Cryo Explorer Ethereum Mainnet

// SPDX-License-Identifier: MIT
// Copied and adjusted from OpenZeppelin
// Adjustments:
// - modifications to support ERC-677
// - removed require messages to save space
// - removed unnecessary require statements
// - removed GSN Context
// - upgraded to 0.8 to drop SafeMath
// - let name() and symbol() be implemented by subclass

pragma solidity >=0.8;

import "./IERC20.sol";
import "./IERC677Receiver.sol";

/**
 * @dev Implementation of the `IERC20` interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using `_mint`.
 * For a generic mechanism see `ERC20Mintable`.
 *
 * *For a detailed writeup see our guide [How to implement supply
 * mechanisms](https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226).*
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an `Approval` event is emitted on calls to `transferFrom`.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard `decreaseAllowance` and `increaseAllowance`
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See `IERC20.approve`.
 */

abstract contract ERC20 is IERC20 {

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    uint8 public override decimals;

    constructor(uint8 _decimals) {
        decimals = _decimals;
    }

    /**
     * @dev See `IERC20.totalSupply`.
     */
    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See `IERC20.balanceOf`.
     */
    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See `IERC20.transfer`.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    /**
     * @dev See `IERC20.allowance`.
     */
    function allowance(address owner, address spender) public view override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See `IERC20.approve`.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 value) public override returns (bool) {
        _approve(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev See `IERC20.transferFrom`.
     *
     * Emits an `Approval` event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of `ERC20`;
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `value`.
     * - the caller must have allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, msg.sender, _allowances[sender][msg.sender] - amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to `approve` that can be used as a mitigation for
     * problems described in `IERC20.approve`.
     *
     * Emits an `Approval` event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender] - subtractedValue);
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to `transfer`, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a `Transfer` event.
     *
     * Requirements:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(recipient != address(0));

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] -= amount;
        _balances[recipient] += amount;
        emit Transfer(sender, recipient, amount);
    }

    // ERC-677 functionality, can be useful for swapping and wrapping tokens
    function transferAndCall(address recipient, uint amount, bytes calldata data) public returns (bool) {
        bool success = transfer(recipient, amount);
        if (success){
            IERC677Receiver(recipient).onTokenTransfer(msg.sender, amount, data);
        }
        return success;
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a `Transfer` event with `from` set to the zero address.
     *
     * Requirements
     *
     * - `to` cannot be the zero address.
     */
    function _mint(address recipient, uint256 amount) internal virtual {
        require(recipient != address(0));

        _beforeTokenTransfer(address(0), recipient, amount);

        _totalSupply += amount;
        _balances[recipient] += amount;
        emit Transfer(address(0), recipient, amount);
    }

     /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a `Transfer` event with `to` set to the zero address.
     *
     * Requirements
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        _beforeTokenTransfer(account, address(0), amount);

        _totalSupply -= amount;
        _balances[account] -= amount;
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an `Approval` event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 value) internal {
        _allowances[owner][spender] = value;
        emit Approval(owner, spender, value);
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be to transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(address from, address to, uint256 amount) virtual internal;
}

/**
* SPDX-License-Identifier: MIT
*
* Copyright (c) 2016-2019 zOS Global Limited
*
*/
pragma solidity >=0.8;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see `ERC20Detailed`.
 */

interface IERC20 {

    // Optional functions
    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through `transferFrom`. This is
     * zero by default.
     *
     * This value changes when `approve` or `transferFrom` are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * > Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an `Approval` event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to `approve`. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
* SPDX-License-Identifier: LicenseRef-Aktionariat
*
* MIT License with Automated License Fee Payments
*
* Copyright (c) 2020 Aktionariat AG (aktionariat.com)
*
* Permission is hereby granted to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software
* without restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies of the
* Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* - The above copyright notice and this permission notice shall be included in
*   all copies or substantial portions of the Software.
* - All automated license fee payments integrated into this and related Software
*   are preserved.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
pragma solidity >=0.8;

