package v1

import "math"

// safeAddInt64 performs safe addition of int64 values, panicking on overflow or underflow
func safeAddInt64(a, b int64) int64 {
	if a > 0 && b > math.MaxInt64-a {
		panic("int64 addition overflow")
	}

	if a < 0 && b < math.MinInt64-a {
		panic("int64 addition underflow")
	}

	return a + b
}

// safeSubInt64 performs safe subtraction of int64 values, panicking on overflow or underflow
func safeSubInt64(a, b int64) int64 {
	if b > 0 && a < math.MinInt64+b {
		panic("int64 subtraction underflow")
	}

	if b < 0 && a > math.MaxInt64+b {
		panic("int64 subtraction overflow")
	}

	return a - b
}

// safeMulDiv performs safe multiplication and division: (a * b) / c
// Prevents overflow in multiplication step by checking bounds
func safeMulDiv(a, b, c int64) int64 {
	if c == 0 {
		panic("division by zero in safeMulDiv")
	}

	// Check for multiplication overflow
	// If a * b would overflow, we need to be careful
	if a != 0 && b != 0 {
		// Check if multiplication would overflow
		if a > 0 && b > 0 && a > math.MaxInt64/b {
			panic("int64 multiplication overflow in safeMulDiv")
		}
		if a > 0 && b < 0 && b < math.MinInt64/a {
			panic("int64 multiplication underflow in safeMulDiv")
		}
		if a < 0 && b > 0 && a < math.MinInt64/b {
			panic("int64 multiplication underflow in safeMulDiv")
		}
		if a < 0 && b < 0 && a < math.MaxInt64/b {
			panic("int64 multiplication overflow in safeMulDiv")
		}
	}

	result := (a * b) / c
	return result
}