/* ===============================================
* Flattened with Solidifier by Coinage
* 
* https://solidifier.coina.ge
* ===============================================
*/


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Owned.sol
version:    1.1
author:     Anton Jurisevic
            Dominic Romanowski

date:       2018-2-26

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

An Owned contract, to be inherited by other contracts.
Requires its owner to be explicitly set in the constructor.
Provides an onlyOwner access modifier.

To change owner, the current owner must nominate the next owner,
who then has to accept the nomination. The nomination can be
cancelled before it is accepted by the new owner by having the
previous owner change the nomination (setting it to 0).

-----------------------------------------------------------------
*/

pragma solidity 0.4.25;

/**
 * @title A contract with an owner.
 * @notice Contract ownership can be transferred by first nominating the new owner,
 * who must then accept the ownership, which prevents accidental incorrect ownership transfers.
 */
contract Owned {
    address public owner;
    address public nominatedOwner;

    /**
     * @dev Owned Constructor
     */
    constructor(address _owner)
        public
    {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    /**
     * @notice Nominate a new owner of this contract.
     * @dev Only the current owner may nominate a new owner.
     */
    function nominateNewOwner(address _owner)
        external
        onlyOwner
    {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    /**
     * @notice Accept the nomination to be owner.
     */
    function acceptOwnership()
        external
    {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner
    {
        require(msg.sender == owner, "Only the contract owner may perform this action");
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Proxy.sol
version:    1.3
author:     Anton Jurisevic

date:       2018-05-29

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxy contract that, if it does not recognise the function
being called on it, passes all value and call data to an
underlying target contract.

This proxy has the capacity to toggle between DELEGATECALL
and CALL style proxy functionality.

The former executes in the proxy's context, and so will preserve 
msg.sender and store data at the proxy address. The latter will not.
Therefore, any contract the proxy wraps in the CALL style must
implement the Proxyable interface, in order that it can pass msg.sender
into the underlying contract as the state parameter, messageSender.

-----------------------------------------------------------------
*/


contract Proxy is Owned {

    Proxyable public target;
    bool public useDELEGATECALL;

    constructor(address _owner)
        Owned(_owner)
        public
    {}

    function setTarget(Proxyable _target)
        external
        onlyOwner
    {
        target = _target;
        emit TargetUpdated(_target);
    }

    function setUseDELEGATECALL(bool value) 
        external
        onlyOwner
    {
        useDELEGATECALL = value;
    }

    function _emit(bytes callData, uint numTopics, bytes32 topic1, bytes32 topic2, bytes32 topic3, bytes32 topic4)
        external
        onlyTarget
    {
        uint size = callData.length;
        bytes memory _callData = callData;

        assembly {
            /* The first 32 bytes of callData contain its length (as specified by the abi). 
             * Length is assumed to be a uint256 and therefore maximum of 32 bytes
             * in length. It is also leftpadded to be a multiple of 32 bytes.
             * This means moving call_data across 32 bytes guarantees we correctly access
             * the data itself. */
            switch numTopics
            case 0 {
                log0(add(_callData, 32), size)
            } 
            case 1 {
                log1(add(_callData, 32), size, topic1)
            }
            case 2 {
                log2(add(_callData, 32), size, topic1, topic2)
            }
            case 3 {
                log3(add(_callData, 32), size, topic1, topic2, topic3)
            }
            case 4 {
                log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
            }
        }
    }

    function()
        external
        payable
    {
        if (useDELEGATECALL) {
            assembly {
                /* Copy call data into free memory region. */
                let free_ptr := mload(0x40)
                calldatacopy(free_ptr, 0, calldatasize)

                /* Forward all gas and call data to the target contract. */
                let result := delegatecall(gas, sload(target_slot), free_ptr, calldatasize, 0, 0)
                returndatacopy(free_ptr, 0, returndatasize)

                /* Revert if the call failed, otherwise return the result. */
                if iszero(result) { revert(free_ptr, returndatasize) }
                return(free_ptr, returndatasize)
            }
        } else {
            /* Here we are as above, but must send the messageSender explicitly 
             * since we are using CALL rather than DELEGATECALL. */
            target.setMessageSender(msg.sender);
            assembly {
                let free_ptr := mload(0x40)
                calldatacopy(free_ptr, 0, calldatasize)

                /* We must explicitly forward ether to the underlying contract as well. */
                let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
                returndatacopy(free_ptr, 0, returndatasize)

                if iszero(result) { revert(free_ptr, returndatasize) }
                return(free_ptr, returndatasize)
            }
        }
    }

    modifier onlyTarget {
        require(Proxyable(msg.sender) == target, "Must be proxy target");
        _;
    }

    event TargetUpdated(Proxyable newTarget);
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       Proxyable.sol
version:    1.1
author:     Anton Jurisevic

date:       2018-05-15

checked:    Mike Spain
approved:   Samuel Brooks

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxyable contract that works hand in hand with the Proxy contract
to allow for anyone to interact with the underlying contract both
directly and through the proxy.

-----------------------------------------------------------------
*/


// This contract should be treated like an abstract contract
contract Proxyable is Owned {
    /* The proxy this contract exists behind. */
    Proxy public proxy;
    Proxy public integrationProxy;

    /* The caller of the proxy, passed through to this contract.
     * Note that every function using this member must apply the onlyProxy or
     * optionalProxy modifiers, otherwise their invocations can use stale values. */
    address messageSender;

    constructor(address _proxy, address _owner)
        Owned(_owner)
        public
    {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setProxy(address _proxy)
        external
        onlyOwner
    {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setIntegrationProxy(address _integrationProxy)
        external
        onlyOwner
    {
        integrationProxy = Proxy(_integrationProxy);
    }

    function setMessageSender(address sender)
        external
        onlyProxy
    {
        messageSender = sender;
    }

    modifier onlyProxy {
        require(Proxy(msg.sender) == proxy || Proxy(msg.sender) == integrationProxy, "Only the proxy can call");
        _;
    }

    modifier optionalProxy
    {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy) {
            messageSender = msg.sender;
        }
        _;
    }

    modifier optionalProxy_onlyOwner
    {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy) {
            messageSender = msg.sender;
        }
        require(messageSender == owner, "Owner only function");
        _;
    }

    event ProxyUpdated(address proxyAddress);
}


/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract IERC20 {
    function totalSupply() public view returns (uint);

    function balanceOf(address owner) public view returns (uint);

    function allowance(address owner, address spender) public view returns (uint);

    function transfer(address to, uint value) public returns (bool);

    function approve(address spender, uint value) public returns (bool);

    function transferFrom(address from, address to, uint value) public returns (bool);

    // ERC20 Optional
    function name() public view returns (string);
    function symbol() public view returns (string);
    function decimals() public view returns (uint8);

    event Transfer(
      address indexed from,
      address indexed to,
      uint value
    );

    event Approval(
      address indexed owner,
      address indexed spender,
      uint value
    );
}


/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------

file:       ProxyERC20.sol
version:    1.0
author:     Jackson Chan, Clinton Ennis

date:       2019-06-19

-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------

A proxy contract that is ERC20 compliant for the Synthetix Network.

If it does not recognise a function being called on it, passes all
value and call data to an underlying target contract.

