ALCH

The Alchemy (ALCH) token is a standard ERC20 token with custom functions to be used as a governance token. This implementation follows the UNI token implementation as a governance token.

// SPDX-License-Identifier: MIT
pragma solidity ^0.7.6;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/math/SafeMath.sol";


/// @author Alchemy Team
/// @title Alchemy
/// @notice The Alchemy Governance Token
contract ALCH {
    /// @notice EIP-20 token name for this token
    string public constant name = "Alchemy";

    /// @notice EIP-20 token symbol for this token
    string public constant symbol = "ALCH";

    /// @notice EIP-20 token decimals for this token
    uint8 public constant decimals = 18;

    /// @notice Address which may mint new tokens
    address public minter;

    /// @notice The timestamp after which minting may occur
    uint256 public mintingAllowedAfter;

    /// @notice Cap on the percentage of totalSupply that can be minted at each mint
    uint8 public constant mintCap = 10;

    /// @notice Minimum time between mints
    uint32 public constant minimumTimeBetweenMints = 90 days;

    /// @notice Total number of tokens in circulation
    uint256 public totalSupply = 10_000_000e18;

    mapping(address => mapping(address => uint96)) internal allowances;

    mapping(address => uint96) internal balances;

    mapping(address => address) public delegates;

    struct Checkpoint {
        uint32 fromBlock;
        uint96 votes;
    }

    mapping(address => mapping(uint32 => Checkpoint)) public checkpoints;

    mapping(address => uint32) public numCheckpoints;

    bytes32 public constant DOMAIN_TYPEHASH = keccak256(
        "EIP712Domain(string name,uint256 chainId,address verifyingContract)"
    );

    bytes32 public constant DELEGATION_TYPEHASH = keccak256(
        "Delegation(address delegatee,uint256 nonce,uint256 expiry)"
    );

    bytes32 public constant PERMIT_TYPEHASH = keccak256(
        "Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
    );

    mapping(address => uint256) public nonces;

    /// @notice An event thats emitted when the minter address is changed
    event MinterChanged(address minter, address newMinter);

    event DelegateChanged(
        address indexed delegator,
        address indexed fromDelegate,
        address indexed toDelegate
    );

    event DelegateVotesChanged(
        address indexed delegate,
        uint256 previousBalance,
        uint256 newBalance
    );

    event Transfer(address indexed from, address indexed to, uint256 amount);

    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 amount
    );

    constructor(address account, address minter_, uint256 mintingAllowedAfter_) {
        require(
            mintingAllowedAfter_ >= block.timestamp,
            "Alc::constructor: minting can only begin after deployment"
        );
        balances[account] = uint96(totalSupply);
        emit Transfer(address(0), account, totalSupply);
        minter = minter_;
        emit MinterChanged(address(0), minter);
        mintingAllowedAfter = mintingAllowedAfter_;
    }

    /**
     * @notice Change the minter address
     * @param minter_ The address of the new minter
     */
    function setMinter(address minter_) external {
        require(msg.sender == minter, "Alch::setMinter: only the minter can change the minter address");
        emit MinterChanged(minter, minter_);
        minter = minter_;
    }

    /**
     * @notice Mint new tokens
     * @param dst The address of the destination account
     * @param rawAmount The number of tokens to be minted
     */
    function mint(address dst, uint rawAmount) external {
        require(msg.sender == minter, "Alch::mint: only the minter can mint");
        require(block.timestamp >= mintingAllowedAfter, "Alch::mint: minting not allowed yet");
        require(dst != address(0), "Alch::mint: cannot transfer to the zero address");

        // record the mint
        mintingAllowedAfter = SafeMath.add(block.timestamp, minimumTimeBetweenMints);

        // mint the amount
        uint96 amount = safe96(rawAmount, "Alch::mint: amount exceeds 96 bits");
        require(amount <= SafeMath.div(SafeMath.mul(totalSupply, mintCap), 100), "Alch::mint: exceeded mint cap");
        totalSupply = safe96(SafeMath.add(totalSupply, amount), "Alch::mint: totalSupply exceeds 96 bits");

        // transfer the amount to the recipient
        balances[dst] = add96(balances[dst], amount, "Alch::mint: transfer amount overflows");
        emit Transfer(address(0), dst, amount);

