harb/onchain/src/Harb.sol

// SPDX-License-Identifier: GPL-3.0-or-later

pragma solidity ^0.8.19;

import { ERC20, IERC20, IERC20Metadata } from "@openzeppelin/token/ERC20/ERC20.sol";
import { ERC20Permit, IERC20Permit } from "@openzeppelin/token/ERC20/extensions/ERC20Permit.sol";
import { SafeCast } from "@openzeppelin/utils/math/SafeCast.sol";
import { IStake } from "./interfaces/IStake.sol";
import { TwabController } from "pt-v5-twab-controller/TwabController.sol";

/**
 * @title  TWAB ERC20 Token
 * @notice This contract creates an ERC20 token with balances stored in a TwabController,
 *         enabling time-weighted average balances for each holder.
 * @dev    The TwabController limits all balances including total token supply to uint96 for
 *         gas savings. Any mints that increase a balance past this limit will fail.
 */
contract Harb is ERC20, ERC20Permit {

    /* ============ Public Variables ============ */

    /// @notice Address of the TwabController used to keep track of balances.
    TwabController public immutable twabController;

    /// @notice Address of the LiquidityManager contract that mints and burns supply
    address public liquidityManager;

    address public stakingPool;

    /* ============ Errors ============ */

    /// @notice Thrown if the some address is unexpectedly the zero address.
    error ZeroAddressInConstructor();

    /// @dev Function modifier to ensure that the caller is the liquidityManager
    modifier onlyLiquidityManager() {
        require(msg.sender == liquidityManager, "Harb/only-lm");
        _;
    }

    /* ============ Constructor ============ */

    /**
     * @notice TwabERC20 Constructor
     * @param name_ The name of the token
     * @param symbol_ The token symbol
     */
    constructor(
        string memory name_,
        string memory symbol_,
        TwabController twabController_
    ) ERC20(name_, symbol_) ERC20Permit(name_) {
        if (address(0) == address(twabController_)) revert ZeroAddressInConstructor();
        twabController = twabController_;
    }

    function setLiquidityManager(address liquidityManager_) external {
        // TODO: add trapdoor
        if (address(0) == liquidityManager_) revert ZeroAddressInConstructor();
        liquidityManager = liquidityManager_;
    }

    function setStakingPool(address stakingPool_) external {
        // TODO: add trapdoor
        if (address(0) == stakingPool_) revert ZeroAddressInConstructor();
        stakingPool = stakingPool_;
    }

    /* ============ External Functions ============ */

    /// @notice Allows the liquidityManager to mint tokens for itself
    /// @dev May be overridden to provide more granular control over minting
    /// @param _amount Amount of tokens to mint
    function mint(uint256 _amount) external onlyLiquidityManager {
        _mintHarb(liquidityManager, _amount);
    }

    /// @notice Allows the liquidityManager to burn tokens from a its account
    /// @dev May be overridden to provide more granular control over burning
    /// @param _amount Amount of tokens to burn
    function burn(uint256 _amount) external onlyLiquidityManager {
        _burnHarb(liquidityManager, _amount);
    }

    /* ============ Public ERC20 Overrides ============ */

    /// @inheritdoc ERC20
    function balanceOf(
        address _account
    ) public view virtual override(ERC20) returns (uint256) {
        return twabController.balanceOf(address(this), _account);
    }

    /// @inheritdoc ERC20
    function totalSupply() public view virtual override(ERC20) returns (uint256) {
        return twabController.totalSupply(address(this));
    }



    /* ============ Internal ERC20 Overrides ============ */

    /**
     * @notice Mints tokens to `_receiver` and increases the total supply.
     * @dev Emits a {Transfer} event with `from` set to the zero address.
     * @dev `receiver` cannot be the zero address.
     * @param receiver Address that will receive the minted tokens
     * @param amount Tokens to mint
     */
    function _mintHarb(address receiver, uint256 amount) internal {
        // make sure staking pool grows proportional to economy
        uint256 stakingPoolBalance = balanceOf(stakingPool);
        uint256 activeSupply = totalSupply - stakingPoolBalance;
        uint256 dormantStake = IStake(stakingPool).dormantSupply();
        if (stakingPoolBalance > 0) {
              uint256 newStake = stakingPoolBalance * amount / (activeSupply + dormantStake);
              _mint(stakingPool, newStake);
        }

        twabController.mint(receiver, SafeCast.toUint96(amount));
        emit Transfer(address(0), receiver, amount);
    }

    /**
     * @notice Destroys tokens from `_owner` and reduces the total supply.
     * @dev Emits a {Transfer} event with `to` set to the zero address.
     * @dev `_owner` cannot be the zero address.
     * @dev `_owner` must have at least `_amount` tokens.
     * @param _owner The owner of the tokens
     * @param _amount The amount of tokens to burn
     */
    function _burnHarb(address _owner, uint256 _amount) internal {
        // TODO
        twabController.burn(_owner, SafeCast.toUint96(_amount));
        emit Transfer(_owner, address(0), _amount);
    }

    /**
     * @notice Transfers tokens from one account to another.
     * @dev Emits a {Transfer} event.
     * @dev `_from` cannot be the zero address.
     * @dev `_to` cannot be the zero address.
     * @dev `_from` must have a balance of at least `_amount`.
     * @param _from Address to transfer from
     * @param _to Address to transfer to
     * @param _amount The amount of tokens to transfer
     */
    function _transfer(address _from, address _to, uint256 _amount) internal virtual override {
        twabController.transfer(_from, _to, SafeCast.toUint96(_amount));
        emit Transfer(_from, _to, _amount);
    }

}