runes-js/src/witness.ts

A typescript library for Runes protocol of Bitcoin

import * as ecc from "@bitcoinerlab/secp256k1"
import * as bitcoin from "bitcoinjs-lib"

export function buildWitnessScript({
  recover = false,
  ...options
}: WitnessScriptOptions) {
  bitcoin.initEccLib(ecc)
  if (!options.mediaType || !options.mediaContent || !options.xkey) {
    throw new OrditSDKError("Failed to build witness script")
  }

  if (recover) {
    return bitcoin.script.compile([
      Buffer.from(options.xkey, "hex"),
      bitcoin.opcodes.OP_CHECKSIG,
    ])
  }

  const contentChunks = chunkContent(
    options.mediaContent,
    !options.mediaType.includes("text") ? "base64" : "utf8",
  )
  const contentStackElements = contentChunks.map(opPush)
  const metaStackElements: (number | Buffer)[] = []

  if (typeof options.meta === "object") {
    metaStackElements.push(
      ...[
        bitcoin.opcodes.OP_FALSE,
        bitcoin.opcodes.OP_IF,
        opPush("ord"),
        1,
        1,
        opPush("application/json;charset=utf-8"),
        bitcoin.opcodes.OP_0,
      ],
    )
    const metaChunks = chunkContent(JSON.stringify(options.meta))

    metaChunks &&
      metaChunks.forEach((chunk) => {
        metaStackElements.push(opPush(chunk))
      })
    metaChunks && metaStackElements.push(bitcoin.opcodes.OP_ENDIF)
  }

  const baseStackElements = [
    Buffer.from(options.xkey, "hex"),
    bitcoin.opcodes.OP_CHECKSIG,
    bitcoin.opcodes.OP_FALSE,
    bitcoin.opcodes.OP_IF,
    opPush("ord"),
    1,
    1,
    opPush(options.mediaType),
    bitcoin.opcodes.OP_0,
  ]

  const commitmentStackElements: (number | Buffer)[] = []
  if (options.commitment) {
    commitmentStackElements.push(options.commitment)
  }

  return bitcoin.script.compile([
    ...baseStackElements,
    ...contentStackElements,
    ...commitmentStackElements,
    bitcoin.opcodes.OP_ENDIF,
    ...metaStackElements,
  ])
}

export type WitnessScriptOptions = {
  xkey: string
  mediaContent: string
  mediaType: string
  meta: any
  commitment?: Buffer
  recover?: boolean
}

export class OrditSDKError extends Error {
  constructor(message: string) {
    super(message)
    this.name = "OrditSDKError"
  }
}

export const MAXIMUM_SCRIPT_ELEMENT_SIZE = 520

export const chunkContent = function (
  str: string,
  encoding: BufferEncoding = "utf8",
) {
  const contentBuffer = Buffer.from(str, encoding)
  const chunks: Buffer[] = []
  let chunkedBytes = 0

  while (chunkedBytes < contentBuffer.byteLength) {
    const chunk = contentBuffer.subarray(
      chunkedBytes,
      chunkedBytes + MAXIMUM_SCRIPT_ELEMENT_SIZE,
    )
    chunkedBytes += chunk.byteLength
    chunks.push(chunk)
  }

  return chunks
}

function opPush(data: string | Buffer) {
  const buff = Buffer.isBuffer(data) ? data : Buffer.from(data, "utf8")
  if (buff.byteLength > MAXIMUM_SCRIPT_ELEMENT_SIZE)
    throw new OrditSDKError(
      "Data is too large to push. Use chunkContent to split data into smaller chunks",
    )

  return Buffer.concat([buff])
}