Add initial simulateMsgs function

wallets/cosmos.ts

@@ -7,6 +7,7 @@ import { Buffer } from "buffer/";
 import {
   AuthInfo,
   Fee,
+  SignerInfo,
   TxBody,
   TxRaw,
 } from "@keplr-wallet/proto-types/cosmos/tx/v1beta1/tx";
@@ -19,7 +20,6 @@ export async function sendMsgs(
   wallet: Wallet,
   chainInfo: {
     readonly chainId: string;
-    readonly rpc: string;
     readonly rest: string;
   },
   sender: string,
@@ -108,6 +108,81 @@ export async function sendMsgs(
   return wallet.broadcastTxSync(chainInfo.chainId, signedTx);
 }
 
+export async function simulateMsgs(
+  chainInfo: {
+    readonly chainId: string;
+    readonly rest: string;
+  },
+  sender: string,
+  msgs: {
+    proto: Any[];
+  },
+  fee: {
+    readonly amount: readonly {
+      readonly amount: string;
+      readonly denom: string;
+    }[];
+  },
+  memo: string = "",
+): Promise<{
+  gasUsed: number;
+}> {
+  const lcdInstance = Axios.create({
+    baseURL: chainInfo.rest,
+  });
+
+  const account = await BaseAccount.fetchFromRest(lcdInstance, sender, true);
+
+  const unsignedTx = TxRaw.encode({
+    bodyBytes: TxBody.encode(
+      TxBody.fromPartial({
+        // XXX: I don't know why typing error occurs.
+        // TODO: Solve typing problem.
+        messages: msgs.proto as any,
+        memo: memo,
+      }),
+    ).finish(),
+    authInfoBytes: AuthInfo.encode({
+      signerInfos: [
+        SignerInfo.fromPartial({
+          modeInfo: {
+            single: {
+              mode: SignMode.SIGN_MODE_LEGACY_AMINO_JSON,
+            },
+            multi: undefined,
+          },
+          sequence: account.getSequence().toString(),
+        }),
+      ],
+      fee: Fee.fromPartial({
+        // XXX: I don't know why typing error occurs.
+        // TODO: Solve typing problem.
+        // amount: fee.amount as {
+        //   amount: string;
+        //   denom: string;
+        // }[],
+        amount: fee.amount as any,
+      }),
+    }).finish(),
+    // Because of the validation of tx itself, the signature must exist.
+    // However, since they do not actually verify the signature, it is okay to use any value.
+    signatures: [new Uint8Array(64)],
+  }).finish();
+
+  const result = await lcdInstance.post("/cosmos/tx/v1beta1/simulate", {
+    tx_bytes: Buffer.from(unsignedTx).toString("base64"),
+  });
+
+  const gasUsed = parseInt(result.data.gas_info.gas_used);
+  if (Number.isNaN(gasUsed)) {
+    throw new Error(`Invalid integer gas: ${result.data.gas_info.gas_used}`);
+  }
+
+  return {
+    gasUsed,
+  };
+}
+
 export function makeCosmwasmExecMsg(
   sender: string,
   contractAddress: string,