Ethereum Programming 10 generate interest

investor deposit 100mDai and earned 100Dapp

investor earned another 100Dapp

investor withdraw principle 100mDai, interest 200Dapp left in token farm

//cmd

truffle exec scripts/issue-token.js

------------------------

//scripts/issue-token.js

const TokenFarm = artifacts.require('TokenFarm')

module.exports = async function (callback) {

    let tokenFarm = await TokenFarm.deployed()

    await tokenFarm.issueTokens()

    console.log("Tokens issued!")

    callback()

}

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//src/contracts/TokenFarm.sol

pragma solidity ^0.5.0;

import "./DappToken.sol";

import "./DaiToken.sol";

contract TokenFarm{

    string public name = "Dapp Token Farm";

    DappToken public dappToken;

    DaiToken public daiToken;

    address public owner;

    address[] public stakers;

    mapping(address => uint) public stakingBalance;

    mapping(address => bool) public hasStaked;

    mapping(address => bool) public isStaking;

    

    constructor(DappToken _dappToken, DaiToken _daiToken) public{

        dappToken = _dappToken;

        daiToken = _daiToken;

        owner = msg.sender;

    }

    function stakeTokens(uint _amount) public{

        require(_amount > 0, "amount greater than 0");

        daiToken.transferFrom(msg.sender, address(this), _amount);

        stakingBalance[msg.sender] = stakingBalance[msg.sender] + _amount;

        if(!hasStaked[msg.sender]){

            stakers.push(msg.sender);

        }

        isStaking[msg.sender] = true;

        hasStaked[msg.sender] = true;

    }

    function unstakeTokens() public {

        uint balance = stakingBalance[msg.sender];

        require(balance > 0, "staking balance greater than 0");

        daiToken.transfer(msg.sender, balance);

        stakingBalance[msg.sender] = 0;

        isStaking[msg.sender] = false;

    }

    function issueTokens() public {

        require(msg.sender == owner, "caller must be the owner");

        for (uint i=0; i<stakers.length; i++){

            uint balance = stakingBalance[stakers[i]];

            if(balance > 0){

                dappToken.transfer(stakers[i], balance);

            }

        }

    }

}

reference:

https://www.youtube.com/watch?v=XLahq4qyors