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packages/api-derive/src/index.ts

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+// Copyright 2017-2019 @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 { Observable } from 'rxjs';
+import { ApiInterface$Rx } from '@plugnet/api/types';
+
+import * as accounts from './accounts';
+import * as balances from './balances';
+import * as chain from './chain';
+import * as democracy from './democracy';
+import * as session from './session';
+import * as staking from './staking';
+
+// Put all derived functions in an object, for easier Object.keys()-ing.
+const functions = { accounts, balances, chain, democracy, session, staking };
+
+/**
+ * T represents the section here (chain, balances...), and P represents
+ * the function name (bestNumber, sessionProgress...).
+ */
+type ReturnTypes<T extends Record<keyof T, (...args: any[]) => any>> = {
+  [P in keyof T]: ReturnType<T[P]>
+};
+
+export interface DeriveCustomMethod {
+  (api: ApiInterface$Rx): (...args: Array<any>) => Observable<any>;
+}
+
+export interface DeriveCustom {
+  [index: string]: {
+    [index: string]: DeriveCustomMethod
+  };
+}
+
+export interface Derive {
+  accounts: ReturnTypes<typeof accounts>;
+  balances: ReturnTypes<typeof balances>;
+  chain: ReturnTypes<typeof chain>;
+  democracy: ReturnTypes<typeof democracy>;
+  session: ReturnTypes<typeof session>;
+  staking: ReturnTypes<typeof staking>;
+}
+
+function injectFunctions (api: ApiInterface$Rx, derive: Derive, functions: DeriveCustom): Derive {
+  Object.keys(functions).forEach((sectionName: string) => {
+    const section = functions[sectionName as keyof Derive];
+    const result = derive[sectionName as keyof Derive] = derive[sectionName as keyof Derive] || {};
+
+    Object.keys(section).forEach((methodName) => {
+      // @ts-ignore No idea how to make this work...
+      result[methodName as keyof section] = section[methodName as keyof section](api);
+    });
+  });
+
+  return derive;
+}
+
+export default function decorateDerive (api: ApiInterface$Rx, custom: DeriveCustom = {}): Derive {
+  const derive = {} as Derive;
+
+  injectFunctions(api, derive, functions);
+  injectFunctions(api, derive, custom);
+
+  return derive;
+}