// File: contracts/CollSurplusPool.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import "./Interfaces/ICollSurplusPool.sol";
import "./Dependencies/SafeMath.sol";
import "./Dependencies/Ownable.sol";
import "./Dependencies/CheckContract.sol";

contract CollSurplusPool is Ownable, CheckContract, ICollSurplusPool {
    using SafeMath for uint256;

    string public constant NAME = "CollSurplusPool";

    address public borrowerOperationsAddress;
    address public troveManagerAddress;
    address public activePoolAddress;

    // deposited ether tracker
    uint256 internal ETH;
    // Collateral surplus claimable by trove owners
    mapping(address => uint256) internal balances;

    // --- Contract setters ---

    function setAddresses(
        address _borrowerOperationsAddress,
        address _troveManagerAddress,
        address _activePoolAddress
    ) external override onlyOwner {
        checkContract(_borrowerOperationsAddress);
        checkContract(_troveManagerAddress);
        checkContract(_activePoolAddress);

        borrowerOperationsAddress = _borrowerOperationsAddress;
        troveManagerAddress = _troveManagerAddress;
        activePoolAddress = _activePoolAddress;

        emit BorrowerOperationsAddressChanged(_borrowerOperationsAddress);
        emit TroveManagerAddressChanged(_troveManagerAddress);
        emit ActivePoolAddressChanged(_activePoolAddress);

        _renounceOwnership();
    }

    /* Returns the ETH state variable at ActivePool address.
       Not necessarily equal to the raw ether balance - ether can be forcibly sent to contracts. */
    function getETH() external view override returns (uint256) {
        return ETH;
    }

    function getCollateral(address _account) external view override returns (uint256) {
        return balances[_account];
    }

    // --- Pool functionality ---

    function accountSurplus(address _account, uint256 _amount) external override {
        _requireCallerIsTroveManager();

        uint256 newAmount = balances[_account].add(_amount);
        balances[_account] = newAmount;

        emit CollBalanceUpdated(_account, newAmount);
    }

    function claimColl(address _account) external override {
        _requireCallerIsBorrowerOperations();
        uint256 claimableColl = balances[_account];
        require(claimableColl > 0, "CollSurplusPool: No collateral available to claim");

        balances[_account] = 0;
        emit CollBalanceUpdated(_account, 0);

        ETH = ETH.sub(claimableColl);
        emit EtherSent(_account, claimableColl);

        (bool success, ) = _account.call{value: claimableColl}("");
        require(success, "CollSurplusPool: sending ETH failed");
    }

    // --- 'require' functions ---

    function _requireCallerIsBorrowerOperations() internal view {
        require(
            msg.sender == borrowerOperationsAddress,
            "CollSurplusPool: Caller is not Borrower Operations"
        );
    }

    function _requireCallerIsTroveManager() internal view {
        require(msg.sender == troveManagerAddress, "CollSurplusPool: Caller is not TroveManager");
    }

    function _requireCallerIsActivePool() internal view {
        require(msg.sender == activePoolAddress, "CollSurplusPool: Caller is not Active Pool");
    }

    // --- Fallback function ---

    receive() external payable {
        _requireCallerIsActivePool();
        ETH = ETH.add(msg.value);
    }
}

// File: contracts/Interfaces/ICollSurplusPool.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

interface ICollSurplusPool {
    // --- Events ---

    event BorrowerOperationsAddressChanged(address _newBorrowerOperationsAddress);
    event TroveManagerAddressChanged(address _newTroveManagerAddress);
    event ActivePoolAddressChanged(address _newActivePoolAddress);

    event CollBalanceUpdated(address indexed _account, uint256 _newBalance);
    event EtherSent(address _to, uint256 _amount);

    // --- Contract setters ---

    function setAddresses(
        address _borrowerOperationsAddress,
        address _troveManagerAddress,
        address _activePoolAddress
    ) external;

    function getETH() external view returns (uint256);

    function getCollateral(address _account) external view returns (uint256);

    function accountSurplus(address _account, uint256 _amount) external;

    function claimColl(address _account) external;
}

// File: contracts/Dependencies/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/**
 * Based on OpenZeppelin's SafeMath:
 * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/math/SafeMath.sol
 *
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    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;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        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;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: contracts/Dependencies/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/**
 * Based on OpenZeppelin's Ownable contract:
 * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol
 *
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract Ownable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), msg.sender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return msg.sender == _owner;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     *
     * NOTE: This function is not safe, as it doesn’t check owner is calling it.
     * Make sure you check it before calling it.
     */
    function _renounceOwnership() internal {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: contracts/Dependencies/CheckContract.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

contract CheckContract {
    /**
     * Check that the account is an already deployed non-destroyed contract.
     * See: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Address.sol#L12
     */
    function checkContract(address _account) internal view {
        require(_account != address(0), "Account cannot be zero address");

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(_account)
        }
        require(size > 0, "Account code size cannot be zero");
    }
}