From 77a9d8ecb017d4c4e6be721c25e97ef55641b4c9 Mon Sep 17 00:00:00 2001
From: Jaco Greeff <jacogr@gmail.com>
Date: Wed, 26 Dec 2018 14:43:59 +0100
Subject: [PATCH] bestNumberFinalised for api-observable (#517)

---
 packages/api-observable/src/Calls.ts | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/packages/api-observable/src/Calls.ts b/packages/api-observable/src/Calls.ts
index 1974d41b37..c1b6f6c75e 100644
--- a/packages/api-observable/src/Calls.ts
+++ b/packages/api-observable/src/Calls.ts
@@ -22,6 +22,18 @@ export default class ApiCalls extends ApiQueries {
       );
   }
 
+  bestNumberFinalised = (): Observable<BlockNumber | undefined> => {
+    return this
+      .subscribeFinalisedHead()
+      .pipe(
+        map((header?: Header): BlockNumber | undefined =>
+          header && header.blockNumber
+            ? header.blockNumber
+            : undefined
+        )
+      );
+  }
+
   chain = (): Observable<Text | undefined> => {
     return this._api.system.chain();
   }
@@ -42,6 +54,12 @@ export default class ApiCalls extends ApiQueries {
     return this._api.chain.getBlock(hash);
   }
 
+  subscribeFinalisedHead = (): Observable<Header | undefined> => {
+    return this._api.chain.subscribeFinalisedHeads().pipe(
+      defaultIfEmpty()
+    );
+  }
+
   subscribeNewHead = (): Observable<Header | undefined> => {
     return this._api.chain.subscribeNewHead().pipe(
       defaultIfEmpty()