Consensys Academy 2018-2019 Developer Program - Final Project

Simple Loan (IOU) Application

A simple IOU (I Owe You) application that allow a user to get a loan from its friends or family member by using Ethereum smart contract.

User Stories

• A user sign into the web app. The web app reads the address and identifies that user by its address. The user is looking for a loan from his/her friends and family by creating a loan request with its address and the amount needed.

• The web app adminstrator (in this case act as the broker) review the request and create and deploy the smart contract to the network.

• A user (act as lender) sign into the web app, select the loan request that he/she wants to fund and submit the amount of fund he/she willing to lend.

• The borrower will withdraw the loan amout from the contract to his/her wallet once the amount of lending match the requested loan amount.

• The broker can refund the ether back to the lender if the borrower hasn't withdraw the money yet.

• The borrower repay the loan by transfering ether from his/her wallet to the contract.

• The broker can withdraw the fund back to the lenders according to the amount they put it.

• The borrower can default the loan if he/she can no longer pay back.

• The borrower or broker can cancel the loan request if there isn't any lender yet.

Contracts

• Owable - The Ownable contract has an owner address, and provides basic authorization control functions, this simplifies the implementation of "user permissions"
• Loan - Abstract class inherit from owable to provide core loan functions and storage
• Simple Loan - Inherit from Loan Implementing simpel loan function
• Loan Util - With only one function to generate a loan ID. This util class is used for demonstrate how to link a smart contract library to a contract
• StringLib - No longer use. Will be Remove. I leave it in there so I can use it as sample how to link the library together in the truffl migration file.

Truffle Testing

To run truffle testing, you need to install truffle-assertions

npm install --save-dev truffle-assertions
npm install dotenv

Ganache is expected to run with the unit test cases

development: {
    host: "127.0.0.1", // Localhost (default: none)
    port: 7545,        // Standard Ethereum port (default: none)
    network_id: "*",   // Any network (default: none)
},

Run the test with the following command

truffle test

Sample output from the test cases

  Contract: SimpleLoan-Setup
    ✓ should create the new contract. (179ms)
    ✓ should create the contract with borrowing info for funding (177ms)

  Contract: SimpleLoan-Fund-Refund
    ✓ should be funded by 3 lenders with the amount of 2, 3, and 5 either (465ms)
    ✓ should refund all the fund to the lender (218ms)
    ✓ should fail because the status is refunded (51ms)

  Contract: SimpleLoan-Fund-Witdrawn
    ✓ should witdrawn all the fund to the borrower (466ms)
    ✓ should fail because the status is withdrawn (42ms)

  Contract: SimpleLoan-Borrower-Repay
    ✓ should re-pay all the fund to the contract (630ms)
    ✓ should return all fund to lenders (339ms)

  Contract: SimpleLoan-Default-Cancel
    ✓ should defaulted by the borrower (339ms)
    ✓ should defaulted by the owner (163ms)
    ✓ should be cancelled by borrower (320ms)
    ✓ should be cancelled by owner (235ms)
    ✓ should not be cancelled when borrower withdrawn the money (170ms)

  Contract: TimeSecuredLoan-Setup
    ✓ should create the new contract. (161ms)
    ✓ should create the contract with borrowing info for funding (239ms)

  Contract: TimeSecuredLoan-Fund-Refund
    ✓ should be funded by 3 lenders with the amount of 1, 2, and 3 either (487ms)
    ✓ should refund all the fund to the lender (173ms)
    ✓ should fail because the status is refunded (38ms)

  Contract: TimeSecuredLoan-Borrower-Withdrawn
    ✓ should fail witdrawn fund to the borrower before 1 day of fully funded (369ms)
    ✓ should witdrawn fund to the borrower after 1 day of fully funded (156ms)

  Contract: TimeSecuredLoan-Lender-Widthdraw
    ✓ should fail return fund to lenders before 2 days after repay. (534ms)
    ✓ should return fund to lenders after 2 days after repay. (150ms)

  Contract: TimeSecuredLoan-Default
    ✓ should fail default by the borrower before the contract created for 5 days (459ms)
    ✓ should defaulted by the borrower after withdrawing the fund and after contract created 5 days  (139ms)


  25 passing (9s)

Front-end Web Application

The front-end web application is in the client folder. The web application is developed with ReactJS with Web3. Please see the READM.md in the client folder for how to run the application.

ROPSTEN Network Deployment

Instead of using a local GETH deploy to ROPSTEN, the truffle is configured to use INFURA.

ropsten: {
      provider: () => new HDWalletProvider(process.env.MNEMONIC, `https://ropsten.infura.io/v3/${process.env.INFURA_API_KEY}`),
      network_id: 3,       // Ropsten's id
      gas: 5500000,        // Ropsten has a lower block limit than mainnet
      confirmations: 2,    // # of confs to wait between deployments. (default: 0)
      timeoutBlocks: 200,  // # of blocks before a deployment times out  (minimum/default: 50)
      skipDryRun: true     // Skip dry run before migrations? (default: false for public nets )
    },

Required NPM packages

npm install --save truffle-hdwallet-provider
npm install --save dotenv

Please update the truffle-config.js to include the require libraries

const HDWalletProvider = require('truffle-hdwallet-provider');
require('dotenv').config();

The configuration values for process.env.XXX are stored in .env file that is not checked-in to GIT to protect the mnemonic and project key (given by INFURA). Sameple .env file shown below

MNEMONIC=[the mnemoic generated from your metamask or wallet account]
INFURA_API_KEY=[INFURA PROJECT KEY]