vyndr/tests/unit/hitsFactors.test.js

'use strict';

/**
 * The three proven hits factors, on the serving path at last.
 *
 * What these lock: the SIGN each factor moves the forecast, and that every
 * unreadable case leaves it completely alone. A factor that nudges toward a
 * default on missing input is fabricating a read from an absence.
 */

const hf = require('../../src/services/model/hitsFactors');

const pullGround = { pull_gb: 0.45, straight_gb: 0.10, oppo_gb: 0.05, pull_air: 0.20, straight_air: 0.12, oppo_air: 0.08 };
const pos = (o) => Object.fromEntries(Object.entries(o).map(([k, v]) => [k, { oaa: v, fielders: 2 }]));
const side = (avg, pa) => ({ pa, atBats: Math.round(pa * 0.9), hits: Math.round(pa * 0.9 * avg) });
const bigSplit = { vl: side(0.284, 183), vr: side(0.221, 291) };

describe('each factor moves the forecast in the direction it proved', () => {
  it('TOUGH spray defence lowers the hit forecast', () => {
    const eliteLeft = pos({ '3B': 12, SS: 10, '1B': 0, '2B': 0, LF: 0, CF: 0, RF: 0 });
    const out = hf.adjustProbability(0.6, { spray: pullGround, bats: 'R', positionOaa: eliteLeft });
    expect(out.p_adjusted).toBeLessThan(0.6);
    expect(out.applied.map((a) => a.factor)).toContain('defense_by_direction');
  });

  it('a CONTACT-ALLOWING pitcher raises it; a bat-misser lowers it', () => {
    const soft = hf.adjustProbability(0.6, { pitcherHardHit: 0.46 });
    const tough = hf.adjustProbability(0.6, { pitcherHardHit: 0.31 });
    expect(soft.p_adjusted).toBeGreaterThan(0.6);
    expect(tough.p_adjusted).toBeLessThan(0.6);
  });

  it('a PLATOON disadvantage lowers it, the edge raises it', () => {
    const edge = hf.adjustProbability(0.6, { platoonSplits: bigSplit, bats: 'R', throws: 'L' });
    const wrongSide = hf.adjustProbability(0.6, { platoonSplits: bigSplit, bats: 'R', throws: 'R' });
    expect(edge.p_adjusted).toBeGreaterThan(0.6);
    expect(wrongSide.p_adjusted).toBeLessThan(0.6);
  });
});

describe('unreadable means UNTOUCHED, never nudged to a default', () => {
  it('a SWITCH hitter gets no spray adjustment', () => {
    const out = hf.adjustProbability(0.6, { spray: pullGround, bats: 'S', positionOaa: pos({ '3B': 12, SS: 10 }) });
    expect(out.applied.find((a) => a.factor === 'defense_by_direction')).toBeUndefined();
    expect(out.skipped.map((s) => s.factor)).toContain('defense_by_direction');
  });

  it('a THIN platoon split is refused, not shrunk toward league', () => {
    const thin = { vl: side(0.350, 25), vr: side(0.250, 400) };
    const out = hf.adjustProbability(0.6, { platoonSplits: thin, bats: 'R', throws: 'L' });
    expect(out.applied.find((a) => a.factor === 'platoon_severity')).toBeUndefined();
  });

  it('no pitcher profile contributes nothing at all', () => {
    expect(hf.pitcherContactMultiplier(null)).toBeNull();
    const out = hf.adjustProbability(0.6, { pitcherHardHit: null });
    expect(out.p_adjusted).toBe(0.6);
  });

  it('with NOTHING readable the forecast is returned exactly', () => {
    const out = hf.adjustProbability(0.6, {});
    expect(out.p_adjusted).toBe(0.6);
    expect(out.multiplier).toBe(1);
    expect(out.factors_fired).toBe(0);
  });

  it('a null forecast stays null — no factor invents one', () => {
    expect(hf.adjustProbability(null, { pitcherHardHit: 0.46 }).p_adjusted).toBeNull();
  });
});

describe('composition', () => {
  it('three factors compound, and the stack is bounded', () => {
    const out = hf.adjustProbability(0.6, {
      spray: pullGround, bats: 'R', positionOaa: pos({ '3B': -12, SS: -12, '1B': -12, '2B': -12, LF: -12, CF: -12, RF: -12 }),
      pitcherHardHit: 0.46, platoonSplits: bigSplit, throws: 'L',
    });
    expect(out.factors_fired).toBe(3);
    expect(out.multiplier).toBeLessThanOrEqual(1 + hf.COMBINED_MAX);
    expect(out.multiplier).toBeGreaterThanOrEqual(1 - hf.COMBINED_MAX);
  });

  it('partial readability applies only what is readable', () => {
    const out = hf.adjustProbability(0.6, { pitcherHardHit: 0.46, bats: 'S', spray: pullGround, positionOaa: pos({ '3B': 5 }) });
    expect(out.factors_fired).toBe(1);
    expect(out.applied[0].factor).toBe('pitcher_contact_profile');
  });
});