vyndr/tests/unit/skillModel.test.js

'use strict';

/**
 * THE FIVE DISCIPLINES, asserted as behaviour.
 *
 * These are not coverage tests. Each block locks one discipline so it cannot be
 * quietly abandoned later — which is exactly how the previous engine drifted
 * into a frequency counter with six wired-but-dead features hanging off it.
 */

const reg = require('../../src/services/model/featureRegistry');
const sk = require('../../src/services/model/skillProjection');

const BOMBER = { k_pct: 0.28, bb_pct: 0.11, barrel_pct: 0.16, hard_hit_pct: 0.52, avg_exit_velo: 93.5, avg_launch_angle: 19 };
const GHOST = { k_pct: 0.14, bb_pct: 0.07, barrel_pct: 0.02, hard_hit_pct: 0.30, avg_exit_velo: 85.0, avg_launch_angle: 6 };
const ACE = { k_pct: 0.32, bb_pct: 0.05, hard_hit_pct: 0.30, whiff_pct: 0.33 };
const BATTING_PRACTICE = { k_pct: 0.15, bb_pct: 0.10, hard_hit_pct: 0.46, whiff_pct: 0.18 };

afterEach(() => reg.__reset());

// ── DISCIPLINE 3 ──────────────────────────────────────────────────────────
describe('D3 — earn its place or it is out', () => {
  it('starts with an essentially EMPTY proven set — nothing is assumed to work', () => {
    const live = reg.liveFeatures('mlb');
    // Only the incumbent counter is PROVEN, and only because it was measured.
    expect([...live]).toEqual(['recent_frequency_prior']);
  });

  it('refuses promotion without a real sample, positive lift, and a CI above zero', () => {
    expect(reg.promote('mlb', 'batter_barrel_pct', null).ok).toBe(false);
    expect(reg.promote('mlb', 'batter_barrel_pct', { n: 10, lift: 0.05, ci95: [0.01, 0.09] }).ok).toBe(false);   // n too small
    expect(reg.promote('mlb', 'batter_barrel_pct', { n: 500, lift: -0.02, ci95: [-0.05, -0.01] }).ok).toBe(false); // negative lift
    expect(reg.promote('mlb', 'batter_barrel_pct', { n: 500, lift: 0.03, ci95: [-0.01, 0.07] }).ok).toBe(false);  // CI straddles zero
    expect(reg.statusOf('mlb', 'batter_barrel_pct')).toBe(reg.STATUS.CANDIDATE);
  });

  it('promotes on sufficient evidence, and records WHY', () => {
    const ev = { n: 600, lift: 0.04, ci95: [0.012, 0.068], measured_at: '2026-09-01' };
    expect(reg.promote('mlb', 'batter_barrel_pct', ev).ok).toBe(true);
    expect(reg.isLive('mlb', 'batter_barrel_pct')).toBe(true);
    expect(reg.liveFeatures('mlb').has('batter_barrel_pct')).toBe(true);
  });

  it('keeps DEAD features BY NAME so they are not silently rebuilt', () => {
    const s = reg.summary('mlb');
    const deadKeys = s.dead.map((d) => d.key);
    expect(deadKeys).toEqual(expect.arrayContaining([
      'champion_opp_rank_adj', 'champion_home_away_adj', 'champion_consistency_pull',
    ]));
    // and each carries the reason it died
    expect(s.dead.find((d) => d.key === 'champion_home_away_adj').why).toMatch(/harmful|IMPROVED/i);
  });

  it('per-sport: a feature proven for MLB says nothing about another sport', () => {
    reg.promote('mlb', 'batter_barrel_pct', { n: 600, lift: 0.04, ci95: [0.01, 0.07] });
    expect(reg.isLive('nba', 'batter_barrel_pct')).toBe(false);
    expect(reg.statusOf('nba', 'batter_barrel_pct')).toBeNull();
  });

