Gradebook Smart Contract

Go up to the CCC HW page (md) | view one-page version

Overview

I need a new gradebook! Because Canvas and my favorite spreadsheet programs are just not doing the job anymore. So I’ve decided to keep everybody’s grades in a public blockchain. Your task is to implement this gradebook for me.

Admittedly, keeping a gradebook of private grades on a public blockchain is not the most realistic use of smart contracts. But it will introduce you to the concepts involved in developing more complicated smart contracts. And there are many very similar applications that would only require a few tweaks to the gradebook contract. For example, there are organizations that coordinate through blockchains, and they have to keep some information on members; while not grades, it involves the same concepts.

The gradebook will need to have the following functionalities:

Writing this homework will require completion of the following assignments:

You will also need to be familiar with the Ethereum slide set and the Solidity slide set.

In addition to your source code, you will submit an edited version of gradebook.py (src).

Changelog

Any changes to this page will be put here for easy reference.

Part 1: IGradebook interface

IGradebook Interface

Formally, your contract will need to be named Gradebook, and saved in a file named Gradebook.sol. It will need to implement the IGradebook.sol (src) interface, which is as follows. NOTE: the interface file itself has many more details and specifications in the comments; most of the comments were stripped from what is shown below.

// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.24;

// See the actual IGradebook.sol file, linked to above, for much more detailed comments

interface IGradebook {

    event assignmentCreationEvent (uint indexed id, string indexed name, uint indexed max_score);

    event gradeEntryEvent (uint indexed id, string indexed name, uint indexed score);


    // The following six methods are done for you automatically -- as long as you make the
    // appropriate variable public, then Solidity will create the getter function for you
    
    function tas(address ta) external returns (bool);

    function max_scores(uint id) external returns (uint);

    function assignment_names(uint id) external returns (string memory);

    function scores(uint id, string memory userid) external returns (uint);

    function num_assignments() external returns (uint);

    function instructor() external returns (address);


    // The following five functions are ones you must implement

    function designateTA(address ta) external;

    function addAssignment(string memory name, uint max_score) external returns (uint);

    function addGrade(string memory student, uint assignment, uint score) external;

    function getAverage(string memory student) external view returns (uint);

    function requestTAAccess() external;


    // The implementation for the following is provided in the HW description

    function supportsInterface(bytes4 interfaceId) external view returns (bool);

}

The supportsInterface() function

We will see the use of supportsInterface() in a future lecture and in a future assignment. For now, you should use this exact implementation:

function supportsInterface(bytes4 interfaceId) external pure returns (bool) {
        return interfaceId == type(IGradebook).interfaceId || interfaceId == 0x01ffc9a7;
}

IGradebook ABI

The ABI for IGradebook.sol is as follows, can can be copied by clicking on: 
[{"anonymous":false,"inputs":[{"indexed":true,"internalType":"uint256","name":"id","type":"uint256"},{"indexed":true,"internalType":"string","name":"name","type":"string"},{"indexed":true,"internalType":"uint256","name":"max_score","type":"uint256"}],"name":"assignmentCreationEvent","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"uint256","name":"id","type":"uint256"},{"indexed":true,"internalType":"string","name":"name","type":"string"},{"indexed":true,"internalType":"uint256","name":"score","type":"uint256"}],"name":"gradeEntryEvent","type":"event"},{"inputs":[{"internalType":"string","name":"name","type":"string"},{"internalType":"uint256","name":"max_score","type":"uint256"}],"name":"addAssignment","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"string","name":"student","type":"string"},{"internalType":"uint256","name":"assignment","type":"uint256"},{"internalType":"uint256","name":"score","type":"uint256"}],"name":"addGrade","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"id","type":"uint256"}],"name":"assignment_names","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"ta","type":"address"}],"name":"designateTA","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"string","name":"student","type":"string"}],"name":"getAverage","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"instructor","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"id","type":"uint256"}],"name":"max_scores","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"num_assignments","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"requestTAAccess","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"id","type":"uint256"},{"internalType":"string","name":"userid","type":"string"}],"name":"scores","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"bytes4","name":"interfaceId","type":"bytes4"}],"name":"supportsInterface","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"ta","type":"address"}],"name":"tas","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"view","type":"function"}]

Implementation details

The first six methods (after the two events) in the IGradebook.sol (src) interface are getter functions. As long as you set the visibility of the field in the contract as public, then the getter method is created for you, as discussed in the lecture slides. For example, for the getter function function num_assignments() external returns (uint), the appropriate field declaration would be uint public override num_assignments;. The lecture slide set explains this a bit more.