/**
 * @title CompanyName Shareholder Agreement
 * @author Luzius Meisser, [email protected]
 * @dev These tokens are based on the ERC20 standard and the open-zeppelin library.
 *
 * This is an ERC-20 token representing shares of CompanyName AG that are bound to
 * a shareholder agreement that can be found at the URL defined in the constant 'terms'
 * of the 'DraggableCompanyNameShares' contract. The agreement is partially enforced
 * through the Swiss legal system, and partially enforced through this smart contract.
 * In particular, this smart contract implements a drag-along clause which allows the
 * majority of token holders to force the minority sell their shares along with them in
 * case of an acquisition. That's why the tokens are called "Draggable CompanyName AG Shares."
 */

import "./ERC20.sol";
import "./IERC20.sol";
import "./IERC677Receiver.sol";

contract ERC20Draggable is ERC20, IERC677Receiver {

    IERC20 public wrapped;                              // The wrapped contract
    IOfferFactory public factory;

    // If the wrapped tokens got replaced in an acquisition, unwrapping might yield many currency tokens
    uint256 public unwrapConversionFactor = 0;

    // The current acquisition attempt, if any. See initiateAcquisition to see the requirements to make a public offer.
    IOffer public offer;

    uint256 public quorum;
    uint256 public votePeriod;

    event MigrationSucceeded(address newContractAddress);

    constructor(
        address offerFactory,
        address wrappedToken,
        uint256 quorum_,
        uint256 votePeriod_
    ) ERC20(0) {
        factory = IOfferFactory(offerFactory);
        wrapped = IERC20(wrappedToken);
        quorum = quorum_;
        votePeriod = votePeriod_;
    }

    function name() public override view returns (string memory){
        if (isBinding()){
            return string(abi.encodePacked("Draggable ", wrapped.name()));
        } else {
            return string(abi.encodePacked("Wrapped ", wrapped.name()));
        }
    }

    function symbol() public override view returns (string memory){
        if (isBinding()){
            return string(abi.encodePacked("D", wrapped.symbol()));
        } else {
            return string(abi.encodePacked("W", wrapped.symbol()));
        }
    }

    function onTokenTransfer(address from, uint256 amount, bytes calldata) override public {
        require(msg.sender == address(wrapped));
        _mint(from, amount);
    }

    /** Increases the number of drag-along tokens. Requires minter to deposit an equal amount of share tokens */
    function wrap(address shareholder, uint256 amount) public {
        require(wrapped.transferFrom(msg.sender, address(this), amount));
        _mint(shareholder, amount);
    }

    /**
     * Indicates that the token holders are bound to the token terms and that:
     * - Conversions back to the wrapped token (unwrap) are not allowed
     * - The drag-along can be performed by making an according offer
     * - They can be migrated to a new version of this contract in accordance with the terms
     */
    function isBinding() public view returns (bool) {
        return unwrapConversionFactor == 0;
    }

    /**
     * Deactivates the drag-along mechanism and enables the unwrap function.
     */
    function deactivate(uint256 factor) internal {
        require(factor >= 1);
        unwrapConversionFactor = factor;
    }

    /** Decrease the number of drag-along tokens. The user gets back their shares in return */
    function unwrap(uint256 amount) public {
        require(!isBinding());
        unwrap(msg.sender, amount, unwrapConversionFactor);
    }
    
    function unwrap(address owner, uint256 amount, uint256 factor) internal {
        _burn(owner, amount);
        require(wrapped.transfer(owner, amount * factor));
    }

