package nson
import (
"encoding/binary"
"encoding/hex"
"fmt"
"strconv"
"strings"
"unsafe"
"github.com/nbd-wtf/go-nostr"
)
/*
nson size
kind chars
content chars
number of tags (let's say it's two)
number of items on the first tag (let's say it's three)
number of chars on the first item
number of chars on the second item
number of chars on the third item
number of items on the second tag (let's say it's two)
number of chars on the first item
number of chars on the second item
"nson":"xxkkccccttnn111122223333nn11112222"
*/
const (
ID_START = 7
ID_END = 7 + 64
PUBKEY_START = 83
PUBKEY_END = 83 + 64
SIG_START = 156
SIG_END = 156 + 128
CREATED_AT_START = 299
CREATED_AT_END = 299 + 10
NSON_STRING_START = 318 // the actual json string for the "nson" field
NSON_VALUES_START = 318 + 2 // skipping the first byte which delimits the nson size
NSON_MARKER_START = 309 // this is used just to determine if an event is nson or not
NSON_MARKER_END = 317 // it's just the `,"nson":` (including ,": garbage to reduce false positives) part
)
var ErrNotNSON = fmt.Errorf("not nson")
func UnmarshalBytes(data []byte, evt *nostr.Event) (err error) {
return Unmarshal(unsafe.String(unsafe.SliceData(data), len(data)), evt)
}
// Unmarshal turns a NSON string into a nostr.Event struct.
func Unmarshal(data string, evt *nostr.Event) (err error) {
defer func() {
if r := recover(); r != nil {
err = fmt.Errorf("failed to decode nson: %v", r)
}
}()
// check if it's nson
if data[NSON_MARKER_START:NSON_MARKER_END] != ",\"nson\":" {
return ErrNotNSON
}
// nson values
nsonSize, nsonDescriptors := parseDescriptors(data)
// static fields
evt.ID = data[ID_START:ID_END]
evt.PubKey = data[PUBKEY_START:PUBKEY_END]
evt.Sig = data[SIG_START:SIG_END]
ts, _ := strconv.ParseUint(data[CREATED_AT_START:CREATED_AT_END], 10, 64)
evt.CreatedAt = nostr.Timestamp(ts)
// dynamic fields
// kind
kindChars := int(nsonDescriptors[0])
kindStart := NSON_VALUES_START + nsonSize + 9 // len(`","kind":`)
evt.Kind, _ = strconv.Atoi(data[kindStart : kindStart+kindChars])
// content
contentChars := int(binary.BigEndian.Uint16(nsonDescriptors[1:3]))
contentStart := kindStart + kindChars + 12 // len(`,"content":"`)
evt.Content, _ = strconv.Unquote(data[contentStart-1 : contentStart+contentChars+1])
// tags
nTags := int(nsonDescriptors[3])
evt.Tags = make(nostr.Tags, nTags)
tagsStart := contentStart + contentChars + 9 // len(`","tags":`)
nsonIndex := 3
tagsIndex := tagsStart
for t := 0; t < nTags; t++ {
nsonIndex++
tagsIndex += 1 // len(`[`) or len(`,`)
nItems := int(nsonDescriptors[nsonIndex])
tag := make(nostr.Tag, nItems)
for n := 0; n < nItems; n++ {
nsonIndex++
itemStart := tagsIndex + 2 // len(`["`) or len(`,"`)
itemChars := int(binary.BigEndian.Uint16(nsonDescriptors[nsonIndex:]))
nsonIndex++
tag[n], _ = strconv.Unquote(data[itemStart-1 : itemStart+itemChars+1])
tagsIndex = itemStart + itemChars + 1 // len(`"`)
}
tagsIndex += 1 // len(`]`)
evt.Tags[t] = tag
}
return err
}
func MarshalBytes(evt *nostr.Event) ([]byte, error) {
v, err := Marshal(evt)
return unsafe.Slice(unsafe.StringData(v), len(v)), err
}
func Marshal(evt *nostr.Event) (string, error) {
// start building the nson descriptors (without the first byte that represents the nson size)
nsonBuf := make([]byte, 256)
// build the tags
nTags := len(evt.Tags)
nsonBuf[3] = uint8(nTags)
nsonIndex := 3 // start here
tagBuilder := strings.Builder{}
tagBuilder.Grow(1000) // a guess
