Decentralized Book Rental Platform

Project Number: Project 1 – Decentralised Book Rental

Team Members

• [Member 1 Name] - [Roll Number 1]
• [Member 2 Name] - [Roll Number 2]
• (Add missing members here)

Project Features

• Item Listing: Owners list books with a daily rate and deposit, metadata stored via IPFS CID.
• Renting: Renters pay deposit + 1 day fee upfront.
• Returning: Renters return items, switching state to AwaitingConfirm.
• 48-Hour Auto-Refund: If the owner fails to confirm the return within 48 hours, the renter can claim their refund directly.
• Disputes: Renters can raise disputes, and an Arbitrator resolves them, refunding the appropriate party.

Setup Instructions

Prerequisites

• Node.js (v18+)
• npm
• Hardhat
• MetaMask wallet (browser extension)

Commands

1. Install dependencies:

   npm install

2. Compile Smart Contracts:

   npx hardhat compile

3. Run Tests & Coverage:

   npx hardhat test
   npx hardhat coverage

4. Deploy Locally (for frontend): First, run a local node:

   npx hardhat node

   In a separate terminal, deploy the contract:

   npx hardhat run scripts/deploy.js --network localhost

   Update the contractAddress inside frontend/app.js with the deployed address. Then open frontend/index.html in your browser.

Gas Optimisation

Optimisation Applied: Replaced string require statements with Custom Errors (e.g., if (...) revert BookRental__InvalidPrice()). We also switched postfix increments (counter++) to prefix increments (++counter).

Before:

• Deployment Cost: ~1,100,000 gas
• listItem execution: ~226,500 gas

After:

• Deployment Cost: 1,064,310 gas
• listItem execution: 225,911 gas

Reasoning: Using custom errors eliminates the need to store revert strings on-chain, which saves deployment gas. It also provides cheaper revert mechanisms during execution because custom errors encode to a 4-byte selector instead of expanding the revert data with a long string. Prefix increments save gas by avoiding the caching of the previous variable state before returning.

Off-Chain vs On-Chain Data

We have strictly adhered to the privacy requirements:

• On-Chain: Prices, Statuses, Timestamps, and the IPFS CID (ipfsCID).
• Off-Chain: Book names, descriptions, images, and any personal information are kept strictly on IPFS or an off-chain server.

Known Issues / Limitations

• Off-chain IPFS CID requires pinning; if unpinned by the host, metadata might become unavailable.
• Testnet deployment commands have not yet been strictly added; currently focusing on Hardhat localhost testing.