Add support for USDT

Author: sisou

src/api.ts

@@ -134,7 +134,7 @@ export async function createSwap(
 export async function confirmSwap(
     swap: PreSwap,
     redeem: {
-        asset: SwapAsset.NIM | SwapAsset.BTC | SwapAsset.USDC | SwapAsset.USDC_MATIC,
+        asset: SwapAsset.NIM | SwapAsset.BTC | SwapAsset.USDC | SwapAsset.USDC_MATIC | SwapAsset.USDT,
         address: string,
     } | {
         asset: SwapAsset.EUR,
@@ -146,7 +146,7 @@ export async function confirmSwap(
         asset: SwapAsset.BTC_LN,
     },
     refund?: {
-        asset: SwapAsset.NIM | SwapAsset.BTC | SwapAsset.USDC | SwapAsset.USDC_MATIC,
+        asset: SwapAsset.NIM | SwapAsset.BTC | SwapAsset.USDC | SwapAsset.USDC_MATIC | SwapAsset.USDT,
         address: string,
     } | {
         asset: SwapAsset.EUR,
@@ -185,6 +185,7 @@ export async function confirmSwap(
         case SwapAsset.BTC:
         case SwapAsset.USDC:
         case SwapAsset.USDC_MATIC:
+        case SwapAsset.USDT:
             beneficiary = { [redeem.asset]: redeem.address };
             break;
     }
@@ -249,7 +250,7 @@ export async function getAssets(): Promise<AssetList> {
             records[record.symbol] = {
                 asset: record.symbol,
                 name: record.name,
-                feePerUnit: coinsToUnits(record.symbol, record.feePerUnit, { treatUsdcAsMatic: true }),
+                feePerUnit: coinsToUnits(record.symbol, record.feePerUnit, { treatPolygonTokenAsMatic: true }),
                 limits: {
                     minimum: record.limits && record.limits.minimum
                         ? coinsToUnits(record.symbol, record.limits.minimum)

src/helpers.ts

@@ -20,12 +20,13 @@ import {
 
 export function coinsToUnits(asset: SwapAsset | ReferenceAsset, value: string | number, options: Partial<{
     roundUp: boolean,
-    treatUsdcAsMatic: boolean,
+    treatPolygonTokenAsMatic: boolean,
 }> = {}): number {
     let decimals = Precision[asset] as number;
 
-    // Some fees for USDC are provided in MATIC, and must be converted accordingly
-    if ((asset === SwapAsset.USDC || asset === SwapAsset.USDC_MATIC) && options.treatUsdcAsMatic) decimals = 18;
+    // Some fees for USDC/T are provided in MATIC, and must be converted accordingly
+    const isPolygonToken = asset === SwapAsset.USDC || asset === SwapAsset.USDC_MATIC || asset === SwapAsset.USDT;
+    if (isPolygonToken && options.treatPolygonTokenAsMatic) decimals = 18;
 
     if (typeof decimals === 'undefined') throw new Error(`Invalid asset ${asset}`);
 
