GM Swap is a decentralized ERC-20 token swap dApp built on Ethereum, enabling users to connect their wallets, select tokens, preview exchange rates and estimated gas fees, and execute swaps directly from their wallets.

The core engineering challenge was transaction reliability. A DeFi swap interface must coordinate wallet connections, token balances, rate calculations, gas estimates, contract interactions, user confirmations, and blockchain transaction states without creating confusion during the trading process.

The Challenge

Executing an ERC-20 swap involves multiple interactions between the frontend, wallet provider, blockchain network, and smart contracts.

Users need clear visibility into the token they're selling, the asset they expect to receive, estimated rates, gas costs, wallet confirmation requests, pending transactions, successful execution, and failed states.

Weak transaction-state handling or unclear wallet feedback can cause duplicate actions, failed transactions, and poor user trust.

GM Swap required a responsive DeFi interface capable of managing these interactions while keeping the swap process clear from wallet connection through final transaction confirmation.

The Engineering Approach

The application was engineered using Next.js, React, and TypeScript for the frontend architecture, with Ethers.js and Web3.js handling Ethereum wallet and blockchain interactions.

The wallet layer was integrated with MetaMask to manage account connections, network interactions, token balances, transaction requests, and confirmation states.

The swap interface was structured around predictable transaction stages, providing users with token details, estimated output, gas information, and transaction previews before execution.

MetaMask Wallet Integration

GM Swap enables users to connect their MetaMask wallet directly to the application.

The wallet integration manages account connectivity and provides the foundation for token balance retrieval, transaction signing, and Ethereum network interactions.

ERC-20 Token Selection

The token selection system allows users to choose assets for the swap workflow and review relevant token information before initiating a transaction.

Token balances are retrieved and displayed within the interface to provide users with visibility into available assets.

Rate & Transaction Preview

Before executing a swap, users can review the expected transaction details.

The interface provides:

• Selected input and output tokens
• Swap amounts
• Estimated exchange rates
• Expected token output
• Gas fee estimates
• Transaction details

This preview layer helps users understand the transaction before submitting it to their wallet.

Gas Fee Estimation

Ethereum gas estimation was integrated into the transaction flow to provide users with expected network costs before execution.

The estimated gas information is presented as part of the transaction preview and confirmation process.

Smart Contract Interaction

The application uses Ethers.js, Web3.js, and Solidity-based contract interactions to execute ERC-20 token operations on Ethereum.

The interaction layer coordinates transaction preparation, wallet requests, blockchain submission, and transaction-state updates.

Transaction-State Management

The swap workflow was structured around clear transaction states.

The interface manages:

• Wallet connection
• Token selection
• Rate calculation
• Transaction preparation
• Gas estimation
• Wallet confirmation
• Pending transactions
• Successful execution
• Failed transactions

This architecture provides users with clear feedback throughout the complete swap lifecycle.

Responsive DeFi Interface

GM Swap features a responsive dark-mode trading interface designed for desktop and mobile users.

The frontend was optimized to keep wallet actions, token selection, transaction previews, and swap execution focused within a straightforward trading workflow.

Technology Stack

Next.js, React, TypeScript, Ethers.js, Web3.js, Solidity, Ethereum, ERC-20, MetaMask, REST APIs

Outcome

GM Swap resulted in a functional decentralized token swap application combining Ethereum wallet connectivity, ERC-20 token selection, balance tracking, rate previews, gas estimation, smart contract interactions, and structured transaction-state management.

The platform provides a technical foundation for executing wallet-based token swaps through a responsive DeFi interface without requiring users to transfer custody of their assets to a centralized trading platform.