bitcoin-tx-lib/src/utils/txutils.ts

A Typescript library for building and signing Bitcoin transactions

import { bech32 } from "bech32"
import { bytesToHex, hexToBytes, mergeUint8Arrays, ripemd160 } from "."
import { base58 } from "@scure/base" 
import { OP_CODES } from "../constants/opcodes"

export function addressToScriptPubKey(address: string): Uint8Array {
    if(["1", "m", "n"].includes(address[0])) {
        // P2PKH Legacy
        const decoded = base58.decode(address)
        const hash = decoded.slice(1, -4) // remove the prefix and checksum
        const prefixScript = new Uint8Array([OP_CODES.OP_DUP, OP_CODES.OP_HASH160, hash.length])
        const sufixScript = new Uint8Array([OP_CODES.OP_EQUALVERIFY, OP_CODES.OP_CHECKSIG])
        return mergeUint8Arrays(prefixScript, hash, sufixScript)
    // wallet not support this type of transaction 
    // } else if (["2", "3"].includes(address[0])) {
    //     // P2SH Legacy
    //     const decoded = hexToBytes(Base58.decode(address))
    //     const hash = decoded.slice(1, -4) // remove the prefix and checksum
    //     const prefixScript = new Uint8Array([OP_CODES.OP_HASH160, hash.length])
    //     const sufixScript = new Uint8Array([OP_CODES.OP_EQUAL])
    //     return mergeUint8Arrays(prefixScript, hash, sufixScript)
    // } 
    } else if (["tb1", "bc1"].includes(address.substring(0,3))) {
        // SegWit (P2WPKH, P2WSH)
        const data = bech32.decode(address)
        const hash = new Uint8Array(bech32.fromWords(data.words.slice(1)))
        if(hash) {
            const prefixScript = new Uint8Array([OP_CODES.OP_0, hash.length])
            return mergeUint8Arrays(prefixScript, hash)
        }
        throw new Error("Invalid bech32 format address")
    }
    throw new Error("not supported format address or type of transaction")
}

export function pubkeyToScriptCode(pubkey: string) {
    const hash = ripemd160(hexToBytes(pubkey), true) as Uint8Array
    
    const prefixScript = new Uint8Array([OP_CODES.OP_DUP, OP_CODES.OP_HASH160, hash.length])
    const sufixScript = new Uint8Array([OP_CODES.OP_EQUALVERIFY, OP_CODES.OP_CHECKSIG])

    const script = mergeUint8Arrays(prefixScript, hash, sufixScript)
    const scriptLength = new Uint8Array([script.length])

    return bytesToHex(mergeUint8Arrays(scriptLength, script))
}

export function scriptPubkeyToScriptCode(script: string) : Uint8Array {
    const scriptPubkey = hexToBytes(script)

    if(scriptPubkey[0] == 0x00 && scriptPubkey[1] == 0x14) {
        const hash = scriptPubkey.slice(2)
        const prefixScript = new Uint8Array([OP_CODES.OP_DUP, OP_CODES.OP_HASH160, hash.length])
        const sufixScript = new Uint8Array([OP_CODES.OP_EQUALVERIFY, OP_CODES.OP_CHECKSIG])
        const scriptCode = mergeUint8Arrays(prefixScript, hash, sufixScript)
        return new Uint8Array([scriptCode.length, ...scriptCode])
    }
    if(scriptPubkey[0] == 0x79 && scriptPubkey[2] == 0x14) {
        return new Uint8Array([scriptPubkey.length, ...scriptPubkey])
    }
        
    throw new Error("scriptPubkey no segwit, expected P2WPKH")
}