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 }