10-Whitelist.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13 ;

// - To whitelist or save the add in the contract for the user
// - Should be able to fetch and check 

contract Whitelist {
    // Max number of whitelisted addresses allowed
    uint8 public maxWhitelistedAddresses;

    // Create a mapping of whitelistedAddresses
    // if an address is whitelisted, we would set it to true, it is false by default for all other addresses.
    mapping(address => bool) public whitelistedAddresses;

    // numAddressesWhitelisted would be used to keep track of how many addresses have been whitelisted
    uint8 public numAddressesWhitelisted;

    // Setting the Max number of whitelisted addresses
    // User will put the value at the time of deployment
    constructor(uint8 _maxWhitelistedAddresses) {
        maxWhitelistedAddresses =  _maxWhitelistedAddresses;
    }

    /**
        addAddressToWhitelist - This function adds the address of the sender to the
        whitelist
     */
    function addAddressToWhitelist() public {
        // check if the user has already been whitelisted
        require(!whitelistedAddresses[msg.sender], "Sender has already been whitelisted");
        // check if the numAddressesWhitelisted < maxWhitelistedAddresses, if not then throw an error.
        require(numAddressesWhitelisted < maxWhitelistedAddresses, "More addresses cant be added, limit reached");
        // Add the address which called the function to the whitelistedAddress array
        whitelistedAddresses[msg.sender] = true;
        // Increase the number of whitelisted addresses
        numAddressesWhitelisted += 1;
    }

    // function to check if the address is whitelisted or not 
    function checkAddress(address user) public view returns(bool) {
        return whitelistedAddresses[user] ;
    } 


}