tagBuilder.WriteString(`[`)
for t, tag := range evt.Tags {
nItems := len(tag)
nsonIndex++
nsonBuf[nsonIndex] = uint8(nItems)
tagBuilder.WriteString(`[`)
for i, item := range tag {
v := strconv.Quote(item)
nsonIndex++
binary.BigEndian.PutUint16(nsonBuf[nsonIndex:], uint16(len(v)-2))
nsonIndex++
tagBuilder.WriteString(v)
if nItems > i+1 {
tagBuilder.WriteString(`,`)
}
}
tagBuilder.WriteString(`]`)
if nTags > t+1 {
tagBuilder.WriteString(`,`)
}
}
tagBuilder.WriteString(`]}`)
nsonBuf = nsonBuf[0 : nsonIndex+1]
kind := strconv.Itoa(evt.Kind)
kindChars := len(kind)
nsonBuf[0] = uint8(kindChars)
content := strconv.Quote(evt.Content)
contentChars := len(content) - 2
binary.BigEndian.PutUint16(nsonBuf[1:3], uint16(contentChars))
// actually build the json
base := strings.Builder{}
base.Grow(NSON_VALUES_START + // everything up to "nson":
2 + len(nsonBuf)*2 + // nson
9 + kindChars + // kind and its label
12 + contentChars + // content and its label
9 + tagBuilder.Len() + // tags and its label
2, // the end
)
base.WriteString(`{"id":"` + evt.ID + `","pubkey":"` + evt.PubKey + `","sig":"` + evt.Sig +
`","created_at":` + strconv.FormatInt(int64(evt.CreatedAt), 10) + `,"nson":"`)
nsonSizeBytes := len(nsonBuf)
if nsonSizeBytes > 255 {
return "", fmt.Errorf("can't encode to nson, there are too many tags or tag items")
}
base.WriteString(hex.EncodeToString([]byte{uint8(nsonSizeBytes)})) // nson size (bytes)
base.WriteString(hex.EncodeToString(nsonBuf)) // nson descriptors
base.WriteString(`","kind":` + kind + `,"content":` + content + `,"tags":`)
base.WriteString(tagBuilder.String() /* includes the end */)
return base.String(), nil
}
func parseDescriptors(data string) (int, []byte) {
nsonSizeBytes, _ := hex.DecodeString(data[NSON_STRING_START:NSON_VALUES_START])
size := int(nsonSizeBytes[0]) * 2 // number of bytes is given, we x2 because the string is in hex
values, _ := hex.DecodeString(data[NSON_VALUES_START : NSON_VALUES_START+size])
return size, values
}
// A nson.Event is basically a wrapper over the string that makes it easy to get each event property (except tags).
type Event struct {
data string
descriptorsSize int
descriptors []byte
}
func New(nsonText string) Event {
return Event{data: nsonText}
}
func (ne *Event) parseDescriptors() {
if ne.descriptors == nil {
ne.descriptorsSize, ne.descriptors = parseDescriptors(ne.data)
}
}
func (ne Event) GetID() string { return ne.data[ID_START:ID_END] }
func (ne Event) GetPubkey() string { return ne.data[PUBKEY_START:PUBKEY_END] }
func (ne Event) GetSig() string { return ne.data[SIG_START:SIG_END] }
func (ne Event) GetCreatedAt() nostr.Timestamp {
ts, _ := strconv.ParseUint(ne.data[CREATED_AT_START:CREATED_AT_END], 10, 64)
return nostr.Timestamp(ts)
}
func (ne *Event) GetKind() int {
ne.parseDescriptors()
kindChars := int(ne.descriptors[0])
kindStart := NSON_VALUES_START + ne.descriptorsSize + 9 // len(`","kind":`)
kind, _ := strconv.Atoi(ne.data[kindStart : kindStart+kindChars])
return kind
}
func (ne *Event) GetContent() string {
ne.parseDescriptors()
kindChars := int(ne.descriptors[0])
kindStart := NSON_VALUES_START + ne.descriptorsSize + 9 // len(`","kind":`)
contentChars := int(binary.BigEndian.Uint16(ne.descriptors[1:3]))
contentStart := kindStart + kindChars + 12 // len(`,"content":"`)
content, _ := strconv.Unquote(`"` + ne.data[contentStart:contentStart+contentChars] + `"`)
return content
}