        // move delegates
        _moveDelegates(address(0), delegates[dst], amount);
    }

    function allowance(address account, address spender)
    external
    view
    returns (uint256)
    {
        return allowances[account][spender];
    }

    function approve(address spender, uint256 rawAmount) external returns (bool) {
        uint96 amount;
        if (rawAmount == uint256(-1)) {
            amount = uint96(-1);
        } else {
            amount = safe96(rawAmount, "Alch::approve: amount exceeds 96 bits");
        }

        allowances[msg.sender][spender] = amount;

        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function permit(
        address owner,
        address spender,
        uint256 rawAmount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external {
        uint96 amount;
        if (rawAmount == uint256(-1)) {
            amount = uint96(-1);
        } else {
            amount = safe96(rawAmount, "Alch::permit: amount exceeds 96 bits");
        }

        bytes32 domainSeparator = keccak256(
            abi.encode(
                DOMAIN_TYPEHASH,
                keccak256(bytes(name)),
                getChainId(),
                address(this)
            )
        );
        bytes32 structHash = keccak256(
            abi.encode(
                PERMIT_TYPEHASH,
                owner,
                spender,
                rawAmount,
                nonces[owner]++,
                deadline
            )
        );
        bytes32 digest = keccak256(
            abi.encodePacked("\x19\x01", domainSeparator, structHash)
        );
        address signatory = ecrecover(digest, v, r, s);
        require(signatory != address(0), "Alch::permit: invalid signature");
        require(signatory == owner, "Alch::permit: unauthorized");
        require(block.timestamp <= deadline, "Alch::permit: signature expired");

        allowances[owner][spender] = amount;

        emit Approval(owner, spender, amount);
    }

    function balanceOf(address account) external view returns (uint256) {
        return balances[account];
    }

    function nonceOf(address account) external view returns (uint256) {
        return nonces[account];
    }

    function transfer(address dst, uint256 rawAmount) external returns (bool) {
        uint96 amount = safe96(rawAmount, "Alch::transfer: amount exceeds 96 bits");
        _transferTokens(msg.sender, dst, amount);
        return true;
    }

    function transferFrom(
        address src,
        address dst,
        uint256 rawAmount
    ) external returns (bool) {
        address spender = msg.sender;
        uint96 spenderAllowance = allowances[src][spender];
        uint96 amount = safe96(rawAmount, "Alch::approve: amount exceeds 96 bits");

        if (spender != src && spenderAllowance != uint96(-1)) {
            uint96 newAllowance = sub96(
                spenderAllowance,
                amount,
                "Alch::transferFrom: transfer amount exceeds spender allowance"
            );
            allowances[src][spender] = newAllowance;

            emit Approval(src, spender, newAllowance);
        }

        _transferTokens(src, dst, amount);
        return true;
    }

    function delegate(address delegatee) public {
        return _delegate(msg.sender, delegatee);
    }

    function delegateBySig(
        address delegatee,
        uint256 nonce,
        uint256 expiry,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public {
        bytes32 domainSeparator = keccak256(
            abi.encode(
                DOMAIN_TYPEHASH,
                keccak256(bytes(name)),
                getChainId(),
                address(this)
            )
        );
        bytes32 structHash = keccak256(
            abi.encode(DELEGATION_TYPEHASH, delegatee, nonce, expiry)
        );
        bytes32 digest = keccak256(
            abi.encodePacked("\x19\x01", domainSeparator, structHash)
        );
        address signatory = ecrecover(digest, v, r, s);
        require(signatory != address(0), "Alch::delegateBySig: invalid signature");
        require(nonce == nonces[signatory]++, "Alch::delegateBySig: invalid nonce");
        require(block.timestamp <= expiry, "Alch::delegateBySig: signature expired");
        return _delegate(signatory, delegatee);
    }

    function getCurrentVotes(address account) external view returns (uint96) {
        uint32 nCheckpoints = numCheckpoints[account];
        return nCheckpoints > 0 ? checkpoints[account][nCheckpoints - 1].votes : 0;
    }

    function getPriorVotes(address account, uint256 blockNumber)
    public
    view
    returns (uint96)
    {
        require(
            blockNumber < block.number,
            "Alch::getPriorVotes: not yet determined"
        );

        uint32 nCheckpoints = numCheckpoints[account];
        if (nCheckpoints == 0) {
            return 0;
        }

        if (checkpoints[account][nCheckpoints - 1].fromBlock <= blockNumber) {
            return checkpoints[account][nCheckpoints - 1].votes;
        }

