import { describe, expect, it } from 'vitest';
import { pegCryptoAmount } from '../src/peg';
import { priceToRateUnits } from '../src/rates';

describe('pegCryptoAmount', () => {
  it('converts $100 at rate 1.000000 to exactly 100 tokens', () => {
    expect(pegCryptoAmount('100', 1_000000n)).toBe(100_000000n);
  });

  it('rounds UP so the merchant never receives less than invoiced ($100 at 0.9997)', () => {
    // 100 / 0.9997 = 100.030009…, must round up to 100.030010
    expect(pegCryptoAmount('100', 999700n)).toBe(100_030010n);
  });

  it('handles small amounts', () => {
    expect(pegCryptoAmount('0.01', 1_000000n)).toBe(10000n);
  });

  it('rejects zero/negative inputs', () => {
    expect(() => pegCryptoAmount('0', 1_000000n)).toThrow();
    expect(() => pegCryptoAmount('100', 0n)).toThrow();
  });
});

describe('priceToRateUnits', () => {
  it('converts typical stablecoin prices', () => {
    expect(priceToRateUnits(1)).toBe(1_000000n);
    expect(priceToRateUnits(0.9997)).toBe(999700n);
    expect(priceToRateUnits(1.0002)).toBe(1_000200n);
  });

  it('truncates precision beyond 6dp rather than rounding money upward', () => {
    expect(priceToRateUnits(0.99976543)).toBe(999765n);
  });

  it('rejects non-positive or non-finite prices', () => {
    expect(() => priceToRateUnits(0)).toThrow();
    expect(() => priceToRateUnits(-1)).toThrow();
    expect(() => priceToRateUnits(Number.NaN)).toThrow();
  });
});