package util

import (
	"crypto/sha1"
	"encoding/hex"
	"errors"
	"hash"
	"io"
	"os"
	"path/filepath"
	"strings"
)

const SHA1ResultLength = 20

type SHA1Result struct {
	result [SHA1ResultLength]byte
	err    error
}

func (s *SHA1Result) Array() [SHA1ResultLength]byte {
	if s.err != nil {
		return [SHA1ResultLength]byte{}
	}
	return s.result
}

func (s *SHA1Result) Slice() []byte {
	if s.err != nil {
		return []byte{}
	}
	return s.result[:]
}

func (s *SHA1Result) Upper() string {
	if s.err != nil {
		return ""
	}
	return strings.ToUpper(hex.EncodeToString(s.result[:]))
}

func (s *SHA1Result) Lower() string {
	if s.err != nil {
		return ""
	}
	return strings.ToLower(hex.EncodeToString(s.result[:]))
}

func (s *SHA1Result) Error() error {
	return s.err
}

func NewSHA1Result(result []byte, err error) *SHA1Result {
	res := &SHA1Result{
		result: [SHA1ResultLength]byte{},
		err:    err,
	}
	copy(res.result[:], result)
	return res
}

type SHA1 struct{}

func NewSHA1() *SHA1 {
	return &SHA1{}
}

func (s *SHA1) FromReader(r io.Reader) *SHA1Result {
	ha := sha1.New()
	if _, err := io.Copy(ha, r); err != nil {
		return NewSHA1Result(nil, err)
	}
	hashInBytes := ha.Sum(nil)
	if len(hashInBytes) != SHA1ResultLength {
		return NewSHA1Result(nil, errors.New("wrong length"))
	}
	return NewSHA1Result(hashInBytes, nil)
}

func (s *SHA1) FromFile(filename string) *SHA1Result {
	file, err := os.Open(filepath.Clean(filename))
	if err != nil {
		return NewSHA1Result(nil, err)
	}
	defer func() {
		_ = file.Close()
	}()
	return s.FromReader(file)
}

func (s *SHA1) FromReaderChunk(r io.Reader, chunksize int) *SHA1Result {
	buf := make([]byte, chunksize)
	s1 := sha1.New()
	var n int
	var err error
	for {
		n, err = r.Read(buf)
		if err != nil {
			if err != io.EOF {
				return NewSHA1Result(nil, err)
			}
			if n > 0 {
				_, err = s1.Write(buf[:n])
				if err != nil {
					return NewSHA1Result(nil, err)
				}
			}
			break
		}
		_, err = s1.Write(buf[:n])
		if err != nil {
			return NewSHA1Result(nil, err)
		}
	}
	return NewSHA1Result(s1.Sum(nil), nil)
}

func (s *SHA1) FromFileChunk(filename string, chunksize int) *SHA1Result {
	file, err := os.Open(filepath.Clean(filename))
	if err != nil {
		return NewSHA1Result(nil, err)
	}
	defer func() {
		_ = file.Close()
	}()
	return s.FromReaderChunk(file, chunksize)
}

func (s *SHA1) FromBytes(b []byte) *SHA1Result {
	res := sha1.Sum(b)
	return NewSHA1Result(res[:], nil)
}

func (s *SHA1) FromString(str string) *SHA1Result {
	res := sha1.Sum([]byte(str))
	return NewSHA1Result(res[:], nil)
}

type SHA1Pip struct {
	sha1 hash.Hash
}

func NewSHA1Pip() *SHA1Pip {
	return &SHA1Pip{sha1: sha1.New()}
}

func (s *SHA1Pip) Write(data []byte) (n int, err error) {
	return s.sha1.Write(data)
}

func (s *SHA1Pip) WriteBytes(data []byte) error {
	_, err := s.Write(data)
	return err
}

func (s *SHA1Pip) WriteString(data string) error {
	_, err := s.Write([]byte(data))
	return err
}

func (s *SHA1Pip) Result() *SHA1Result {
	return NewSHA1Result(s.sha1.Sum(nil), nil)
}