vyndr/tests/unit/bookComparisonService.test.js

// Unit: book comparison service. Pure functions.
// Book Comparison order (Phase 3) — the crown is now HONEST + threshold-gated:
//   - single-book / flat-market props render with NO crown
//   - the crown fires only among ≥2 books at the SAME line with DIFFERING prices
//   - and only when enabled (BOOK_CROWN_ENABLED / opts.crownEnabled), OFF until
//     Phase 2's spread measurement clears the bar.
// The crown-logic cases below pass { crownEnabled: true } explicitly.

const { compareProp, bestLines } = require('../../src/services/bookComparisonService');

const prop = {
  player: 'Wembanyama',
  stat_type: 'points',
  lines: [
    { book: 'draftkings', line: 28.5, over_odds: -110, under_odds: -110 },
    { book: 'fanduel', line: 28.5, over_odds: -105, under_odds: -115 }, // best over
    { book: 'betmgm', line: 28.5, over_odds: -120, under_odds: -102 },  // best under
  ],
};

describe('compareProp — crown enabled (real spread)', () => {
  const on = { crownEnabled: true };
  test('identifies the best OVER line (highest payout)', () => {
    const c = compareProp(prop, 'over', on);
    expect(c.crowned).toBe(true);
    expect(c.bestBook).toBe('fanduel'); // -105 pays more than -110/-120
    expect(c.bestOdds).toBe(-105);
    expect(c.books.find((b) => b.book === 'fanduel').isBest).toBe(true);
    expect(c.bookCount).toBe(3);
  });

  test('identifies the best UNDER line', () => {
    const c = compareProp(prop, 'under', on);
    expect(c.bestBook).toBe('betmgm'); // -102 pays more than -110/-115
    expect(c.bestOdds).toBe(-102);
  });

  test('savings is positive (best beats the field average)', () => {
    expect(compareProp(prop, 'over', on).savings).toBeGreaterThan(0);
  });
});

describe('compareProp — honest-absent', () => {
  test('single-book prop renders the one book, NO crown', () => {
    const c = compareProp({ player: 'X', stat_type: 'hits', lines: [{ book: 'dk', line: 0.5, over_odds: -110 }] }, 'over', { crownEnabled: true });
    expect(c.bookCount).toBe(1);
    expect(c.bestBook).toBeNull();
    expect(c.crowned).toBe(false);
    expect(c.books[0].isBest).toBe(false);
    expect(c.savings).toBe(0);
  });

  test('crown DISABLED by default → multi-book prop shows all books, none crowned', () => {
    const c = compareProp(prop, 'over'); // no opts → env default (off in tests)
    expect(c.crowned).toBe(false);
    expect(c.books.every((b) => b.isBest === false)).toBe(true);
    expect(c.bestBook).toBeNull();
  });

  test('identical prices at the same line → no crown even when enabled', () => {
    const flat = { player: 'X', stat_type: 'hits', lines: [
      { book: 'draftkings', line: 0.5, over_odds: -110, under_odds: -110 },
      { book: 'fanduel', line: 0.5, over_odds: -110, under_odds: -110 },
    ] };
    expect(compareProp(flat, 'over', { crownEnabled: true }).crowned).toBe(false);
  });

  test('no usable lines → null, not crash', () => {
    expect(compareProp({ player: 'X', stat_type: 'hits', lines: [] }, 'over')).toBeNull();
    expect(compareProp({ player: 'X', stat_type: 'hits' }, 'over')).toBeNull();
  });

  test('reads a grouped `books` array (bookprices store shape)', () => {
    const c = compareProp({ player: 'Y', stat_type: 'hits', books: [
      { book: 'draftkings', line: 1.5, over_odds: -115 },
      { book: 'betmgm', line: 1.5, over_odds: -105 },
    ] }, 'over', { crownEnabled: true });
    expect(c.bestBook).toBe('betmgm');
  });
});

describe('bestLines', () => {
  test('makes no crown claim when gated off (returns [])', () => {
    expect(bestLines([prop], { side: 'over', crownEnabled: false })).toEqual([]);
  });

  test('enabled: drops single-book props and sorts by savings desc', () => {
    const props = [
      prop,
      { player: 'Solo', stat_type: 'reb', lines: [{ book: 'dk', line: 5.5, over_odds: -110 }] }, // 1 book → dropped
      {
        player: 'BigEdge', stat_type: 'ast',
        lines: [
          { book: 'dk', line: 5.5, over_odds: -200 },
          { book: 'fd', line: 5.5, over_odds: +120 }, // huge spread → big savings
        ],
      },
    ];
    const lines = bestLines(props, { side: 'over', crownEnabled: true });
    expect(lines.map((l) => l.player)).not.toContain('Solo');
    expect(lines[0].player).toBe('BigEdge'); // biggest savings first
  });

  test('non-array input → empty', () => {
    expect(bestLines(null)).toEqual([]);
  });
});