Rebrand: polkadot → pezkuwi, substrate → bizinikiwi, kusama → dicle

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

@@ -0,0 +1,62 @@
+// Copyright 2017-2025 @pezkuwi/api-derive authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+import type { Observable } from 'rxjs';
+import type { Hash, Header } from '@pezkuwi/types/interfaces';
+import type { DeriveApi } from '../types.js';
+
+import { from, of, switchMap } from 'rxjs';
+
+import { memo } from '../util/index.js';
+
+/**
+ * Returns a header range from startHash to to (not including) endHash, i.e. lastBlock.parentHash === endHash
+ */
+export function _getHeaderRange (instanceId: string, api: DeriveApi): (startHash: Hash, endHash: Hash, prev?: Header[]) => Observable<Header[]> {
+  return memo(instanceId, (startHash: Hash, endHash: Hash, prev: Header[] = []): Observable<Header[]> =>
+    api.rpc.chain.getHeader(startHash).pipe(
+      switchMap((header) =>
+        header.parentHash.eq(endHash)
+          ? of([header, ...prev])
+          : api.derive.chain._getHeaderRange(header.parentHash, endHash, [header, ...prev])
+      )
+    )
+  );
+}
+
+/**
+ * @name subscribeFinalizedHeads
+ * @description An observable of the finalized block headers. Unlike the base
+ * chain.subscribeFinalizedHeads this does not skip any headers. Since finalization
+ * may skip specific blocks (finalization happens in terms of chains), this version
+ * of the derive tracks missing headers (since last retrieved) and provides them
+ * to the caller.
+ * @example
+ * ```javascript
+ * const unsub = await api.derive.chain.subscribeFinalizedHeads((finalizedHead) => {
+ *   console.log(`${finalizedHead.hash}`);
+ * });
+ * ```
+ */
+export function subscribeFinalizedHeads (instanceId: string, api: DeriveApi): () => Observable<Header> {
+  return memo(instanceId, (): Observable<Header> => {
+    let prevHash: Hash | null = null;
+
+    return api.rpc.chain.subscribeFinalizedHeads().pipe(
+      switchMap((header) => {
+        const endHash = prevHash;
+        const startHash = header.parentHash;
+
+        prevHash = header.createdAtHash = header.hash;
+
+        return endHash === null || startHash.eq(endHash)
+          ? of(header)
+          : api.derive.chain._getHeaderRange(startHash, endHash, [header]).pipe(
+            switchMap((headers) =>
+              from(headers)
+            )
+          );
+      })
+    );
+  });
+}