Added functionality to get estimated fee for a transaction

CHANGELOG.md

@@ -9,4 +9,5 @@
 - Added functionality to sign message
 - Added get balance method to fetch SOL balance of an account
 - Added functionality to sign SOL and fungible tokens transfer transaction
-- Added functionality to broadcast a signed transaction
+- Added functionality to broadcast a signed transaction
+- Added functionality to get estimated fee for a transaction

src/helper/signTransaction.js

@@ -4,13 +4,14 @@ async function sign(transaction, signer, connection, otherSigners) {
         await connection.getRecentBlockhash('max')
     ).blockhash;
 
+    transaction.feePayer = signer.publicKey;
+
     transaction.sign(signer)
     if (otherSigners.length > 0) {
         transaction.partialSign(...otherSigners);
     }
 
-    const rawTransaction = transaction.serialize();
-    return rawTransaction;
+    return transaction;
 }
 
 module.exports = sign

src/index.js

@@ -78,7 +78,7 @@ class KeyringController {
   }
 
   async signTransaction(transaction) {
-    const { mnemonic, address, network, networkType } = this.store.getState();
+    const { mnemonic, address, network } = this.store.getState();
 
     const { from } = transaction;
     const idx = address.indexOf(from);
@@ -91,9 +91,11 @@ class KeyringController {
       const connection = new solanaWeb3.Connection(network, "confirmed");
 
       const rawTx = await helper.generateTransactionObject(transaction, signer, connection);
+
       const rawSignedTxn = await helper.signTransaction(rawTx, signer, connection, []);
 
-      const signedTxn = rawSignedTxn.toString("hex");
+      const signedTxn = rawSignedTxn.serialize().toString("hex");
+
       return { signedTransaction: signedTxn };
     } catch (err) {
       throw err;
@@ -116,6 +118,28 @@ class KeyringController {
     }
   }
 
+  async getFees(rawTransaction) {
+    const { mnemonic, address, network } = this.store.getState();
+
+    const { from } = rawTransaction;
+    const idx = address.indexOf(from);
+    if (idx < 0)
+      throw "Invalid address, the address is not available in the wallet";
+
+      const signer = helper.setupAccount(mnemonic, helper.getHDPath(idx));
+
+      const connection = new solanaWeb3.Connection(network, "confirmed");
+
+      const rawTx = await helper.generateTransactionObject(rawTransaction, signer, connection);
+
+      const rawSignedTxn = await helper.signTransaction(rawTx, signer, connection, []);
+
+      const fees = await connection.getFeeForMessage(rawSignedTxn.compileMessage());
+
+      return { fees: fees.value };
+
+  }
+
   persistAllAddress(_address) {
     const { address } = this.store.getState();
     let newAdd = address;