The ERC20 standard has been explicitly implemented to ensure
contract to contract calls are compatable on MAINNET

-----------------------------------------------------------------
*/


contract ProxyERC20 is Proxy, IERC20 {

    constructor(address _owner)
        Proxy(_owner)
        public
    {}

    // ------------- ERC20 Details ------------- //

    function name() public view returns (string){
        // Immutable static call from target contract
        return IERC20(target).name();
    }

    function symbol() public view returns (string){
         // Immutable static call from target contract
        return IERC20(target).symbol();
    }

    function decimals() public view returns (uint8){
         // Immutable static call from target contract
        return IERC20(target).decimals();
    }

    // ------------- ERC20 Interface ------------- //

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        // Immutable static call from target contract
        return IERC20(target).totalSupply();
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param owner The address to query the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address owner) public view returns (uint256) {
        // Immutable static call from target contract
        return IERC20(target).balanceOf(owner);
    }

    /**
    * @dev Function to check the amount of tokens that an owner allowed to a spender.
    * @param owner address The address which owns the funds.
    * @param spender address The address which will spend the funds.
    * @return A uint256 specifying the amount of tokens still available for the spender.
    */
    function allowance(
        address owner,
        address spender
    )
        public
        view
        returns (uint256)
    {
        // Immutable static call from target contract
        return IERC20(target).allowance(owner, spender);
    }

    /**
    * @dev Transfer token for a specified address
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function transfer(address to, uint256 value) public returns (bool) {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).transfer(to, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }

    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    * 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
    * @param spender The address which will spend the funds.
    * @param value The amount of tokens to be spent.
    */
    function approve(address spender, uint256 value) public returns (bool) {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).approve(spender, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }

    /**
    * @dev Transfer tokens from one address to another
    * @param from address The address which you want to send tokens from
    * @param to address The address which you want to transfer to
    * @param value uint256 the amount of tokens to be transferred
    */
    function transferFrom(
        address from,
        address to,
        uint256 value
    )
        public
        returns (bool)
    {
        // Mutable state call requires the proxy to tell the target who the msg.sender is.
        target.setMessageSender(msg.sender);

        // Forward the ERC20 call to the target contract
        IERC20(target).transferFrom(from, to, value);

        // Event emitting will occur via Synthetix.Proxy._emit()
        return true;
    }
}

/*

⚠⚠⚠ WARNING WARNING WARNING ⚠⚠⚠

This is a TARGET contract - DO NOT CONNECT TO IT DIRECTLY IN YOUR CONTRACTS or DAPPS!

This contract has an associated PROXY that MUST be used for all integrations - this TARGET will be REPLACED in an upcoming Synthetix release!
The proxy for this contract can be found here:

https://contracts.synthetix.io/ProxyERC20

*//*
   ____            __   __        __   _
  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: Synthetix.sol
*
* Latest source (may be newer): https://github.com/Synthetixio/synthetix/blob/master/contracts/Synthetix.sol
* Docs: https://docs.synthetix.io/contracts/Synthetix
*
* Contract Dependencies: 
*	- ExternStateToken
*	- IAddressResolver
*	- IERC20
*	- ISynthetix
*	- MixinResolver
*	- Owned
*	- Proxyable
*	- SelfDestructible
*	- State
* Libraries: 
*	- Math
*	- SafeDecimalMath
*	- SafeMath
*
* MIT License
* ===========
*
* Copyright (c) 2020 Synthetix
*
* Permission is hereby granted, free of charge, 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.
*
* 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
*/



pragma solidity >=0.4.24;


interface IERC20 {
    // ERC20 Optional Views
    function name() external view returns (string memory);

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

    function decimals() external view returns (uint8);

    // Views
    function totalSupply() external view returns (uint);

    function balanceOf(address owner) external view returns (uint);

    function allowance(address owner, address spender) external view returns (uint);

    // Mutative functions
    function transfer(address to, uint value) external returns (bool);

    function approve(address spender, uint value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Events
    event Transfer(address indexed from, address indexed to, uint value);

    event Approval(address indexed owner, address indexed spender, uint value);
}


// https://docs.synthetix.io/contracts/Owned
contract Owned {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

    function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner {
        require(msg.sender == owner, "Only the contract owner may perform this action");
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}


// Inheritance


// https://docs.synthetix.io/contracts/SelfDestructible
contract SelfDestructible is Owned {
    uint public constant SELFDESTRUCT_DELAY = 4 weeks;

    uint public initiationTime;
    bool public selfDestructInitiated;

    address public selfDestructBeneficiary;

    constructor() internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");
        selfDestructBeneficiary = owner;
        emit SelfDestructBeneficiaryUpdated(owner);
    }

    /**
     * @notice Set the beneficiary address of this contract.
     * @dev Only the contract owner may call this. The provided beneficiary must be non-null.
     * @param _beneficiary The address to pay any eth contained in this contract to upon self-destruction.
     */
    function setSelfDestructBeneficiary(address payable _beneficiary) external onlyOwner {
        require(_beneficiary != address(0), "Beneficiary must not be zero");
        selfDestructBeneficiary = _beneficiary;
        emit SelfDestructBeneficiaryUpdated(_beneficiary);
    }

    /**
     * @notice Begin the self-destruction counter of this contract.
     * Once the delay has elapsed, the contract may be self-destructed.
     * @dev Only the contract owner may call this.
     */
    function initiateSelfDestruct() external onlyOwner {
        initiationTime = now;
        selfDestructInitiated = true;
        emit SelfDestructInitiated(SELFDESTRUCT_DELAY);
    }

    /**
     * @notice Terminate and reset the self-destruction timer.
     * @dev Only the contract owner may call this.
     */
    function terminateSelfDestruct() external onlyOwner {
        initiationTime = 0;
        selfDestructInitiated = false;
        emit SelfDestructTerminated();
    }

    /**
     * @notice If the self-destruction delay has elapsed, destroy this contract and
     * remit any ether it owns to the beneficiary address.
     * @dev Only the contract owner may call this.
     */
    function selfDestruct() external onlyOwner {
        require(selfDestructInitiated, "Self Destruct not yet initiated");
        require(initiationTime + SELFDESTRUCT_DELAY < now, "Self destruct delay not met");
        emit SelfDestructed(selfDestructBeneficiary);
        selfdestruct(address(uint160(selfDestructBeneficiary)));
    }

    event SelfDestructTerminated();
    event SelfDestructed(address beneficiary);
    event SelfDestructInitiated(uint selfDestructDelay);
    event SelfDestructBeneficiaryUpdated(address newBeneficiary);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/Proxy
contract Proxy is Owned {
    Proxyable public target;

    constructor(address _owner) public Owned(_owner) {}

    function setTarget(Proxyable _target) external onlyOwner {
        target = _target;
        emit TargetUpdated(_target);
    }

    function _emit(
        bytes calldata callData,
        uint numTopics,
        bytes32 topic1,
        bytes32 topic2,
        bytes32 topic3,
        bytes32 topic4
    ) external onlyTarget {
        uint size = callData.length;
        bytes memory _callData = callData;

        assembly {
            /* The first 32 bytes of callData contain its length (as specified by the abi).
             * Length is assumed to be a uint256 and therefore maximum of 32 bytes
             * in length. It is also leftpadded to be a multiple of 32 bytes.
             * This means moving call_data across 32 bytes guarantees we correctly access
             * the data itself. */
            switch numTopics
                case 0 {
                    log0(add(_callData, 32), size)
                }
                case 1 {
                    log1(add(_callData, 32), size, topic1)
                }
                case 2 {
                    log2(add(_callData, 32), size, topic1, topic2)
                }
                case 3 {
                    log3(add(_callData, 32), size, topic1, topic2, topic3)
                }
                case 4 {
                    log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
                }
        }
    }

    // solhint-disable no-complex-fallback
    function() external payable {
        // Mutable call setting Proxyable.messageSender as this is using call not delegatecall
        target.setMessageSender(msg.sender);

        assembly {
            let free_ptr := mload(0x40)
            calldatacopy(free_ptr, 0, calldatasize)

            /* We must explicitly forward ether to the underlying contract as well. */
            let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
            returndatacopy(free_ptr, 0, returndatasize)

            if iszero(result) {
                revert(free_ptr, returndatasize)
            }
            return(free_ptr, returndatasize)
        }
    }

    modifier onlyTarget {
        require(Proxyable(msg.sender) == target, "Must be proxy target");
        _;
    }

    event TargetUpdated(Proxyable newTarget);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/Proxyable
contract Proxyable is Owned {
    // This contract should be treated like an abstract contract

    /* The proxy this contract exists behind. */
    Proxy public proxy;
    Proxy public integrationProxy;