    /**
     * Burns both the token itself as well as the wrapped token!
     * If you want to get out of the shareholder agreement, use unwrap after it has been
     * deactivated by a majority vote or acquisition.
     *
     * Burning only works if wrapped token supports burning. Also, the exact meaning of this
     * operation might depend on the circumstances. Burning and reussing the wrapped token
     * does not free the sender from the legal obligations of the shareholder agreement.
     */
    function burn(uint256 amount) public {
        _burn(msg.sender, amount);
        uint256 factor = isBinding() ? 1 : unwrapConversionFactor;
        IBurnable(address(wrapped)).burn(amount * factor);
    }

    function makeAcquisitionOffer(bytes32 salt, uint256 pricePerShare, address currency) public payable {
        require(isBinding());
        address newOffer = factory.create{value: msg.value}(salt, msg.sender, pricePerShare, currency, quorum, votePeriod);
        if (offerExists()) {
            require(IOffer(newOffer).isWellFunded());
            offer.contest(newOffer);
        }
        offer = IOffer(newOffer);
    }

    function drag(address buyer, address currency) public {
        require(msg.sender == address(offer));
        unwrap(buyer, balanceOf(buyer), 1);
        replaceWrapped(currency, buyer);
    }

    function notifyOfferEnded() public {
        if (msg.sender == address(offer)){
            offer = IOffer(address(0));
        }
    }

    function replaceWrapped(address newWrapped, address oldWrappedDestination) internal {
        require(isBinding());
        // Free all old wrapped tokens we have
        require(wrapped.transfer(oldWrappedDestination, wrapped.balanceOf(address(this))));
        // Count the new wrapped tokens
        wrapped = IERC20(newWrapped);
        deactivate(wrapped.balanceOf(address(this)) / totalSupply());
    }

    function migrate() public {
        address successor = msg.sender;
        require(!offerExists()); // if you have 80%, you can easily cancel the offer first if necessary
        require(balanceOf(successor) * 10000 >= totalSupply() * 8000, "Quorum not reached");
        replaceWrapped(successor, successor);
        emit MigrationSucceeded(successor);
    }

    function _beforeTokenTransfer(address from, address to, uint256 amount) override internal {
        if (offerExists()) {
            offer.notifyMoved(from, to, amount);
        }
    }

    function offerExists() internal view returns (bool) {
        return address(offer) != address(0);
    }

}

abstract contract IBurnable {
    function burn(uint256) virtual public;
}

abstract contract IOffer {
    function isWellFunded() virtual public returns (bool);
    function contest(address newOffer) virtual public;
    function notifyMoved(address from, address to, uint256 value) virtual public;
}

abstract contract IOfferFactory {
    function create(bytes32 salt, address buyer, uint256 pricePerShare, address currency, uint256 quorum, uint256 votePeriod) virtual public payable returns (address);
}

/**
* SPDX-License-Identifier: LicenseRef-Aktionariat
*
* MIT License with Automated License Fee Payments
*
* Copyright (c) 2020 Aktionariat AG (aktionariat.com)
*
* Permission is hereby granted to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software
* without restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies of the
* Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* - The above copyright notice and this permission notice shall be included in
*   all copies or substantial portions of the Software.
* - All automated license fee payments integrated into this and related Software
*   are preserved.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
pragma solidity >=0.8;

import "./ERC20Recoverable.sol";
import "./ERC20Draggable.sol";

/**
 * @title Draggable CompanyName AG Shares
 * @author Luzius Meisser, [email protected]
 *
 * This is an ERC-20 token representing shares of CompanyName AG that are bound to
 * a shareholder agreement that can be found at the URL defined in the constant 'terms'.
 * The shareholder agreement is partially enforced through this smart contract. The agreement
 * is designed to facilitate a complete acquisition of the firm even if a minority of shareholders
 * disagree with the acquisition, to protect the interest of the minority shareholders by requiring
 * the acquirer to offer the same conditions to everyone when acquiring the company, and to
 * facilitate an update of the shareholder agreement even if a minority of the shareholders that
 * are bound to this agreement disagree. The name "draggable" stems from the convention of calling
 * the right to drag a minority along with a sale of the company "drag-along" rights. The name is
 * chosen to ensure that token holders are aware that they are bound to such an agreement.
 *
 * The percentage of token holders that must agree with an update of the terms is defined by the
 * constant UPDATE_QUORUM. The percentage of yes-votes that is needed to successfully complete an
 * acquisition is defined in the constant ACQUISITION_QUORUM. Note that the update quorum is based
 * on the total number of tokens in circulation. In contrast, the acquisition quorum is based on the
 * number of votes cast during the voting period, not taking into account those who did not bother
 * to vote.
 */

contract DraggableShares is ERC20Recoverable, ERC20Draggable {

    string public terms;

