package util

import (
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"hash"
	"io"
	"os"
	"path/filepath"
	"strings"
)

const SHA256ResultLength = 32

type SHA256Result struct {
	result [SHA256ResultLength]byte
	err    error
}

func (s *SHA256Result) Array() [SHA256ResultLength]byte {
	if s.err != nil {
		return [SHA256ResultLength]byte{}
	}
	return s.result
}

func (s *SHA256Result) Slice() []byte {
	if s.err != nil {
		return []byte{}
	}
	return s.result[:]
}

func (s *SHA256Result) Upper() string {
	if s.err != nil {
		return ""
	}
	return strings.ToUpper(hex.EncodeToString(s.result[:]))
}

func (s *SHA256Result) Lower() string {
	if s.err != nil {
		return ""
	}
	return strings.ToLower(hex.EncodeToString(s.result[:]))
}

func (s *SHA256Result) Error() error {
	return s.err
}

func NewSHA256Result(result []byte, err error) *SHA256Result {
	res := &SHA256Result{
		result: [SHA256ResultLength]byte{},
		err:    err,
	}
	copy(res.result[:], result)
	return res
}

type SHA256 struct{}

func NewSHA256() *SHA256 {
	return &SHA256{}
}

func (s *SHA256) FromReader(r io.Reader) *SHA256Result {
	ha := sha256.New()
	if _, err := io.Copy(ha, r); err != nil {
		return NewSHA256Result(nil, err)
	}
	hashInBytes := ha.Sum(nil)
	if len(hashInBytes) != SHA256ResultLength {
		return NewSHA256Result(nil, errors.New("wrong length"))
	}
	return NewSHA256Result(hashInBytes, nil)
}

func (s *SHA256) FromFile(filename string) *SHA256Result {
	file, err := os.Open(filepath.Clean(filename))
	if err != nil {
		return NewSHA256Result(nil, err)
	}
	defer func() {
		_ = file.Close()
	}()
	return s.FromReader(file)
}

func (s *SHA256) FromReaderChunk(r io.Reader, chunksize int) *SHA256Result {
	buf := make([]byte, chunksize)
	s1 := sha256.New()
	var n int
	var err error
	for {
		n, err = r.Read(buf)
		if err != nil {
			if err != io.EOF {
				return NewSHA256Result(nil, err)
			}
			if n > 0 {
				_, err = s1.Write(buf[:n])
				if err != nil {
					return NewSHA256Result(nil, err)
				}
			}
			break
		}
		_, err = s1.Write(buf[:n])
		if err != nil {
			return NewSHA256Result(nil, err)
		}
	}
	return NewSHA256Result(s1.Sum(nil), nil)
}

func (s *SHA256) FromFileChunk(filename string, chunksize int) *SHA256Result {
	file, err := os.Open(filepath.Clean(filename))
	if err != nil {
		return NewSHA256Result(nil, err)
	}
	defer func() {
		_ = file.Close()
	}()
	return s.FromReaderChunk(file, chunksize)
}

func (s *SHA256) FromBytes(b []byte) *SHA256Result {
	res := sha256.Sum256(b)
	return NewSHA256Result(res[:], nil)
}

func (s *SHA256) FromString(str string) *SHA256Result {
	res := sha256.Sum256([]byte(str))
	return NewSHA256Result(res[:], nil)
}

type SHA256Pip struct {
	sha256 hash.Hash
}

func NewSHA256Pip() *SHA256Pip {
	return &SHA256Pip{sha256: sha256.New()}
}

func (s *SHA256Pip) Write(data []byte) (n int, err error) {
	return s.sha256.Write(data)
}

func (s *SHA256Pip) WriteBytes(data []byte) error {
	_, err := s.Write(data)
	return err
}

func (s *SHA256Pip) WriteString(data string) error {
	_, err := s.Write([]byte(data))
	return err
}

func (s *SHA256Pip) Result() *SHA256Result {
	return NewSHA256Result(s.sha256.Sum(nil), nil)
}