proof of concept: pay with usdt on statemint

package.json

@@ -33,6 +33,7 @@
     "xcm-cross-chain-transfer": "ts-node scripts/xcm-cross-chain-transfer",
     "xcm-return-unknown-tokens": "ts-node scripts/xcm-return-unknown-tokens",
     "democracy": "ts-node scripts/democracy",
+    "statemint-usdt-fee": "ts-node scripts/statemint-usdt-fee",
     "create-proposal": "ts-node scripts/create-proposal",
     "undercollateralized-borrowers": "ts-node scripts/get-undercollateralized-borrowers",
     "test": "run-s build test:*",

scripts/statemint-usdt-fee.ts

@@ -0,0 +1,52 @@
+
+import { createSubstrateAPI } from "../src/factory";
+import { Keyring } from "@polkadot/api";
+import { SubmittableExtrinsic } from "@polkadot/api/types";
+import { ISubmittableResult } from "@polkadot/types/types";
+
+
+async function sendTx(
+    transaction: SubmittableExtrinsic<"promise">,
+    onlyInBlock?: boolean
+): Promise<ISubmittableResult> {
+    const keyring = new Keyring({ type: "sr25519" });
+    const account = keyring.addFromUri("//Alice");
+    const { unsubscribe, result } = await new Promise((resolve, reject) => {
+        let unsubscribe: () => void;
+        transaction
+            .signAndSend(account, { nonce: -1, assetId: 1984 }, (result: ISubmittableResult) => callback({ unsubscribe, result }))
+            .then((u: () => void) => (unsubscribe = u))
+            .catch((error) => reject(error));
+
+        let foundStatus = false;
+        // only need to check this if we do want to wait for the success event
+        function callback(callbackObject: { unsubscribe: () => void; result: ISubmittableResult }): void {
+            const status = callbackObject.result.status;
+            foundStatus = foundStatus || (onlyInBlock && status.isInBlock) || status.isFinalized;
+
+            if (foundStatus) {
+                resolve(callbackObject);
+            }
+        }
+    });
+
+    if (result.status.isInBlock) {
+        console.log(`Transaction included at blockHash ${result.status.asInBlock}`);
+    } else if (result.status.isFinalized) {
+        console.log(`Transaction finalized at blockHash ${result.status.asFinalized}`);
+    }
+    unsubscribe(result);
+
+    if (result.dispatchError) {
+        return Promise.reject();
+    }
+    return result;
+}
+
+async function main(): Promise<void> {
+    const api = await createSubstrateAPI("ws://127.0.0.1:8000");
+    let tx = api.tx.system.remark("test");
+    await sendTx(tx, true);
+}
+
+main();