feat: Get current fees (#109)

src/client/RESTClient.ts

@@ -6,6 +6,7 @@ import {OrderAPI} from '../order/OrderAPI';
 import {ProductAPI} from '../product/ProductAPI';
 import {TimeAPI} from '../time/TimeAPI';
 import {UserAPI} from '../user/UserAPI';
+import {FeeAPI} from '../fee/FeeAPI';
 import {FillAPI} from '../fill/FillAPI';
 import querystring from 'querystring';
 import {ProfileAPI} from '../profile/ProfileAPI';
@@ -25,6 +26,7 @@ export class RESTClient {
   }
 
   readonly account: AccountAPI;
+  readonly fee: FeeAPI;
   readonly fill: FillAPI;
   readonly order: OrderAPI;
   readonly product: ProductAPI;
@@ -92,6 +94,7 @@ export class RESTClient {
     });
 
     this.account = new AccountAPI(this.httpClient);
+    this.fee = new FeeAPI(this.httpClient);
     this.fill = new FillAPI(this.httpClient);
     this.order = new OrderAPI(this.httpClient);
     this.product = new ProductAPI(this.httpClient);

src/fee/FeeAPI.test.ts

@@ -0,0 +1,16 @@
+import nock from 'nock';
+
+describe('FeeAPI', () => {
+  describe('getCurrentFees', () => {
+    it('returns maker & taker fee rates', async () => {
+      const response = {
+        maker_fee_rate: '0.0050',
+        taker_fee_rate: '0.0050',
+        usd_volume: null,
+      };
+      nock(global.REST_URL).get('/fees').reply(200, response);
+      const canceledOrderIds = await global.client.rest.fee.getCurrentFees();
+      expect(canceledOrderIds).toEqual(response);
+    });
+  });
+});

src/fee/FeeAPI.ts

@@ -0,0 +1,31 @@
+import {AxiosInstance} from 'axios';
+
+export interface Fee {
+  /** A maker fee is paid when you create ("make") liquidity on the order book, i.e. you create an order which is not matched immediately. */
+  maker_fee_rate: string;
+  /** A taker fee is paid when you remove ("take") liquidity from the order book, i.e. you create an order which matches an existing order (this includes all market orders). */
+  taker_fee_rate: string;
+  /** Your 30-day trailing volume which impacts your fee rates. */
+  usd_volume: string | null;
+}
+
+export class FeeAPI {
+  static readonly URL = {
+    FEES: `/fees`,
+  };
+
+  constructor(private readonly apiClient: AxiosInstance) {}
+
+  /**
+   * Get your current maker & taker fee rates, as well as your 30-day trailing volume. Quoted rates are subject to
+   * change.
+   *
+   * @see https://docs.pro.coinbase.com/#fees
+   * @see https://help.coinbase.com/en/pro/trading-and-funding/trading-rules-and-fees/fees.html
+   */
+  async getCurrentFees(): Promise<Fee> {
+    const resource = FeeAPI.URL.FEES;
+    const response = await this.apiClient.get(resource);
+    return response.data;
+  }
+}