Blockchain

1"syntax-comment">// SPDX-License-Identifier: MIT
2"syntax-keyword">pragma "syntax-keyword">solidity ^0.8.20;
3
4"syntax-keyword">import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
5"syntax-keyword">import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
6"syntax-keyword">import "@openzeppelin/contracts/access/Ownable.sol";
7
8"syntax-comment">/// @title SimpleStaking - Stake tokens, earn rewards
9"syntax-comment">/// @author Koustav Manna
10"syntax-keyword">contract SimpleStaking is ReentrancyGuard, Ownable {
11    IERC20 "syntax-keyword">public "syntax-keyword">immutable stakingToken;
12    "syntax-keyword">uint256 "syntax-keyword">public rewardRate = 100; "syntax-comment">// tokens per block
13
14    "syntax-keyword">mapping("syntax-keyword">address => "syntax-keyword">uint256) "syntax-keyword">public stakedBalance;
15    "syntax-keyword">mapping("syntax-keyword">address => "syntax-keyword">uint256) "syntax-keyword">public lastClaimBlock;
16
17    "syntax-keyword">event Staked("syntax-keyword">address "syntax-keyword">indexed user, "syntax-keyword">uint256 amount);
18    "syntax-keyword">event Withdrawn("syntax-keyword">address "syntax-keyword">indexed user, "syntax-keyword">uint256 amount);
19    "syntax-keyword">event RewardClaimed("syntax-keyword">address "syntax-keyword">indexed user, "syntax-keyword">uint256 reward);
20
21    "syntax-keyword">constructor("syntax-keyword">address _token) Ownable(msg.sender) {
22        stakingToken = IERC20(_token);
23    }
24
25    "syntax-keyword">function stake("syntax-keyword">uint256 amount) "syntax-keyword">external nonReentrant {
26        "syntax-keyword">require(amount > 0, "Amount must be > 0");
27        _claimRewards();
28        stakingToken.transferFrom(msg.sender, "syntax-keyword">address(this), amount);
29        stakedBalance[msg.sender] += amount;
30        "syntax-keyword">emit Staked(msg.sender, amount);
31    }
32
33    "syntax-keyword">function pendingRewards("syntax-keyword">address user) "syntax-keyword">public "syntax-keyword">view "syntax-keyword">returns ("syntax-keyword">uint256) {
34        "syntax-keyword">uint256 blocks = block.number - lastClaimBlock[user];
35        "syntax-keyword">return (stakedBalance[user] * rewardRate * blocks) / 1e18;
36    }
37
38    "syntax-keyword">function _claimRewards() "syntax-keyword">internal {
39        "syntax-keyword">uint256 reward = pendingRewards(msg.sender);
40        lastClaimBlock[msg.sender] = block.number;
41        if (reward > 0) {
42            "syntax-keyword">emit RewardClaimed(msg.sender, reward);
43        }
44    }
45}