import { describe, it, expect } from 'vitest';
import { SwapDetails } from './swap-details';

describe('SwapDetails.getAmountOut invariant rounding', () => {
  it('computes amountOut for token1-in -> token0-out (adjusted-balance model)', () => {
    // Given reserves: token0 = 300_000_000_000, token1 = 300_000
    // Input: 888 of token1, feeTier = 10_000 (hundredths of a basis point base 1_000_000)
    // Expected amountOut under adjusted-balance model: 876_551_353
    const amountIn = 888n;
    const reserveIn = 300_000n; // token1 reserve
    const reserveOut = 300_000_000_000n; // token0 reserve
    const feeTier = 10_000n;

    const swapDetails = new SwapDetails({} as any);
    const out = (swapDetails as any).getAmountOut(
      amountIn,
      reserveIn,
      reserveOut,
      feeTier,
    ) as bigint;

    expect(out).toBe(876_551_353n);
  });

  it('satisfies adjusted-balance invariant at boundary case from logs', () => {
    // From program log (updated model): validate adjusted-balance inequality holds.
    const amountIn = 888n;
    const reserveIn = 293_741n; // token1 reserve
    const reserveOut = 306_456_968_222n; // token0 reserve
    const feeTier = 10_000n;

    const swapDetails = new SwapDetails({} as any);
    const out = (swapDetails as any).getAmountOut(
      amountIn,
      reserveIn,
      reserveOut,
      feeTier,
    ) as bigint;

    // Adjusted-balance invariant check:
    const D = 1_000_000n;
    const fee = BigInt(feeTier);
    const b0Adj = (reserveOut - out) * D; // token0 in amount is 0
    const b1Adj = reserveIn * D + amountIn * (D - fee);
    const rhs = reserveOut * reserveIn * D * D;
    expect(b0Adj * b1Adj >= rhs).toBe(true);
  });
});