Add kind to nevent decode and encode (#304)

nip19.ts

@@ -11,6 +11,19 @@ const Bech32MaxSize = 5000
  */
 export const BECH32_REGEX = /[\x21-\x7E]{1,83}1[023456789acdefghjklmnpqrstuvwxyz]{6,}/
 
+function integerToUint8Array(number: number) {
+  // Create a Uint8Array with enough space to hold a 32-bit integer (4 bytes).
+  const uint8Array = new Uint8Array(4)
+
+  // Use bitwise operations to extract the bytes.
+  uint8Array[0] = (number >> 24) & 0xff // Most significant byte (MSB)
+  uint8Array[1] = (number >> 16) & 0xff
+  uint8Array[2] = (number >> 8) & 0xff
+  uint8Array[3] = number & 0xff // Least significant byte (LSB)
+
+  return uint8Array
+}
+
 export type ProfilePointer = {
   pubkey: string // hex
   relays?: string[]
@@ -20,6 +33,7 @@ export type EventPointer = {
   id: string // hex
   relays?: string[]
   author?: string
+  kind?: number
 }
 
 export type AddressPointer = {
@@ -73,6 +87,7 @@ export function decode(nip19: string): DecodeResult {
       if (!tlv[0]?.[0]) throw new Error('missing TLV 0 for nevent')
       if (tlv[0][0].length !== 32) throw new Error('TLV 0 should be 32 bytes')
       if (tlv[2] && tlv[2][0].length !== 32) throw new Error('TLV 2 should be 32 bytes')
+      if (tlv[3] && tlv[3][0].length !== 4) throw new Error('TLV 3 should be 4 bytes')
 
       return {
         type: 'nevent',
@@ -80,6 +95,7 @@ export function decode(nip19: string): DecodeResult {
           id: bytesToHex(tlv[0][0]),
           relays: tlv[1] ? tlv[1].map(d => utf8Decoder.decode(d)) : [],
           author: tlv[2]?.[0] ? bytesToHex(tlv[2][0]) : undefined,
+          kind: tlv[3]?.[0] ? parseInt(bytesToHex(tlv[3][0]), 16) : undefined,
         },
       }
     }
@@ -172,11 +188,18 @@ export function nprofileEncode(profile: ProfilePointer): `nprofile1${string}` {
 }
 
 export function neventEncode(event: EventPointer): `nevent1${string}` {
+  let kindArray
+  if (event.kind != undefined) {
+    kindArray = integerToUint8Array(event.kind)
+  }
+
   let data = encodeTLV({
     0: [hexToBytes(event.id)],
     1: (event.relays || []).map(url => utf8Encoder.encode(url)),
     2: event.author ? [hexToBytes(event.author)] : [],
+    3: kindArray ? [new Uint8Array(kindArray)] : [],
   })
+
   return encodeBech32('nevent', data)
 }