project.sol

// SPDX-License-Identifier: SEE LICENSE IN LICENSE
pragma solidity 0.8.13;

contract ChatApp {
    struct user {
        string name;
        friend[] friendList;
    }

    struct friend {
        address pubkey;
        string name;
    }

    struct message {
        address sender;
        uint256 timestamp;
        string msg;
    }

    mapping(address => user) userList;
    mapping(bytes32 => message[]) allMessages;

    //Check is user Exist
    function checkUserExists(address pubkey) public view returns (bool) {
        return bytes(userList[pubkey].name).length > 0;
    }

    //Create Account
    function createAccount(string calldata name) external {
        require(checkUserExists(msg.sender) == false, "User Already Exist");
        require(bytes(name).length > 0, "Username cannot be empty");

        userList[msg.sender].name = name;
    }

    //Get Username
    function getUsername(address pubkey) external view returns (string memory) {
        require(checkUserExists(pubkey), "User is not registered");
        return userList[pubkey].name;
    }

    //Add Friend
    function addFriend(address friend_key, string calldata name) external {
        require(checkUserExists(msg.sender), "Please create an account");
        require(checkUserExists(friend_key), "User is not registered");
        require(msg.sender != friend_key, "user can not themselves as friend");
        require(
            checkAlredyFriend(msg.sender, friend_key) == false,
            "This users are already friends"
        );

        _addFriend(msg.sender, friend_key, name);
        _addFriend(friend_key, msg.sender, userList[msg.sender].name);
    }

    //Check if we are friend already
    function checkAlredyFriend(
        address pubkey1,
        address pubkey2
    ) internal view returns (bool) {
        if (
            userList[pubkey1].friendList.length >
            userList[pubkey2].friendList.length
        ) {
            address tmp = pubkey1;
            pubkey1 = pubkey2;
            pubkey2 = tmp;
        }

        for (uint256 i = 0; i < userList[pubkey1].friendList.length; i++) {
            if (userList[pubkey1].friendList[i].pubkey == pubkey2) return true;
        }
        return false;
    }

    function _addFriend(
        address me,
        address friend_key,
        string memory name
    ) internal {
        friend memory newFriend = friend(friend_key, name);
        userList[me].friendList.push(newFriend);
    }

    //Get my Friend

    function getMyFriendList() external view returns (friend[] memory) {
        return userList[msg.sender].friendList;
    }

    //Get Chat Code

    function _getChatCode(
        address pubkey1,
        address pubkey2
    ) internal pure returns (bytes32) {
        if (pubkey1 < pubkey2) {
            return keccak256(abi.encodePacked(pubkey1, pubkey2));
        } else return keccak256(abi.encodePacked(pubkey2, pubkey1));
    }
}