asset.go

/*
Copyright (c) 2018 Zettant Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package bbclib

import (
	"bytes"
	"crypto/sha256"
	"encoding/binary"
	"fmt"
	"github.com/ugorji/go/codec"
)

/*
BBcAsset definition

"IDLength" and "digestCalculating" are not included in a packed data. They are for internal use only.

"AssetID" is the SHA256 digest of packed BBcAsset data, which contains from "UserID" to "AssetBody".
The length of "AssetID" and "UserID" is defined by "IDLength".
"Nonce" is automatically determined with random value.
BBcAsset can contain a digest of a file, string, map[string]interface{} object as asset.
*/
type (
	BBcAsset struct {
		IdLengthConf      *BBcIdConfig
		Version			  uint32
		digestCalculating bool
		AssetID           []byte
		UserID            []byte
		Nonce             []byte
		AssetFileSize     uint32
		AssetFileDigest   []byte
		AssetBodyType     uint16
		AssetBodySize     uint16
		AssetBody         []byte
	}
)

// An object for messagepack encoding/decoding
var (
	mh codec.MsgpackHandle
)

// encodeMessagePack encodes object in messagepack data
func encodeMessagePack(values interface{}) ([]byte, error) {
	buf := make([]byte, 0, 65536)

	err := codec.NewEncoderBytes(&buf, &mh).Encode(values)
	if err != nil {
		return nil, err
	}
	return buf, nil
}

// decodeMessagePack decodes messagepack data
func decodeMessagePack(buf []byte) (interface{}, error) {
	var values interface{}

	err := codec.NewDecoderBytes(buf, &mh).Decode(&values)
	if err != nil {
		return nil, err
	}
	return values, nil
}

// Stringer outputs the content of the object
func (p *BBcAsset) Stringer() string {
	ret := "  Asset:\n"
	ret += fmt.Sprintf("     asset_id: %x\n", p.AssetID)
	ret += fmt.Sprintf("     user_id: %x\n", p.UserID)
	ret += fmt.Sprintf("     nonce: %x\n", p.Nonce)
	ret += fmt.Sprintf("     file_size: %d\n", p.AssetFileSize)
	if p.AssetFileDigest != nil {
		ret += fmt.Sprintf("     file_digest: %x\n", p.AssetFileDigest)
	} else {
		ret += "     file_digest: None\n"
	}
	ret += fmt.Sprintf("     body_size: %d\n", p.AssetBodySize)
	ret += fmt.Sprintf("     body: %v\n", p.AssetBody)
	return ret
}

// Set ID length configuration
func (p *BBcAsset) SetIdLengthConf(conf * BBcIdConfig) {
	p.IdLengthConf = conf
}

// Add sets userID in the BBcAsset object
func (p *BBcAsset) Add(userID *[]byte) {
	if userID != nil {
		p.UserID = make([]byte, p.IdLengthConf.UserIdLength)
		copy(p.UserID, (*userID)[:p.IdLengthConf.UserIdLength])
	}
	p.Nonce = GetRandomValue(p.IdLengthConf.NonceLength)
}

// AddFile add the digest of file in the BBcAsset object
// Note that this method adds the SHA256 digest of the file content (not file binary itself)
func (p *BBcAsset) AddFile(fileContent *[]byte) {
	p.AssetFileSize = uint32(binary.Size(fileContent))
	digest := sha256.Sum256(*fileContent)
	p.AssetFileDigest = digest[:]
}

// AddBody sets data in the BBcAsset object
func (p *BBcAsset) AddBody(bodyContent interface{}) {
	if body, ok := bodyContent.(string); ok {
		p.AssetBody = []byte(body)
		p.AssetBodySize = uint16(len(body))
	} else if body, ok := bodyContent.([]byte); ok {
		copy(p.AssetBody, body)
		p.AssetBodySize = uint16(len(body))
	} else {
		_ = p.AddBodyObject(bodyContent)
	}
}

// AddBodyString sets a string data in the BBcAsset object
func (p *BBcAsset) AddBodyString(bodyContent string) {
	p.AssetBodyType = 0
	p.AssetBody = []byte(bodyContent)
	p.AssetBodySize = uint16(len(bodyContent))
}

// AddBodyObject sets an object data in the BBcAsset object and convert it in MessagePack format
func (p *BBcAsset) AddBodyObject(bodyContent interface{}) error {
	p.AssetBodyType = 1
	var err error
	p.AssetBody, err = encodeMessagePack(bodyContent)
	if err != nil {
		return err
	}
	p.AssetBodySize = uint16(len(p.AssetBody))
	return nil
}

// GetBodyObject returns the object which is in MessagePack format
func (p *BBcAsset) GetBodyObject() (interface{}, error) {
	if p.AssetBodyType != 1 {
		return nil, nil
	}
	return decodeMessagePack(p.AssetBody)
}

// Digest calculates the SHA256 digest of the AssetID value of the BBcAsset object
func (p *BBcAsset) Digest() []byte {
	p.digestCalculating = true
	asset, err := p.Pack()
	if err != nil {
		p.digestCalculating = false
		return nil
	}

	digest := sha256.Sum256(asset)
	if p.AssetID == nil {
		p.AssetID = make([]byte, p.IdLengthConf.AssetIdLength)
	}
	p.AssetID = digest[:p.IdLengthConf.AssetIdLength]
	p.digestCalculating = false
	return digest[:]
}

// Pack returns the binary data of the BBcAsset object
func (p *BBcAsset) Pack() ([]byte, error) {
	buf := new(bytes.Buffer)

	if !p.digestCalculating {
		if p.AssetID == nil {
			p.Digest()
		}
		PutBigInt(buf, &p.AssetID, p.IdLengthConf.AssetIdLength)
	}
	PutBigInt(buf, &p.UserID, p.IdLengthConf.UserIdLength)
	PutBigInt(buf, &p.Nonce, len(p.Nonce))
	Put4byte(buf, p.AssetFileSize)
	if p.AssetFileSize > 0 {
		PutBigInt(buf, &p.AssetFileDigest, 32)
	}

	Put2byte(buf, p.AssetBodyType)
	Put2byte(buf, p.AssetBodySize)
	if p.AssetBodySize > 0 {
		if err := binary.Write(buf, binary.LittleEndian, p.AssetBody); err != nil {
			return nil, err
		}
	}
	return buf.Bytes(), nil
}

// Unpack the BBcAsset object to the binary data
func (p *BBcAsset) Unpack(dat *[]byte) error {
	if p.IdLengthConf == nil {
		p.IdLengthConf = &BBcIdConfig{}
	}

	var err error
	buf := bytes.NewBuffer(*dat)

	p.AssetID, p.IdLengthConf.AssetIdLength, err = GetBigInt(buf)
	if err != nil {
		return err
	}

	p.UserID, p.IdLengthConf.UserIdLength, err = GetBigInt(buf)
	if err != nil {
		return err
	}

	p.Nonce, p.IdLengthConf.NonceLength, err = GetBigInt(buf)
	if err != nil {
		return err
	}

	p.AssetFileSize, err = Get4byte(buf)
	if err != nil {
		return err
	}
	if p.AssetFileSize > 0 {
		p.AssetFileDigest, _, err = GetBigInt(buf)
		if err != nil {
			return err
		}
	}

	p.AssetBodyType, err = Get2byte(buf)
	if err != nil {
		return err
	}
	p.AssetBodySize, err = Get2byte(buf)
	if err != nil {
		return err
	}
	p.AssetBody, _, err = GetBytes(buf, int(p.AssetBodySize))

	return err
}