前言
最近卡塔尔世界杯如火如荼，让我们一起来尝试利用 solidity 语言做一个世界杯竞猜的 Dapp 实战项目，本次实战学习主要参考：https://github.com/dukedaily/solidity-expert，我会针对原始项目做更详尽的注解，持续更新中…
业务需求
参赛球队一经设定不可改变，整个活动结束后无法投票；全⺠均可参与，无权限控制；每次投票为 1 ether，且只能选择一支球队；每个人可以投注多次；仅管理员公布最终结果，完成奖金分配，开奖后逻辑：winner 共享整个奖金池（一部分是自己的本金，一部分是利润）；winner 需自行领取奖金（因为有手续费）；下一期自行开始
基础合约实现
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
import "hardhat/console.sol";
contract WorldCup {
// 1. 状态变量：管理员、所有玩家、获奖者地址、第几期、参赛球队
// 2. 核心方法：下注、开奖、兑现
// 3. 辅助方法：获取奖金池金额、管理员地址、当前期数、参与人数、所有玩家、参赛球队
// 管理员
address public admin;
// 第几期
uint8 public currRound;
// 参赛球队
string[] public countries = ["GERMANY", "FRANCH", "CHINA", "BRIZAL", "KOREA"];
// 期数 => 玩家
mapping(uint8 => mapping(address => Player)) players;
// 期数 => 投注各球队的玩家
mapping(uint8 => mapping(Country => address[])) public countryToPlayers;
// 玩家对应赢取的奖金
mapping(address => uint256) public winnerVaults;
// 投注截止时间-使用不可变量，可通过构造函数传值，部署后无法改变
uint256 public immutable deadline;
// 所有玩家待兑现的奖金
uint256 public lockedAmts;
enum Country {
GERMANY,
FRANCH,
CHINA,
BRAZIL,
KOREA
}
event Play(uint8 _currRound, address _player, Country _country);
event Finialize(uint8 _currRound, uint256 _country);
event ClaimReward(address _claimer, uint256 _amt);
// 验证管理员身份
modifier onlyAdmin {
require(msg.sender == admin, "not authorized!");
_;
}
// 玩家投注信息
struct Player {
// 是否开奖
bool isSet;
// 投注的球队份额
mapping(Country => uint256) counts;
}
constructor(uint256 _deadline) {
admin = msg.sender;
require(_deadline > block.timestamp, "WorldCupLottery: invalid deadline!");
deadline = _deadline;
}
// 下注过程
function play(Country _selected) payable external {
// 参数校验
require(msg.value == 1 gwei, "invalid funds provided!");
require(block.timestamp < deadline, "it's all over!");
// 更新 countryToPlayers
countryToPlayers[currRound][_selected].push(msg.sender);
// 更新 players（storage 是引用传值，修改会同步修改原变量）
Player storage player = players[currRound][msg.sender];
// player.isSet = false;
player.counts[_selected] += 1;
emit Play(currRound, msg.sender, _selected);
}
// 开奖过程
function finialize(Country _country) onlyAdmin external {
// 找到 winners
address[] memory winners = countryToPlayers[currRound][_country];
// 分发给所有压中玩家的实际奖金
uint256 distributeAmt;
// 本期总奖励金额（奖池金额 - 所有玩家待兑现的奖金）
uint currAvalBalance = getVaultBalance() - lockedAmts;
console.log("currAvalBalance:", currAvalBalance, "winners count:", winners.length);
for (uint i = 0; i < winners.length; i++) {
address currWinner = winners[i];
// 获取每个地址应该得到的份额
Player storage winner = players[currRound][currWinner];
if (winner.isSet) {
console.log("this winner has been set already, will be skipped!");
continue;
}
winner.isSet = true;
// 玩家购买的份额
uint currCounts = winner.counts[_country];
// （本期总奖励 / 总获奖人数）* 当前地址持有份额
uint amt = (currAvalBalance / countryToPlayers[currRound][_country].length) * currCounts;
// 玩家对应赢取的奖金
winnerVaults[currWinner] += amt;
distributeAmt += amt;
// 放入待兑现的奖金池
lockedAmts += amt;
console.log("winner:", currWinner, "currCounts:", currCounts);
console.log("reward amt curr:", amt, "total:", winnerVaults[currWinner]);
}
// 未分完的奖励即为平台收益
uint giftAmt = currAvalBalance - distributeAmt;
if (giftAmt > 0) {
winnerVaults[admin] += giftAmt;
}
emit Finialize(currRound++, uint256(_country));
}
// 奖金兑现
function claimReward() external {
uint256 rewards = winnerVaults[msg.sender];
require(rewards > 0, "nothing to claim!");
// 玩家领取完奖金置为 0
winnerVaults[msg.sender] = 0;
// 从待兑现奖金池中移除该玩家份额
lockedAmts -= rewards;
(bool succeed,) = msg.sender.call{value: rewards}("");
require(succeed, "claim reward failed!");
console.log("rewards:", rewards);
emit ClaimReward(msg.sender, rewards);
}
// 获取奖池金额
function getVaultBalance() public view returns(uint256 bal) {
bal = address(this).balance;
}
// 获取当期下注当前球队的人数
function getCountryPlayers(uint8 _round, Country _country) external view returns(uint256) {
return countryToPlayers[_round][_country].length;
}
// 获取当前玩家当期押注份额
function getPlayerInfo(uint8 _round, address _player, Country _country) external view returns(uint256 _counts) {
return players[_round][_player].counts[_country];
}
}