// Copyright 2017 gf Author(https://github.com/gogf/gf). All Rights Reserved.
//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://github.com/gogf/gf.

// Package gbinary provides useful API for handling binary/bytes data.
//
// 注意gbinary模块统一使用LittleEndian进行编码。
package gbinary

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"math"
)

// 二进制位(0|1)
type Bit int8

// 针对基本类型进行二进制打包，支持的基本数据类型包括:int/8/16/32/64、uint/8/16/32/64、float32/64、bool、string、[]byte
// 其他未知类型使用 fmt.Sprintf("%v", value) 转换为字符串之后处理
func Encode(vs ...interface{}) []byte {
	buf := new(bytes.Buffer)
	for i := 0; i < len(vs); i++ {
		if vs[i] == nil {
			return buf.Bytes()
		}

		switch value := vs[i].(type) {
		case int:
			buf.Write(EncodeInt(value))
		case int8:
			buf.Write(EncodeInt8(value))
		case int16:
			buf.Write(EncodeInt16(value))
		case int32:
			buf.Write(EncodeInt32(value))
		case int64:
			buf.Write(EncodeInt64(value))
		case uint:
			buf.Write(EncodeUint(value))
		case uint8:
			buf.Write(EncodeUint8(value))
		case uint16:
			buf.Write(EncodeUint16(value))
		case uint32:
			buf.Write(EncodeUint32(value))
		case uint64:
			buf.Write(EncodeUint64(value))
		case bool:
			buf.Write(EncodeBool(value))
		case string:
			buf.Write(EncodeString(value))
		case []byte:
			buf.Write(value)
		case float32:
			buf.Write(EncodeFloat32(value))
		case float64:
			buf.Write(EncodeFloat64(value))
		default:
			if err := binary.Write(buf, binary.LittleEndian, value); err != nil {
				buf.Write(EncodeString(fmt.Sprintf("%v", value)))
			}
		}
	}
	return buf.Bytes()
}

// 将变量转换为二进制[]byte，并指定固定的[]byte长度返回，长度单位为字节(byte)；
// 如果转换的二进制长度超过指定长度，那么进行截断处理
func EncodeByLength(length int, vs ...interface{}) []byte {
	b := Encode(vs...)
	if len(b) < length {
		b = append(b, make([]byte, length-len(b))...)
	} else if len(b) > length {
		b = b[0:length]
	}
	return b
}

// 整形二进制解包，注意第二个及其后参数为字长确定的整形变量的指针地址，以便确定解析的[]byte长度，
// 例如：int8/16/32/64、uint8/16/32/64、float32/64等等
func Decode(b []byte, vs ...interface{}) error {
	buf := bytes.NewBuffer(b)
	for i := 0; i < len(vs); i++ {
		err := binary.Read(buf, binary.LittleEndian, vs[i])
		if err != nil {
			return err
		}
	}
	return nil
}

func EncodeString(s string) []byte {
	return []byte(s)
}

func DecodeToString(b []byte) string {
	return string(b)
}

func EncodeBool(b bool) []byte {
	if b == true {
		return []byte{1}
	} else {
		return []byte{0}
	}
}

// 自动识别int类型长度，转换为[]byte
func EncodeInt(i int) []byte {
	if i <= math.MaxInt8 {
		return EncodeInt8(int8(i))
	} else if i <= math.MaxInt16 {
		return EncodeInt16(int16(i))
	} else if i <= math.MaxInt32 {
		return EncodeInt32(int32(i))
	} else {
		return EncodeInt64(int64(i))
	}
}

// 自动识别uint类型长度，转换为[]byte
func EncodeUint(i uint) []byte {
	if i <= math.MaxUint8 {
		return EncodeUint8(uint8(i))
	} else if i <= math.MaxUint16 {
		return EncodeUint16(uint16(i))
	} else if i <= math.MaxUint32 {
		return EncodeUint32(uint32(i))
	} else {
		return EncodeUint64(uint64(i))
	}
}

func EncodeInt8(i int8) []byte {
	return []byte{byte(i)}
}

func EncodeUint8(i uint8) []byte {
	return []byte{byte(i)}
}

func EncodeInt16(i int16) []byte {
	bytes := make([]byte, 2)
	binary.LittleEndian.PutUint16(bytes, uint16(i))
	return bytes
}

func EncodeUint16(i uint16) []byte {
	bytes := make([]byte, 2)
	binary.LittleEndian.PutUint16(bytes, i)
	return bytes
}

func EncodeInt32(i int32) []byte {
	bytes := make([]byte, 4)
	binary.LittleEndian.PutUint32(bytes, uint32(i))
	return bytes
}

func EncodeUint32(i uint32) []byte {
	bytes := make([]byte, 4)
	binary.LittleEndian.PutUint32(bytes, i)
	return bytes
}

func EncodeInt64(i int64) []byte {
	bytes := make([]byte, 8)
	binary.LittleEndian.PutUint64(bytes, uint64(i))
	return bytes
}

func EncodeUint64(i uint64) []byte {
	bytes := make([]byte, 8)
	binary.LittleEndian.PutUint64(bytes, i)
	return bytes
}

func EncodeFloat32(f float32) []byte {
	bits := math.Float32bits(f)
	bytes := make([]byte, 4)
	binary.LittleEndian.PutUint32(bytes, bits)
	return bytes
}

func EncodeFloat64(f float64) []byte {
	bits := math.Float64bits(f)
	bytes := make([]byte, 8)
	binary.LittleEndian.PutUint64(bytes, bits)
	return bytes
}