    /* The caller of the proxy, passed through to this contract.
     * Note that every function using this member must apply the onlyProxy or
     * optionalProxy modifiers, otherwise their invocations can use stale values. */
    address public messageSender;

    constructor(address payable _proxy) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setProxy(address payable _proxy) external onlyOwner {
        proxy = Proxy(_proxy);
        emit ProxyUpdated(_proxy);
    }

    function setIntegrationProxy(address payable _integrationProxy) external onlyOwner {
        integrationProxy = Proxy(_integrationProxy);
    }

    function setMessageSender(address sender) external onlyProxy {
        messageSender = sender;
    }

    modifier onlyProxy {
        require(Proxy(msg.sender) == proxy || Proxy(msg.sender) == integrationProxy, "Only the proxy can call");
        _;
    }

    modifier optionalProxy {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
        _;
    }

    modifier optionalProxy_onlyOwner {
        if (Proxy(msg.sender) != proxy && Proxy(msg.sender) != integrationProxy && messageSender != msg.sender) {
            messageSender = msg.sender;
        }
        require(messageSender == owner, "Owner only function");
        _;
    }

    event ProxyUpdated(address proxyAddress);
}


/**
 * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        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-solidity/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) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        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) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}


// Libraries


// https://docs.synthetix.io/contracts/SafeDecimalMath
library SafeDecimalMath {
    using SafeMath for uint;

    /* Number of decimal places in the representations. */
    uint8 public constant decimals = 18;
    uint8 public constant highPrecisionDecimals = 27;

    /* The number representing 1.0. */
    uint public constant UNIT = 10**uint(decimals);

    /* The number representing 1.0 for higher fidelity numbers. */
    uint public constant PRECISE_UNIT = 10**uint(highPrecisionDecimals);
    uint private constant UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR = 10**uint(highPrecisionDecimals - decimals);

    /**
     * @return Provides an interface to UNIT.
     */
    function unit() external pure returns (uint) {
        return UNIT;
    }

    /**
     * @return Provides an interface to PRECISE_UNIT.
     */
    function preciseUnit() external pure returns (uint) {
        return PRECISE_UNIT;
    }

    /**
     * @return The result of multiplying x and y, interpreting the operands as fixed-point
     * decimals.
     *
     * @dev A unit factor is divided out after the product of x and y is evaluated,
     * so that product must be less than 2**256. As this is an integer division,
     * the internal division always rounds down. This helps save on gas. Rounding
     * is more expensive on gas.
     */
    function multiplyDecimal(uint x, uint y) internal pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        return x.mul(y) / UNIT;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of the specified precision unit.
     *
     * @dev The operands should be in the form of a the specified unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function _multiplyDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        /* Divide by UNIT to remove the extra factor introduced by the product. */
        uint quotientTimesTen = x.mul(y) / (precisionUnit / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a precise unit.
     *
     * @dev The operands should be in the precise unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @return The result of safely multiplying x and y, interpreting the operands
     * as fixed-point decimals of a standard unit.
     *
     * @dev The operands should be in the standard unit factor which will be
     * divided out after the product of x and y is evaluated, so that product must be
     * less than 2**256.
     *
     * Unlike multiplyDecimal, this function rounds the result to the nearest increment.
     * Rounding is useful when you need to retain fidelity for small decimal numbers
     * (eg. small fractions or percentages).
     */
    function multiplyDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _multiplyDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is a high
     * precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and UNIT must be less than 2**256. As
     * this is an integer division, the result is always rounded down.
     * This helps save on gas. Rounding is more expensive on gas.
     */
    function divideDecimal(uint x, uint y) internal pure returns (uint) {
        /* Reintroduce the UNIT factor that will be divided out by y. */
        return x.mul(UNIT).div(y);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * decimal in the precision unit specified in the parameter.
     *
     * @dev y is divided after the product of x and the specified precision unit
     * is evaluated, so the product of x and the specified precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function _divideDecimalRound(
        uint x,
        uint y,
        uint precisionUnit
    ) private pure returns (uint) {
        uint resultTimesTen = x.mul(precisionUnit * 10).div(y);

        if (resultTimesTen % 10 >= 5) {
            resultTimesTen += 10;
        }

        return resultTimesTen / 10;
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * standard precision decimal.
     *
     * @dev y is divided after the product of x and the standard precision unit
     * is evaluated, so the product of x and the standard precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRound(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, UNIT);
    }

    /**
     * @return The result of safely dividing x and y. The return value is as a rounded
     * high precision decimal.
     *
     * @dev y is divided after the product of x and the high precision unit
     * is evaluated, so the product of x and the high precision unit must
     * be less than 2**256. The result is rounded to the nearest increment.
     */
    function divideDecimalRoundPrecise(uint x, uint y) internal pure returns (uint) {
        return _divideDecimalRound(x, y, PRECISE_UNIT);
    }

    /**
     * @dev Convert a standard decimal representation to a high precision one.
     */
    function decimalToPreciseDecimal(uint i) internal pure returns (uint) {
        return i.mul(UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR);
    }

    /**
     * @dev Convert a high precision decimal to a standard decimal representation.
     */
    function preciseDecimalToDecimal(uint i) internal pure returns (uint) {
        uint quotientTimesTen = i / (UNIT_TO_HIGH_PRECISION_CONVERSION_FACTOR / 10);

        if (quotientTimesTen % 10 >= 5) {
            quotientTimesTen += 10;
        }

        return quotientTimesTen / 10;
    }
}


// Inheritance


// https://docs.synthetix.io/contracts/State
contract State is Owned {
    // the address of the contract that can modify variables
    // this can only be changed by the owner of this contract
    address public associatedContract;

    constructor(address _associatedContract) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== SETTERS ========== */

    // Change the associated contract to a new address
    function setAssociatedContract(address _associatedContract) external onlyOwner {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== MODIFIERS ========== */

    modifier onlyAssociatedContract {
        require(msg.sender == associatedContract, "Only the associated contract can perform this action");
        _;
    }

    /* ========== EVENTS ========== */

    event AssociatedContractUpdated(address associatedContract);
}


// Inheritance


// https://docs.synthetix.io/contracts/TokenState
contract TokenState is Owned, State {
    /* ERC20 fields. */
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint)) public allowance;

    constructor(address _owner, address _associatedContract) public Owned(_owner) State(_associatedContract) {}

    /* ========== SETTERS ========== */

    /**
     * @notice Set ERC20 allowance.
     * @dev Only the associated contract may call this.
     * @param tokenOwner The authorising party.
     * @param spender The authorised party.
     * @param value The total value the authorised party may spend on the
     * authorising party's behalf.
     */
    function setAllowance(
        address tokenOwner,
        address spender,
        uint value
    ) external onlyAssociatedContract {
        allowance[tokenOwner][spender] = value;
    }

    /**
     * @notice Set the balance in a given account
     * @dev Only the associated contract may call this.
     * @param account The account whose value to set.
     * @param value The new balance of the given account.
     */
    function setBalanceOf(address account, uint value) external onlyAssociatedContract {
        balanceOf[account] = value;
    }
}


// Inheritance


// Libraries


// Internal references


// https://docs.synthetix.io/contracts/ExternStateToken
contract ExternStateToken is Owned, SelfDestructible, Proxyable {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    /* ========== STATE VARIABLES ========== */

    /* Stores balances and allowances. */
    TokenState public tokenState;

    /* Other ERC20 fields. */
    string public name;
    string public symbol;
    uint public totalSupply;
    uint8 public decimals;

    constructor(
        address payable _proxy,
        TokenState _tokenState,
        string memory _name,
        string memory _symbol,
        uint _totalSupply,
        uint8 _decimals,
        address _owner
    ) public Owned(_owner) SelfDestructible() Proxyable(_proxy) {
        tokenState = _tokenState;

        name = _name;
        symbol = _symbol;
        totalSupply = _totalSupply;
        decimals = _decimals;
    }

    /* ========== VIEWS ========== */

    /**
     * @notice Returns the ERC20 allowance of one party to spend on behalf of another.
     * @param owner The party authorising spending of their funds.
     * @param spender The party spending tokenOwner's funds.
     */
    function allowance(address owner, address spender) public view returns (uint) {
        return tokenState.allowance(owner, spender);
    }

    /**
     * @notice Returns the ERC20 token balance of a given account.
     */
    function balanceOf(address account) external view returns (uint) {
        return tokenState.balanceOf(account);
    }

