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contracts..._coin.sol

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.4;

contract Coin {
    // The keyword "public" makes variables
    // accessible from other contracts
    address public minter;
    address public faucet;
    mapping (address => uint) public balances;

    // Events allow clients to react to specific
    // contract changes you declare
    event Sent(address from, address to, uint amount);

    // Constructor code is only run when the contract
    // is created
    constructor() {
        minter = msg.sender;
    }

    // Sends an amount of newly created coins to an address
    // Can only be called by the contract creator
    function mint(address receiver, uint amount) public {
        require(msg.sender == minter);
        balances[receiver] += amount;
    }

    // Errors allow you to provide information about
    // why an operation failed. They are returned
    // to the caller of the function.
    error InsufficientBalance(uint requested, uint available);
    error wrongFaucetBalanceRequest(uint requested, string available);

    // Sends an amount of existing coins
    // from any caller to an address
    function send(address receiver, uint amount) public {
        if (amount > balances[msg.sender])
            revert InsufficientBalance({
                requested: amount,
                available: balances[msg.sender]
            });

        balances[msg.sender] -= amount;
        balances[receiver] += amount;
        emit Sent(msg.sender, receiver, amount);
    }
    
    //Sends an amount of newly minted tokens to a designated faucet address
    //Can only be called by the contract creator
    function fundFaucet(address _to, uint amount) public {
        require(msg.sender == minter);
        faucet = _to;
        balances[faucet] += amount;
    } 
    
    //An address can request from token from the faucet
    //Requested tokens must be < 1000 per address
    function requestFundsFromFaucet(address _to, uint amount) public {
        if (amount > 1000 ) 
            revert wrongFaucetBalanceRequest({
                requested: amount,
                available: "You can not withdraw more than 1000 tokens. Thank you"
            });
        balances[faucet] -= amount;
        balances[_to] += amount;
        
        emit Sent(faucet, _to, amount);
    }
}