// Package client
// @program: file_client_go
// @author: ygt
// @create: 2022/7/25 17:52
package client

import (
	"bufio"
	"crypto/md5"
	"crypto/sha1"
	"crypto/sha256"
	"encoding/hex"
	"github.com/cespare/xxhash/v2"
	"hash"
	"hash/crc32"
	"io"
	"os"
)

var defaultAlgorithm = getDefault()

type uniqueAlgorithm struct{}

var (
	Ic = newIC()
)

func newIC() iu {
	return &uniqueAlgorithm{}
}

type iu interface {
	GetStringIdentifier(src string) string
	GetFileIdentifier(file string) string
}

func (i *uniqueAlgorithm) GetStringIdentifier(src string) string {
	if "" == src {
		return ""
	}
	algorithm := defaultAlgorithm
	var h hash.Hash
	switch algorithm {
	case XXH:
		h = xxhash.New()
		break
	case MD5:
		h = md5.New()
		break
	case SHA1:
		h = sha1.New()
		break
	case SHA256:
		h = sha256.New()
		break
	case CRC32:
		h = crc32.NewIEEE()
		break
	}
	h.Write([]byte(src))
	return hex.EncodeToString(h.Sum(nil))
}

func (i *uniqueAlgorithm) GetFileIdentifier(file string) string {
	f, err := os.Open(file)
	if err != nil {
		return ""
	}
	algorithm := defaultAlgorithm
	defer f.Close()
	r := bufio.NewReader(f)
	var h hash.Hash
	switch algorithm {
	case XXH:
		h = xxhash.New()
		break
	case MD5:
		h = md5.New()
		break
	case SHA1:
		h = sha1.New()
		break
	case SHA256:
		h = sha256.New()
		break
	case CRC32:
		h = crc32.NewIEEE()
		break
	}
	_, err = io.Copy(h, r)
	if err != nil {
		return ""
	}
	return hex.EncodeToString(h.Sum(nil))
}

func getDefault() string {
	ua := os.Getenv("F_UNIQUE_ALGORITHM")
	if "" == ua {
		ua = XXH
	}
	return ua
}