From 35162e1a84b827537dcf492d6ad7899438672e93 Mon Sep 17 00:00:00 2001
From: Sam Holmes <sam@edge.app>
Date: Tue, 8 Jul 2025 17:55:07 -0700
Subject: [PATCH] Fix syncing races between periodic and change-server syncing

This fixes the race between periodic syncing and change-server
subscriptions by introducing a `usesChangeServer` flag on
`EdgeCurrencyInfo` which tells the core to not invoke periodic syncing.

In addition, we introduce a `resubscribing` state to the subscription
status to differentiate initial `subscription` with intermittent
subscription issues from the change server.
---
 CHANGELOG.md                                   |  3 +++
 src/core/currency/currency-pixie.ts            | 18 +++++++++---------
 .../currency/wallet/currency-wallet-pixie.ts   |  6 +++---
 .../currency/wallet/currency-wallet-reducer.ts |  1 +
 src/types/types.ts                             |  1 +
 5 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9ca9d27d..cd1290ef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## Unreleased
 
+- added: Added `usesChangeServer` flag to `EdgeCurrencyInfo` to optimize syncing for engines which subscribe to the change-server.
+- fixed: Race condition between engine change-server subscription and periodic sync.
+
 ## 2.32.1 (2025-07-18)
 
 - fixed: Don't write the enabled tokens file until after we've read it from disk.
diff --git a/src/core/currency/currency-pixie.ts b/src/core/currency/currency-pixie.ts
index 70141f5d..d53d2b98 100644
--- a/src/core/currency/currency-pixie.ts
+++ b/src/core/currency/currency-pixie.ts
@@ -217,7 +217,9 @@ export const currency: TamePixie<RootProps> = combinePixies({
       if (changeService?.connected === true && changeServiceConnected) {
         const filteredWallets = supportedWallets.filter(([, wallet]) =>
           wallet.changeServiceSubscriptions.some(
-            subscription => subscription.status === 'subscribing'
+            subscription =>
+              subscription.status === 'subscribing' ||
+              subscription.status === 'resubscribing'
           )
         )
         const indexToWalletId: Array<{
@@ -282,7 +284,7 @@ export const currency: TamePixie<RootProps> = combinePixies({
             // subscribe to the address:
             case 0:
               // Try subscribing again later:
-              status = 'subscribing'
+              status = 'resubscribing'
               break
             // Change server does support this wallet plugin, and there are no
             // changes for the address:
@@ -298,15 +300,13 @@ export const currency: TamePixie<RootProps> = combinePixies({
               break
           }
 
-          // The status for the subscription is already set to subscribing, so
-          // we don't need to update it:
-          if (status === 'subscribing') {
-            continue
-          }
-
           // Update the status for the subscription:
           const subscriptions = wallet.changeServiceSubscriptions
-            .filter(subscription => subscription.status === 'subscribing')
+            .filter(
+              subscription =>
+                subscription.status === 'subscribing' ||
+                subscription.status === 'resubscribing'
+            )
             .map(subscription => ({
               ...subscription,
               status
diff --git a/src/core/currency/wallet/currency-wallet-pixie.ts b/src/core/currency/wallet/currency-wallet-pixie.ts
index 7bccf4d4..640c2962 100644
--- a/src/core/currency/wallet/currency-wallet-pixie.ts
+++ b/src/core/currency/wallet/currency-wallet-pixie.ts
@@ -373,12 +373,12 @@ export const walletPixie: TamePixie<CurrencyWalletProps> = combinePixies({
       !props.state.paused &&
       !props.walletState.paused &&
       props.walletState.engineStarted &&
-      (props.walletState.changeServiceSubscriptions.length === 0 ||
+      (props.walletState.currencyInfo.usesChangeServer !== true ||
         props.walletState.changeServiceSubscriptions.some(
           subscription =>
             subscription.status === 'avoiding' ||
-            subscription.status === 'subscribing' ||
-            subscription.status === 'reconnecting'
+            subscription.status === 'reconnecting' ||
+            subscription.status === 'resubscribing'
         ))
         ? props
         : undefined
diff --git a/src/core/currency/wallet/currency-wallet-reducer.ts b/src/core/currency/wallet/currency-wallet-reducer.ts
index ca26097d..e7ea110d 100644
--- a/src/core/currency/wallet/currency-wallet-reducer.ts
+++ b/src/core/currency/wallet/currency-wallet-reducer.ts
@@ -106,6 +106,7 @@ export type ChangeServiceSubscriptionStatus =
   | 'listening' // The wallet is connected and listening for changes
   | 'reconnecting' // The wallet is reconnecting to the change service while its not available
   | 'subscribing' // The wallet is in the process of subscribing (supported)
+  | 'resubscribing' // The wallet is in the process of resubscribing due to a change-server issue (supported)
   | 'syncing' // The wallet is syncing historical data
 
 export interface CurrencyWalletNext {
diff --git a/src/types/types.ts b/src/types/types.ts
index 9175f371..93f69adf 100644
--- a/src/types/types.ts
+++ b/src/types/types.ts
@@ -505,6 +505,7 @@ export interface EdgeCurrencyInfo {
   unsafeBroadcastTx?: boolean
   unsafeMakeSpend?: boolean
   unsafeSyncNetwork?: boolean
+  usesChangeServer?: boolean
 
   /** @deprecated The default user settings are always `{}` */
   defaultSettings?: JsonObject