api.derive.chain.getBlock(<hash>) with author getter (#2555)

* api.derive.chain.getBlock<hash>) with author getter

* Update CHANGELOG.md

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

@@ -0,0 +1,44 @@
+// Copyright 2017-2020 @polkadot/api-derive authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { ApiInterfaceRx } from '@polkadot/api/types';
+
+import { Observable, combineLatest, of } from 'rxjs';
+import { catchError, map } from 'rxjs/operators';
+
+import { SignedBlockExtended } from '../type';
+import { memo } from '../util';
+
+/**
+ * @name getBlock
+ * @param {( Uint8Array | string )} hash - A block hash as U8 array or string.
+ * @description Get a specific block (e.g. rpc.chain.getBlock) and extend it with the author
+ * @example
+ * <BR>
+ *
+ * ```javascript
+ * const { author, number } = await api.derive.chain.getHeader('0x123...456');
+ *
+ * console.log(`block #${number} was authored by ${author}`);
+ * ```
+ */
+export function getHeader (api: ApiInterfaceRx): (hash: Uint8Array | string) => Observable<SignedBlockExtended | undefined> {
+  return memo((hash: Uint8Array | string): Observable<SignedBlockExtended | undefined> =>
+    combineLatest([
+      api.rpc.chain.getBlock(hash),
+      api.query.session
+        ? api.query.session.validators.at(hash)
+        : of([])
+    ]).pipe(
+      map(([signedBlock, validators]): SignedBlockExtended =>
+        new SignedBlockExtended(api.registry, signedBlock, validators)
+      ),
+      catchError((): Observable<undefined> =>
+        // where rpc.chain.getHeader throws, we will land here - it can happen that
+        // we supplied an invalid hash. (Due to defaults, storeage will have an
+        // empty value, so only the RPC is affected). So return undefined
+        of()
+      )
+    ));
+}

packages/api-derive/src/type/HeaderExtended.ts

@@ -8,6 +8,8 @@ import { AnyJson, Constructor, Registry } from '@polkadot/types/types';
 import runtimeTypes from '@polkadot/types/interfaces/runtime/definitions';
 import { Struct } from '@polkadot/types';
 
+import { extractAuthor } from './util';
+
 // We can ignore the properties, added via Struct.with
 const _Header = Struct.with(runtimeTypes.types.Header as any) as Constructor<Header>;
 
@@ -22,29 +24,7 @@ export default class HeaderExtended extends _Header {
   constructor (registry: Registry, header?: Header, sessionValidators?: AccountId[]) {
     super(registry, header);
 
-    this.#author = this._extractAuthor(sessionValidators);
-  }
-
-  private _extractAuthor (sessionValidators: AccountId[] = []): AccountId | undefined {
-    const [pitem] = this.digest.logs.filter(({ type }) => type === 'PreRuntime');
-
-    // extract from the substrate 2.0 PreRuntime digest
-    if (pitem) {
-      const [engine, data] = pitem.asPreRuntime;
-
-      return engine.extractAuthor(data, sessionValidators);
-    } else {
-      const [citem] = this.digest.logs.filter(({ type }) => type === 'Consensus');
-
-      // extract author from the consensus (substrate 1.0, digest)
-      if (citem) {
-        const [engine, data] = citem.asConsensus;
-
-        return engine.extractAuthor(data, sessionValidators);
-      }
-    }
-
-    return undefined;
+    this.#author = extractAuthor(this.digest, sessionValidators);
   }
 
   /**

packages/api-derive/src/type/SignedBlockExtended.ts

@@ -0,0 +1,60 @@
+// Copyright 2017-2020 @polkadot/api-derive authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { AccountId, SignedBlock } from '@polkadot/types/interfaces';
+import { AnyJson, Constructor, Registry } from '@polkadot/types/types';
+
+import runtimeTypes from '@polkadot/types/interfaces/runtime/definitions';
+import { Struct } from '@polkadot/types';
+
+import { extractAuthor } from './util';
+
+// We can ignore the properties, added via Struct.with
+const _SignedBlock = Struct.with(runtimeTypes.types.SignedBlock as any) as Constructor<SignedBlock>;
+
+/**
+ * @name SignedBlockExtended
+ * @description
+ * A [[Block]] header with an additional `author` field that indicates the block author
+ */
+export default class BlockExtended extends _SignedBlock {
+  readonly #author?: AccountId;
+
+  constructor (registry: Registry, block?: SignedBlock, sessionValidators?: AccountId[]) {
+    super(registry, block);
+
+    this.#author = extractAuthor(this.block.header.digest, sessionValidators);
+  }
+
+  /**
+   * @description Convenience method, returns the author for the block
+   */
+  public get author (): AccountId | undefined {
+    return this.#author;
+  }
+
+  /**
+   * @description Creates a human-friendly JSON representation
+   */
+  public toHuman (isExtended?: boolean): AnyJson {
+    return {
+      ...super.toHuman(isExtended) as { [index: string]: AnyJson },
+      author: this.author
+        ? this.author.toHuman()
+        : undefined
+    };
+  }
+
+  /**
+   * @description Creates the JSON representation
+   */
+  public toJSON (): AnyJson {
+    return {
+      ...super.toJSON() as { [index: string]: AnyJson },
+      author: this.author
+        ? this.author.toJSON()
+        : undefined
+    };
+  }
+}

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

@@ -3,3 +3,4 @@
 // of the Apache-2.0 license. See the LICENSE file for details.
 
 export { default as HeaderExtended } from './HeaderExtended';
+export { default as SignedBlockExtended } from './SignedBlockExtended';

packages/api-derive/src/type/util.ts

@@ -0,0 +1,27 @@
+// Copyright 2017-2020 @polkadot/api-derive authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { AccountId, Digest } from '@polkadot/types/interfaces';
+
+export function extractAuthor (digest: Digest, sessionValidators: AccountId[] = []): AccountId | undefined {
+  const [pitem] = digest.logs.filter(({ type }) => type === 'PreRuntime');
+
+  // extract from the substrate 2.0 PreRuntime digest
+  if (pitem) {
+    const [engine, data] = pitem.asPreRuntime;
+
+    return engine.extractAuthor(data, sessionValidators);
+  } else {
+    const [citem] = digest.logs.filter(({ type }) => type === 'Consensus');
+
+    // extract author from the consensus (substrate 1.0, digest)
+    if (citem) {
+      const [engine, data] = citem.asConsensus;
+
+      return engine.extractAuthor(data, sessionValidators);
+    }
+  }
+
+  return undefined;
+}