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learn_Ballot.sol

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

/// @title 委托投票项目
///为每个选项提供简称, 然后作为合约的创造者——即主席，将给予每个独立的地址以投票权。
///地址后面的人可以选择自己投票，或者委托给他们信任的人来投票。
///在投票时间结束时，winningProposal() 将返回获得最多投票的提案。
contract Ballot {

    struct Voter {
        address selfAddr;
        address delegate;
        uint weight;
        bool voted; 
        uint propocalIndex;   // 投票提案的索引
    }

    struct Proposal {
        uint voteCount; //票数
        string name;  //提案名字（最长32个字节）
    }
    
    // 创始人
    Voter public firstMan;

    // 所有提案数组
    Proposal[] public proposals;

    // 所有地址对应的投票者
    mapping(address => Voter) public voters;

    //初始化方法，入参：所有提案的名字
    constructor(string[] memory allAvaliableProposalNames) {
        firstMan = Voter({selfAddr: msg.sender, delegate:address(0), weight: 1, voted: false, propocalIndex:0});
        voters[firstMan.selfAddr]=firstMan;
        for (uint i = 0; i < allAvaliableProposalNames.length; i++) {
            Proposal memory temp = Proposal({name: allAvaliableProposalNames[i], voteCount:0});
            proposals.push(temp);
        }
    }


    // 授权 `voter` 对这个（投票）表决进行投票；只有创始人可以指定谁有权限
    function getRightToVoter(address voterAddress) public {
        require(msg.sender == firstMan.selfAddr, "only first man can decide who have rights");
        require(!voters[voterAddress].voted, "Already voted");
        require(voters[voterAddress].weight==0);
        voters[voterAddress]=Voter({selfAddr: voterAddress, delegate:address(0), weight: 1, voted: false, propocalIndex:0});
        // voters[voterAddress].weight = 1;
    }


    /// 把你的投票委托到投票者 `to`
    /// 若委托者也设置了委托，需要传递，不能超过5个（太长了，可能超过 gas limit）
    /// 不能存在闭环
    /// 若最后的被委托者已经投过票了，直接给提案加票；如果还没，加权重。
    function setDelegateTo(address to) public {
        // 投过不能再设置代理了，会导致权重重复增加
        require(!voters[msg.sender].voted, "You are already voted");

        address delegate = voters[to].delegate;
        while (delegate != address(0)) {
            delegate = voters[delegate].delegate;
            require(msg.sender!=delegate,"can not have circle");
        }

        voters[msg.sender].delegate = delegate;
        voters[msg.sender].voted = true;
        if (voters[delegate].voted) {
            proposals[voters[delegate].propocalIndex].voteCount ++;
        } else {
            voters[delegate].weight ++;
        }
        
    }


    /// 把你的票(包括委托给你的票)，投给提案，入参：提案索引uint
    function voteToProposal(uint proposalIndex) public {
        // 修改信息
        Voter storage vter = voters[msg.sender];
        require(!vter.voted,"already voted");
        vter.voted = true;
        vter.propocalIndex = proposalIndex;

        // 找出对应的地址对应的 vote，因此全局需要一个映射表
        proposals[proposalIndex].voteCount += vter.weight;
    }


    /// @dev 结合之前所有的投票，计算出最终胜出的提案
    function winningProposal() public view returns (uint) {
        uint maxIndex = 0;
        uint _nowMax = 0;
        for (uint index = 0; index<proposals.length; index++) {
            uint _temp = proposals[index].voteCount;
            if (_temp > _nowMax) {
                _nowMax = _temp;
                maxIndex = index;
            }
        }
        return maxIndex;
    }

    // 调用 winningProposal() 函数以获取提案数组中获胜者的索引，并以此返回获胜者的名称
    function winPropocalName() external view returns (string memory) {
        uint index = winningProposal();
        return proposals[index].name;
    }

}