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contracts...Learning...IdentityManagement.sol

//SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

contract IdentityManagement{

    //address owner;
    //structure to hold user data
    struct User{
        string firstName;
        string lastName;
        string email;
        uint256 phone;
        address walletAddress;
        bool isRegistered;
        bool isAdmin;
    }

    mapping(address => User) private users;

    event UserRegister(address userAddress);

    event UserUpdate(address userAddress);

    modifier isOnlyAdmin{
        require(users[msg.sender].isAdmin,"User not admin");
        _;
    }
    modifier onlyRegistered{
        require(users[msg.sender].isRegistered,"User not Regsitered");
        _;
    }

    constructor(){
       User memory adminUser = User({
            firstName: "Admin",
            lastName: "User",
            email: "admin@gmail.com",
            phone : 23432412312,
            walletAddress : msg.sender,
            isRegistered : true,
            isAdmin :true
        });

        users[msg.sender] = adminUser;
    }
    //funciton to register a new user
    function registerUser(string memory _firstName,string memory _lastName,string memory _email,uint256 _phone,address _walletAddress) public {
        //check user is registered or not

        require(!users[msg.sender].isRegistered,"User is already registered");  
        //add new User

        User memory newUser =  User({
            firstName : _firstName,
            lastName : _lastName,
            email : _email,
            phone : _phone,
            walletAddress: _walletAddress,
            isRegistered : true,
            isAdmin:false
        });

        users[msg.sender] =  newUser;

        emit UserRegister(msg.sender);
    }

    function updateUserData(string memory _firstName,
                            string memory _lastName,
                            string memory _email,
                            uint256 _phone,
                            address _walletAddress
                            )
                             public onlyRegistered{
            users[msg.sender].firstName = _firstName;
            users[msg.sender].lastName = _lastName;
            users[msg.sender].email = _email;
            users[msg.sender].phone = _phone;
            users[msg.sender].walletAddress = _walletAddress;

            emit UserUpdate(msg.sender);
    }

    function grantAdminAccess(address _user) public isOnlyAdmin{
        require(users[_user].isRegistered,"User is not registered");
        users[_user].isAdmin = true;
    }

    function revokeAdminAccess(address _user)public isOnlyAdmin{
        require(users[_user].isRegistered,"User is not registered");
        users[_user].isAdmin = false;
    }

    function deleteUser(address _user) public isOnlyAdmin{
        require(users[_user].isRegistered,"User isn't exist");
        delete users[_user];
    }

    function getUserDetails(address _user) public isOnlyAdmin onlyRegistered view returns(User memory){
        require(users[_user].isRegistered,"User isn't Registered");
        return users[_user];
    }

    function compareStrings(string memory a, string memory b) public pure returns(bool){
        return keccak256(bytes(a)) == keccak256(bytes(b));
    }


}