erc-3643/contracts/compliance/legacy/features/SupplyLimit.sol

// SPDX-License-Identifier: GPL-3.0
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/**
 *     NOTICE
 *
 *     The T-REX software is licensed under a proprietary license or the GPL v.3.
 *     If you choose to receive it under the GPL v.3 license, the following applies:
 *     T-REX is a suite of smart contracts implementing the ERC-3643 standard and
 *     developed by Tokeny to manage and transfer financial assets on EVM blockchains
 *
 *     Copyright (C) 2023, Tokeny sàrl.
 *
 *     This program is free software: you can redistribute it and/or modify
 *     it under the terms of the GNU General Public License as published by
 *     the Free Software Foundation, either version 3 of the License, or
 *     (at your option) any later version.
 *
 *     This program is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *     GNU General Public License for more details.
 *
 *     You should have received a copy of the GNU General Public License
 *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

pragma solidity ^0.8.17;

import "../BasicCompliance.sol";

/**
 *  this feature allows to put a supply limit on the token
 *  If an agent tries to mint more tokens than the maximum threshold, the minting will fail
 */
abstract contract SupplyLimit is BasicCompliance {

    /// supply limit variable
    uint256 public supplyLimit;

    /**
     *  this event is emitted when the supply limit has been set.
     *  `_limit` is the max amount of tokens in circulation.
     */
    event SupplyLimitSet(uint256 _limit);

    /**
     *  @dev sets supply limit.
     *  Supply limit has to be smaller or equal to the actual supply.
     *  @param _limit max amount of tokens to be created
     *  Only the owner of the Compliance smart contract can call this function
     *  emits an `SupplyLimitSet` event
     */
    function setSupplyLimit(uint256 _limit) external onlyOwner {
        supplyLimit = _limit;
        emit SupplyLimitSet(_limit);
    }

    /**
    *  @dev check on the compliance status of a transaction.
    *  This check always returns true, real check is done at the creation action level
    */
    function complianceCheckOnSupplyLimit (address /*_from*/, address /*_to*/, uint256 /*_value*/)
    public view returns (bool) {
        return true;
    }

    /**
    *  @dev state update of the compliance feature post-transfer.
    *  this compliance feature doesn't require state update post-transfer
    *  @param _from the address of the transfer sender
    *  @param _to the address of the transfer receiver
    *  @param _value the amount of tokens that `_from` sent to `_to`
    *  internal function, can be called only from the functions of the Compliance smart contract
    */
    // solhint-disable-next-line no-empty-blocks
    function _transferActionOnSupplyLimit(address _from, address _to, uint256 _value) internal {}

    /**
    *  @dev state update of the compliance feature post-minting.
    *  reverts if the post-minting supply is higher than the max supply
    *  internal function, can be called only from the functions of the Compliance smart contract
    */
    function _creationActionOnSupplyLimit(address /*_to*/, uint256 /*_value*/) internal {
        require(tokenBound.totalSupply() <= supplyLimit, "cannot mint more tokens");
    }

    /**
    *  @dev state update of the compliance feature post-burning.
    *  this compliance feature doesn't require state update post-burning
    *  @param _from the wallet address on which tokens burnt
    *  @param _value the amount of tokens burnt from `_from` wallet
    *  internal function, can be called only from the functions of the Compliance smart contract
    */
    // solhint-disable-next-line no-empty-blocks
    function _destructionActionOnSupplyLimit(address _from, uint256 _value) internal {}
}