    /**
     * Designed to be used with the Crypto Franc as currency token. See also parent constructor.
     */
    constructor(string memory _terms, address offerFactory, address wrappedToken, uint256 quorum, uint256 votePeriod)
        ERC20Draggable(offerFactory, wrappedToken, quorum, votePeriod) {
        IRecoverable(wrappedToken).setRecoverable(false);
        terms = _terms; // to update the terms, migrate to a new contract. That way it is ensured that the terms can only be updated when the quorom agrees.
    }

    function transfer(address to, uint256 value) override(ERC20Recoverable, ERC20) public returns (bool) {
        return super.transfer(to, value);
    }

    function getClaimDeleter() public view override returns (address) {
        return IRecoverable(address(wrapped)).getClaimDeleter();
    }

    function getCollateralRate(address collateralType) public view override returns (uint256) {
        uint256 rate = super.getCollateralRate(collateralType);
        if (rate > 0) {
            return rate;
        } else if (collateralType == address(wrapped)) {
            return unwrapConversionFactor;
        } else {
            // If the wrapped contract allows for a specific collateral, we should too.
            // If the wrapped contract is not IRecoverable, we will fail here, but would fail anyway.
            return IRecoverable(address(wrapped)).getCollateralRate(collateralType) * unwrapConversionFactor;
        }
    }

}

abstract contract IRecoverable {
    function setRecoverable(bool) public virtual;
    function getCollateralRate(address) public virtual view returns (uint256);
    function getClaimDeleter() public virtual view returns (address);
}

// SPDX-License-Identifier: MIT
// Copied from https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/UniswapV2Router02.sol
pragma solidity >=0.8;

interface IERC677Receiver {

    function onTokenTransfer(address from, uint256 amount, bytes calldata data) external;

}

/**
* SPDX-License-Identifier: LicenseRef-Aktionariat
*
* MIT License with Automated License Fee Payments
*
* Copyright (c) 2020 Aktionariat AG (aktionariat.com)
*
* Permission is hereby granted to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software
* without restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies of the
* Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* - The above copyright notice and this permission notice shall be included in
*   all copies or substantial portions of the Software.
* - All automated license fee payments integrated into this and related Software
*   are preserved.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
pragma solidity >=0.8;

import "./ERC20.sol";
import "./IERC20.sol";

/**
 * @title Recoverable
 * In case of tokens that represent real-world assets such as shares of a company, one needs a way
 * to handle lost private keys. With physical certificates, courts can declare share certificates as
 * invalid so the company can issue replacements. Here, we want a solution that does not depend on
 * third parties to resolve such cases. Instead, when someone has lost a private key, he can use the
 * declareLost function to post a deposit and claim that the shares assigned to a specific address are
 * lost. To prevent front running, a commit reveal scheme is used. If he actually is the owner of the shares,
 * he needs to wait for a certain period and can then reclaim the lost shares as well as the deposit.
 * If he is an attacker trying to claim shares belonging to someone else, he risks losing the deposit
 * as it can be claimed at anytime by the rightful owner.
 * Furthermore, if "getClaimDeleter" is defined in the subclass, the returned address is allowed to
 * delete claims, returning the collateral. This can help to prevent obvious cases of abuse of the claim
 * function.
 */

abstract contract ERC20Recoverable is ERC20 {

    // A struct that represents a claim made
    struct Claim {
        address claimant; // the person who created the claim
        uint256 collateral; // the amount of collateral deposited
        uint256 timestamp;  // the timestamp of the block in which the claim was made
        address currencyUsed; // The currency (XCHF) can be updated, we record the currency used for every request
    }

    uint256 public claimPeriod = 180 days; // Default of 180 days;

    mapping(address => Claim) public claims; // there can be at most one claim per address, here address is claimed address
    mapping(address => bool) public recoveryDisabled; // disable claimability (e.g. for long term storage)

