HBAR Allowances and Atomic Transfers

This repository demonstrates how to perform HBAR allowances and atomic crypto transfers (HBAR, HTS fungible tokens, and HTS NFTs in the same transfer via a contract transaction). It uses a Hardhat project to test the flow of creating HTS tokens, approving allowances (HBAR & HTS), associating HTS tokens to Hedera accounts, and performing the atomic crypto transfer.

HIP 206: Hedera Token Service Precompiled Contract for Hedera SmartContract Service

• Defines a new function to the Hedera Token Service system contract that allows for the atomic transfer of HBAR, fungible tokens and non-fungible tokens.
• Function cryptoTransfer(TransferList transferList,TokenTransferList[] tokenTransfer)
• Exposes an existing HAPI call via smart contracts.
• Transfer honors granted allowances.

Benefits:

• Enables native royalty support on the EVM since native $hbar can now be transferred using spending allowances
• Direct interaction with HBAR and HTS tokens
• Eliminates the need for token wrapping.
• Enhances efficiency and reduces complexity.
• Cuts costs by removing intermediary steps i.e., wrapping assets to interact with them.
• Enables native royalty support on the EVM since native HBAR can now be transferred using spending allowances

HIP 906: Proxy Redirect Contract for Hbar Allowance and Approval

• Introduces a new Hedera Account Service system contract.
• Enables querying and granting approval of HBAR to a spender account from smart contracts code
• hbarAllowance, hbarApprove
• Developers do not have to context switch out of smart contract code

Benefits:

• Introduces new account proxy contract for HBAR allowances
• Enables grant, retrieve, and manage HBAR allowances within smart contracts
• Developers do not have to context switch out of smart contracts code
• Simplifies workflows and enhances security
• Expands potential use cases, especially for DeFi and token marketplaces

Try It on the Browser:

Open with GitPod

Try It Locally:

Prerequisites

• Node.js
• npm
• A Hedera account with ECDSA credentials

Instructions

1. Clone the repository:

   git clone https://github.com/ed-marquez/hedera-example-hbar-allowances-and-atomic-transfers.git
   cd hedera-example-hbar-allowances-and-atomic-transfers

2. Rename the example.env file to .env and enter the ECDSA credentials for the 3 accounts needed:

   mv example.env .env

3. Install dependencies:

   npm install

4. Run the test script::

   npx hardhat test

Project Structure

• .env: Environment variables file (be sure to rename example.env to .env and fill in your credentials).
• constants.js: Contains constants and network configurations.
• hardhat.config.js: Hardhat configuration file.
• atomicTransfer.test.js: Contains the test script for performing the atomic transfers.

Flow Description

1. Initialize Environment Variables:
   • Rename example.env to .env and fill in your ECDSA account credentials.
2. Use Environment Variables:
   • The credentials from .env are used in constants.js.
3. Configure Hardhat:
   • The constants from constants.js are used in hardhat.config.js for network and account configuration.
4. Run Tests:
   • Tests in atomicTransfer.test.js create tokens, approve allowances, associate HTS tokens to Hedera accounts, and perform the atomic crypto transfer.