  it('THE GATE: with only PROVEN features allowed, the skill model REFUSES', () => {
    // The proven set carries no contact-quality feature yet, so there is no
    // forward read to make. Refusing is the correct output — this is what stops
    // an unproven model reaching a user by accident.
    const out = sk.projectSkill({
      batter: BOMBER, pitcher: ACE, archetype: 'BOMBER', statType: 'hits', line: 0.5,
      expectedPa: 4.2, allowed: reg.liveFeatures('mlb'),
    });
    expect(out).toBeNull();
  });

  it('with CANDIDATES allowed (the challenger), it produces a read', () => {
    const out = sk.projectSkill({
      batter: BOMBER, pitcher: ACE, archetype: 'BOMBER', statType: 'hits', line: 0.5,
      expectedPa: 4.2, allowed: reg.candidateFeatures('mlb'),
    });
    expect(out).not.toBeNull();
    expect(out.p_over_line).toBeGreaterThan(0);
  });
});

describe('D3 — verdicts are PER STAT, because the physics differ', () => {
  it('a feature can be DEAD for one stat and still CANDIDATE for another', () => {
    // The first real gate run: every skill feature failed for `hits` (n=570,
    // max |r| 0.062) while hard-hit rate showed the strongest marginal
    // correlation yet seen for `total_bases` (r=0.153). A sport-wide DEAD mark
    // would have killed, on hits evidence, the features most alive on TB.
    reg.recordStatVerdict('mlb', 'hits', 'batter_barrel_pct', reg.STATUS.DEAD,
      { n: 570, r: -0.037, note: 'failed the gate for hits' });
    expect(reg.statusForStat('mlb', 'hits', 'batter_barrel_pct')).toBe(reg.STATUS.DEAD);
    expect(reg.statusForStat('mlb', 'total_bases', 'batter_barrel_pct')).toBe(reg.STATUS.CANDIDATE);
    expect(reg.candidateFeaturesForStat('mlb', 'hits').has('batter_barrel_pct')).toBe(false);
    expect(reg.candidateFeaturesForStat('mlb', 'total_bases').has('batter_barrel_pct')).toBe(true);
  });

  it('a stat with no verdict inherits the sport-level status', () => {
    expect(reg.statusForStat('mlb', 'runs', 'batter_exit_velo')).toBe(reg.STATUS.CANDIDATE);
    expect(reg.statusForStat('mlb', 'runs', 'champion_home_away_adj')).toBe(reg.STATUS.DEAD);
  });

  it('the live gate is per stat too, and still PROVEN-only', () => {
    expect(reg.liveFeaturesForStat('mlb', 'hits').has('batter_barrel_pct')).toBe(false);
    expect([...reg.liveFeaturesForStat('mlb', 'hits')]).toEqual(['recent_frequency_prior']);
  });
});

// ── DISCIPLINE 1 ──────────────────────────────────────────────────────────
describe('D1 — skill, not results: the pitcher actually moves the read', () => {
  const run = (pitcher) => sk.projectSkill({
    batter: BOMBER, pitcher, archetype: 'BOMBER', statType: 'hits', line: 0.5, expectedPa: 4.2,
  });

  it('a better pitcher LOWERS the projection for the same hitter', () => {
    const vsAce = run(ACE);
    const vsBP = run(BATTING_PRACTICE);
    expect(vsAce.p_over_line).toBeLessThan(vsBP.p_over_line);
    expect(vsAce.projected_value).toBeLessThan(vsBP.projected_value);
  });

  it('this is the thing the counter cannot do — no pitcher at all is a different read', () => {
    const noPitcher = run(null);
    expect(noPitcher).not.toBeNull();
    expect(noPitcher.pitcher_applied).toBe(false);
    expect(run(ACE).pitcher_applied).toBe(true);
  });

  it('the odds ratio returns league when both sides are league (the identity)', () => {
    expect(sk.oddsRatio(0.222, 0.222, 0.222)).toBeCloseTo(0.222, 6);
  });

  it('an average pitcher leaves the batter rate untouched', () => {
    expect(sk.oddsRatio(0.30, 0.222, 0.222)).toBeCloseTo(0.30, 6);
  });

  it('shrinks a thin sample toward its anchor, and leaves a full one alone', () => {
    expect(sk.shrink(0.60, 10, 200, 0.39)).toBeLessThan(0.45);   // 10-PA callup
    expect(sk.shrink(0.60, 5000, 200, 0.39)).toBeGreaterThan(0.59); // established
  });
});