    // ERC-20 token that can be used as collateral or 0x0 if disabled
    address public customCollateralAddress;
    uint256 public customCollateralRate;

    /**
     * Returns the collateral rate for the given collateral type and 0 if that type
     * of collateral is not accepted. By default, only the token itself is accepted at
     * a rate of 1:1.
     *
     * Subclasses should override this method if they want to add additional types of
     * collateral.
     */
    function getCollateralRate(address collateralType) public virtual view returns (uint256) {
        if (collateralType == address(this)) {
            return 1;
        } else if (collateralType == customCollateralAddress) {
            return customCollateralRate;
        } else {
            return 0;
        }
    }

    /**
     * Allows subclasses to set a custom collateral besides the token itself.
     * The collateral must be an ERC-20 token that returns true on successful transfers and
     * throws an exception or returns false on failure.
     * Also, do not forget to multiply the rate in accordance with the number of decimals of the collateral.
     * For example, rate should be 7*10**18 for 7 units of a collateral with 18 decimals.
     */
    function _setCustomClaimCollateral(address collateral, uint256 rate) internal {
        customCollateralAddress = collateral;
        if (customCollateralAddress == address(0)) {
            customCollateralRate = 0; // disabled
        } else {
            require(rate > 0, "Collateral rate can't be zero");
            customCollateralRate = rate;
        }
        emit CustomClaimCollateralChanged(collateral, rate);
    }

    function getClaimDeleter() virtual public view returns (address);

    /**
     * Allows subclasses to change the claim period, but not to fewer than 90 days.
     */
    function _setClaimPeriod(uint256 claimPeriodInDays) internal {
        require(claimPeriodInDays > 90, "Claim period must be at least 90 days"); // must be at least 90 days
        uint256 claimPeriodInSeconds = claimPeriodInDays * (1 days);
        claimPeriod = claimPeriodInSeconds;
        emit ClaimPeriodChanged(claimPeriod);
    }

    function setRecoverable(bool enabled) public {
        recoveryDisabled[msg.sender] = !enabled;
    }

    /**
     * Some users might want to disable claims for their address completely.
     * For example if they use a deep cold storage solution or paper wallet.
     */
    function isRecoveryEnabled(address target) public view returns (bool) {
        return !recoveryDisabled[target];
    }

    event ClaimMade(address indexed lostAddress, address indexed claimant, uint256 balance);
    event ClaimCleared(address indexed lostAddress, uint256 collateral);
    event ClaimDeleted(address indexed lostAddress, address indexed claimant, uint256 collateral);
    event ClaimResolved(address indexed lostAddress, address indexed claimant, uint256 collateral);
    event ClaimPeriodChanged(uint256 newClaimPeriodInDays);
    event CustomClaimCollateralChanged(address newCustomCollateralAddress, uint256 newCustomCollareralRate);

