From 45c2c40a3e7f68543d8ec2fe86afd3399f0771b1 Mon Sep 17 00:00:00 2001
From: Jaco Greeff <jacogr@gmail.com>
Date: Wed, 9 Sep 2020 13:31:06 +0200
Subject: [PATCH] derive.staking.stakerPrefs (#2594)

---
 CHANGELOG.md                                  |  3 +-
 packages/api-derive/src/staking/index.ts      |  1 +
 .../api-derive/src/staking/stakerPrefs.ts     | 34 +++++++++++++++++++
 packages/api-derive/src/staking/types.ts      |  5 +++
 4 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 packages/api-derive/src/staking/stakerPrefs.ts

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 12859a6f84..2fc24e0eb6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,8 +4,9 @@
 
 Changes:
 
-- Optimize derive `receivedHeartbeats` to not re-create the full object
 - Allow `paymentInfo` on any extrinsic (already signed) with optional `{ blockHash: <hash> }` param for historic queries
+- Optimize derive `receivedHeartbeats` to not re-create the full object
+- Add `staking.stakerPrefs` derive to retrieve validatorPrefs over a range of eras
 
 
 ## 1.32.1 Sep 7, 2020
diff --git a/packages/api-derive/src/staking/index.ts b/packages/api-derive/src/staking/index.ts
index 8b4a96e125..43dc7a0927 100644
--- a/packages/api-derive/src/staking/index.ts
+++ b/packages/api-derive/src/staking/index.ts
@@ -18,6 +18,7 @@ export * from './ownSlashes';
 export * from './query';
 export * from './stakerExposure';
 export * from './stakerPoints';
+export * from './stakerPrefs';
 export * from './stakerRewards';
 export * from './stakerSlashes';
 export * from './stashes';
diff --git a/packages/api-derive/src/staking/stakerPrefs.ts b/packages/api-derive/src/staking/stakerPrefs.ts
new file mode 100644
index 0000000000..eb47797c9f
--- /dev/null
+++ b/packages/api-derive/src/staking/stakerPrefs.ts
@@ -0,0 +1,34 @@
+// 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 { EraIndex, ValidatorPrefs } from '@polkadot/types/interfaces';
+import { DeriveStakerPrefs } from '../types';
+
+import { Observable } from 'rxjs';
+import { map, switchMap } from 'rxjs/operators';
+
+import { memo } from '../util';
+
+export function _stakerPrefs (instanceId: string, api: ApiInterfaceRx): (accountId: Uint8Array | string, eras: EraIndex[], withActive: boolean) => Observable<DeriveStakerPrefs[]> {
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  return memo(instanceId, (accountId: Uint8Array | string, eras: EraIndex[], _withActive: boolean): Observable<DeriveStakerPrefs[]> => {
+    return api.query.staking.erasValidatorPrefs.multi<ValidatorPrefs>(eras.map((era) => [era, accountId])).pipe(
+      map((all): DeriveStakerPrefs[] =>
+        all.map((validatorPrefs, index): DeriveStakerPrefs => ({
+          era: eras[index],
+          validatorPrefs
+        }))
+      )
+    );
+  });
+}
+
+export function stakerPrefs (instanceId: string, api: ApiInterfaceRx): (accountId: Uint8Array | string, withActive?: boolean) => Observable<DeriveStakerPrefs[]> {
+  return memo(instanceId, (accountId: Uint8Array | string, withActive = false): Observable<DeriveStakerPrefs[]> =>
+    api.derive.staking.erasHistoric(withActive).pipe(
+      switchMap((eras) => api.derive.staking._stakerPrefs(accountId, eras, withActive))
+    )
+  );
+}
diff --git a/packages/api-derive/src/staking/types.ts b/packages/api-derive/src/staking/types.ts
index 8ede11abfe..c66ba69cc7 100644
--- a/packages/api-derive/src/staking/types.ts
+++ b/packages/api-derive/src/staking/types.ts
@@ -69,6 +69,11 @@ export interface DeriveStakerExposure {
   validators: DeriveEraValidatorExposure;
 }
 
+export interface DeriveStakerPrefs {
+  era: EraIndex;
+  validatorPrefs: ValidatorPrefs;
+}
+
 export interface DeriveStakerRewardValidator {
   total: Balance;
   value: Balance;