package util

import (
	"crypto/md5"
	"encoding/hex"
	"errors"
	"hash"
	"io"
	"os"
	"path/filepath"
	"strings"
)

const MD5ResultLength = 16

type MD5Result struct {
	result [MD5ResultLength]byte
	err    error
}

func (m *MD5Result) Array() [MD5ResultLength]byte {
	if m.err != nil {
		return [MD5ResultLength]byte{}
	}
	return m.result
}

func (m *MD5Result) Slice() []byte {
	if m.err != nil {
		return []byte{}
	}
	return m.result[:]
}

func (m *MD5Result) Upper() string {
	if m.err != nil {
		return ""
	}
	return strings.ToUpper(hex.EncodeToString(m.result[:]))
}

func (m *MD5Result) Lower() string {
	if m.err != nil {
		return ""
	}
	return strings.ToLower(hex.EncodeToString(m.result[:]))
}

func (m *MD5Result) Error() error {
	return m.err
}

func NewMD5Result(result []byte, err error) *MD5Result {
	res := &MD5Result{
		result: [MD5ResultLength]byte{},
		err:    err,
	}
	copy(res.result[:], result)
	return res
}

type MD5 struct{}

func NewMD5() *MD5 {
	return &MD5{}
}

func (m *MD5) FromReader(r io.Reader) *MD5Result {
	ha := md5.New()
	if _, err := io.Copy(ha, r); err != nil {
		return NewMD5Result(nil, err)
	}
	hashInBytes := ha.Sum(nil)
	if len(hashInBytes) != MD5ResultLength {
		return NewMD5Result(nil, errors.New("wrong length"))
	}
	return NewMD5Result(hashInBytes, nil)
}

func (m *MD5) FromFile(filename string) *MD5Result {
	file, err := os.Open(filepath.Clean(filename))
	if err != nil {
		return NewMD5Result(nil, err)
	}
	defer func() {
		_ = file.Close()
	}()
	return m.FromReader(file)
}

func (m *MD5) FromReaderChunk(r io.Reader, chunksize int) *MD5Result {
	buf := make([]byte, chunksize)
	m5 := md5.New()
	var n int
	var err error
	for {
		n, err = r.Read(buf)
		if err != nil {
			if err != io.EOF {
				return NewMD5Result(nil, err)
			}
			if n > 0 {
				_, err = m5.Write(buf[:n])
				if err != nil {
					return NewMD5Result(nil, err)
				}
			}
			break
		}
		_, err = m5.Write(buf[:n])
		if err != nil {
			return NewMD5Result(nil, err)
		}
	}
	return NewMD5Result(m5.Sum(nil), nil)
}

func (m *MD5) FromFileChunk(filename string, chunksize int) *MD5Result {
	file, err := os.Open(filepath.Clean(filename))
	if err != nil {
		return NewMD5Result(nil, err)
	}
	defer func() {
		_ = file.Close()
	}()
	return m.FromReaderChunk(file, chunksize)
}

func (m *MD5) FromBytes(b []byte) *MD5Result {
	res := md5.Sum(b)
	return NewMD5Result(res[:], nil)
}

func (m *MD5) FromString(str string) *MD5Result {
	res := md5.Sum([]byte(str))
	return NewMD5Result(res[:], nil)
}

type MD5Pip struct {
	md5 hash.Hash
}

func NewMD5Pip() *MD5Pip {
	return &MD5Pip{md5: md5.New()}
}

func (m *MD5Pip) Write(data []byte) (n int, err error) {
	return m.md5.Write(data)
}

func (m *MD5Pip) WriteBytes(data []byte) error {
	_, err := m.Write(data)
	return err
}

func (m *MD5Pip) WriteString(data string) error {
	_, err := m.Write([]byte(data))
	return err
}

func (m *MD5Pip) Result() *MD5Result {
	return NewMD5Result(m.md5.Sum(nil), nil)
}