Make Blockchain Subscribe methods return Unsubscribe callback

packages/stack/src/blockchain/base-blockchain.ts

@@ -4,6 +4,7 @@ import {
   type BlockchainCallback,
   type BlockchainUTXOs,
   type BlockchainTransactions,
+  type BlockchainUnsubscribeCallback,
 } from './types.js';
 
 import { Transaction } from '@xocash/primitives';
@@ -109,7 +110,7 @@ export abstract class BaseBlockchain<
   abstract subscribeLockscript(
     lockscript: string | Uint8Array,
     callback: BlockchainCallback<AddressNotificationPayload>,
-  ): Promise<void>;
+  ): Promise<BlockchainUnsubscribeCallback>;
 
   /**
    * Removes a subscription for a specific blockchain address.
@@ -136,7 +137,7 @@ export abstract class BaseBlockchain<
   abstract subscribeAddress(
     address: string,
     callback: BlockchainCallback<AddressNotificationPayload>,
-  ): Promise<void>;
+  ): Promise<BlockchainUnsubscribeCallback>;
 
   /**
    * Removes a subscription for a specific blockchain address.
@@ -163,7 +164,7 @@ export abstract class BaseBlockchain<
   abstract subscribeTransaction(
     transactionHash: string,
     callback: BlockchainCallback<TransactionNotificationPayload>,
-  ): Promise<void>;
+  ): Promise<BlockchainUnsubscribeCallback>;
 
   /**
    * Removes a subscription for a specific transaction.

packages/stack/src/blockchain/blockchain-electrum.ts

@@ -397,6 +397,9 @@ export class BlockchainElectrum extends BaseBlockchain<
 
     // Add the callback to the set
     callbacks.add(callback);
+
+    // Return an unsubscribe callback.
+    return async () => await this.unsubscribeAddress(address, callback);
   }
 
   async unsubscribeAddress(
@@ -464,6 +467,9 @@ export class BlockchainElectrum extends BaseBlockchain<
 
     // Add the callback to the set
     callbacks.add(callback);
+
+    // Return an unsubscribe callback.
+    return async () => this.unsubscribeTransaction(transactionHash, callback);
   }
 
   async unsubscribeTransaction(

packages/stack/src/blockchain/blockchain-inmemory.ts

@@ -173,6 +173,9 @@ export class BlockchainInMemory extends BaseBlockchain {
 
     // Add the address notification callback.
     this.addressSubscriptions.get(lockscriptHex)!.add(callback);
+
+    // Return an unsubscribe callback.
+    return async () => await this.unsubscribeAddress(address, callback);
   }
 
   async unsubscribeAddress(address: string, callback: BlockchainCallback) {
@@ -206,6 +209,10 @@ export class BlockchainInMemory extends BaseBlockchain {
       this.transactionSubscriptions.set(transactionHash, new Set());
     }
     this.transactionSubscriptions.get(transactionHash)!.add(callback);
+
+    // Return an unsubscribe callback.
+    return async () =>
+      await this.unsubscribeTransaction(transactionHash, callback);
   }
 
   async unsubscribeTransaction(

packages/stack/src/blockchain/types.ts

@@ -7,6 +7,8 @@ export type BlockchainCallback<Payload = undefined> = (
   payload?: Payload | undefined,
 ) => void;
 
+export type BlockchainUnsubscribeCallback = () => Promise<boolean>;
+
 export type BlockchainTransaction = {
   hash: TransactionHash;
   height: number;