  /** Anyone can declare that the private key to a certain address was lost by calling declareLost
    * providing a deposit/collateral. There are three possibilities of what can happen with the claim:
    * 1) The claim period expires and the claimant can get the deposit and the shares back by calling recover
    * 2) The "lost" private key is used at any time to call clearClaim. In that case, the claim is deleted and
    *    the deposit sent to the shareholder (the owner of the private key). It is recommended to call recover
    *    whenever someone transfers funds to let claims be resolved automatically when the "lost" private key is
    *    used again.
    * 3) The owner deletes the claim and assigns the deposit to the claimant. This is intended to be used to resolve
    *    disputes. Generally, using this function implies that you have to trust the issuer of the tokens to handle
    *    the situation well. As a rule of thumb, the contract owner should assume the owner of the lost address to be the
    *    rightful owner of the deposit.
    * It is highly recommended that the owner observes the claims made and informs the owners of the claimed addresses
    * whenever a claim is made for their address (this of course is only possible if they are known to the owner, e.g.
    * through a shareholder register).
    */
    function declareLost(address collateralType, address lostAddress) public {
        require(isRecoveryEnabled(lostAddress), "Claims disabled for this address");
        uint256 collateralRate = getCollateralRate(collateralType);
        require(collateralRate > 0, "Unsupported collateral");
        address claimant = msg.sender;
        uint256 balance = balanceOf(lostAddress);
        uint256 collateral = balance * collateralRate;
        IERC20 currency = IERC20(collateralType);
        require(balance > 0, "Claimed address holds no shares");
        require(claims[lostAddress].collateral == 0, "Address already claimed");
        require(currency.transferFrom(claimant, address(this), collateral), "Collateral transfer failed");

        claims[lostAddress] = Claim({
            claimant: claimant,
            collateral: collateral,
            timestamp: block.timestamp,
            currencyUsed: collateralType
        });

        emit ClaimMade(lostAddress, claimant, balance);
    }

    function getClaimant(address lostAddress) public view returns (address) {
        return claims[lostAddress].claimant;
    }

    function getCollateral(address lostAddress) public view returns (uint256) {
        return claims[lostAddress].collateral;
    }

    function getCollateralType(address lostAddress) public view returns (address) {
        return claims[lostAddress].currencyUsed;
    }

    function getTimeStamp(address lostAddress) public view returns (uint256) {
        return claims[lostAddress].timestamp;
    }

    function transfer(address recipient, uint256 amount) override virtual public returns (bool) {
        require(super.transfer(recipient, amount), "Transfer failed");
        clearClaim();
        return true;
    }

    /**
     * Clears a claim after the key has been found again and assigns the collateral to the "lost" address.
     * This is the price an adverse claimer pays for filing a false claim and makes it risky to do so.
     */
    function clearClaim() public {
        if (claims[msg.sender].collateral != 0) {
            uint256 collateral = claims[msg.sender].collateral;
            IERC20 currency = IERC20(claims[msg.sender].currencyUsed);
            delete claims[msg.sender];
            require(currency.transfer(msg.sender, collateral), "Collateral transfer failed");
            emit ClaimCleared(msg.sender, collateral);
        }
    }

   /**
    * After the claim period has passed, the claimant can call this function to send the
    * tokens on the lost address as well as the collateral to himself.
    */
    function recover(address lostAddress) public {
        Claim memory claim = claims[lostAddress];
        uint256 collateral = claim.collateral;
        IERC20 currency = IERC20(claim.currencyUsed);
        require(collateral != 0, "No claim found");
        require(claim.claimant == msg.sender, "Only claimant can resolve claim");
        require(claim.timestamp + claimPeriod <= block.timestamp, "Claim period not over yet");
        address claimant = claim.claimant;
        delete claims[lostAddress];
        require(currency.transfer(claimant, collateral), "Collateral transfer failed");
        _transfer(lostAddress, claimant, balanceOf(lostAddress));
        emit ClaimResolved(lostAddress, claimant, collateral);
    }

    /**
     * This function is to be executed by the claim deleter only in case a dispute needs to be resolved manually.
     */
    function deleteClaim(address lostAddress) public {
        require(msg.sender == getClaimDeleter(), "You cannot delete claims");
        Claim memory claim = claims[lostAddress];
        IERC20 currency = IERC20(claim.currencyUsed);
        require(claim.collateral != 0, "No claim found");
        delete claims[lostAddress];
        require(currency.transfer(claim.claimant, claim.collateral), "Collateral transfer failed");
        emit ClaimDeleted(lostAddress, claim.claimant, claim.collateral);
    }

}