    /* ========== MUTATIVE FUNCTIONS ========== */

    /**
     * @notice Set the address of the TokenState contract.
     * @dev This can be used to "pause" transfer functionality, by pointing the tokenState at 0x000..
     * as balances would be unreachable.
     */
    function setTokenState(TokenState _tokenState) external optionalProxy_onlyOwner {
        tokenState = _tokenState;
        emitTokenStateUpdated(address(_tokenState));
    }

    function _internalTransfer(
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        /* Disallow transfers to irretrievable-addresses. */
        require(to != address(0) && to != address(this) && to != address(proxy), "Cannot transfer to this address");

        // Insufficient balance will be handled by the safe subtraction.
        tokenState.setBalanceOf(from, tokenState.balanceOf(from).sub(value));
        tokenState.setBalanceOf(to, tokenState.balanceOf(to).add(value));

        // Emit a standard ERC20 transfer event
        emitTransfer(from, to, value);

        return true;
    }

    /**
     * @dev Perform an ERC20 token transfer. Designed to be called by transfer functions possessing
     * the onlyProxy or optionalProxy modifiers.
     */
    function _transferByProxy(
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        return _internalTransfer(from, to, value);
    }

    /*
     * @dev Perform an ERC20 token transferFrom. Designed to be called by transferFrom functions
     * possessing the optionalProxy or optionalProxy modifiers.
     */
    function _transferFromByProxy(
        address sender,
        address from,
        address to,
        uint value
    ) internal returns (bool) {
        /* Insufficient allowance will be handled by the safe subtraction. */
        tokenState.setAllowance(from, sender, tokenState.allowance(from, sender).sub(value));
        return _internalTransfer(from, to, value);
    }

    /**
     * @notice Approves spender to transfer on the message sender's behalf.
     */
    function approve(address spender, uint value) public optionalProxy returns (bool) {
        address sender = messageSender;

        tokenState.setAllowance(sender, spender, value);
        emitApproval(sender, spender, value);
        return true;
    }

    /* ========== EVENTS ========== */
    function addressToBytes32(address input) internal pure returns (bytes32) {
        return bytes32(uint256(uint160(input)));
    }

    event Transfer(address indexed from, address indexed to, uint value);
    bytes32 internal constant TRANSFER_SIG = keccak256("Transfer(address,address,uint256)");

    function emitTransfer(
        address from,
        address to,
        uint value
    ) internal {
        proxy._emit(abi.encode(value), 3, TRANSFER_SIG, addressToBytes32(from), addressToBytes32(to), 0);
    }

    event Approval(address indexed owner, address indexed spender, uint value);
    bytes32 internal constant APPROVAL_SIG = keccak256("Approval(address,address,uint256)");

    function emitApproval(
        address owner,
        address spender,
        uint value
    ) internal {
        proxy._emit(abi.encode(value), 3, APPROVAL_SIG, addressToBytes32(owner), addressToBytes32(spender), 0);
    }

    event TokenStateUpdated(address newTokenState);
    bytes32 internal constant TOKENSTATEUPDATED_SIG = keccak256("TokenStateUpdated(address)");

    function emitTokenStateUpdated(address newTokenState) internal {
        proxy._emit(abi.encode(newTokenState), 1, TOKENSTATEUPDATED_SIG, 0, 0, 0);
    }
}


interface IAddressResolver {
    function getAddress(bytes32 name) external view returns (address);

    function getSynth(bytes32 key) external view returns (address);

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address);
}


interface ISynth {
    // Views
    function currencyKey() external view returns (bytes32);

    function transferableSynths(address account) external view returns (uint);

    // Mutative functions
    function transferAndSettle(address to, uint value) external returns (bool);

    function transferFromAndSettle(
        address from,
        address to,
        uint value
    ) external returns (bool);

    // Restricted: used internally to Synthetix
    function burn(address account, uint amount) external;

    function issue(address account, uint amount) external;
}


interface IIssuer {
    // Views
    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function canBurnSynths(address account) external view returns (bool);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function collateralisationRatioAndAnyRatesInvalid(address _issuer)
        external
        view
        returns (uint cratio, bool anyRateIsInvalid);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint debtBalance);

    function issuanceRatio() external view returns (uint);

    function lastIssueEvent(address account) external view returns (uint);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function minimumStakeTime() external view returns (uint);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey, bool excludeEtherCollateral) external view returns (uint);

    function transferableSynthetixAndAnyRateIsInvalid(address account, uint balance)
        external
        view
        returns (uint transferable, bool anyRateIsInvalid);

    // Restricted: used internally to Synthetix
    function issueSynths(address from, uint amount) external;

    function issueSynthsOnBehalf(
        address issueFor,
        address from,
        uint amount
    ) external;

    function issueMaxSynths(address from) external;

    function issueMaxSynthsOnBehalf(address issueFor, address from) external;

    function burnSynths(address from, uint amount) external;

    function burnSynthsOnBehalf(
        address burnForAddress,
        address from,
        uint amount
    ) external;

    function burnSynthsToTarget(address from) external;

    function burnSynthsToTargetOnBehalf(address burnForAddress, address from) external;

    function liquidateDelinquentAccount(
        address account,
        uint susdAmount,
        address liquidator
    ) external returns (uint totalRedeemed, uint amountToLiquidate);
}


// Inheritance


// https://docs.synthetix.io/contracts/AddressResolver
contract AddressResolver is Owned, IAddressResolver {
    mapping(bytes32 => address) public repository;

    constructor(address _owner) public Owned(_owner) {}

    /* ========== MUTATIVE FUNCTIONS ========== */

    function importAddresses(bytes32[] calldata names, address[] calldata destinations) external onlyOwner {
        require(names.length == destinations.length, "Input lengths must match");

        for (uint i = 0; i < names.length; i++) {
            repository[names[i]] = destinations[i];
        }
    }

    /* ========== VIEWS ========== */

    function getAddress(bytes32 name) external view returns (address) {
        return repository[name];
    }

    function requireAndGetAddress(bytes32 name, string calldata reason) external view returns (address) {
        address _foundAddress = repository[name];
        require(_foundAddress != address(0), reason);
        return _foundAddress;
    }

    function getSynth(bytes32 key) external view returns (address) {
        IIssuer issuer = IIssuer(repository["Issuer"]);
        require(address(issuer) != address(0), "Cannot find Issuer address");
        return address(issuer.synths(key));
    }
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/MixinResolver
contract MixinResolver is Owned {
    AddressResolver public resolver;

    mapping(bytes32 => address) private addressCache;

    bytes32[] public resolverAddressesRequired;

    uint public constant MAX_ADDRESSES_FROM_RESOLVER = 24;

    constructor(address _resolver, bytes32[MAX_ADDRESSES_FROM_RESOLVER] memory _addressesToCache) internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");

        for (uint i = 0; i < _addressesToCache.length; i++) {
            if (_addressesToCache[i] != bytes32(0)) {
                resolverAddressesRequired.push(_addressesToCache[i]);
            } else {
                // End early once an empty item is found - assumes there are no empty slots in
                // _addressesToCache
                break;
            }
        }
        resolver = AddressResolver(_resolver);
        // Do not sync the cache as addresses may not be in the resolver yet
    }

    /* ========== SETTERS ========== */
    function setResolverAndSyncCache(AddressResolver _resolver) external onlyOwner {
        resolver = _resolver;

        for (uint i = 0; i < resolverAddressesRequired.length; i++) {
            bytes32 name = resolverAddressesRequired[i];
            // Note: can only be invoked once the resolver has all the targets needed added
            addressCache[name] = resolver.requireAndGetAddress(name, "Resolver missing target");
        }
    }

    /* ========== VIEWS ========== */

    function requireAndGetAddress(bytes32 name, string memory reason) internal view returns (address) {
        address _foundAddress = addressCache[name];
        require(_foundAddress != address(0), reason);
        return _foundAddress;
    }

    // Note: this could be made external in a utility contract if addressCache was made public
    // (used for deployment)
    function isResolverCached(AddressResolver _resolver) external view returns (bool) {
        if (resolver != _resolver) {
            return false;
        }

