Staking Token

This repo shows an example of a simple Defi smart contract for staking ERC20 tokens, with a simple reward calculation, developed using the hardhat framework

Motivation

This is the first of a series of Defi smart contracts using solidity. This Defi series covers the basic codes in varioius areas of Defi projects such as :

• Staking tokens
• borrow & loan ETH, borrow & loan ERC20 tokens
• token swap
• flash loan
• etc

Functional Description

There are 2 main features here : one is related to token staking, the other is reward earned.

• token staking :
  • stake token
  • unstake token
  • add and delete stakeholder
  • total staking balance
• rewards earned :
  • calculate rewards
  • distribute rewards
  • total rewards
  • stakeholders reward balance
  • withdraw reward

Owner only functions

• total staking balance
• distrubute rewards
• check individual's rewards

User functions

• stake token
• unstake token
• staking balance
• calculate reward
• reward balance
• withdraw reward

Contract (internal) functions

• add and delete stakeholders

Technical Description

Technical background

• As this smart contract project is built using the hardhat framework, please refer to this project/repo basic smart contract using hardhat regarding building a basic smart contract using the hardhat framwork.
• The README section contains a quick overview and usage of various hardhat commands etc. It serves as a good, quick refresher.

Technical dependencis

Below is a brief summary of the technical libraries or tools that is used in this project :

• development fraemwork : hardhat
• coding libraries : openzeppelin - ERC20.sol, and Ownable.sol
• unit test libraries : chai assertion, ether.js

Technical consideration

States

• constant is used to initialize
  • minimum amount of tokens to stake
• mapping data structure :
  • stakeholder's staking balance
  • stakeholder's stake existence
  • accumulated reward for each stakeholder
• array :
  • list of stakeholders
    • for use in distributing rewards and calcuation of total rewards
• storage variable :
  • none

Functions

• calculate rewards
  • a very simple and straight forward method is used, i.e. 10% of total stakes.
  • no time factor is used here (normally staking involves a specific time frame in order to earn some rewards).

Testing

Unit Test

• staking/unstaking tests :

  • user should stake token and get his staking balance correctly
  • after staking, user balance should decrease and contract balance increase correctly
  • user should unstake token and get his staking balance correctly
  • after unstaking, user balance should increase, and contract balance should decrease correctly
  • after unstaking, totalStakingBalance in contract should decrease correctly.

• rewards tests :

  • should calculate rewards correctly
  • owner should distribute rewards correctly
  • owner should be able to check user's reward correctly
  • user should be able to check his own reward correctly
  • user should withdraw his own rewards correctly.