Simple Bitcoin Transaction

bitcoin-simple-transaction.go

package main

import (
	"bytes"
	"encoding/hex"
	"fmt"
	"github.com/btcsuite/btcd/btcec/v2"
	"github.com/btcsuite/btcd/btcec/v2/schnorr"
	"github.com/btcsuite/btcd/btcutil"
	"github.com/btcsuite/btcd/chaincfg"
	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/txscript"
	"github.com/btcsuite/btcd/wire"
	"log"
)

func main() {
	cfg := &chaincfg.TestNet3Params

	wif, err = btcutil.DecodeWIF("cViUtGHsa6XUxxk2Qht23NKJvEzQq5mJYQVFRsEbB1PmSHMmBs4T")

	taprootAddr, err := btcutil.NewAddressTaproot(
		schnorr.SerializePubKey(
			txscript.ComputeTaprootKeyNoScript(
				wif.PrivKey.PubKey())),
		&chaincfg.TestNet3Params)
	log.Printf("Taproot testnet address: %s\n", taprootAddr.String())

	point, fetcher := GetUnspent(taprootAddr.String())
	destStr := "tb1pvwak065fek4y0mup9p4l7t03ey2nu8as7zgcrlgm9mdfl8gs5rzss490qd"

	byteAddr, _ := DecodeTaprootAddress(destStr, cfg)


	tx := wire.NewMsgTx(wire.TxVersion)

	in := wire.NewTxIn(point, nil, nil)
	tx.AddTxIn(in)

	out := wire.NewTxOut(int64(800), byteAddr)
	tx.AddTxOut(out)

	prevOutput := fetcher.FetchPrevOutput(in.PreviousOutPoint)
	witness, _ := txscript.TaprootWitnessSignature(tx,
		txscript.NewTxSigHashes(tx, fetcher), 0, prevOutput.Value,
		prevOutput.PkScript, txscript.SigHashDefault, wif.PrivKey)
	tx.TxIn[0].Witness = witness

	var signedTx bytes.Buffer
	tx.Serialize(&signedTx)
	finalRawTx := hex.EncodeToString(signedTx.Bytes())

	fmt.Printf("Signed Transaction:\n%s", finalRawTx)
}

func GetUnspent(address string) (*wire.OutPoint, *txscript.MultiPrevOutFetcher) {
	txHash, _ := chainhash.NewHashFromStr(
		"7282d54f485561dd21ba22a971b096eb6d0f45ed2fe6bf8c29d87cee162633b4")
	point := wire.NewOutPoint(txHash, uint32(0))

	script, _ := hex.DecodeString("51208b63f2ee8d7a385e12c0e0f7599cd86ef6e2aed7b9e033762afb177f16c2f309")
	output := wire.NewTxOut(int64(1000), script)
	fetcher := txscript.NewMultiPrevOutFetcher(nil)
	fetcher.AddPrevOut(*point, output)

	return point, fetcher
}

func DecodeTaprootAddress(strAddr string, cfg *chaincfg.Params) ([]byte,
	error) {
	taprootAddr, err := btcutil.DecodeAddress(strAddr, cfg)
	if err != nil {
		return nil, err
	}

	byteAddr, err := txscript.PayToAddrScript(taprootAddr)
	if err != nil {
		return nil, err
	}

	return byteAddr, nil
}