// 当b位数不够时，进行高位补0
func fillUpSize(b []byte, l int) []byte {
	if len(b) >= l {
		return b
	}
	c := make([]byte, 0)
	c = append(c, b...)
	for i := 0; i < l-len(b); i++ {
		c = append(c, 0x00)
	}
	return c
}

// 将二进制解析为int类型，根据[]byte的长度进行自动转换.
// 注意内部使用的是uint*，使用int会造成位丢失。
func DecodeToInt(b []byte) int {
	if len(b) < 2 {
		return int(DecodeToUint8(b))
	} else if len(b) < 3 {
		return int(DecodeToUint16(b))
	} else if len(b) < 5 {
		return int(DecodeToUint32(b))
	} else {
		return int(DecodeToUint64(b))
	}
}

// 将二进制解析为uint类型，根据[]byte的长度进行自动转换
func DecodeToUint(b []byte) uint {
	if len(b) < 2 {
		return uint(DecodeToUint8(b))
	} else if len(b) < 3 {
		return uint(DecodeToUint16(b))
	} else if len(b) < 5 {
		return uint(DecodeToUint32(b))
	} else {
		return uint(DecodeToUint64(b))
	}
}

// 将二进制解析为bool类型，识别标准是判断二进制中数值是否都为0，或者为空
func DecodeToBool(b []byte) bool {
	if len(b) == 0 {
		return false
	}
	if bytes.Compare(b, make([]byte, len(b))) == 0 {
		return false
	}
	return true
}

func DecodeToInt8(b []byte) int8 {
	return int8(b[0])
}

func DecodeToUint8(b []byte) uint8 {
	return uint8(b[0])
}

func DecodeToInt16(b []byte) int16 {
	return int16(binary.LittleEndian.Uint16(fillUpSize(b, 2)))
}

func DecodeToUint16(b []byte) uint16 {
	return binary.LittleEndian.Uint16(fillUpSize(b, 2))
}

func DecodeToInt32(b []byte) int32 {
	return int32(binary.LittleEndian.Uint32(fillUpSize(b, 4)))
}

func DecodeToUint32(b []byte) uint32 {
	return binary.LittleEndian.Uint32(fillUpSize(b, 4))
}

func DecodeToInt64(b []byte) int64 {
	return int64(binary.LittleEndian.Uint64(fillUpSize(b, 8)))
}

func DecodeToUint64(b []byte) uint64 {
	return binary.LittleEndian.Uint64(fillUpSize(b, 8))
}

func DecodeToFloat32(b []byte) float32 {
	return math.Float32frombits(binary.LittleEndian.Uint32(fillUpSize(b, 4)))
}

func DecodeToFloat64(b []byte) float64 {
	return math.Float64frombits(binary.LittleEndian.Uint64(fillUpSize(b, 8)))
}

// 默认编码
func EncodeBits(bits []Bit, i int, l int) []Bit {
	return EncodeBitsWithUint(bits, uint(i), l)
}

// 将ui按位合并到bits数组中，并占length长度位(注意：uis数组中存放的是二进制的0|1数字)
func EncodeBitsWithUint(bits []Bit, ui uint, l int) []Bit {
	a := make([]Bit, l)
	for i := l - 1; i >= 0; i-- {
		a[i] = Bit(ui & 1)
		ui >>= 1
	}
	if bits != nil {
		return append(bits, a...)
	} else {
		return a
	}
}

// 将bits转换为[]byte，从左至右进行编码，不足1 byte按0往末尾补充
func EncodeBitsToBytes(bits []Bit) []byte {
	if len(bits)%8 != 0 {
		for i := 0; i < len(bits)%8; i++ {
			bits = append(bits, 0)
		}
	}
	b := make([]byte, 0)
	for i := 0; i < len(bits); i += 8 {
		b = append(b, byte(DecodeBitsToUint(bits[i:i+8])))
	}
	return b
}

// 解析为int
func DecodeBits(bits []Bit) int {
	v := int(0)
	for _, i := range bits {
		v = v<<1 | int(i)
	}
	return v
}

// 解析为uint
func DecodeBitsToUint(bits []Bit) uint {
	v := uint(0)
	for _, i := range bits {
		v = v<<1 | uint(i)
	}
	return v
}

// 解析[]byte为字位数组[]uint8
func DecodeBytesToBits(bs []byte) []Bit {
	bits := make([]Bit, 0)
	for _, b := range bs {
		bits = EncodeBitsWithUint(bits, uint(b), 8)
	}
	return bits
}