adds UnsignedTransaction primitive (#4619)

ironfish/src/primitives/unsignedTransaction.ts

@@ -0,0 +1,58 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+import { UnsignedTransaction as NativeUnsignedTransaction } from '@ironfish/rust-nodejs'
+
+export class UnsignedTransaction {
+  private readonly unsignedTransactionSerialized: Buffer
+  private referenceCount = 0
+  private nativeUnsignedTransaction: NativeUnsignedTransaction | null = null
+
+  constructor(unsignedTransactionSerialized: Buffer) {
+    this.unsignedTransactionSerialized = unsignedTransactionSerialized
+  }
+
+  serialize(): Buffer {
+    return this.unsignedTransactionSerialized
+  }
+
+  /**
+   * Preallocate any resources necessary for using the transaction.
+   */
+  takeReference(): NativeUnsignedTransaction {
+    this.referenceCount++
+    if (this.nativeUnsignedTransaction === null) {
+      this.nativeUnsignedTransaction = new NativeUnsignedTransaction(
+        this.unsignedTransactionSerialized,
+      )
+    }
+    return this.nativeUnsignedTransaction
+  }
+
+  /**
+   * Return any resources necessary for using the transaction.
+   */
+  returnReference(): void {
+    this.referenceCount--
+    if (this.referenceCount <= 0) {
+      this.referenceCount = 0
+      this.nativeUnsignedTransaction = null
+    }
+  }
+
+  /**
+   * Wraps the given callback in takeReference and returnReference.
+   */
+  withReference<R>(callback: (transaction: NativeUnsignedTransaction) => R): R {
+    const transaction = this.takeReference()
+
+    const result = callback(transaction)
+
+    void Promise.resolve(result).finally(() => {
+      this.returnReference()
+    })
+
+    return result
+  }
+}