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contracts...saveEther.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

error INSUFFICIENT_FUNDS();
error AMOUNT_CANT_BE_ZERO();
error ADDRESS_CANT_BE_ZERO();


contract SaveEther {
    mapping(address => uint256) savings;

    event SavingSuccessful(address indexed user, uint256 indexed amount);

    function deposit() external payable {
        if(msg.sender == address(0))
            revert ADDRESS_CANT_BE_ZERO();
            
        if(msg.value <= 0)
            revert AMOUNT_CANT_BE_ZERO();

        savings[msg.sender] = savings[msg.sender] + msg.value;
        emit SavingSuccessful(msg.sender, msg.value);
    }
    function withdraw() external {
        if(msg.sender == address(0))
            revert ADDRESS_CANT_BE_ZERO();

        uint256 _userSavings = savings[msg.sender];
        
        if(_userSavings <= 0)
            revert INSUFFICIENT_FUNDS();

        savings[msg.sender] -= _userSavings;

        payable(msg.sender).transfer(_userSavings);
    }

    function checkSavings(address _user) external view returns (uint256) {
        return savings[_user];
    }

    function checkContractBal() external view returns (uint256) {
        return address(this).balance;
    }
}