Add FeeBumpTransaction class (#328)

* Handle transaction envelope with MuxedAccount in sourceAccount.

* Add FeeBumpTransaction.

* Add more test for FeeBumpTransaction.

* Improve docs.

* Add TransactionBase and extend from it.

* Use named import and inherit documentation.

* Inherit TransactionBase in Transaction.

* Document readonly attrs.

* Document properties on fee bump tx.

* Show M accounts.

* Return a copy of tx and signatures when building toEnvelope.

* Add helper function fromXDR.

* Update types.

* Update XDR.

* Handle muxed accoutns in fee bump transactions.

* Add link to fromXDR in Transaction and FeeBumpTransaction docs.

* Extend fromXDR to take a xdr object or a string.

src/fee_bump_transaction.js

@@ -0,0 +1,102 @@
+import xdr from './generated/stellar-xdr_generated';
+import { hash } from './hashing';
+
+import { StrKey } from './strkey';
+import { Transaction } from './transaction';
+import { TransactionBase } from './transaction_base';
+
+/**
+ * Use {@link TransactionBuilder.buildFeeBumpTransaction} to build a
+ * FeeBumpTransaction object. If you have an object or base64-encoded string of
+ * the transaction envelope XDR use {@link TransactionBuilder.fromXDR}.
+ *
+ * Once a {@link FeeBumpTransaction} has been created, its attributes and operations
+ * should not be changed. You should only add signatures (using {@link FeeBumpTransaction#sign}) before
+ * submitting to the network or forwarding on to additional signers.
+ * @param {string|xdr.TransactionEnvelope} envelope - The transaction envelope object or base64 encoded string.
+ * @param {string} networkPassphrase passphrase of the target stellar network (e.g. "Public Global Stellar Network ; September 2015").
+ * @extends TransactionBase
+ */
+export class FeeBumpTransaction extends TransactionBase {
+  constructor(envelope, networkPassphrase) {
+    if (typeof envelope === 'string') {
+      const buffer = Buffer.from(envelope, 'base64');
+      envelope = xdr.TransactionEnvelope.fromXDR(buffer);
+    }
+
+    const envelopeType = envelope.switch();
+    if (envelopeType !== xdr.EnvelopeType.envelopeTypeTxFeeBump()) {
+      throw new Error(
+        `Invalid TransactionEnvelope: expected an envelopeTypeTxFeeBump but received an ${envelopeType.name}.`
+      );
+    }
+
+    const txEnvelope = envelope.value();
+    const tx = txEnvelope.tx();
+    const fee = tx.fee().toString();
+    // clone signatures
+    const signatures = (txEnvelope.signatures() || []).slice();
+
+    super(tx, signatures, fee, networkPassphrase);
+
+    const innerTxEnvelope = xdr.TransactionEnvelope.envelopeTypeTx(
+      tx.innerTx().v1()
+    );
+
+    this._innerTransaction = new Transaction(
+      innerTxEnvelope,
+      networkPassphrase
+    );
+  }
+
+  /**
+   * @type {Transaction}
+   * @readonly
+   */
+  get innerTransaction() {
+    return this._innerTransaction;
+  }
+
+  /**
+   * @type {string}
+   * @readonly
+   */
+  get feeSource() {
+    return this._muxedToString(this.tx.feeSource());
+  }
+
+  /**
+   * Returns the "signature base" of this transaction, which is the value
+   * that, when hashed, should be signed to create a signature that
+   * validators on the Stellar Network will accept.
+   *
+   * It is composed of a 4 prefix bytes followed by the xdr-encoded form
+   * of this transaction.
+   * @returns {Buffer}
+   */
+  signatureBase() {
+    const taggedTransaction = new xdr.TransactionSignaturePayloadTaggedTransaction.envelopeTypeTxFeeBump(
+      this.tx
+    );
+
+    const txSignature = new xdr.TransactionSignaturePayload({
+      networkId: xdr.Hash.fromXDR(hash(this.networkPassphrase)),
+      taggedTransaction
+    });
+
+    return txSignature.toXDR();
+  }
+
+  /**
+   * To envelope returns a xdr.TransactionEnvelope which can be submitted to the network.
+   * @returns {xdr.TransactionEnvelope}
+   */
+  toEnvelope() {
+    const envelope = new xdr.FeeBumpTransactionEnvelope({
+      tx: xdr.FeeBumpTransaction.fromXDR(this.tx.toXDR()), // make a copy of the tx
+      signatures: this.signatures.slice() // make a copy of the signatures
+    });
+
+    return new xdr.TransactionEnvelope.envelopeTypeTxFeeBump(envelope);
+  }
+}

src/generated/stellar-xdr_generated.js

@@ -1,4 +1,4 @@
-// Automatically generated on 2020-04-14T16:01:24-05:00
+// Automatically generated on 2020-04-16T16:15:58-05:00
 // DO NOT EDIT or your changes may be overwritten
 
 /* jshint maxstatements:2147483647  */
@@ -1481,7 +1481,7 @@ xdr.union("FeeBumpTransactionExt", {
 //
 //   struct FeeBumpTransaction
 //   {
-//       AccountID feeSource;
+//       MuxedAccount feeSource;
 //       int64 fee;
 //       union switch (EnvelopeType type)
 //       {
@@ -1499,7 +1499,7 @@ xdr.union("FeeBumpTransactionExt", {
 //
 // ===========================================================================
 xdr.struct("FeeBumpTransaction", [
-  ["feeSource", xdr.lookup("AccountId")],
+  ["feeSource", xdr.lookup("MuxedAccount")],
   ["fee", xdr.lookup("Int64")],
   ["innerTx", xdr.lookup("FeeBumpTransactionInnerTx")],
   ["ext", xdr.lookup("FeeBumpTransactionExt")],

src/index.js

@@ -5,7 +5,9 @@ export { hash } from './hashing';
 export { sign, verify, FastSigning } from './signing';
 export { Keypair } from './keypair';
 export { UnsignedHyper, Hyper } from 'js-xdr';
+export { TransactionBase } from './transaction_base';
 export { Transaction } from './transaction';
+export { FeeBumpTransaction } from './fee_bump_transaction';
 export {
   TransactionBuilder,
   TimeoutInfinite,