feat: add slippage endpoint (#67)

sdk/src/index.ts

@@ -1,6 +1,7 @@
 export * from './wrappedAsset';
 export * from './types';
 export * from './quotes';
+export * from './slippage';
 export * from './utils/constants';
 export * from './utils/permit';
 export * from './utils/sources';

sdk/src/slippage.ts

@@ -0,0 +1,92 @@
+import { BigNumberish } from '@ethersproject/bignumber';
+import {
+  ChainId,
+  EthereumAddress,
+  Slippage,
+  SlippageError,
+  SlippageParams,
+} from './types';
+import { API_BASE_URL } from './utils/constants';
+
+/**
+ * Function to get a slippage formatted quote url to use with backend
+ *
+ * @param {ChainId} params.chainId
+ * @param {ChainId} params.toChainId
+ * @param {EthereumAddress} params.sellTokenAddress
+ * @param {EthereumAddress} params.buyTokenAddress
+ * @param {BigNumberish} params.buyAmount
+ * @param {BigNumberish} params.sellAmount
+ * @returns {string}
+ */
+const buildRainbowSlippageUrl = ({
+  chainId,
+  toChainId,
+  sellTokenAddress,
+  buyTokenAddress,
+  buyAmount,
+  sellAmount,
+}: {
+  chainId: number;
+  toChainId?: number;
+  sellTokenAddress: EthereumAddress;
+  buyTokenAddress: EthereumAddress;
+  buyAmount?: BigNumberish;
+  sellAmount?: BigNumberish;
+}) => {
+  const searchParams = new URLSearchParams({
+    buyToken: buyTokenAddress,
+    chainId: String(chainId),
+    sellToken: sellTokenAddress,
+    toChainId: String(toChainId),
+    ...(sellAmount
+      ? { sellAmount: String(sellAmount) }
+      : { buyAmount: String(buyAmount) }),
+  });
+  return `${API_BASE_URL}/v1/slippage?` + searchParams.toString();
+};
+
+/**
+ * Function to get slippage from rainbow's swap aggregator backend
+ *
+ * @param {SlippageParams} params
+ * @param {ChainId} params.chainId
+ * @param {ChainId} params.toChainId
+ * @param {EthereumAddress} params.sellTokenAddress
+ * @param {EthereumAddress} params.buyTokenAddress
+ * @param {BigNumberish} params.sellAmount
+ * @param {BigNumberish} params.buyAmount
+ * @returns {Promise<Slippage | SlippageError | null>}
+ */
+export const getSlippage = async (
+  params: SlippageParams
+): Promise<Slippage | SlippageError | null> => {
+  const {
+    chainId = ChainId.mainnet,
+    toChainId,
+    sellTokenAddress,
+    buyTokenAddress,
+    sellAmount,
+    buyAmount,
+  } = params;
+
+  if (isNaN(Number(sellAmount)) && isNaN(Number(buyAmount))) {
+    return null;
+  }
+
+  const url = buildRainbowSlippageUrl({
+    buyAmount,
+    buyTokenAddress,
+    chainId,
+    sellAmount,
+    sellTokenAddress,
+    toChainId,
+  });
+
+  const response = await fetch(url);
+  const slippage = await response.json();
+  if (slippage.error) {
+    return slippage as SlippageError;
+  }
+  return slippage?.data as Slippage;
+};

sdk/src/types/index.ts

@@ -257,3 +257,22 @@ export interface CrosschainQuoteExecutionDetails {
   method: any;
   params: TransactionOptions;
 }
+
+export interface SlippageParams {
+  chainId: number;
+  sellTokenAddress: EthereumAddress;
+  buyTokenAddress: EthereumAddress;
+  sellAmount?: BigNumberish;
+  buyAmount?: BigNumberish;
+  toChainId?: number;
+}
+
+export interface SlippageError {
+  error: boolean;
+  error_code?: number;
+  message: string;
+}
+
+export interface Slippage {
+  slippagePercent: number;
+}