        // otherwise, check everything
        for (uint i = 0; i < resolverAddressesRequired.length; i++) {
            bytes32 name = resolverAddressesRequired[i];
            // false if our cache is invalid or if the resolver doesn't have the required address
            if (resolver.getAddress(name) != addressCache[name] || addressCache[name] == address(0)) {
                return false;
            }
        }

        return true;
    }

    // Note: can be made external into a utility contract (used for deployment)
    function getResolverAddressesRequired()
        external
        view
        returns (bytes32[MAX_ADDRESSES_FROM_RESOLVER] memory addressesRequired)
    {
        for (uint i = 0; i < resolverAddressesRequired.length; i++) {
            addressesRequired[i] = resolverAddressesRequired[i];
        }
    }

    /* ========== INTERNAL FUNCTIONS ========== */
    function appendToAddressCache(bytes32 name) internal {
        resolverAddressesRequired.push(name);
        require(resolverAddressesRequired.length < MAX_ADDRESSES_FROM_RESOLVER, "Max resolver cache size met");
        // Because this is designed to be called internally in constructors, we don't
        // check the address exists already in the resolver
        addressCache[name] = resolver.getAddress(name);
    }
}


interface ISynthetix {
    // Views
    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid);

    function availableCurrencyKeys() external view returns (bytes32[] memory);

    function availableSynthCount() external view returns (uint);

    function availableSynths(uint index) external view returns (ISynth);

    function collateral(address account) external view returns (uint);

    function collateralisationRatio(address issuer) external view returns (uint);

    function debtBalanceOf(address issuer, bytes32 currencyKey) external view returns (uint);

    function isWaitingPeriod(bytes32 currencyKey) external view returns (bool);

    function maxIssuableSynths(address issuer) external view returns (uint maxIssuable);

    function remainingIssuableSynths(address issuer)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        );

    function synths(bytes32 currencyKey) external view returns (ISynth);

    function synthsByAddress(address synthAddress) external view returns (bytes32);

    function totalIssuedSynths(bytes32 currencyKey) external view returns (uint);

    function totalIssuedSynthsExcludeEtherCollateral(bytes32 currencyKey) external view returns (uint);

    function transferableSynthetix(address account) external view returns (uint transferable);

    // Mutative Functions
    function burnSynths(uint amount) external;

    function burnSynthsOnBehalf(address burnForAddress, uint amount) external;

    function burnSynthsToTarget() external;

    function burnSynthsToTargetOnBehalf(address burnForAddress) external;

    function exchange(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external returns (uint amountReceived);

    function exchangeOnBehalf(
        address exchangeForAddress,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external returns (uint amountReceived);

    function exchangeWithTracking(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address originator,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeOnBehalfWithTracking(
        address exchangeForAddress,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address originator,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function issueMaxSynths() external;

    function issueMaxSynthsOnBehalf(address issueForAddress) external;

    function issueSynths(uint amount) external;

    function issueSynthsOnBehalf(address issueForAddress, uint amount) external;

    function mint() external returns (bool);

    function settle(bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );

    function liquidateDelinquentAccount(address account, uint susdAmount) external returns (bool);
}


interface ISynthetixState {
    // Views
    function debtLedger(uint index) external view returns (uint);

    function issuanceData(address account) external view returns (uint initialDebtOwnership, uint debtEntryIndex);

    function debtLedgerLength() external view returns (uint);

    function hasIssued(address account) external view returns (bool);

    function lastDebtLedgerEntry() external view returns (uint);

    // Mutative functions
    function incrementTotalIssuerCount() external;

    function decrementTotalIssuerCount() external;

    function setCurrentIssuanceData(address account, uint initialDebtOwnership) external;

    function appendDebtLedgerValue(uint value) external;

    function clearIssuanceData(address account) external;
}


interface ISystemStatus {
    struct Status {
        bool canSuspend;
        bool canResume;
    }

    struct Suspension {
        bool suspended;
        // reason is an integer code,
        // 0 => no reason, 1 => upgrading, 2+ => defined by system usage
        uint248 reason;
    }

    // Views
    function accessControl(bytes32 section, address account) external view returns (bool canSuspend, bool canResume);

    function requireSystemActive() external view;

    function requireIssuanceActive() external view;

    function requireExchangeActive() external view;

    function requireSynthActive(bytes32 currencyKey) external view;

    function requireSynthsActive(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey) external view;

    function synthSuspension(bytes32 currencyKey) external view returns (bool suspended, uint248 reason);

    // Restricted functions
    function suspendSynth(bytes32 currencyKey, uint256 reason) external;

    function updateAccessControl(
        bytes32 section,
        address account,
        bool canSuspend,
        bool canResume
    ) external;
}


interface IExchanger {
    // Views
    function calculateAmountAfterSettlement(
        address from,
        bytes32 currencyKey,
        uint amount,
        uint refunded
    ) external view returns (uint amountAfterSettlement);

    function isSynthRateInvalid(bytes32 currencyKey) external view returns (bool);

    function maxSecsLeftInWaitingPeriod(address account, bytes32 currencyKey) external view returns (uint);

    function settlementOwing(address account, bytes32 currencyKey)
        external
        view
        returns (
            uint reclaimAmount,
            uint rebateAmount,
            uint numEntries
        );

    function hasWaitingPeriodOrSettlementOwing(address account, bytes32 currencyKey) external view returns (bool);

    function feeRateForExchange(bytes32 sourceCurrencyKey, bytes32 destinationCurrencyKey)
        external
        view
        returns (uint exchangeFeeRate);

    function getAmountsForExchange(
        uint sourceAmount,
        bytes32 sourceCurrencyKey,
        bytes32 destinationCurrencyKey
    )
        external
        view
        returns (
            uint amountReceived,
            uint fee,
            uint exchangeFeeRate
        );

    function priceDeviationThresholdFactor() external view returns (uint);

    function waitingPeriodSecs() external view returns (uint);

    // Mutative functions
    function exchange(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress
    ) external returns (uint amountReceived);

    function exchangeOnBehalf(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external returns (uint amountReceived);

    function exchangeWithTracking(
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address destinationAddress,
        address originator,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function exchangeOnBehalfWithTracking(
        address exchangeForAddress,
        address from,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address originator,
        bytes32 trackingCode
    ) external returns (uint amountReceived);

    function settle(address from, bytes32 currencyKey)
        external
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntries
        );

    function setLastExchangeRateForSynth(bytes32 currencyKey, uint rate) external;

    function suspendSynthWithInvalidRate(bytes32 currencyKey) external;
}


// Libraries


// https://docs.synthetix.io/contracts/Math
library Math {
    using SafeMath for uint;
    using SafeDecimalMath for uint;

    /**
     * @dev Uses "exponentiation by squaring" algorithm where cost is 0(logN)
     * vs 0(N) for naive repeated multiplication.
     * Calculates x^n with x as fixed-point and n as regular unsigned int.
     * Calculates to 18 digits of precision with SafeDecimalMath.unit()
     */
    function powDecimal(uint x, uint n) internal pure returns (uint) {
        // https://mpark.github.io/programming/2014/08/18/exponentiation-by-squaring/

        uint result = SafeDecimalMath.unit();
        while (n > 0) {
            if (n % 2 != 0) {
                result = result.multiplyDecimal(x);
            }
            x = x.multiplyDecimal(x);
            n /= 2;
        }
        return result;
    }
}


// Inheritance


// Libraries


// Internal references


// https://docs.synthetix.io/contracts/SupplySchedule
contract SupplySchedule is Owned {
    using SafeMath for uint;
    using SafeDecimalMath for uint;
    using Math for uint;

    // Time of the last inflation supply mint event
    uint public lastMintEvent;

    // Counter for number of weeks since the start of supply inflation
    uint public weekCounter;

    // The number of SNX rewarded to the caller of Synthetix.mint()
    uint public minterReward = 200 * SafeDecimalMath.unit();

    // The initial weekly inflationary supply is 75m / 52 until the start of the decay rate.
    // 75e6 * SafeDecimalMath.unit() / 52
    uint public constant INITIAL_WEEKLY_SUPPLY = 1442307692307692307692307;

