pragma solidity ^0.6.0;

contract Collaboration {
// User addresses and their associated roles
mapping(address => bool) public admins;
mapping(address => bool) public users;

// Chat message history
string[] public messages;

// Tip jar balance
uint public balance;

// Event for when a new message is received
event NewMessage(string message);

// Function to send a message to the chat
function sendMessage(string memory message) public {
// Check if the user is a member of the chat
require(admins[msg.sender] || users[msg.sender], "Unauthorized");

// Add the message to the message history
messages.push(message);

// Emit the NewMessage event
emit NewMessage(message);
}

// Function to add a new user to the chat
function addUser(address user) public {
// Only administrators can add new users
require(admins[msg.sender], "Unauthorized");

// Add the user to the chat
users[user] = true;
}

// Function to remove a user from the chat
function removeUser(address user) public {
// Only administrators can remove users
require(admins[msg.sender], "Unauthorized");

// Remove the user from the chat
delete users[user];
}

// Function to ban a user from the chat
function banUser(address user) public {
// Only administrators can ban users
require(admins[msg.sender], "Unauthorized");

// Ban the user from the chat
delete users[user];
delete admins[user];
}

// Function to tip the chat
function tip(uint amount) public payable {
// Only members of the chat can tip
require(admins[msg.sender] || users[msg.sender], "Unauthorized");

// Add the tip to the balance
balance += amount;
}
}