how can i check hashcode and th amount

Question

I'm new in Solidity, therefore if I have a wrong concept of anything kindly do explain.

I'm working for a personal escrow smart contract that should include these functions:

1- function deposit from the owner wallet to the smart contract

2- function gethash this function requires (amount) and returns hashcode

• amount should not equal 0

3- function transfer amount to address this function requires (hashcode, address)

• the amount is taken from the hashcode generated by gethash function

• check that hashcode is not in conflict or used before

4- function withdraw to withdraw all money in the smart contract to the owner

I use this code :

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

contract mypayable {

   // Payable address can receive Ether
    address payable public owner;

    // Payable constructor can receive Ether
    constructor() payable {
        owner = payable(msg.sender);
    }

    function deposit() public payable {}

  uint deposit_count;
  mapping(bytes32 => uint256) balances;
  function getHash(uint amount) public view returns(bytes32 result){
    return keccak256(abi.encodePacked(msg.sender, deposit_count, amount,block.timestamp));
  }

  
  function transferto(address payable _to, bytes32 trx_hash, uint amount ) external {

    balances[trx_hash] = amount;
    deposit_count++;

      // Transaction hash cannot be empty
    require(trx_hash[0] != 0, "Transaction hash cannot be empty!");
    // Escrow amount cannot be equal to 0
    require(amount != 0, "Escrow amount cannot be equal to 0.");

    // Transaction hash is already in use
    require(balances[trx_hash] == 0, "Unique hash conflict, hash is already in use.");
    // Transaction hash cannot be empty
    require(trx_hash[0] != 0, "Transaction hash cannot be empty!");
    // Check if trx_hash exists in balances
    require(balances[trx_hash] != 0, "Escrow with transaction hash doesn't exist.");
    // Transfer escrow to sender
   // require(_token.transfer(msg.sender, balances[trx_hash]), "Escrow retrieval failed!");
    (bool success, ) = _to.call{value: balances[trx_hash]}("");
        require(success, "Failed to send Ether");

    // If all is done, status amounts to 0
    balances[trx_hash] = 0;
  }

    function withdraw() public {
        // get the amount of Ether stored in this contract
        uint amount = address(this).balance;

        // send all Ether to the owner
        // Owner can receive Ether since the address of the owner is payable
        (bool success, ) = owner.call{value: amount}("");
        require(success, "Failed to send Ether");
    }


}

• functions deposit and withdraw work correctly no issues

• function gethash returned hash code correctly and changeable

• I guess the whole issue in function transferto:

firstly: I added parameter {amount} because I didn't know how to get the amount value from gethash function

second: I faced this error when I tried the transferto function

Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? 
execution reverted: Unique hash conflict, hash is already in use.
{
  "originalError": {
    "code": 3,
    "data": "0x08c379a00000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000002d556e69717565206861736820636f6e666c6963742c206861736820697320616c726561647920696e207573652e00000000000000000000000000000000000000",
    "message": "execution reverted: Unique hash conflict, hash is already in use."
  }
}

What is the best way to generate and store code/hashcode including amount value and check it in another function like transferto function?

so the withdrawal will input his address and code I provide it and he will receive the exact amount in gethash function

if there's something missing please tell me to clear more Thanks in Advance

---------------------------- update

I would like to thank (Jeremy Then) for his helping

the message error was gone, but there's something wrong

the hashcode is valid forever not expired I can send many transactions in the same hashcode and this is not logical

Also, If I input the amount in the gethash function with different values of the amount in transferto, the code will take the amount value of the transferto function

I would like if can take the amount from the gethash function and delete the parameter (amount) from the function transferto.

Answer 1

The first thing that you are doing in the transferto function is:

balances[trx_hash] = amount;

But then, you do this check:

require(balances[trx_hash] == 0, "Unique hash conflict, hash is already in use.");

Which is not compatible with balances[trx_hash] = amount;, becase you already added data to the balances[trx_hash], and then you require it to be empty, but it's not empty because you just assigned an amount to it. That's the problem.

Maybe you need to add require(balances[trx_hash] == 0, "Unique hash conflict, hash is already in use."); before balances[trx_hash] = amount;, what do you think?

By the way, I don't think this check is right:

require(trx_hash[0] != 0, "Transaction hash cannot be empty!");

Because it is literally just checking the first byte of the trx_hash, and in really that first byte could be 0 and all the other bytes could have value.

For example, this check would fail for a valid hash like this: 0x00f6c4584609ab7d77c6af1a7d07a765ffb7d8f5bcec07c613a6c9f6fb00729b, notice the first byte is 00, but it's a valid hash that the keccak256 could return.

So, better do this:

require(trx_hash != 0, "Transaction hash cannot be empty!");

Here we are comparing the whole 32 bytes of trx_hash value with 0. If all the 32 bytes of trx_hash are empty, then its value is 0 and we can compare it with 0.

For your transferto function to work, it should look something like this:

function transferto(address payable _to, bytes32 trx_hash, uint amount ) external {

    require(balances[trx_hash] == 0, "Unique hash conflict, hash is already in use.");

    balances[trx_hash] = amount;
    deposit_count++;

      // Transaction hash cannot be empty
    require(trx_hash != 0, "Transaction hash cannot be empty!");
    // Escrow amount cannot be equal to 0
    require(amount != 0, "Escrow amount cannot be equal to 0.");

    // Transaction hash is already in use
    
    // Transaction hash cannot be empty
    //require(trx_hash[0] != 0, "Transaction hash cannot be empty!");
    // Check if trx_hash exists in balances
    require(balances[trx_hash] != 0, "Escrow with transaction hash doesn't exist.");
    // Transfer escrow to sender
   // require(_token.transfer(msg.sender, balances[trx_hash]), "Escrow retrieval failed!");
    (bool success, ) = _to.call{value: balances[trx_hash]}("");
        require(success, "Failed to send Ether");

    // If all is done, status is amounted to 0
    balances[trx_hash] = 0;
  }