Custom Contract

This is a scratch of the Inflation Extension, extracted from the template of the Covenants Frontend, which can be found here.

This version just implements an owner-based logic where there is a host wallet that rules the writable functions (e.g. to set new operations).

The constructor cannot be used to link the extension to the inflation contract (because the extension address is needed to create it). However, Covenant farming contracts support a lazy initialization approach which allows for the passing of ABI-encoded method payload during Farming Contract creation. E.g., this template reports the optional init(address host) method to specify initialization arguments.

The only mandatory functions are function active() public view returns (bool), function receiveTokens(address[] memory tokenAddresses, uint256[] memory transferAmounts, uint256[] memory amountsToMint) public and function deactivationByFailure() public because their method signatures are used in the Inflation Contract, but of course their bodies can be changed to follow your logic.

contract FixedInflationExtension {

    address private _host;

    address private _fixedInflationContract;

    bool public active;

    modifier fixedInflationOnly() {
        require(_fixedInflationContract == msg.sender, "Unauthorized");

    modifier hostOnly() {
        require(_host == msg.sender, "Unauthorized");

    receive() external payable {

    function init(address host) public {
        require(_host == address(0), "Already init");
        require((_host = host) != address(0), "blank host");
        _fixedInflationContract = msg.sender;

    function setHost(address host) public virtual hostOnly {
        _host = host;

    function data() view public returns(address fixedInflationContract, address host) {
        return(_fixedInflationContract, _host);

    function setActive(bool _active) public virtual hostOnly {
        active = _active;

    function receiveTokens(address[] memory tokenAddresses, uint256[] memory transferAmounts, uint256[] memory amountsToMint) public fixedInflationOnly {
        for(uint256 i = 0; i < tokenAddresses.length; i++) {
            if(transferAmounts[i] > 0) {
                if(tokenAddresses[i] == address(0)) {
                    (bool result,) ={value:transferAmounts[i]}("");
                    require(result, "ETH transfer failed");
                _safeTransfer(tokenAddresses[i], msg.sender, transferAmounts[i]);
            if(amountsToMint[i] > 0) {
                _mintAndTransfer(tokenAddresses[i], msg.sender, amountsToMint[i]);

    function setEntry(FixedInflationEntry memory newEntry, FixedInflationOperation[] memory newOperations) public hostOnly {
        IFixedInflation(_fixedInflationContract).setEntry(newEntry, newOperations);

    function flushBack(address[] memory tokenAddresses) public hostOnly {

    function deactivationByFailure() public fixedInflationOnly {
        active = false;

    function _mintAndTransfer(address erc20TokenAddress, address recipient, uint256 value) internal virtual {
        IERC20Mintable(erc20TokenAddress).mint(recipient, value);

    function _safeTransfer(address erc20TokenAddress, address to, uint256 value) internal virtual {
        bytes memory returnData = _call(erc20TokenAddress, abi.encodeWithSelector(IERC20(erc20TokenAddress).transfer.selector, to, value));
        require(returnData.length == 0 || abi.decode(returnData, (bool)), 'TRANSFER_FAILED');

    function _call(address location, bytes memory payload) private returns(bytes memory returnData) {
        assembly {
            let result := call(gas(), location, 0, add(payload, 0x20), mload(payload), 0, 0)
            let size := returndatasize()
            returnData := mload(0x40)
            mstore(returnData, size)
            let returnDataPayloadStart := add(returnData, 0x20)
            returndatacopy(returnDataPayloadStart, 0, size)
            mstore(0x40, add(returnDataPayloadStart, size))
            switch result case 0 {revert(returnDataPayloadStart, size)}

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