Fee calculation: Support blank fixed or percent costs (#82)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@stellar/wallet-sdk",
-  "version": "0.0.3-rc.12",
+  "version": "0.0.3-rc.13",
   "description": "Libraries to help you write Stellar-enabled wallets in Javascript",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

src/transfers/DepositProvider.test.ts

@@ -0,0 +1,65 @@
+import { DepositProvider } from "./DepositProvider";
+
+import { DepositInfo } from "../types";
+
+describe("fetchFinalFee", () => {
+  test("AnchorUSD", async () => {
+    const info: DepositInfo = {
+      USD: {
+        assetCode: "USD",
+        fee: { type: "simple", fixed: 5, percent: 1 },
+        minAmount: 15,
+        fields: [
+          {
+            description: "your email address for transaction status updates",
+            name: "email_address",
+          },
+          {
+            description: "amount in USD that you plan to deposit",
+            name: "amount",
+          },
+        ],
+      },
+    };
+
+    const provider = new DepositProvider("test");
+
+    expect(
+      await provider.fetchFinalFee({
+        supportedAssets: info,
+        assetCode: info.USD.assetCode,
+        amount: "15",
+        type: "",
+      }),
+    ).toEqual(5.15);
+  });
+
+  test("EUR from Nucleo staging", async () => {
+    const info: DepositInfo = {
+      EUR: {
+        assetCode: "EUR",
+        fee: { type: "simple", percent: 0.5 },
+        minAmount: 1,
+        maxAmount: 1000000000,
+        fields: [
+          {
+            description: "Type of deposit method for EUR",
+            choices: ["SWIFT", "SEPA"],
+            name: "type",
+          },
+        ],
+      },
+    };
+
+    const provider = new DepositProvider("test");
+
+    expect(
+      await provider.fetchFinalFee({
+        supportedAssets: info,
+        assetCode: info.EUR.assetCode,
+        amount: "10",
+        type: "",
+      }),
+    ).toEqual(0.05);
+  });
+});

src/transfers/TransferProvider.ts

@@ -2,6 +2,7 @@ import queryString from "query-string";
 
 import {
   DepositInfo,
+  Fee,
   FeeArgs,
   Info,
   RawInfoResponse,
@@ -33,33 +34,32 @@ export abstract class TransferProvider {
     | Promise<DepositInfo>;
 
   protected async fetchFinalFee(args: FeeArgs): Promise<number> {
-    const { supportedAssets, ...rest } = args;
+    const { supportedAssets, assetCode, amount } = args;
 
-    if (!supportedAssets[rest.assetCode]) {
-      throw new Error(
-        `Can't get fee for an unsupported asset, '${rest.assetCode}`,
-      );
+    if (!supportedAssets[assetCode]) {
+      throw new Error(`Can't get fee for an unsupported asset, '${assetCode}`);
     }
-    const { fee } = supportedAssets[rest.assetCode];
+    const { fee } = supportedAssets[assetCode];
     switch (fee.type) {
       case "none":
         return 0;
       case "simple":
         const simpleFee = fee as SimpleFee;
         return (
-          (simpleFee.percent / 100) * Number(rest.amount) + simpleFee.fixed
+          ((simpleFee.percent || 0) / 100) * Number(amount) +
+          (simpleFee.fixed || 0)
         );
       case "complex":
         const response = await fetch(
-          `${this.transferServer}/fee?${queryString.stringify(rest)}`,
+          `${this.transferServer}/fee?${queryString.stringify(args)}`,
         );
         const { fee: feeResponse } = await response.json();
         return feeResponse as number;
 
       default:
         throw new Error(
           `Invalid fee type found! Got '${
-            fee.type
+            (fee as Fee).type
           }' but expected one of 'none', 'simple', 'complex'`,
         );
     }

src/transfers/parseInfo.ts

@@ -52,7 +52,7 @@ const parseFee = (
   } else {
     return {
       type: feeEnabled ? "complex" : "none",
-    };
+    } as Fee;
   }
 };
 

src/types/transfers.ts

@@ -92,7 +92,7 @@ export interface DepositAssetInfo {
   assetCode: string;
   fee: Fee;
   minAmount: number;
-  maxAmount: number;
+  maxAmount?: number;
   fields: Field[];
 }
 
@@ -195,16 +195,22 @@ export interface Field {
   choices?: string[];
 }
 
-export interface Fee {
-  type: "none" | "simple" | "complex";
+export interface NoneFee {
+  type: "none";
 }
 
-export interface SimpleFee extends Fee {
+export interface ComplexFee {
+  type: "complex";
+}
+
+export interface SimpleFee {
   type: "simple";
-  fixed: number;
-  percent: number;
+  fixed?: number;
+  percent?: number;
 }
 
+export type Fee = NoneFee | ComplexFee | SimpleFee;
+
 export interface Memo {
   type: "text" | "id" | "hash";
   value: string;