vyndr/tests/unit/opportunityDrift.test.js

'use strict';

/**
 * opportunity_drift — the axis, its input, and the guards that keep it honest
 * (2026-08-01).
 *
 * The three properties that matter more than the arithmetic:
 *   1. UNDEFINED drift is a NO-OP. `Number(null) === 0` would read as "zero
 *      at-bats" — the strongest possible fade — invented from missing data.
 *   2. It is a RATIO, not a level. The level is collinear with l20_avg (same
 *      denominator), so using it would double-count opportunity the projection
 *      already contains.
 *   3. It is labelled a PROXY. The real input is the confirmed batting order,
 *      which no wired source exposes.
 */

const { __internals } = require('../../src/services/intelligence/featureCache');
const { mlbGameLogFeatures, MLB_LOG_FIELD } = __internals;
const challenger = require('../../src/services/challengerProjection');
const { adjust, opportunityNudge, OPPORTUNITY_DEADBAND, MAX_OPPORTUNITY_NUDGE } = challenger;

const g = (atBats, hits) => ({ stat: { atBats, hits } });
const season = (hits, atBats, games) => ({ hits, atBats, gamesPlayed: games });

describe('per-game at-bats is mapped for the OPPORTUNITY input only', () => {
  it('MLB_LOG_FIELD maps at_bats to the real boxscore field', () => {
    expect(MLB_LOG_FIELD.at_bats).toBe('atBats');
  });

  it('is NOT added to the settlement map — nothing grades at-bats', () => {
    // The three MLB maps are split on purpose (CLAUDE.md). Adding at_bats to
    // the settle map would imply a settlement path for a market we don't carry.
    const outcome = require('../../src/services/outcomeService');
    const settleMap = (outcome.__internals && outcome.__internals.MLB_LOG_FIELD) || {};
    expect(settleMap.at_bats).toBeUndefined();
  });
});

describe('mlbGameLogFeatures — drift computation', () => {
  const logs = [g(4, 1), g(4, 2), g(4, 1), g(2, 0), g(2, 1), g(2, 0), g(2, 1), g(2, 0)];

  it('computes recent-5 AB/G over the season baseline', () => {
    const out = mlbGameLogFeatures({ found: true, last10: logs, season: season(60, 300, 75) }, 'hits');
    expect(out.ab_per_game).toBe(4);            // 300/75
    expect(out.recent_ab_per_game).toBe(2);     // last five games are 2 AB each
    expect(out.opportunity_drift).toBeCloseTo(0.5, 3);
  });

  it('is UNDEFINED when the logs carry no at-bats — never 1.0, never 0', () => {
    const noAb = [{ stat: { hits: 1 } }, { stat: { hits: 2 } }, { stat: { hits: 0 } }];
    const out = mlbGameLogFeatures({ found: true, last10: noAb, season: season(60, undefined, 75) }, 'hits');
    expect(out.opportunity_drift).toBeUndefined();
    expect(out.recent_ab_per_game).toBeUndefined();
  });

  it('is UNDEFINED without a season baseline to drift FROM', () => {
    const out = mlbGameLogFeatures({ found: true, last10: logs, season: season(60, undefined, 75) }, 'hits');
    expect(out.recent_ab_per_game).toBe(2);      // recent is knowable
    expect(out.opportunity_drift).toBeUndefined(); // the ratio is not
  });

  it('needs at least 3 at-bat rows — two games is noise, not a role change', () => {
    const out = mlbGameLogFeatures({ found: true, last10: [g(4, 1), g(4, 2)], season: season(60, 300, 75) }, 'hits');
    expect(out.opportunity_drift).toBeUndefined();
  });
});

describe('opportunityNudge — the guards', () => {
  it('an ABSENT drift is a no-op, not a maximal fade', () => {
    for (const v of [null, undefined, '', NaN, 0, -1]) expect(opportunityNudge(v, 1)).toBe(0);
  });

  it('a drift inside the deadband is treated as noise', () => {
    expect(opportunityNudge(1, 1)).toBe(0);
    expect(opportunityNudge(1 + (OPPORTUNITY_DEADBAND / 2), 1)).toBe(0);
    expect(opportunityNudge(1 - (OPPORTUNITY_DEADBAND / 2), 1)).toBe(0);
  });

  it('is capped so a noisy 5-game proxy cannot outvote the measured axes', () => {
    expect(opportunityNudge(0.01, 1)).toBe(-MAX_OPPORTUNITY_NUDGE);
    expect(opportunityNudge(100, 1)).toBe(MAX_OPPORTUNITY_NUDGE);
  });

  it('flips sign with direction — less opportunity helps the UNDER', () => {
    expect(opportunityNudge(0.5, 1)).toBeLessThan(0);
    expect(opportunityNudge(0.5, -1)).toBeGreaterThan(0);
  });
});

describe('adjust — the opportunity axis on the challenger', () => {
  const base = { pWin: 0.55, direction: 'over', statType: 'hits' };

  it('stands ALONE when there is no archetype, park or platoon', () => {
    const r = adjust({ ...base, opportunity: { drift: 0.5, recent_ab_per_game: 2, season_ab_per_game: 4 } });
    expect(r.adjustments.map((a) => a.axis)).toEqual(['opportunity']);
    expect(r.p_win_challenger).toBeLessThan(0.55);
  });

  it('labels itself a PROXY, so nothing downstream can mistake it for a lineup', () => {
    const r = adjust({ ...base, opportunity: { drift: 1.6 } });
    expect(r.adjustments[0]).toMatchObject({ is_proxy: true, proxy_for: 'confirmed_batting_order', label: 'ROLE UP' });
  });

  it('leaves the challenger IDENTICAL to the champion when drift is absent', () => {
    const r = adjust({ ...base, opportunity: { drift: null } });
    expect(r.p_win_challenger).toBe(0.55);
    expect(r.delta).toBe(0);
    expect(r.adjustments).toEqual([]);
  });
});

describe('attachChallenger — reads opportunity off the grade (zero extra I/O)', () => {
  it('uses the drift the grader already attached', async () => {
    const out = await challenger.attachChallenger([
      { player: 'A', stat_type: 'hits', direction: 'over', p_win: 0.6, opportunity_drift: 0.62, recent_ab_per_game: 2.5, ab_per_game: 4 },
      { player: 'B', stat_type: 'hits', direction: 'over', p_win: 0.6 },
    ], () => null, null);
    expect(out[0].challenger_delta).toBeLessThan(0);
    expect(out[0].challenger_adjustments[0].axis).toBe('opportunity');
    // No drift on the grade => challenger is the champion, exactly.
    expect(out[1].p_win_challenger).toBe(0.6);
    expect(out[1].challenger_delta).toBe(0);
  });
});