// ── DISCIPLINE 2 ──────────────────────────────────────────────────────────
describe('D2 — archetype SELECTS features, it does not nudge', () => {
  it('the SAME hitter read through two archetypes gets materially different reads', () => {
    const asBomber = sk.projectSkill({ batter: BOMBER, pitcher: ACE, archetype: 'BOMBER', statType: 'hits', line: 0.5, expectedPa: 4.2 });
    const asGhost = sk.projectSkill({ batter: BOMBER, pitcher: ACE, archetype: 'GHOST', statType: 'hits', line: 0.5, expectedPa: 4.2 });
    // Not a rounding difference — a different feature map entirely.
    expect(Math.abs(asBomber.p_over_line - asGhost.p_over_line)).toBeGreaterThan(0.15);
  });

  it("a BOMBER's read is driven by barrels; a GHOST's is nearly blind to them", () => {
    expect(sk.featureMapFor('BOMBER').hitWeights.barrel).toBeGreaterThan(0.4);
    expect(sk.featureMapFor('GHOST').hitWeights.barrel).toBeLessThan(0.1);
    expect(sk.featureMapFor('GHOST').hitWeights.gb_speed).toBeGreaterThan(0.5);
    expect(sk.featureMapFor('BOMBER').hitWeights.gb_speed).toBe(0);
  });

  it('barrel rate moves a BOMBER and barely moves a GHOST — features silent where they do not apply', () => {
    const move = (arch) => {
      const lo = sk.hitOnContact({ batter: { ...BOMBER, barrel_pct: 0.04 }, pitcher: ACE, park: 1, archetype: arch });
      const hi = sk.hitOnContact({ batter: { ...BOMBER, barrel_pct: 0.20 }, pitcher: ACE, park: 1, archetype: arch });
      return hi - lo;
    };
    expect(move('BOMBER')).toBeGreaterThan(move('GHOST') * 3);
  });

  it('an unknown archetype falls back to a balanced map, not a refusal', () => {
    const out = sk.projectSkill({ batter: BOMBER, pitcher: ACE, archetype: 'NOT_A_REAL_ONE', statType: 'hits', line: 0.5, expectedPa: 4.2 });
    expect(out).not.toBeNull();
    expect(out.archetype).toBe('NOT_A_REAL_ONE');
  });
});

// ── HONESTY ───────────────────────────────────────────────────────────────
describe('honesty — unknown is not zero, and absent beats invented', () => {
  it('no hitter profile → NO forward read (null), never a league-average guess', () => {
    expect(sk.projectSkill({ batter: null, pitcher: ACE, statType: 'hits', line: 0.5 })).toBeNull();
    expect(sk.projectSkill({ batter: {}, pitcher: ACE, statType: 'hits', line: 0.5 })).toBeNull();
  });

  it('a missing skill input is SILENT — it does not act as a measured zero', () => {
    const full = sk.hitOnContact({ batter: BOMBER, pitcher: ACE, park: 1, archetype: 'BOMBER' });
    const noBarrel = sk.hitOnContact({ batter: { ...BOMBER, barrel_pct: null }, pitcher: ACE, park: 1, archetype: 'BOMBER' });
    const zeroBarrel = sk.hitOnContact({ batter: { ...BOMBER, barrel_pct: 0 }, pitcher: ACE, park: 1, archetype: 'BOMBER' });
    expect(noBarrel).not.toBeNull();
    // A REAL zero is a fact and must read far lower than an ABSENT one.
    expect(zeroBarrel).toBeLessThan(noBarrel);
    expect(Math.abs(noBarrel - full)).toBeLessThan(Math.abs(zeroBarrel - full));
  });