    // Address of the SynthetixProxy for the onlySynthetix modifier
    address payable public synthetixProxy;

    // Max SNX rewards for minter
    uint public constant MAX_MINTER_REWARD = 200 * 1e18;

    // How long each inflation period is before mint can be called
    uint public constant MINT_PERIOD_DURATION = 1 weeks;

    uint public constant INFLATION_START_DATE = 1551830400; // 2019-03-06T00:00:00+00:00
    uint public constant MINT_BUFFER = 1 days;
    uint8 public constant SUPPLY_DECAY_START = 40; // Week 40
    uint8 public constant SUPPLY_DECAY_END = 234; //  Supply Decay ends on Week 234 (inclusive of Week 234 for a total of 195 weeks of inflation decay)

    // Weekly percentage decay of inflationary supply from the first 40 weeks of the 75% inflation rate
    uint public constant DECAY_RATE = 12500000000000000; // 1.25% weekly

    // Percentage growth of terminal supply per annum
    uint public constant TERMINAL_SUPPLY_RATE_ANNUAL = 25000000000000000; // 2.5% pa

    constructor(
        address _owner,
        uint _lastMintEvent,
        uint _currentWeek
    ) public Owned(_owner) {
        lastMintEvent = _lastMintEvent;
        weekCounter = _currentWeek;
    }

    // ========== VIEWS ==========

    /**
     * @return The amount of SNX mintable for the inflationary supply
     */
    function mintableSupply() external view returns (uint) {
        uint totalAmount;

        if (!isMintable()) {
            return totalAmount;
        }

        uint remainingWeeksToMint = weeksSinceLastIssuance();

        uint currentWeek = weekCounter;

        // Calculate total mintable supply from exponential decay function
        // The decay function stops after week 234
        while (remainingWeeksToMint > 0) {
            currentWeek++;

            if (currentWeek < SUPPLY_DECAY_START) {
                // If current week is before supply decay we add initial supply to mintableSupply
                totalAmount = totalAmount.add(INITIAL_WEEKLY_SUPPLY);
                remainingWeeksToMint--;
            } else if (currentWeek <= SUPPLY_DECAY_END) {
                // if current week before supply decay ends we add the new supply for the week
                // diff between current week and (supply decay start week - 1)
                uint decayCount = currentWeek.sub(SUPPLY_DECAY_START - 1);

                totalAmount = totalAmount.add(tokenDecaySupplyForWeek(decayCount));
                remainingWeeksToMint--;
            } else {
                // Terminal supply is calculated on the total supply of Synthetix including any new supply
                // We can compound the remaining week's supply at the fixed terminal rate
                uint totalSupply = IERC20(synthetixProxy).totalSupply();
                uint currentTotalSupply = totalSupply.add(totalAmount);

                totalAmount = totalAmount.add(terminalInflationSupply(currentTotalSupply, remainingWeeksToMint));
                remainingWeeksToMint = 0;
            }
        }

        return totalAmount;
    }

    /**
     * @return A unit amount of decaying inflationary supply from the INITIAL_WEEKLY_SUPPLY
     * @dev New token supply reduces by the decay rate each week calculated as supply = INITIAL_WEEKLY_SUPPLY * ()
     */
    function tokenDecaySupplyForWeek(uint counter) public pure returns (uint) {
        // Apply exponential decay function to number of weeks since
        // start of inflation smoothing to calculate diminishing supply for the week.
        uint effectiveDecay = (SafeDecimalMath.unit().sub(DECAY_RATE)).powDecimal(counter);
        uint supplyForWeek = INITIAL_WEEKLY_SUPPLY.multiplyDecimal(effectiveDecay);

        return supplyForWeek;
    }

    /**
     * @return A unit amount of terminal inflation supply
     * @dev Weekly compound rate based on number of weeks
     */
    function terminalInflationSupply(uint totalSupply, uint numOfWeeks) public pure returns (uint) {
        // rate = (1 + weekly rate) ^ num of weeks
        uint effectiveCompoundRate = SafeDecimalMath.unit().add(TERMINAL_SUPPLY_RATE_ANNUAL.div(52)).powDecimal(numOfWeeks);

        // return Supply * (effectiveRate - 1) for extra supply to issue based on number of weeks
        return totalSupply.multiplyDecimal(effectiveCompoundRate.sub(SafeDecimalMath.unit()));
    }

    /**
     * @dev Take timeDiff in seconds (Dividend) and MINT_PERIOD_DURATION as (Divisor)
     * @return Calculate the numberOfWeeks since last mint rounded down to 1 week
     */
    function weeksSinceLastIssuance() public view returns (uint) {
        // Get weeks since lastMintEvent
        // If lastMintEvent not set or 0, then start from inflation start date.
        uint timeDiff = lastMintEvent > 0 ? now.sub(lastMintEvent) : now.sub(INFLATION_START_DATE);
        return timeDiff.div(MINT_PERIOD_DURATION);
    }

    /**
     * @return boolean whether the MINT_PERIOD_DURATION (7 days)
     * has passed since the lastMintEvent.
     * */
    function isMintable() public view returns (bool) {
        if (now - lastMintEvent > MINT_PERIOD_DURATION) {
            return true;
        }
        return false;
    }

    // ========== MUTATIVE FUNCTIONS ==========

    /**
     * @notice Record the mint event from Synthetix by incrementing the inflation
     * week counter for the number of weeks minted (probabaly always 1)
     * and store the time of the event.
     * @param supplyMinted the amount of SNX the total supply was inflated by.
     * */
    function recordMintEvent(uint supplyMinted) external onlySynthetix returns (bool) {
        uint numberOfWeeksIssued = weeksSinceLastIssuance();

        // add number of weeks minted to weekCounter
        weekCounter = weekCounter.add(numberOfWeeksIssued);

        // Update mint event to latest week issued (start date + number of weeks issued * seconds in week)
        // 1 day time buffer is added so inflation is minted after feePeriod closes
        lastMintEvent = INFLATION_START_DATE.add(weekCounter.mul(MINT_PERIOD_DURATION)).add(MINT_BUFFER);

        emit SupplyMinted(supplyMinted, numberOfWeeksIssued, lastMintEvent, now);
        return true;
    }

    /**
     * @notice Sets the reward amount of SNX for the caller of the public
     * function Synthetix.mint().
     * This incentivises anyone to mint the inflationary supply and the mintr
     * Reward will be deducted from the inflationary supply and sent to the caller.
     * @param amount the amount of SNX to reward the minter.
     * */
    function setMinterReward(uint amount) external onlyOwner {
        require(amount <= MAX_MINTER_REWARD, "Reward cannot exceed max minter reward");
        minterReward = amount;
        emit MinterRewardUpdated(minterReward);
    }

    // ========== SETTERS ========== */

    /**
     * @notice Set the SynthetixProxy should it ever change.
     * SupplySchedule requires Synthetix address as it has the authority
     * to record mint event.
     * */
    function setSynthetixProxy(ISynthetix _synthetixProxy) external onlyOwner {
        require(address(_synthetixProxy) != address(0), "Address cannot be 0");
        synthetixProxy = address(uint160(address(_synthetixProxy)));
        emit SynthetixProxyUpdated(synthetixProxy);
    }

    // ========== MODIFIERS ==========

    /**
     * @notice Only the Synthetix contract is authorised to call this function
     * */
    modifier onlySynthetix() {
        require(
            msg.sender == address(Proxy(address(synthetixProxy)).target()),
            "Only the synthetix contract can perform this action"
        );
        _;
    }

    /* ========== EVENTS ========== */
    /**
     * @notice Emitted when the inflationary supply is minted
     * */
    event SupplyMinted(uint supplyMinted, uint numberOfWeeksIssued, uint lastMintEvent, uint timestamp);

    /**
     * @notice Emitted when the SNX minter reward amount is updated
     * */
    event MinterRewardUpdated(uint newRewardAmount);

    /**
     * @notice Emitted when setSynthetixProxy is called changing the Synthetix Proxy address
     * */
    event SynthetixProxyUpdated(address newAddress);
}


interface IRewardsDistribution {
    // Structs
    struct DistributionData {
        address destination;
        uint amount;
    }

