Beginner
Intro to Hardhat / Foundry — Kudos board build (step 6/6)
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Developer Beginner
7/7 — Intro to Hardhat / Foundry — Kudos board build (step 6/6)
GoalFinalize the contract for tooling and tests—no new logic, just polish and readiness.
What to write
- Lock surface
review functions/events and confirm modifiers/visibility are intentional. - Keep payable logic
same guarded sendKudos with tipping and events. - Ready for tests
note what to cover: emits event, cooldown enforced, tip forwarded, counters increment.
Why This is the version you’ll deploy and test with Hardhat/Foundry; consistency matters for scripts and ABIs.
Try it Write a deploy script plus two tests: one for event + counters, one that expects the cooldown revert.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;
contract KudosBoard {
error EmptyMessage();
error TooLong();
error TooSoon(uint256 readyAt);
uint256 private constant MAX_LEN = 140;
uint256 private constant COOLDOWN = 60;
mapping(address => string) private _lastKudos;
mapping(address => uint256) public kudosCount;
mapping(address => uint256) private _lastSent;
mapping(address => uint256) public tipsReceived;
uint256 public totalKudos;
event KudosSent(address indexed from, address indexed to, string message, uint256 tip);
function sendKudos(address to, string calldata message) external payable {
if (bytes(message).length == 0) revert EmptyMessage();
if (bytes(message).length > MAX_LEN) revert TooLong();
uint256 ready = _lastSent[msg.sender] + COOLDOWN;
if (block.timestamp < ready) revert TooSoon(ready);
_lastKudos[to] = message;
kudosCount[to] += 1;
totalKudos += 1;
_lastSent[msg.sender] = block.timestamp;
if (msg.value > 0) {
tipsReceived[to] += msg.value;
(bool ok, ) = to.call{value: msg.value}('');
require(ok, 'tip failed');
}
emit KudosSent(msg.sender, to, message, msg.value);
}
function lastKudos(address user) external view returns (string memory) {
return _lastKudos[user];
}
}NextWe’ll keep extending this in the following lesson; this version already deploys and runs.