  it('total_bases is COMPOUND, not a relabelled hits curve', () => {
    // The first cut multiplied hits by a constant bases-per-hit, which made
    // P(TB>=2) EXACTLY equal to P(hits>=1) — a relabel carrying no information a
    // hits model did not already have. It was refused rather than shipped. It is
    // now a real convolution over per-PA base outcomes, and this test locks the
    // property that distinguishes the two.
    const tb = sk.projectSkill({ batter: BOMBER, pitcher: ACE, archetype: 'BOMBER', statType: 'total_bases', line: 1.5, expectedPa: 4.2 });
    const hits = sk.projectSkill({ batter: BOMBER, pitcher: ACE, archetype: 'BOMBER', statType: 'hits', line: 0.5, expectedPa: 4.2 });
    expect(tb).not.toBeNull();
    expect(tb.family).toBe('pa_compound_bases_convolution');
    expect(tb.p_over_line).not.toBeCloseTo(hits.p_over_line, 3);   // NOT degenerate
    expect(tb.distribution.reduce((a, b) => a + b, 0)).toBeCloseTo(1, 2);
  });

  it('hit-type shares respond to power skill — a slugger homers more per hit', () => {
    const slugger = sk.hitTypeShares({ batter: BOMBER, archetype: 'BOMBER' });
    const slap = sk.hitTypeShares({ batter: GHOST, archetype: 'GHOST' });
    expect(slugger.homer).toBeGreaterThan(slap.homer * 3);
    expect(slap.single).toBeGreaterThan(slugger.single);
    // Shares are a distribution over hit types.
    for (const s of [slugger, slap]) {
      expect(s.single + s.double + s.triple + s.homer).toBeCloseTo(1, 6);
    }
  });

  it('an absent power read leaves the shares at league — never a guessed lean', () => {
    const noSkill = sk.hitTypeShares({ batter: { k_pct: 0.2 }, archetype: 'DEFAULT' });
    expect(noSkill).toEqual(sk.LEAGUE_HIT_SHARES);
  });

  it('the distribution is a real distribution and P(>=k) is monotone', () => {
    const out = sk.projectSkill({ batter: BOMBER, pitcher: ACE, archetype: 'BOMBER', statType: 'hits', line: 0.5, expectedPa: 4.2 });
    expect(out.distribution.reduce((a, b) => a + b, 0)).toBeCloseTo(1, 2);
    let prev = 1;
    for (let k = 1; k <= 5; k += 1) {
      const p = sk.atLeast(out.distribution, k);
      expect(p).toBeLessThanOrEqual(prev + 1e-9);
      prev = p;
    }
  });

  it('a hitter exactly at league on every axis lands on league BABIP — no invented lean', () => {
    const leagueBat = {
      k_pct: sk.LEAGUE.k_pct, bb_pct: sk.LEAGUE.bb_pct,
      barrel_pct: sk.LEAGUE.barrel_pct, hard_hit_pct: sk.LEAGUE.hard_hit_pct,
      avg_exit_velo: sk.LEAGUE.avg_exit_velo, avg_launch_angle: 12,
    };
    const boc = sk.hitOnContact({ batter: leagueBat, pitcher: { hard_hit_pct: sk.LEAGUE.hard_hit_pct }, park: 1, archetype: 'DEFAULT' });
    expect(boc).toBeCloseTo(sk.LEAGUE.babip, 2);
  });

  it('opportunity matters: more projected PA means a higher chance of one hit', () => {
    const few = sk.projectSkill({ batter: BOMBER, pitcher: ACE, archetype: 'BOMBER', statType: 'hits', line: 0.5, expectedPa: 2 });
    const many = sk.projectSkill({ batter: BOMBER, pitcher: ACE, archetype: 'BOMBER', statType: 'hits', line: 0.5, expectedPa: 5 });
    expect(many.p_over_line).toBeGreaterThan(few.p_over_line);
  });
});