🚀 Project Overview

This is a decentralized e-commerce DApp where users can:

• Buy products using MNEE stablecoin
• Interact directly through their crypto wallet
• Avoid signup, login, and personal data sharing
• Request refunds transparently via smart contracts

Wallet address = User identity

No email. No password. No data leakage.

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❓ Problem

Traditional e-commerce platforms require users to:

• Create accounts
• Share phone numbers, emails, and bank details
• Trust centralized systems with sensitive data

This creates privacy risks and unnecessary friction.

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✅ Solution

This DApp removes all centralized identity requirements.

• Users connect their wallet
• Pay using MNEE stablecoin
• Transactions are tracked by public address
• Refunds are handled through programmable smart contracts
• Analytics are handled off-chain

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🧠 Architecture (Hybrid Model)

• Frontend: Web-based DApp (React / Web3)
• Smart Contracts: Solidity (payment & refund only)
• Blockchain: Ethereum (MNEE stablecoin)
• Backend: Transaction indexing & analytics
• Database: PostgreSQL (off-chain data storage)

Smart contracts handle money
AI + backend handle logic & insights

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💰 How MNEE is Used

• All purchases are made using MNEE stablecoin
• Payments are sent directly from user wallets
• Refunds are executed through the smart contract
• Events emitted on-chain are used for analytics

This showcases real programmable money in commerce.

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🧪 Demo

▶ Demo Video (Local Environment):

The project is demonstrated using a fully functional local setup.
All payment and refund flows are shown in the demo video.

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🛠️ Tech Stack

• Solidity
• Hardhat
• Ethers.js
• React
• Web3 Wallets
• PostgreSQL
• Node.js

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1️⃣ Install dependencies

npm install
1. Backend Dependencies
npm install express cors pg ethers fs path dotenv
2. Frontend Dependencies
npm install react react-dom react-router-dom ethers
3. Development Dependencies
npm install -D nodemon @types/node @types/express @types/cors @types/pg

🗄️ Database Schema for PostgreSQL

-- Create database
CREATE DATABASE mnee_commerce;

-- Connect to the database
\c mnee_commerce;

-- 1. Orders table (main table for storing purchases)
CREATE TABLE orders (
    id SERIAL PRIMARY KEY,
    chain_id INTEGER NOT NULL,
    contract_address VARCHAR(42) NOT NULL,
    order_id VARCHAR(255) NOT NULL,
    buyer_address VARCHAR(42) NOT NULL,
    amount NUMERIC(36, 18) NOT NULL,
    product_name VARCHAR(255) DEFAULT 'Unknown Product',
    tx_hash VARCHAR(66) UNIQUE NOT NULL,
    block_number INTEGER NOT NULL,
    timestamp TIMESTAMP WITH TIME ZONE NOT NULL,
    refunded BOOLEAN DEFAULT FALSE,
    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

-- 2. Indexer state table (tracks last synced block)
CREATE TABLE indexer_state (
    id SERIAL PRIMARY KEY,
    chain_id INTEGER NOT NULL,
    contract_address VARCHAR(42) NOT NULL,
    last_block INTEGER DEFAULT 0,
    updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
    UNIQUE(chain_id, contract_address)
);

-- Create indexes for better performance
CREATE INDEX idx_orders_buyer ON orders(buyer_address);
CREATE INDEX idx_orders_timestamp ON orders(timestamp DESC);
CREATE INDEX idx_orders_contract ON orders(contract_address);
CREATE INDEX idx_orders_refunded ON orders(refunded);

-- Create composite index for common queries
CREATE INDEX idx_orders_buyer_contract ON orders(buyer_address, contract_address);

-- Insert sample products (optional, for reference)
CREATE TABLE products (
    id SERIAL PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    price NUMERIC(36, 18) NOT NULL,
    description TEXT,
    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

-- Insert sample products matching your frontend
INSERT INTO products (name, price) VALUES
    ('Eminem Music', 48),
    ('Blockchain Course', 115),
    ('Web3 Book', 58),
    ('R.R. Martin Book', 45),
    ('Quantum Computing', 99);

## ▶️ How to Run Locally

2️⃣ Start local blockchain
npx hardhat node
3️⃣ Deploy smart contracts
npx hardhat run scripts/deploy-and-save.js --network localhost
4️⃣ Start backend
cd backend
node index.js
node listener.js
5️⃣ Start frontend
cd frontend
npm run dev

--MetaMask--
Network Name: MNEE Cloud Node

RPC URL: https://outlieralgo.cloud/rpc

Chain ID: 31337

Currency Symbol: ETH