From 5c2bf8f7e1bbb51a06eabd961b5ad9ce1d3f11cd Mon Sep 17 00:00:00 2001
From: natsoni <natsoni@protonmail.com>
Date: Tue, 23 Sep 2025 23:14:48 +0200
Subject: [PATCH] Fallback to core for stale blocks on $getBlock calls

---
 .../api/bitcoin/bitcoin-api-abstract-factory.ts  |  2 +-
 backend/src/api/bitcoin/bitcoin-api.ts           |  2 +-
 backend/src/api/bitcoin/esplora-api.ts           | 16 ++++++++++++++--
 backend/src/api/blocks.ts                        |  2 +-
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/backend/src/api/bitcoin/bitcoin-api-abstract-factory.ts b/backend/src/api/bitcoin/bitcoin-api-abstract-factory.ts
index e1aead616..dc5960f5d 100644
--- a/backend/src/api/bitcoin/bitcoin-api-abstract-factory.ts
+++ b/backend/src/api/bitcoin/bitcoin-api-abstract-factory.ts
@@ -15,7 +15,7 @@ export interface AbstractBitcoinApi {
   $getTxsForBlock(hash: string, fallbackToCore?: boolean): Promise<IEsploraApi.Transaction[]>;
   $getBlockHash(height: number): Promise<string>;
   $getBlockHeader(hash: string): Promise<string>;
-  $getBlock(hash: string): Promise<IEsploraApi.Block>;
+  $getBlock(hash: string, fallbackToCore?: boolean): Promise<IEsploraApi.Block>;
   $getRawBlock(hash: string): Promise<Buffer>;
   $getAddress(address: string): Promise<IEsploraApi.Address>;
   $getAddressTransactions(address: string, lastSeenTxId: string): Promise<IEsploraApi.Transaction[]>;
diff --git a/backend/src/api/bitcoin/bitcoin-api.ts b/backend/src/api/bitcoin/bitcoin-api.ts
index 5c5691c35..df7569dd2 100644
--- a/backend/src/api/bitcoin/bitcoin-api.ts
+++ b/backend/src/api/bitcoin/bitcoin-api.ts
@@ -141,7 +141,7 @@ class BitcoinApi implements AbstractBitcoinApi {
     return this.bitcoindClient.getBlockHeader(hash, false);
   }
 
-  async $getBlock(hash: string): Promise<IEsploraApi.Block> {
+  async $getBlock(hash: string, fallbackToCore = false): Promise<IEsploraApi.Block> {
     const foundBlock = blocks.getBlocks().find((block) => block.id === hash);
     if (foundBlock) {
       return foundBlock;
diff --git a/backend/src/api/bitcoin/esplora-api.ts b/backend/src/api/bitcoin/esplora-api.ts
index 8d2e088c1..ff51d7559 100644
--- a/backend/src/api/bitcoin/esplora-api.ts
+++ b/backend/src/api/bitcoin/esplora-api.ts
@@ -449,8 +449,20 @@ class ElectrsApi implements AbstractBitcoinApi {
     return this.failoverRouter.$get<string>('/block/' + hash + '/header');
   }
 
-  $getBlock(hash: string): Promise<IEsploraApi.Block> {
-    return this.failoverRouter.$get<IEsploraApi.Block>('/block/' + hash);
+  async $getBlock(hash: string, fallbackToCore = false): Promise<IEsploraApi.Block> {
+    try {
+      const block = await this.failoverRouter.$get<IEsploraApi.Block>('/block/' + hash);
+      return block;
+    } catch (e: any) {
+      if (fallbackToCore && isAxiosError(e) && e.response?.status === 404) {
+        // might be a stale block, see if Core has it?
+        const coreBlock = await bitcoinCoreApi.$getBlock(hash);
+        if (coreBlock?.stale) {
+          return coreBlock;
+        }
+      }
+      throw e;
+    }
   }
 
   $getRawBlock(hash: string): Promise<Buffer> {
diff --git a/backend/src/api/blocks.ts b/backend/src/api/blocks.ts
index ff233f3a3..4eb7ea09c 100644
--- a/backend/src/api/blocks.ts
+++ b/backend/src/api/blocks.ts
@@ -1324,7 +1324,7 @@ class Blocks {
       summaryVersion = 1;
     }
     if (height == null) {
-      const block = await bitcoinApi.$getBlock(hash);
+      const block = await bitcoinApi.$getBlock(hash, true);
       height = block.height;
     }