The two events, listed at the top of the interface, should be emitted at the appropriate time. The addAssignment() function should emit the assignmentCreationEvent() event upon successful completion, and the addGrade() function should emit the gradeEntryEvent() event upon successful completion. It’s a good idea to emit the events after any require() calls! It is often the case (but not required) that the event emission is done at the very end of the function.

Address checksums

Note that Remix may complain if an Ethernet address is not checksummed. Remix will provide, in the error, the checksummed address – you can use that value (cut-and-paste it into your code) instead to silence this warning. You can also use ethsum.netlify.app to checksum an Ethernet address.

Also note that compilation warnings will appear to Gradescope as a compilation error. Thus, you will have to remove them by the time you submit your assignment.

Part 2: Testing and Deployment

Debugging

We have provided a Debug.sol (src) file to help with your debugging. You can call an event, and the parameter will be visible in the blockchain explorer. Viewing the page for the contract – which will limit the events displayed to only those emitted by that contract – will make it easier to find things.

Once imported, you can use it as follows:

import "./Debug.sol";

...

Debug.debugEventUint(42);
Debug.debugEventInt(-42);
string memory s = string.concat("hello"," ","world")
Debug.debugString(s);
// also:
// Debug.debugAddress(msg.sender);

Then, in the explorer, you will see something similar to:

solidity event debugging

Testing

You will invariably run into issues testing and debugging your code. We have a few tips and tricks.

Deployment

Once done, you will need to deploy your CoruseGradebook smart contract to our private Ethereum blockchain. Save the contract address, as you will need to submit that, below. It’s okay if you deploy it multiple times (for testing, debugging, errors, etc.). Just submit the address of the last one you deployed.

On the deployed contract, you do not need to designate anybody as a TA – we are going to make ourselves a TA in your gradebook via the requestTAAccess() function, so make sure that works properly.

Part 3: Your average

I’ve deployed a gradebook with your (fake) grades. The address for that smart contract is on the blockchain explorer (in the section for this semester’s links). You will need to find out your overall average as well as a few other items of information. Your scores are kept by your UVA userid. These scores are fake, and were randomly generated, so don’t feel bad if your score(s) are low.

There are two ways you can access the gradebook on the blockchain. One is through Remix, like was done in the dApp introduction assignment (md) – you load the IGradebook.sol interface, and then enter the address of the deployed Gradebook contract into the ‘At Address’ text box in the deployment window. The other way is through geth, as in the live coding example in class – the geth commands start about 8 slides down in that slide column. For this you will also need the ABI. You can compile the IGradebook.sol interface in Remix, and then copy the ABI – after you compile it, the copy ABI link is at the very bottom of the compilation pane. Note that you may have to reformat that ABI a bit – what you copy is on many lines, and you may have to reformat it to one line.

The steps to access the gradebook via Remix are:

The steps to access the gradebook via a geth terminal are (adapted from here):

The information you need to obtain is:

Submission

You will need to fill in the various values from this assignment into the gradebook.py (src) file. That file clearly indicates all the values that need to be filled in. That file, along with your Solidity source code, are the only two files that must be submitted. The sanity_checks dictionary is intended to be a checklist to ensure that you perform the various other aspects to ensure this assignment is fully submitted.

There are two forms of submission for this assignment; you must do both.

Submission 1: You must deploy your smart contract to our private Ethereum blockchain – this was probably done above. It’s fine if you deploy it a few times because you were testing it, messed something up, or whatever. But the final deployment should not have any other transactions to the deployed contract.

Submission 2: You should submit your Gradebook.sol file, as well as your gradebook.py file, and ONLY those two files, to Gradescope. All your Solidity code should be in that first file, and you should specifically import the IGradebook interface. That interface file will be placed in the same directory on Gradescope when you submit. NOTE: Gradescope cannot fully test this assignment, as it does not have access to the private blockchain. So it can only do a few sanity tests (correct files submitted, successful compilation, valid values in auction.py, etc.).