From 86f30a216cdd82d9fd8bde88fdebf0fbcd468b71 Mon Sep 17 00:00:00 2001
From: Konstantin Ullrich <konstantinullrich12@gmail.com>
Date: Mon, 1 Dec 2025 21:43:46 +0100
Subject: [PATCH] fix: crypto amount calculation logic with max decimals
 (#2697)

* fix: crypto amount calculation logic with max decimals

* refactor: remove `_setCryptoNumMaximumFractionDigits` and `_cryptoNumberFormat` to simplify `OutputBase` logic
---
 cw_core/lib/crypto_currency.dart | 17 +++++++++--
 lib/view_model/send/output.dart  | 52 +++++---------------------------
 2 files changed, 21 insertions(+), 48 deletions(-)

diff --git a/cw_core/lib/crypto_currency.dart b/cw_core/lib/crypto_currency.dart
index b35531b72..68066b12a 100644
--- a/cw_core/lib/crypto_currency.dart
+++ b/cw_core/lib/crypto_currency.dart
@@ -1,6 +1,9 @@
 import 'package:cw_core/currency.dart';
 import 'package:cw_core/enumerable_item.dart';
 import 'package:collection/collection.dart';
+import 'package:cw_core/parse_fixed.dart';
+
+import 'format_fixed.dart';
 
 class CryptoCurrency extends EnumerableItem<int> with Serializable<int> implements Currency {
   const CryptoCurrency({
@@ -394,7 +397,15 @@ class CryptoCurrency extends EnumerableItem<int> with Serializable<int> implemen
   @override
   String toString() => title;
 
-  bool titleAndTagEqual(CryptoCurrency other) {
-    return title == other.title && tag == other.tag;
-  }
+  bool titleAndTagEqual(CryptoCurrency other) => title == other.title && tag == other.tag;
+
+  /// Format the raw amount into its decimal representation eg. turn Sats into Bitcoin
+  String formatAmount(BigInt amount, {int? fractionalDigits, bool trimZeros = true}) =>
+      formatFixed(amount, decimals, fractionalDigits: fractionalDigits, trimZeros: trimZeros);
+
+  /// Parse the [value] and turn it into the smallest denomination eg. turn Bitcoin into Sats
+  BigInt parseAmount(String value) => parseFixed(value, decimals);
+
+  /// Try parsing the [value] and turn it into the smallest denomination eg. turn Bitcoin into Sats
+  BigInt? tryParseAmount(String value) => tryParseFixed(value, decimals);
 }
diff --git a/lib/view_model/send/output.dart b/lib/view_model/send/output.dart
index 0badd16df..c2e69dfcb 100644
--- a/lib/view_model/send/output.dart
+++ b/lib/view_model/send/output.dart
@@ -19,7 +19,6 @@ import 'package:cw_core/transaction_history.dart';
 import 'package:cw_core/transaction_info.dart';
 import 'package:cw_core/utils/print_verbose.dart';
 import 'package:flutter/material.dart';
-import 'package:intl/intl.dart';
 import 'package:mobx/mobx.dart';
 import 'package:cw_core/wallet_base.dart';
 import 'package:cake_wallet/monero/monero.dart';
@@ -42,8 +41,7 @@ class Output = OutputBase with _$Output;
 abstract class OutputBase with Store {
   OutputBase(
       this._wallet, this._settingsStore, this._fiatConversationStore, this.cryptoCurrencyHandler)
-      : _cryptoNumberFormat = NumberFormat(cryptoNumberPattern),
-        key = UniqueKey(),
+      : key = UniqueKey(),
         sendAll = false,
         cryptoAmount = '',
         cryptoFullBalance = '',
@@ -53,7 +51,6 @@ abstract class OutputBase with Store {
         extractedAddress = '',
         estimatedFee = '0.0',
         parsedAddress = ParsedAddress(addresses: []) {
-    _setCryptoNumMaximumFractionDigits();
     autorun((_) {
       final status = _wallet.syncStatus;
       printV("Sync status changed to $status. Recalculating fees");
@@ -289,7 +286,6 @@ abstract class OutputBase with Store {
   WalletBase<Balance, TransactionHistoryBase<TransactionInfo>, TransactionInfo> _wallet;
   final SettingsStore _settingsStore;
   final FiatConversionStore _fiatConversationStore;
-  final NumberFormat _cryptoNumberFormat;
 
   @action
   void setSendAll(String fullBalance) {
@@ -302,7 +298,6 @@ abstract class OutputBase with Store {
   void updateWallet(
       WalletBase<Balance, TransactionHistoryBase<TransactionInfo>, TransactionInfo> newWallet) {
     _wallet = newWallet;
-    _setCryptoNumMaximumFractionDigits();
   }
 
   @action
@@ -355,11 +350,12 @@ abstract class OutputBase with Store {
   @action
   void _updateCryptoAmount() {
     try {
-      final crypto = double.parse(fiatAmount.replaceAll(',', '.')) /
-          _fiatConversationStore.prices[cryptoCurrencyHandler()]!;
-      final cryptoAmountTmp = _cryptoNumberFormat.format(crypto);
-      if (cryptoAmount != cryptoAmountTmp) {
-        cryptoAmount = cryptoAmountTmp;
+      final crypto = (double.parse(fiatAmount.replaceAll(',', '.')) /
+              _fiatConversationStore.prices[cryptoCurrencyHandler()]!)
+          .toStringAsFixed(cryptoCurrencyHandler().decimals);
+
+      if (cryptoAmount != crypto) {
+        cryptoAmount = crypto;
       }
     } catch (e) {
       cryptoAmount = '';
@@ -375,40 +371,6 @@ abstract class OutputBase with Store {
     return fields;
   }
 
-  void _setCryptoNumMaximumFractionDigits() {
-    var maximumFractionDigits = 0;
-
-    switch (_wallet.type) {
-      case WalletType.monero:
-      case WalletType.ethereum:
-      case WalletType.polygon:
-      case WalletType.base:
-      case WalletType.arbitrum:
-      case WalletType.solana:
-      case WalletType.tron:
-      case WalletType.haven:
-      case WalletType.zano:
-      case WalletType.nano:
-      case WalletType.decred:
-        maximumFractionDigits = 12;
-        break;
-      case WalletType.bitcoin:
-      case WalletType.litecoin:
-      case WalletType.bitcoinCash:
-      case WalletType.dogecoin:
-        maximumFractionDigits = 8;
-        break;
-      case WalletType.wownero:
-        maximumFractionDigits = 11;
-        break;
-      case WalletType.none:
-      case WalletType.banano:
-        break;
-    }
-
-    _cryptoNumberFormat.maximumFractionDigits = maximumFractionDigits;
-  }
-
   Future<void> fetchParsedAddress(BuildContext context) async {
     final domain = address;
     final currency = cryptoCurrencyHandler();