// Package checksum contain algorithms to checksum files
package checksum

import (
	"crypto/sha256"
	"encoding/hex"
	"hash"
	"io"
	"os"
)

// SHA256 sum of the given file
func SHA256(path string) (string, error) {
	return calculate(sha256.New(), path)
}

func calculate(hash hash.Hash, path string) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer file.Close() // nolint: errcheck

	return doCalculate(hash, file)
}

func doCalculate(hash hash.Hash, file io.Reader) (string, error) {
	_, err := io.Copy(hash, file)
	if err != nil {
		return "", err
	}
	return hex.EncodeToString(hash.Sum(nil)), nil
}