mev-beta/tools/math-audit/internal/checks/checks.go

package checks

import (
	"fmt"
	"math"
	"math/big"
	"math/rand"

	"github.com/fraktal/mev-beta/pkg/uniswap"
	"github.com/fraktal/mev-beta/tools/math-audit/internal/audit"
)

// Run executes deterministic property/fuzz-style checks reused from the unit test suites.
func Run() []audit.TestResult {
	return []audit.TestResult{
		runPriceConversionRoundTrip(),
		runTickConversionRoundTrip(),
		runPriceMonotonicity(),
		runPriceSymmetry(),
	}
}

func newResult(name string) audit.TestResult {
	return audit.TestResult{
		Name: name,
		Type: "property",
	}
}

func runPriceConversionRoundTrip() audit.TestResult {
	res := newResult("price_conversion_round_trip")
	rng := rand.New(rand.NewSource(1337))
	const tolerance = 0.001 // 0.1%
	failures := 0

	for i := 0; i < 256; i++ {
		exponent := rng.Float64()*12 - 6
		price := math.Pow(10, exponent)
		if price <= 0 {
			continue
		}

		priceBig := new(big.Float).SetFloat64(price)
		sqrt := uniswap.PriceToSqrtPriceX96(priceBig)
		converted := uniswap.SqrtPriceX96ToPrice(sqrt)
		convertedFloat, _ := converted.Float64()

		if price == 0 {
			continue
		}
		relErr := math.Abs(price-convertedFloat) / price
		if relErr > tolerance {
			failures++
			if failures >= 3 {
				break
			}
		}
	}

	if failures == 0 {
		res.Passed = true
		res.Details = "all samples within 0.1% tolerance"
	} else {
		res.Passed = false
		res.Details = fmt.Sprintf("%d samples exceeded tolerance", failures)
	}
	return res
}

func runTickConversionRoundTrip() audit.TestResult {
	res := newResult("tick_conversion_round_trip")
	rng := rand.New(rand.NewSource(4242))
	failures := 0

	for i := 0; i < 256; i++ {
		tick := rng.Intn(1774544) - 887272
		sqrt := uniswap.TickToSqrtPriceX96(tick)
		convertedTick := uniswap.SqrtPriceX96ToTick(sqrt)
		if diff := absInt(tick - convertedTick); diff > 1 {
			failures++
			if failures >= 3 {
				break
			}
		}
	}

	if failures == 0 {
		res.Passed = true
		res.Details = "ticks round-trip within ±1"
	} else {
		res.Passed = false
		res.Details = fmt.Sprintf("%d tick samples exceeded tolerance", failures)
	}
	return res
}

func runPriceMonotonicity() audit.TestResult {
	res := newResult("price_monotonicity")
	rng := rand.New(rand.NewSource(9001))
	const tickStep = 500
	failures := 0

	for i := 0; i < 128; i++ {
		base := rng.Intn(1774544) - 887272
		tick1 := base
		tick2 := base + tickStep
		if tick2 > 887272 {
			tick2 = 887272
		}

		sqrt1 := uniswap.TickToSqrtPriceX96(tick1)
		sqrt2 := uniswap.TickToSqrtPriceX96(tick2)
		price1 := uniswap.SqrtPriceX96ToPrice(sqrt1)
		price2 := uniswap.SqrtPriceX96ToPrice(sqrt2)

		p1, _ := price1.Float64()
		p2, _ := price2.Float64()
		if p2 <= p1 {
			failures++
			if failures >= 3 {
				break
			}
		}
	}

	if failures == 0 {
		res.Passed = true
		res.Details = "higher ticks produced higher prices"
	} else {
		res.Passed = false
		res.Details = fmt.Sprintf("%d monotonicity violations detected", failures)
	}
	return res
}

func runPriceSymmetry() audit.TestResult {
	res := newResult("price_symmetry")
	rng := rand.New(rand.NewSource(2025))
	const tolerance = 0.001
	failures := 0

	for i := 0; i < 128; i++ {
		price := math.Pow(10, rng.Float64()*6-3) // range around 0.001 - 1000
		if price <= 0 {
			continue
		}

		inverse := 1.0 / price
		priceBig := new(big.Float).SetFloat64(price)
		invBig := new(big.Float).SetFloat64(inverse)

		sqrtPrice := uniswap.PriceToSqrtPriceX96(priceBig)
		sqrtInverse := uniswap.PriceToSqrtPriceX96(invBig)

		convertedPrice := uniswap.SqrtPriceX96ToPrice(sqrtPrice)
		convertedInverse := uniswap.SqrtPriceX96ToPrice(sqrtInverse)

		p, _ := convertedPrice.Float64()
		inv, _ := convertedInverse.Float64()
		if math.Abs(p*inv-1) > tolerance {
			failures++
			if failures >= 3 {
				break
			}
		}
	}

	if failures == 0 {
		res.Passed = true
		res.Details = "price * inverse remained within 0.1%"
	} else {
		res.Passed = false
		res.Details = fmt.Sprintf("%d symmetry samples exceeded tolerance", failures)
	}
	return res
}

func absInt(v int) int {
	if v < 0 {
		return -v
	}
	return v
}