package sha512

import (
	"io"

	"crypto/sha512"
)

// The size of a SHA512 checksum in bytes.
const (
	Size = sha512.Size
)

// Sum512 - single caller sha512 helper
func Sum512(data []byte) []byte {
	d := sha512.New()
	d.Write(data)
	return d.Sum(nil)
}

// Sum - io.Reader based streaming sha512 helper
func Sum(reader io.Reader) ([]byte, error) {
	d := sha512.New()
	var err error
	for err == nil {
		length := 0
		byteBuffer := make([]byte, 1024*1024)
		length, err = reader.Read(byteBuffer)
		byteBuffer = byteBuffer[0:length]
		d.Write(byteBuffer)
	}
	if err != io.EOF {
		return nil, err
	}
	return d.Sum(nil), nil
}

// SumStream - similar to 'Sum()' but returns a [sha512.Size]byte
func SumStream(reader io.Reader) ([sha512.Size]byte, error) {
	var returnValue [sha512.Size]byte
	sumSlice, err := Sum(reader)
	if err != nil {
		return returnValue, err
	}
	copy(returnValue[:], sumSlice)
	return returnValue, err
}