Add derive.chain.subscribeNewBlocks (#2765)

* Add derive.chain.subscribeNewBlocks

* Expand

packages/api-derive/src/chain/index.ts

@@ -5,4 +5,5 @@ export * from './bestNumber';
 export * from './bestNumberFinalized';
 export * from './bestNumberLag';
 export * from './getHeader';
+export * from './subscribeNewBlocks';
 export * from './subscribeNewHeads';

packages/api-derive/src/chain/subscribeNewBlocks.ts

@@ -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 }))
+    )
+  );
+}

packages/api-derive/src/chain/subscribeNewHeads.ts

@@ -11,7 +11,7 @@ import { memo } from '../util';
 
 /**
  * @name subscribeNewHeads
- * @returns An array containing the block header and the block author
+ * @returns A header with the current header (including extracted author)
  * @description An observable of the current block header and it's author
  * @example
  * <BR>

packages/api-derive/src/chain/types.ts

@@ -0,0 +1,12 @@
+// Copyright 2017-2020 @polkadot/api-derive authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+import { Block, BlockNumber, EventRecord, Hash, Justification } from '@polkadot/types/interfaces';
+
+export interface FullNewBlock {
+  block: Block;
+  blockHash: Hash;
+  blockNumber: BlockNumber;
+  events: EventRecord[];
+  justification: Justification;
+}

packages/api-derive/src/types.ts

@@ -7,6 +7,7 @@ import { AccountId, Balance, BalanceLock, BalanceLockTo212, BalanceOf, Bid, BidK
 import { u32 } from '@polkadot/types';
 
 export * from './accounts/types';
+export * from './chain/types';
 export * from './council/types';
 export * from './democracy/types';
 export * from './elections/types';