Add derive.chain.subscribeNewBlocks (#2765)

* Add derive.chain.subscribeNewBlocks * Expand
2020-10-22 19:52:03 +02:00
parent 9f83f5cac3
commit fb82db382e
5 changed files with 47 additions and 1 deletions
@@ -0,0 +1,32 @@
+// Copyright 2017-2020 @polkadot/api-derive authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+import { ApiInterfaceRx } from '@polkadot/api/types';
+import { EventRecord, Hash, SignedBlock } from '@polkadot/types/interfaces';
+import { FullNewBlock } from '../types';
+
+import { Observable, combineLatest, of } from 'rxjs';
+import { map, switchMap } from 'rxjs/operators';
+
+import { memo } from '../util';
+
+/**
+ * @name subscribeNewBlocks
+ * @returns The latest block & events for that block
+ */
+export function subscribeNewBlocks (instanceId: string, api: ApiInterfaceRx): () => Observable<FullNewBlock> {
+  return memo(instanceId, (): Observable<FullNewBlock> =>
+    api.derive.chain.subscribeNewHeads().pipe(
+      switchMap((header): Observable<[Hash, EventRecord[], SignedBlock]> => {
+        const blockHash = header.hash;
+
+        return combineLatest(
+          of(blockHash),
+          api.query.system.events.at(blockHash),
+          api.rpc.chain.getBlock(header.hash)
+        );
+      }),
+      map(([blockHash, events, block]) => ({ block: block.block, blockHash, blockNumber: block.block.header.number.unwrap(), events, justification: block.justification }))
+    )
+  );
+}