pragma solidity ^0.6.0;
pragma experimental ABIEncoderV2;


interface ERC20 {
    function totalSupply() external view returns (uint256 supply);

    function balanceOf(address _owner) external view returns (uint256 balance);

    function transfer(address _to, uint256 _value) external returns (bool success);

    function transferFrom(address _from, address _to, uint256 _value)
        external
        returns (bool success);

    function approve(address _spender, uint256 _value) external returns (bool success);

    function allowance(address _owner, address _spender) external view returns (uint256 remaining);

    function decimals() external view returns (uint256 digits);

    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

library Address {
    function isContract(address account) internal view returns (bool) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// SPDX-License-Identifier: MIT
library SafeMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(ERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(ERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     */
    function safeApprove(ERC20 token, address spender, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(ERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(ERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function _callOptionalReturn(ERC20 token, bytes memory data) private {

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

contract AdminAuth {

    using SafeERC20 for ERC20;

    address public owner;
    address public admin;

    modifier onlyOwner() {
        require(owner == msg.sender);
        _;
    }

    constructor() public {
        owner = msg.sender;
    }

    /// @notice Admin is set by owner first time, after that admin is super role and has permission to change owner
    /// @param _admin Address of multisig that becomes admin
    function setAdminByOwner(address _admin) public {
        require(msg.sender == owner);
        require(admin == address(0));

        admin = _admin;
    }

    /// @notice Admin is able to set new admin
    /// @param _admin Address of multisig that becomes new admin
    function setAdminByAdmin(address _admin) public {
        require(msg.sender == admin);

        admin = _admin;
    }

    /// @notice Admin is able to change owner
    /// @param _owner Address of new owner
    function setOwnerByAdmin(address _owner) public {
        require(msg.sender == admin);

        owner = _owner;
    }

    /// @notice Destroy the contract
    function kill() public onlyOwner {
        selfdestruct(payable(owner));
    }

    /// @notice  withdraw stuck funds
    function withdrawStuckFunds(address _token, uint _amount) public onlyOwner {
        if (_token == 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE) {
            payable(owner).transfer(_amount);
        } else {
            ERC20(_token).safeTransfer(owner, _amount);
        }
    }
}

/// @title Stores subscription information for Compound automatization
contract CompoundSubscriptions is AdminAuth {

    struct CompoundHolder {
        address user;
        uint128 minRatio;
        uint128 maxRatio;
        uint128 optimalRatioBoost;
        uint128 optimalRatioRepay;
        bool boostEnabled;
    }

    struct SubPosition {
        uint arrPos;
        bool subscribed;
    }

    CompoundHolder[] public subscribers;
    mapping (address => SubPosition) public subscribersPos;

    uint public changeIndex;

    event Subscribed(address indexed user);
    event Unsubscribed(address indexed user);
    event Updated(address indexed user);
    event ParamUpdates(address indexed user, uint128, uint128, uint128, uint128, bool);

    /// @dev Called by the DSProxy contract which owns the Compound position
    /// @notice Adds the users Compound poistion in the list of subscriptions so it can be monitored
    /// @param _minRatio Minimum ratio below which repay is triggered
    /// @param _maxRatio Maximum ratio after which boost is triggered
    /// @param _optimalBoost Ratio amount which boost should target
    /// @param _optimalRepay Ratio amount which repay should target
    /// @param _boostEnabled Boolean determing if boost is enabled
    function subscribe(uint128 _minRatio, uint128 _maxRatio, uint128 _optimalBoost, uint128 _optimalRepay, bool _boostEnabled) external {

        // if boost is not enabled, set max ratio to max uint
        uint128 localMaxRatio = _boostEnabled ? _maxRatio : uint128(-1);
        require(checkParams(_minRatio, localMaxRatio), "Must be correct params");

        SubPosition storage subInfo = subscribersPos[msg.sender];

