separation', () => {
    // Predicted-best pens averaged 0.2114 actual quality and a 0.2231 realized
    // hit rate; predicted-worst 0.2425 and 0.2501 — a 2.70pp gap.
    const gap = pq.hitRateShift(0.2425) - pq.hitRateShift(0.2114);
    expect(gap).toBeGreaterThan(0.02);
    expect(gap).toBeLessThan(0.035);
  });
});

describe('reasoning is true or absent', () => {
  it('no read means no sentence', () => {
    expect(pq.explain(null)).toBeNull();
    expect(pq.explain({ readable: false })).toBeNull();
  });

  it('names the direction and how much was read', () => {
    expect(pq.explain(pq.projectPen(games(12, 0.25)))).toMatch(/weaker than league over 12 prior games/);
    expect(pq.explain(pq.projectPen(games(12, 0.20)))).toMatch(/stronger than league/);
    expect(pq.explain(pq.projectPen(games(12, 0.2261)))).toMatch(/league-average/);
  });
});