SimpleStaking

1// SPDX-License-Identifier: MIT
2pragma solidity ^0.8.20;
3 
4interface IERC20 {
5    function transfer(address to, uint256 amount) external returns (bool);
6    function transferFrom(address from, address to, uint256 amount) external returns (bool);
7}
8 
9contract SimpleStaking {
10    IERC20 public immutable stakingToken;
11    IERC20 public immutable rewardToken;
12    uint256 public immutable rewardRatePerBlock;
13    address public owner;
14 
15    uint256 public totalStaked;
16    uint256 public rewardPerTokenStored;
17    uint256 public lastUpdateBlock;
18 
19    mapping(address => uint256) public staked;
20    mapping(address => uint256) public userRewardPerTokenPaid;
21    mapping(address => uint256) public rewards;
22 
23    event Staked(address indexed user, uint256 amount);
24    event Withdrawn(address indexed user, uint256 amount);
25    event RewardPaid(address indexed user, uint256 reward);
26 
27    constructor(address stakingToken_, address rewardToken_, uint256 rewardRatePerBlock_, address initialOwner_) {
28        require(initialOwner_ != address(0), "ZERO_OWNER");
29        stakingToken = IERC20(stakingToken_);
30        rewardToken = IERC20(rewardToken_);
31        rewardRatePerBlock = rewardRatePerBlock_;
32        owner = initialOwner_;
33        lastUpdateBlock = block.number;
34    }
35 
36    function rewardPerToken() public view returns (uint256) {
37        if (totalStaked == 0) return rewardPerTokenStored;
38        return rewardPerTokenStored + ((block.number - lastUpdateBlock) * rewardRatePerBlock * 1e18) / totalStaked;
39    }
40 
41    function earned(address account) public view returns (uint256) {
42        return (staked[account] * (rewardPerToken() - userRewardPerTokenPaid[account])) / 1e18 + rewards[account];
43    }
44 
45    modifier updateReward(address account) {
46        rewardPerTokenStored = rewardPerToken();
47        lastUpdateBlock = block.number;
48        rewards[account] = earned(account);
49        userRewardPerTokenPaid[account] = rewardPerTokenStored;
50        _;
51    }
52 
53    function stake(uint256 amount) external updateReward(msg.sender) {
54        require(amount > 0, "ZERO");
55        totalStaked += amount;
56        staked[msg.sender] += amount;
57        require(stakingToken.transferFrom(msg.sender, address(this), amount), "TRANSFER_FAILED");
58        emit Staked(msg.sender, amount);
59    }
60 
61    function withdraw(uint256 amount) external updateReward(msg.sender) {
62        require(staked[msg.sender] >= amount, "BALANCE");
63        totalStaked -= amount;
64        staked[msg.sender] -= amount;
65        require(stakingToken.transfer(msg.sender, amount), "TRANSFER_FAILED");
66        emit Withdrawn(msg.sender, amount);
67    }
68 
69    function claimReward() external updateReward(msg.sender) {
70        uint256 reward = rewards[msg.sender];
71        require(reward > 0, "NO_REWARD");
72        rewards[msg.sender] = 0;
73        require(rewardToken.transfer(msg.sender, reward), "TRANSFER_FAILED");
74        emit RewardPaid(msg.sender, reward);
75    }
76}