package math

import (
	"errors"
	"math"
)

var ErrOverflowInt32 = errors.New("int32 overflow")
var ErrOverflowUint8 = errors.New("uint8 overflow")
var ErrOverflowInt8 = errors.New("int8 overflow")

// SafeAddInt32 adds two int32 integers.
func SafeAddInt32(a, b int32) (int32, error) {
	if b > 0 && (a > math.MaxInt32-b) {
		return 0, ErrOverflowInt32
	} else if b < 0 && (a < math.MinInt32-b) {
		return 0, ErrOverflowInt32
	}
	return a + b, nil
}

// SafeSubInt32 subtracts two int32 integers.
func SafeSubInt32(a, b int32) (int32, error) {
	if b > 0 && (a < math.MinInt32+b) {
		return 0, ErrOverflowInt32
	} else if b < 0 && (a > math.MaxInt32+b) {
		return 0, ErrOverflowInt32
	}
	return a - b, nil
}

// SafeConvertInt32 takes a int and checks if it overflows.
func SafeConvertInt32(a int64) (int32, error) {
	if a > math.MaxInt32 {
		return 0, ErrOverflowInt32
	} else if a < math.MinInt32 {
		return 0, ErrOverflowInt32
	}
	return int32(a), nil
}

// SafeConvertUint8 takes an int64 and checks if it overflows.
func SafeConvertUint8(a int64) (uint8, error) {
	if a > math.MaxUint8 {
		return 0, ErrOverflowUint8
	} else if a < 0 {
		return 0, ErrOverflowUint8
	}
	return uint8(a), nil
}

// SafeConvertInt8 takes an int64 and checks if it overflows.
func SafeConvertInt8(a int64) (int8, error) {
	if a > math.MaxInt8 {
		return 0, ErrOverflowInt8
	} else if a < math.MinInt8 {
		return 0, ErrOverflowInt8
	}
	return int8(a), nil
}