add new bitcoin electrum SPV provider

providers/bitcoinElectrum/bitcoin.go

@@ -0,0 +1,91 @@
+package bitcoinElectrum
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"log"
+	"sync/atomic"
+
+	"github.com/btcsuite/btcd/btcutil"
+	"github.com/btcsuite/btcd/btcutil/hdkeychain"
+	"github.com/btcsuite/btcd/chaincfg"
+	"github.com/btcsuite/btcd/txscript"
+)
+
+// Derives a P2WPKH address at a specific index from a branch key.
+func deriveAddress(branchKey *hdkeychain.ExtendedKey, index uint32) (btcutil.Address, error) {
+	childKey, err := branchKey.Derive(index)
+	if err != nil {
+		return nil, err
+	}
+	pubKey, err := childKey.ECPubKey()
+	if err != nil {
+		return nil, err
+	}
+	// Note: For zpub/vpub, use NewAddressWitnessPubKeyHash.
+	// For ypub/upub, use NewAddressScriptHash with a P2WPKH script.
+	// For xpub/tpub, use NewAddressPubKeyHash.
+	return btcutil.NewAddressWitnessPubKeyHash(btcutil.Hash160(pubKey.SerializeCompressed()), &chaincfg.MainNetParams)
+}
+
+// Converts a btcutil.Address to an Electrum scripthash.
+func addressToScriptHash(address btcutil.Address) (string, error) {
+	script, err := txscript.PayToAddrScript(address)
+	if err != nil {
+		return "", err
+	}
+	hash := sha256.Sum256(script)
+	// Reverse byte order for Electrum protocol
+	for i, j := 0, len(hash)-1; i < j; i, j = i+1, j-1 {
+		hash[i], hash[j] = hash[j], hash[i]
+	}
+	return hex.EncodeToString(hash[:]), nil
+}
+
+// Scans a derivation branch (m/0 or m/1) for balances until the gap limit is reached.
+func scanBranch(masterKey *hdkeychain.ExtendedKey, branch uint32, gapLimit int, spvServer string) int64 {
+	log.Printf("Scanning branch m/%d/k...", branch)
+
+	branchKey, err := masterKey.Derive(branch)
+	if err != nil {
+		log.Printf("Error deriving branch %d: %v", branch, err)
+		return 0
+	}
+
+	var branchTotalBalance int64
+	unusedAddressCount := 0
+
+	for i := uint32(0); ; i++ {
+		if unusedAddressCount >= gapLimit {
+			log.Printf("Gap limit of %d reached on branch m/%d. Stopping scan.", gapLimit, branch)
+			break
+		}
+
+		// 3. Derive child address
+		address, err := deriveAddress(branchKey, i)
+		if err != nil {
+			log.Printf("Could not derive address at index %d on branch %d: %v", i, branch, err)
+			continue
+		}
+
+		// 4. Get balance from Electrum server
+		balance, err := getAddressBalance(spvServer, address)
+		if err != nil {
+			log.Printf("Error getting balance for %s: %v", address.EncodeAddress(), err)
+			// On error, we can't know if it's used, so we continue scanning.
+			unusedAddressCount = 0
+			continue
+		}
+
+		total := balance.Result.Confirmed + balance.Result.Unconfirmed
+		if total > 0 {
+			log.Printf("Found balance for m/%d/%d (%s): %.8f BTC", branch, i, address.EncodeAddress(), btcutil.Amount(total).ToBTC())
+			atomic.AddInt64(&branchTotalBalance, total)
+			unusedAddressCount = 0 // Reset gap counter on finding a used address
+		} else {
+			log.Printf("No balance for m/%d/%d (%s)", branch, i, address.EncodeAddress())
+			unusedAddressCount++
+		}
+	}
+	return branchTotalBalance
+}