    // Views
    function authority() external view returns (address);

    function distributions(uint index) external view returns (address destination, uint amount); // DistributionData

    function distributionsLength() external view returns (uint);

    // Mutative Functions
    function distributeRewards(uint amount) external returns (bool);
}


// Inheritance


// Internal references


// https://docs.synthetix.io/contracts/Synthetix
contract Synthetix is IERC20, ExternStateToken, MixinResolver, ISynthetix {
    // ========== STATE VARIABLES ==========

    // Available Synths which can be used with the system
    string public constant TOKEN_NAME = "Synthetix Network Token";
    string public constant TOKEN_SYMBOL = "SNX";
    uint8 public constant DECIMALS = 18;
    bytes32 public constant sUSD = "sUSD";

    /* ========== ADDRESS RESOLVER CONFIGURATION ========== */

    bytes32 private constant CONTRACT_SYNTHETIXSTATE = "SynthetixState";
    bytes32 private constant CONTRACT_SYSTEMSTATUS = "SystemStatus";
    bytes32 private constant CONTRACT_EXCHANGER = "Exchanger";
    bytes32 private constant CONTRACT_ISSUER = "Issuer";
    bytes32 private constant CONTRACT_SUPPLYSCHEDULE = "SupplySchedule";
    bytes32 private constant CONTRACT_REWARDSDISTRIBUTION = "RewardsDistribution";

    bytes32[24] private addressesToCache = [
        CONTRACT_SYSTEMSTATUS,
        CONTRACT_EXCHANGER,
        CONTRACT_ISSUER,
        CONTRACT_SUPPLYSCHEDULE,
        CONTRACT_REWARDSDISTRIBUTION,
        CONTRACT_SYNTHETIXSTATE
    ];

    // ========== CONSTRUCTOR ==========

    constructor(
        address payable _proxy,
        TokenState _tokenState,
        address _owner,
        uint _totalSupply,
        address _resolver
    )
        public
        ExternStateToken(_proxy, _tokenState, TOKEN_NAME, TOKEN_SYMBOL, _totalSupply, DECIMALS, _owner)
        MixinResolver(_resolver, addressesToCache)
    {}

    /* ========== VIEWS ========== */

    function synthetixState() internal view returns (ISynthetixState) {
        return ISynthetixState(requireAndGetAddress(CONTRACT_SYNTHETIXSTATE, "Missing SynthetixState address"));
    }

    function systemStatus() internal view returns (ISystemStatus) {
        return ISystemStatus(requireAndGetAddress(CONTRACT_SYSTEMSTATUS, "Missing SystemStatus address"));
    }

    function exchanger() internal view returns (IExchanger) {
        return IExchanger(requireAndGetAddress(CONTRACT_EXCHANGER, "Missing Exchanger address"));
    }

    function issuer() internal view returns (IIssuer) {
        return IIssuer(requireAndGetAddress(CONTRACT_ISSUER, "Missing Issuer address"));
    }

    function supplySchedule() internal view returns (SupplySchedule) {
        return SupplySchedule(requireAndGetAddress(CONTRACT_SUPPLYSCHEDULE, "Missing SupplySchedule address"));
    }

    function rewardsDistribution() internal view returns (IRewardsDistribution) {
        return
            IRewardsDistribution(requireAndGetAddress(CONTRACT_REWARDSDISTRIBUTION, "Missing RewardsDistribution address"));
    }

    function debtBalanceOf(address account, bytes32 currencyKey) external view returns (uint) {
        return issuer().debtBalanceOf(account, currencyKey);
    }

    function totalIssuedSynths(bytes32 currencyKey) external view returns (uint) {
        return issuer().totalIssuedSynths(currencyKey, false);
    }

    function totalIssuedSynthsExcludeEtherCollateral(bytes32 currencyKey) external view returns (uint) {
        return issuer().totalIssuedSynths(currencyKey, true);
    }

    function availableCurrencyKeys() external view returns (bytes32[] memory) {
        return issuer().availableCurrencyKeys();
    }

    function availableSynthCount() external view returns (uint) {
        return issuer().availableSynthCount();
    }

    function availableSynths(uint index) external view returns (ISynth) {
        return issuer().availableSynths(index);
    }

    function synths(bytes32 currencyKey) external view returns (ISynth) {
        return issuer().synths(currencyKey);
    }

    function synthsByAddress(address synthAddress) external view returns (bytes32) {
        return issuer().synthsByAddress(synthAddress);
    }

    function isWaitingPeriod(bytes32 currencyKey) external view returns (bool) {
        return exchanger().maxSecsLeftInWaitingPeriod(messageSender, currencyKey) > 0;
    }

    function anySynthOrSNXRateIsInvalid() external view returns (bool anyRateInvalid) {
        return issuer().anySynthOrSNXRateIsInvalid();
    }

    function maxIssuableSynths(address account) external view returns (uint maxIssuable) {
        return issuer().maxIssuableSynths(account);
    }

    function remainingIssuableSynths(address account)
        external
        view
        returns (
            uint maxIssuable,
            uint alreadyIssued,
            uint totalSystemDebt
        )
    {
        return issuer().remainingIssuableSynths(account);
    }

    function _canTransfer(address account, uint value) internal view returns (bool) {
        (uint initialDebtOwnership, ) = synthetixState().issuanceData(account);

        if (initialDebtOwnership > 0) {
            (uint transferable, bool anyRateIsInvalid) = issuer().transferableSynthetixAndAnyRateIsInvalid(
                account,
                tokenState.balanceOf(account)
            );
            require(value <= transferable, "Cannot transfer staked or escrowed SNX");
            require(!anyRateIsInvalid, "A synth or SNX rate is invalid");
        }
        return true;
    }

    // ========== MUTATIVE FUNCTIONS ==========

    function transfer(address to, uint value) external optionalProxy systemActive returns (bool) {
        // Ensure they're not trying to exceed their locked amount -- only if they have debt.
        _canTransfer(messageSender, value);

        // Perform the transfer: if there is a problem an exception will be thrown in this call.
        _transferByProxy(messageSender, to, value);

        return true;
    }

    function transferFrom(
        address from,
        address to,
        uint value
    ) external optionalProxy systemActive returns (bool) {
        // Ensure they're not trying to exceed their locked amount -- only if they have debt.
        _canTransfer(from, value);

        // Perform the transfer: if there is a problem,
        // an exception will be thrown in this call.
        return _transferFromByProxy(messageSender, from, to, value);
    }

    function issueSynths(uint amount) external issuanceActive optionalProxy {
        return issuer().issueSynths(messageSender, amount);
    }

    function issueSynthsOnBehalf(address issueForAddress, uint amount) external issuanceActive optionalProxy {
        return issuer().issueSynthsOnBehalf(issueForAddress, messageSender, amount);
    }

    function issueMaxSynths() external issuanceActive optionalProxy {
        return issuer().issueMaxSynths(messageSender);
    }

    function issueMaxSynthsOnBehalf(address issueForAddress) external issuanceActive optionalProxy {
        return issuer().issueMaxSynthsOnBehalf(issueForAddress, messageSender);
    }

    function burnSynths(uint amount) external issuanceActive optionalProxy {
        return issuer().burnSynths(messageSender, amount);
    }

    function burnSynthsOnBehalf(address burnForAddress, uint amount) external issuanceActive optionalProxy {
        return issuer().burnSynthsOnBehalf(burnForAddress, messageSender, amount);
    }

    function burnSynthsToTarget() external issuanceActive optionalProxy {
        return issuer().burnSynthsToTarget(messageSender);
    }

    function burnSynthsToTargetOnBehalf(address burnForAddress) external issuanceActive optionalProxy {
        return issuer().burnSynthsToTargetOnBehalf(burnForAddress, messageSender);
    }

    function exchange(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external exchangeActive(sourceCurrencyKey, destinationCurrencyKey) optionalProxy returns (uint amountReceived) {
        return exchanger().exchange(messageSender, sourceCurrencyKey, sourceAmount, destinationCurrencyKey, messageSender);
    }

