From e9466bebc5a9ddeddf92d267182ff085cd6925d0 Mon Sep 17 00:00:00 2001
From: Steven Polley <himself@stevenpolley.net>
Date: Tue, 30 Sep 2025 23:02:07 -0600
Subject: [PATCH] pass errors up rather than logging directly

---
 providers/bitcoinElectrum/bitcoin.go      | 22 ++++++----------------
 providers/bitcoinElectrum/providerImpl.go | 18 ++++++------------
 2 files changed, 12 insertions(+), 28 deletions(-)

diff --git a/providers/bitcoinElectrum/bitcoin.go b/providers/bitcoinElectrum/bitcoin.go
index 366a274..96f2081 100644
--- a/providers/bitcoinElectrum/bitcoin.go
+++ b/providers/bitcoinElectrum/bitcoin.go
@@ -3,7 +3,7 @@ package bitcoinElectrum
 import (
 	"crypto/sha256"
 	"encoding/hex"
-	"log"
+	"fmt"
 	"sync/atomic"
 
 	"github.com/btcsuite/btcd/btcutil"
@@ -43,13 +43,10 @@ func addressToScriptHash(address btcutil.Address) (string, error) {
 }
 
 // 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)
-
+func scanBranch(masterKey *hdkeychain.ExtendedKey, branch uint32, gapLimit int, spvServer string) (int64, error) {
 	branchKey, err := masterKey.Derive(branch)
 	if err != nil {
-		log.Printf("Error deriving branch %d: %v", branch, err)
-		return 0
+		return 0, fmt.Errorf("error deriving branch %d: %v", branch, err)
 	}
 
 	var branchTotalBalance int64
@@ -57,35 +54,28 @@ func scanBranch(masterKey *hdkeychain.ExtendedKey, branch uint32, gapLimit int,
 
 	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
+			return 0, fmt.Errorf("could not derive address at index %d on branch %d: %v", i, branch, err)
 		}
 
 		// 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
+			return 0, fmt.Errorf("error getting balance for %s: %v", address.EncodeAddress(), err)
 		}
 
 		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
+	return branchTotalBalance, nil
 }
diff --git a/providers/bitcoinElectrum/providerImpl.go b/providers/bitcoinElectrum/providerImpl.go
index 61228c2..50fe6fe 100644
--- a/providers/bitcoinElectrum/providerImpl.go
+++ b/providers/bitcoinElectrum/providerImpl.go
@@ -3,8 +3,6 @@ package bitcoinElectrum
 import (
 	"fmt"
 	"os"
-	"sync"
-	"sync/atomic"
 
 	"github.com/btcsuite/btcd/btcutil/hdkeychain"
 )
@@ -27,7 +25,7 @@ func (p *Provider) Configure() error {
 	p.ynabAccountID = os.Getenv("bitcoin_ynab_account")
 	p.spvServer = os.Getenv("bitcoin_spv_server")
 	p.coinGeckoApiKey = os.Getenv("bitcoin_coingecko_api_key")
-	p.gapLimit = 20
+	p.gapLimit = 10
 	if zpub == "" || p.ynabAccountID == "" || p.spvServer == "" || p.coinGeckoApiKey == "" {
 		return fmt.Errorf("this account provider is not configured")
 	}
@@ -43,21 +41,17 @@ func (p *Provider) Configure() error {
 // Returns slices of account balances and mapped YNAB account IDs, along with an error
 func (p *Provider) GetBalances() ([]int, []string, error) {
 	var totalSats int64
-	var wg sync.WaitGroup
 
 	// branch 0 = regular
 	// branch 1 = change addresses
 	for _, branch := range []uint32{0, 1} {
-		wg.Add(1)
-		go func(branch uint32) {
-			defer wg.Done()
-			branchSats := scanBranch(p.masterKey, branch, p.gapLimit, p.spvServer)
-			atomic.AddInt64(&branchSats, totalSats)
-		}(branch)
+		branchSats, err := scanBranch(p.masterKey, branch, p.gapLimit, p.spvServer)
+		if err != nil {
+			return nil, nil, fmt.Errorf("failed to scan branch '%v': %v", branch, err)
+		}
+		totalSats += branchSats
 	}
 
-	wg.Wait()
-
 	cad, err := convertBTCToCAD(totalSats, p.coinGeckoApiKey)
 	if err != nil {
 		return nil, nil, fmt.Errorf("failed to convert sats to CAD: %v", err)