@@ -50,7 +51,7 @@ export function convertFromData(from: FastspotPrice): PriceData {
             ? {
                 feePerUnit: coinsToUnits(asset, from.fundingNetworkFee.perUnit, {
                     roundUp: true,
-                    treatUsdcAsMatic: true,
+                    treatPolygonTokenAsMatic: true,
                 }),
             }
             : {}),
@@ -69,7 +70,7 @@ export function convertToData(to: FastspotPrice): PriceData {
             ? {
                 feePerUnit: coinsToUnits(asset, to.finalizeNetworkFee.perUnit, {
                     roundUp: true,
-                    treatUsdcAsMatic: true,
+                    treatPolygonTokenAsMatic: true,
                 }),
             }
             : {}),
@@ -100,10 +101,15 @@ export function convertContract<T extends SwapAsset>(contract: FastspotContract<
             break;
         case SwapAsset.USDC:
         case SwapAsset.USDC_MATIC:
+        case SwapAsset.USDT:
             htlc = {
                 address: contract.id.substring(0, 2) === '0x' ? contract.id : `0x${contract.id}`,
-                contract: (contract as FastspotContract<SwapAsset.USDC | SwapAsset.USDC_MATIC>).intermediary.address,
-                data: (contract as FastspotContract<SwapAsset.USDC | SwapAsset.USDC_MATIC>).intermediary.data,
+                contract:
+                    (contract as FastspotContract<SwapAsset.USDC | SwapAsset.USDC_MATIC | SwapAsset.USDT>).intermediary
+                        .address,
+                data:
+                    (contract as FastspotContract<SwapAsset.USDC | SwapAsset.USDC_MATIC | SwapAsset.USDT>).intermediary
+                        .data,
             };
             break;
         case SwapAsset.EUR:
@@ -122,7 +128,9 @@ export function convertContract<T extends SwapAsset>(contract: FastspotContract<
         refundAddress: contract.refund?.address || '',
         redeemAddress: contract.asset === SwapAsset.EUR
             ? JSON.stringify((contract as FastspotContract<SwapAsset.EUR>).recipient)
-            : (contract as FastspotContract<SwapAsset.NIM | SwapAsset.BTC | SwapAsset.USDC | SwapAsset.USDC_MATIC>)
+            : (contract as FastspotContract<
+                SwapAsset.NIM | SwapAsset.BTC | SwapAsset.USDC | SwapAsset.USDC_MATIC | SwapAsset.USDT
+            >)
                 .recipient.address,
         amount: coinsToUnits(contract.asset, contract.amount),
         timeout: contract.timeout,

src/types.ts

@@ -4,6 +4,7 @@ export enum SwapAsset {
     BTC_LN = 'BTC_LN',
     USDC = 'USDC',
     USDC_MATIC = 'USDC_MATIC',
+    USDT = 'USDT', // Alternatively USDT_MATIC
     EUR = 'EUR',
 }
 
@@ -22,6 +23,7 @@ export const Precision = {
     [SwapAsset.BTC_LN]: 8,
     [SwapAsset.USDC]: 6,
     [SwapAsset.USDC_MATIC]: 6,
+    [SwapAsset.USDT]: 6,
     [SwapAsset.EUR]: 2,
     [ReferenceAsset.USD]: 2,
 } as const;
@@ -125,7 +127,7 @@ export type FastspotContract<T extends SwapAsset> = {
                 hash: string,
                 request: string,
             }
-        : T extends SwapAsset.USDC | SwapAsset.USDC_MATIC ? {
+        : T extends SwapAsset.USDC | SwapAsset.USDC_MATIC | SwapAsset.USDT ? {
                 address: string,
                 data?: string, // Only provided for 'send' direction
             }
@@ -250,13 +252,13 @@ export type EurHtlcDetails = {
     address: string,
 };
 
-export type UsdcHtlcDetails = {
+export type Erc20HtlcDetails = {
     address: string,
     contract: string,
     data?: string,
 };
 
-export type HtlcDetails = NimHtlcDetails | BtcHtlcDetails | BtcLnHtlcDetails | UsdcHtlcDetails | EurHtlcDetails;
+export type HtlcDetails = NimHtlcDetails | BtcHtlcDetails | BtcLnHtlcDetails | Erc20HtlcDetails | EurHtlcDetails;
 
 export type Contract<T extends SwapAsset> = {
     id: string,
@@ -270,7 +272,7 @@ export type Contract<T extends SwapAsset> = {
     htlc: T extends SwapAsset.NIM ? NimHtlcDetails
         : T extends SwapAsset.BTC ? BtcHtlcDetails
         : T extends SwapAsset.BTC_LN ? BtcLnHtlcDetails
-        : T extends SwapAsset.USDC | SwapAsset.USDC_MATIC ? UsdcHtlcDetails
+        : T extends SwapAsset.USDC | SwapAsset.USDC_MATIC | SwapAsset.USDT ? Erc20HtlcDetails
         : T extends SwapAsset.EUR ? EurHtlcDetails
         : never,
 };