        CompoundHolder memory subscription = CompoundHolder({
                minRatio: _minRatio,
                maxRatio: localMaxRatio,
                optimalRatioBoost: _optimalBoost,
                optimalRatioRepay: _optimalRepay,
                user: msg.sender,
                boostEnabled: _boostEnabled
            });

        changeIndex++;

        if (subInfo.subscribed) {
            subscribers[subInfo.arrPos] = subscription;

            emit Updated(msg.sender);
            emit ParamUpdates(msg.sender, _minRatio, localMaxRatio, _optimalBoost, _optimalRepay, _boostEnabled);
        } else {
            subscribers.push(subscription);

            subInfo.arrPos = subscribers.length - 1;
            subInfo.subscribed = true;

            emit Subscribed(msg.sender);
        }
    }

    /// @notice Called by the users DSProxy
    /// @dev Owner who subscribed cancels his subscription
    function unsubscribe() external {
        _unsubscribe(msg.sender);
    }

    /// @dev Checks limit if minRatio is bigger than max
    /// @param _minRatio Minimum ratio, bellow which repay can be triggered
    /// @param _maxRatio Maximum ratio, over which boost can be triggered
    /// @return Returns bool if the params are correct
    function checkParams(uint128 _minRatio, uint128 _maxRatio) internal pure returns (bool) {

        if (_minRatio > _maxRatio) {
            return false;
        }

        return true;
    }

    /// @dev Internal method to remove a subscriber from the list
    /// @param _user The actual address that owns the Compound position
    function _unsubscribe(address _user) internal {
        require(subscribers.length > 0, "Must have subscribers in the list");

        SubPosition storage subInfo = subscribersPos[_user];

        require(subInfo.subscribed, "Must first be subscribed");

        address lastOwner = subscribers[subscribers.length - 1].user;

        SubPosition storage subInfo2 = subscribersPos[lastOwner];
        subInfo2.arrPos = subInfo.arrPos;

        subscribers[subInfo.arrPos] = subscribers[subscribers.length - 1];
        subscribers.pop(); // remove last element and reduce arr length

        changeIndex++;
        subInfo.subscribed = false;
        subInfo.arrPos = 0;

        emit Unsubscribed(msg.sender);
    }

    /// @dev Checks if the user is subscribed
    /// @param _user The actual address that owns the Compound position
    /// @return If the user is subscribed
    function isSubscribed(address _user) public view returns (bool) {
        SubPosition storage subInfo = subscribersPos[_user];

        return subInfo.subscribed;
    }

    /// @dev Returns subscribtion information about a user
    /// @param _user The actual address that owns the Compound position
    /// @return Subscription information about the user if exists
    function getHolder(address _user) public view returns (CompoundHolder memory) {
        SubPosition storage subInfo = subscribersPos[_user];

        return subscribers[subInfo.arrPos];
    }

    /// @notice Helper method to return all the subscribed CDPs
    /// @return List of all subscribers
    function getSubscribers() public view returns (CompoundHolder[] memory) {
        return subscribers;
    }

    /// @notice Helper method for the frontend, returns all the subscribed CDPs paginated
    /// @param _page What page of subscribers you want
    /// @param _perPage Number of entries per page
    /// @return List of all subscribers for that page
    function getSubscribersByPage(uint _page, uint _perPage) public view returns (CompoundHolder[] memory) {
        CompoundHolder[] memory holders = new CompoundHolder[](_perPage);

        uint start = _page * _perPage;
        uint end = start + _perPage;

        end = (end > holders.length) ? holders.length : end;

        uint count = 0;
        for (uint i = start; i < end; i++) {
            holders[count] = subscribers[i];
            count++;
        }

        return holders;
    }

    ////////////// ADMIN METHODS ///////////////////

    /// @notice Admin function to unsubscribe a CDP
    /// @param _user The actual address that owns the Compound position
    function unsubscribeByAdmin(address _user) public onlyOwner {
        SubPosition storage subInfo = subscribersPos[_user];

        if (subInfo.subscribed) {
            _unsubscribe(_user);
        }
    }
}