package util

import (
	"bytes"
	"crypto/md5"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"io"
	"math"
	"strconv"
	"strings"
	"unicode"
)

// BytesToHumanReadable returns the converted human readable representation of the bytes.
func BytesToHumanReadable(b uint64) string {
	const unit = 1024
	if b < unit {
		return fmt.Sprintf("%d B", b)
	}

	div, exp := uint64(unit), 0
	for n := b / unit; n >= unit; n /= unit {
		div *= unit
		exp++
	}

	return fmt.Sprintf("%.2f %ciB", float64(b)/float64(div), "KMGTPE"[exp])
}

// big endian

func BytesToUint64(b []byte) (v uint64) {
	length := uint(len(b))
	for i := uint(0); i < length-1; i++ {
		v += uint64(b[i])
		v <<= 8
	}
	v += uint64(b[length-1])
	return
}
func BytesToUint32(b []byte) (v uint32) {
	length := uint(len(b))
	for i := uint(0); i < length-1; i++ {
		v += uint32(b[i])
		v <<= 8
	}
	v += uint32(b[length-1])
	return
}
func BytesToUint16(b []byte) (v uint16) {
	v += uint16(b[0])
	v <<= 8
	v += uint16(b[1])
	return
}
func Uint64toBytes(b []byte, v uint64) {
	for i := uint(0); i < 8; i++ {
		b[7-i] = byte(v >> (i * 8))
	}
}
func Uint32toBytes(b []byte, v uint32) {
	for i := uint(0); i < 4; i++ {
		b[3-i] = byte(v >> (i * 8))
	}
}
func Uint16toBytes(b []byte, v uint16) {
	b[0] = byte(v >> 8)
	b[1] = byte(v)
}
func Uint8toBytes(b []byte, v uint8) {
	b[0] = byte(v)
}

// returns a 64 bit big int
func HashStringToLong(dir string) (v int64) {
	h := md5.New()
	io.WriteString(h, dir)

	b := h.Sum(nil)

	v += int64(b[0])
	v <<= 8
	v += int64(b[1])
	v <<= 8
	v += int64(b[2])
	v <<= 8
	v += int64(b[3])
	v <<= 8
	v += int64(b[4])
	v <<= 8
	v += int64(b[5])
	v <<= 8
	v += int64(b[6])
	v <<= 8
	v += int64(b[7])

	return
}

func HashToInt32(data []byte) (v int32) {
	h := md5.New()
	h.Write(data)

	b := h.Sum(nil)

	v += int32(b[0])
	v <<= 8
	v += int32(b[1])
	v <<= 8
	v += int32(b[2])
	v <<= 8
	v += int32(b[3])

	return
}

func Base64Encode(data []byte) string {
	return base64.StdEncoding.EncodeToString(data)
}

func Base64Md5(data []byte) string {
	return Base64Encode(Md5(data))
}

func Md5(data []byte) []byte {
	hash := md5.New()
	hash.Write(data)
	return hash.Sum(nil)
}

func Md5String(data []byte) string {
	return fmt.Sprintf("%x", Md5(data))
}

func Base64Md5ToBytes(contentMd5 string) []byte {
	data, err := base64.StdEncoding.DecodeString(contentMd5)
	if err != nil {
		return nil
	}
	return data
}

func RandomInt32() int32 {
	buf := make([]byte, 4)
	rand.Read(buf)
	return int32(BytesToUint32(buf))
}

func RandomBytes(byteCount int) []byte {
	buf := make([]byte, byteCount)
	rand.Read(buf)
	return buf
}

type BytesReader struct {
	Bytes []byte
	*bytes.Reader
}

func NewBytesReader(b []byte) *BytesReader {
	return &BytesReader{
		Bytes:  b,
		Reader: bytes.NewReader(b),
	}
}

// EmptyTo returns to if s is empty.
func EmptyTo(s, to string) string {
	if s == "" {
		return to
	}

	return s
}

// IfElse works like b ? this : that.
func IfElse(b bool, this, that string) string {
	if b {
		return this
	}
	return that
}

// ParseBytes parses a string representation of bytes into the number
// of bytes it represents.
//
// See Also: Bytes, IBytes.
//
// ParseBytes("42MB") -> 42000000, nil
// ParseBytes("42 MB") -> 42000000, nil
// ParseBytes("42 mib") -> 44040192, nil
func ParseBytes(s string) (uint64, error) {
	lastDigit := 0
	hasComma := false
	for _, r := range s {
		if !(unicode.IsDigit(r) || r == '.' || r == ',') {
			break
		}
		if r == ',' {
			hasComma = true
		}
		lastDigit++
	}

	num := s[:lastDigit]
	if hasComma {
		num = strings.Replace(num, ",", "", -1)
	}

	f, err := strconv.ParseFloat(num, 64)
	if err != nil {
		return 0, err
	}

	extra := strings.ToLower(strings.TrimSpace(s[lastDigit:]))
	if m, ok := bytesSizeTable[extra]; ok {
		f *= float64(m)
		if f >= math.MaxUint64 {
			return 0, fmt.Errorf("too large: %v", s)
		}
		return uint64(f), nil
	}

	return 0, fmt.Errorf("unhandled size name: %v", extra)
}

var bytesSizeTable = map[string]uint64{
	"b": Byte, "kib": KiByte, "kb": KByte, "mib": MiByte, "mb": MByte, "gib": GiByte, "gb": GByte,
	"tib": TiByte, "tb": TByte, "pib": PiByte, "pb": PByte, "eib": EiByte, "eb": EByte,
	// Without suffix
	"": Byte, "ki": KiByte, "k": KByte, "mi": MiByte, "m": MByte, "gi": GiByte, "g": GByte,
	"ti": TiByte, "t": TByte, "pi": PiByte, "p": PByte, "ei": EiByte, "e": EByte,
}

// IEC Sizes.
// kibis of bits
const (
	Byte = 1 << (iota * 10)
	KiByte
	MiByte
	GiByte
	TiByte
	PiByte
	EiByte
)

// SI Sizes.
const (
	IByte = 1
	KByte = IByte * 1000
	MByte = KByte * 1000
	GByte = MByte * 1000
	TByte = GByte * 1000
	PByte = TByte * 1000
	EByte = PByte * 1000
)