        if (checkpoints[account][0].fromBlock > blockNumber) {
            return 0;
        }

        uint32 lower = 0;
        uint32 upper = nCheckpoints - 1;
        while (upper > lower) {
            uint32 center = upper - (upper - lower) / 2;
            Checkpoint memory cp = checkpoints[account][center];
            if (cp.fromBlock == blockNumber) {
                return cp.votes;
            } else if (cp.fromBlock < blockNumber) {
                lower = center;
            } else {
                upper = center - 1;
            }
        }
        return checkpoints[account][lower].votes;
    }

    function _delegate(address delegator, address delegatee) internal {
        address currentDelegate = delegates[delegator];
        uint96 delegatorBalance = balances[delegator];
        delegates[delegator] = delegatee;

        emit DelegateChanged(delegator, currentDelegate, delegatee);

        _moveDelegates(currentDelegate, delegatee, delegatorBalance);
    }

    function _transferTokens(
        address src,
        address dst,
        uint96 amount
    ) internal {
        require(
            src != address(0),
            "Alch::_transferTokens: cannot transfer from the zero address"
        );
        require(
            dst != address(0),
            "Alch::_transferTokens: cannot transfer to the zero address"
        );

        balances[src] = sub96(
            balances[src],
            amount,
            "Alch::_transferTokens: transfer amount exceeds balance"
        );
        balances[dst] = add96(
            balances[dst],
            amount,
            "Alch::_transferTokens: transfer amount overflows"
        );
        emit Transfer(src, dst, amount);

        _moveDelegates(delegates[src], delegates[dst], amount);
    }

    function _moveDelegates(
        address srcRep,
        address dstRep,
        uint96 amount
    ) internal {
        if (srcRep != dstRep && amount > 0) {
            if (srcRep != address(0)) {
                uint32 srcRepNum = numCheckpoints[srcRep];
                uint96 srcRepOld = srcRepNum > 0
                ? checkpoints[srcRep][srcRepNum - 1].votes
                : 0;
                uint96 srcRepNew = sub96(
                    srcRepOld,
                    amount,
                    "Alch::_moveVotes: vote amount underflows"
                );
                _writeCheckpoint(srcRep, srcRepNum, srcRepOld, srcRepNew);
            }

            if (dstRep != address(0)) {
                uint32 dstRepNum = numCheckpoints[dstRep];
                uint96 dstRepOld = dstRepNum > 0
                ? checkpoints[dstRep][dstRepNum - 1].votes
                : 0;
                uint96 dstRepNew = add96(
                    dstRepOld,
                    amount,
                    "Alch::_moveVotes: vote amount overflows"
                );
                _writeCheckpoint(dstRep, dstRepNum, dstRepOld, dstRepNew);
            }
        }
    }

    function _writeCheckpoint(
        address delegatee,
        uint32 nCheckpoints,
        uint96 oldVotes,
        uint96 newVotes
    ) internal {
        uint32 blockNumber = safe32(
            block.number,
            "Alch::_writeCheckpoint: block number exceeds 32 bits"
        );

        if (
            nCheckpoints > 0 &&
            checkpoints[delegatee][nCheckpoints - 1].fromBlock == blockNumber
        ) {
            checkpoints[delegatee][nCheckpoints - 1].votes = newVotes;
        } else {
            checkpoints[delegatee][nCheckpoints] = Checkpoint(blockNumber, newVotes);
            numCheckpoints[delegatee] = nCheckpoints + 1;
        }

        emit DelegateVotesChanged(delegatee, oldVotes, newVotes);
    }

    function safe32(uint256 n, string memory errorMessage)
    internal
    pure
    returns (uint32)
    {
        require(n < 2**32, errorMessage);
        return uint32(n);
    }

    function safe96(uint256 n, string memory errorMessage)
    internal
    pure
    returns (uint96)
    {
        require(n < 2**96, errorMessage);
        return uint96(n);
    }

    function add96(
        uint96 a,
        uint96 b,
        string memory errorMessage
    ) internal pure returns (uint96) {
        uint96 c = a + b;
        require(c >= a, errorMessage);
        return c;
    }

    function sub96(
        uint96 a,
        uint96 b,
        string memory errorMessage
    ) internal pure returns (uint96) {
        require(b <= a, errorMessage);
        return a - b;
    }

    function getChainId() internal pure returns (uint256) {
        uint256 chainId;
        assembly {
            chainId := chainid()
        }
        return chainId;
    }
}