voting.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Voting {
    struct Candidate {
        uint id;
        string name;
        uint voteCount;
    }

    struct Voter {
        bool hasVoted;
        uint votedCandidateId;
    }

    address public owner;
    mapping(uint => Candidate) public candidates;
    mapping(address => Voter) public voters;
    uint public candidatesCount;

    event CandidateAdded(uint indexed candidateId, string name);
    event Voted(address indexed voter, uint indexed candidateId);

    modifier onlyOwner() {
        require(msg.sender == owner, "Only owner can perform this action");
        _;
    }

    constructor() {
        owner = msg.sender;
    }

    function addCandidate(string memory _name) public onlyOwner {
        candidatesCount++;
        candidates[candidatesCount] = Candidate(candidatesCount, _name, 0);
        emit CandidateAdded(candidatesCount, _name);
    }

    function vote(uint _candidateId) public {
        require(!voters[msg.sender].hasVoted, "You have already voted");
        require(_candidateId > 0 && _candidateId <= candidatesCount, "Invalid candidate ID");

        voters[msg.sender].hasVoted = true;
        voters[msg.sender].votedCandidateId = _candidateId;

        candidates[_candidateId].voteCount++;

        emit Voted(msg.sender, _candidateId);
    }

    function getCandidate(uint _candidateId) public view returns (uint, string memory, uint) {
        Candidate memory candidate = candidates[_candidateId];
        return (candidate.id, candidate.name, candidate.voteCount);
    }

    function getVoteCount(uint _candidateId) public view returns (uint) {
        require(_candidateId > 0 && _candidateId <= candidatesCount, "Invalid candidate ID");
        return candidates[_candidateId].voteCount;
    }
}