refactor(sdk-coin-icp): introduce NetworkID enum and enhance transact…

…ion serialization with SignedTransactionRequest

TICKET: WIN-4641

modules/sdk-coin-icp/src/lib/iface.ts

@@ -25,6 +25,10 @@ export enum MethodName {
   SEND_PB = 'send_pb', // send_pb is the method name for ICP transfer transaction
 }
 
+export enum NetworkID {
+  MAINNET = '00000000000000020101', // ICP does not have different network IDs for mainnet and testnet
+}
+
 export interface IcpTransactionData {
   senderAddress: string;
   receiverAddress: string;
@@ -170,3 +174,13 @@ export interface IcpTransactionExplanation extends BaseTransactionExplanation {
   sender?: string;
   type?: BitGoTransactionType;
 }
+
+export interface NetworkIdentifier {
+  blockchain: string;
+  network: string;
+}
+
+export interface SignedTransactionRequest {
+  network_identifier: NetworkIdentifier;
+  signed_transaction: string;
+}

modules/sdk-coin-icp/src/lib/transaction.ts

@@ -15,6 +15,8 @@ import {
   Signatures,
   TxData,
   IcpTransactionExplanation,
+  SignedTransactionRequest,
+  NetworkID,
 } from './iface';
 import { Utils } from './utils';
 import { KeyPair } from './keyPair';
@@ -167,8 +169,22 @@ export class Transaction extends BaseTransaction {
   }
 
   /** @inheritdoc */
-  toBroadcastFormat(): void {
-    throw new Error('Method not implemented.');
+  toBroadcastFormat(): string {
+    if (!this._signedTransaction) {
+      throw new InvalidTransactionError('Empty transaction');
+    }
+    return this.serialize();
+  }
+
+  serialize(): string {
+    const transaction: SignedTransactionRequest = {
+      signed_transaction: this._signedTransaction,
+      network_identifier: {
+        blockchain: this._coinConfig.fullName,
+        network: NetworkID.MAINNET,
+      },
+    };
+    return Buffer.from(JSON.stringify(transaction)).toString('base64');
   }
 
   /** @inheritdoc */