package splco

// why doesnt Go have this built in
// 30% of AI generated code
// simple helper

import "errors"

var (
	ErrDataTooShort      = errors.New("data too short for specified sizes")
	ErrInvalidDataLength = errors.New("data length does not match sum of specified sizes")
)

func Append(data ...[]byte) []byte {
	expLen := 0
	for _, b := range data {
		expLen += len(b)
	}
	return AppendWithSize(expLen, data...)
}

func AppendWithSize(size int, data ...[]byte) []byte {
	return AppendInto(make([]byte, 0, size), data...)
}

func AppendInto(dest []byte, data ...[]byte) []byte {
	for _, b := range data {
		dest = append(dest, b...)
	}
	return dest
}

func Split(data []byte, sizes ...int) ([][]byte, error) {
	result := make([][]byte, len(sizes))
	offset := 0
	for i, size := range sizes {
		if offset+size > len(data) {
			return nil, ErrDataTooShort
		}
		result[i] = data[offset : offset+size]
		offset += size
	}
	if offset != len(data) {
		return nil, ErrInvalidDataLength
	}
	return result, nil
}