    function exchangeOnBehalf(
        address exchangeForAddress,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey
    ) external exchangeActive(sourceCurrencyKey, destinationCurrencyKey) optionalProxy returns (uint amountReceived) {
        return
            exchanger().exchangeOnBehalf(
                exchangeForAddress,
                messageSender,
                sourceCurrencyKey,
                sourceAmount,
                destinationCurrencyKey
            );
    }

    function exchangeWithTracking(
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address originator,
        bytes32 trackingCode
    ) external exchangeActive(sourceCurrencyKey, destinationCurrencyKey) optionalProxy returns (uint amountReceived) {
        return
            exchanger().exchangeWithTracking(
                messageSender,
                sourceCurrencyKey,
                sourceAmount,
                destinationCurrencyKey,
                messageSender,
                originator,
                trackingCode
            );
    }

    function exchangeOnBehalfWithTracking(
        address exchangeForAddress,
        bytes32 sourceCurrencyKey,
        uint sourceAmount,
        bytes32 destinationCurrencyKey,
        address originator,
        bytes32 trackingCode
    ) external exchangeActive(sourceCurrencyKey, destinationCurrencyKey) optionalProxy returns (uint amountReceived) {
        return
            exchanger().exchangeOnBehalfWithTracking(
                exchangeForAddress,
                messageSender,
                sourceCurrencyKey,
                sourceAmount,
                destinationCurrencyKey,
                originator,
                trackingCode
            );
    }

    function settle(bytes32 currencyKey)
        external
        optionalProxy
        returns (
            uint reclaimed,
            uint refunded,
            uint numEntriesSettled
        )
    {
        return exchanger().settle(messageSender, currencyKey);
    }

    function collateralisationRatio(address _issuer) external view returns (uint) {
        return issuer().collateralisationRatio(_issuer);
    }

    function collateral(address account) external view returns (uint) {
        return issuer().collateral(account);
    }

    function transferableSynthetix(address account) external view returns (uint transferable) {
        (transferable, ) = issuer().transferableSynthetixAndAnyRateIsInvalid(account, tokenState.balanceOf(account));
    }

    function mint() external issuanceActive returns (bool) {
        require(address(rewardsDistribution()) != address(0), "RewardsDistribution not set");

        SupplySchedule _supplySchedule = supplySchedule();
        IRewardsDistribution _rewardsDistribution = rewardsDistribution();

        uint supplyToMint = _supplySchedule.mintableSupply();
        require(supplyToMint > 0, "No supply is mintable");

        // record minting event before mutation to token supply
        _supplySchedule.recordMintEvent(supplyToMint);

        // Set minted SNX balance to RewardEscrow's balance
        // Minus the minterReward and set balance of minter to add reward
        uint minterReward = _supplySchedule.minterReward();
        // Get the remainder
        uint amountToDistribute = supplyToMint.sub(minterReward);

        // Set the token balance to the RewardsDistribution contract
        tokenState.setBalanceOf(
            address(_rewardsDistribution),
            tokenState.balanceOf(address(_rewardsDistribution)).add(amountToDistribute)
        );
        emitTransfer(address(this), address(_rewardsDistribution), amountToDistribute);

        // Kick off the distribution of rewards
        _rewardsDistribution.distributeRewards(amountToDistribute);

        // Assign the minters reward.
        tokenState.setBalanceOf(msg.sender, tokenState.balanceOf(msg.sender).add(minterReward));
        emitTransfer(address(this), msg.sender, minterReward);

        totalSupply = totalSupply.add(supplyToMint);

        return true;
    }

    function liquidateDelinquentAccount(address account, uint susdAmount)
        external
        systemActive
        optionalProxy
        returns (bool)
    {
        (uint totalRedeemed, uint amountLiquidated) = issuer().liquidateDelinquentAccount(
            account,
            susdAmount,
            messageSender
        );

        emitAccountLiquidated(account, totalRedeemed, amountLiquidated, messageSender);

        // Transfer SNX redeemed to messageSender
        // Reverts if amount to redeem is more than balanceOf account, ie due to escrowed balance
        return _transferByProxy(account, messageSender, totalRedeemed);
    }

    // ========== MODIFIERS ==========

    modifier onlyExchanger() {
        require(msg.sender == address(exchanger()), "Only Exchanger can invoke this");
        _;
    }

    modifier systemActive() {
        systemStatus().requireSystemActive();
        _;
    }

    modifier issuanceActive() {
        systemStatus().requireIssuanceActive();
        _;
    }

    modifier exchangeActive(bytes32 src, bytes32 dest) {
        systemStatus().requireExchangeActive();
        systemStatus().requireSynthsActive(src, dest);
        _;
    }

    // ========== EVENTS ==========
    event SynthExchange(
        address indexed account,
        bytes32 fromCurrencyKey,
        uint256 fromAmount,
        bytes32 toCurrencyKey,
        uint256 toAmount,
        address toAddress
    );
    bytes32 internal constant SYNTHEXCHANGE_SIG = keccak256(
        "SynthExchange(address,bytes32,uint256,bytes32,uint256,address)"
    );

    function emitSynthExchange(
        address account,
        bytes32 fromCurrencyKey,
        uint256 fromAmount,
        bytes32 toCurrencyKey,
        uint256 toAmount,
        address toAddress
    ) external onlyExchanger {
        proxy._emit(
            abi.encode(fromCurrencyKey, fromAmount, toCurrencyKey, toAmount, toAddress),
            2,
            SYNTHEXCHANGE_SIG,
            addressToBytes32(account),
            0,
            0
        );
    }

    event ExchangeTracking(bytes32 indexed trackingCode, bytes32 toCurrencyKey, uint256 toAmount);
    bytes32 internal constant EXCHANGE_TRACKING_SIG = keccak256("ExchangeTracking(bytes32,bytes32,uint256)");

    function emitExchangeTracking(
        bytes32 trackingCode,
        bytes32 toCurrencyKey,
        uint256 toAmount
    ) external onlyExchanger {
        proxy._emit(
            abi.encode(toCurrencyKey, toAmount),
            2,
            EXCHANGE_TRACKING_SIG,
            trackingCode,
            0,
            0
        );
    }

    event ExchangeReclaim(address indexed account, bytes32 currencyKey, uint amount);
    bytes32 internal constant EXCHANGERECLAIM_SIG = keccak256("ExchangeReclaim(address,bytes32,uint256)");

    function emitExchangeReclaim(
        address account,
        bytes32 currencyKey,
        uint256 amount
    ) external onlyExchanger {
        proxy._emit(abi.encode(currencyKey, amount), 2, EXCHANGERECLAIM_SIG, addressToBytes32(account), 0, 0);
    }

    event ExchangeRebate(address indexed account, bytes32 currencyKey, uint amount);
    bytes32 internal constant EXCHANGEREBATE_SIG = keccak256("ExchangeRebate(address,bytes32,uint256)");

    function emitExchangeRebate(
        address account,
        bytes32 currencyKey,
        uint256 amount
    ) external onlyExchanger {
        proxy._emit(abi.encode(currencyKey, amount), 2, EXCHANGEREBATE_SIG, addressToBytes32(account), 0, 0);
    }

    event AccountLiquidated(address indexed account, uint snxRedeemed, uint amountLiquidated, address liquidator);
    bytes32 internal constant ACCOUNTLIQUIDATED_SIG = keccak256("AccountLiquidated(address,uint256,uint256,address)");

    function emitAccountLiquidated(
        address account,
        uint256 snxRedeemed,
        uint256 amountLiquidated,
        address liquidator
    ) internal {
        proxy._emit(
            abi.encode(snxRedeemed, amountLiquidated, liquidator),
            2,
            ACCOUNTLIQUIDATED_SIG,
            addressToBytes32(account),
            0,
            0
        );
    }
}

    

/*
-----------------------------------------------------------------
FILE HEADER
-----------------------------------------------------------------

file:       TokenState.sol
version:    1.0
author:     Dominic Romanowski
            Anton Jurisevic

date:       2018-2-24
checked:    Anton Jurisevic
approved:   Samuel Brooks

repo:       https://github.com/Havven/havven
commit:     34e66009b98aa18976226c139270970d105045e3

-----------------------------------------------------------------
CONTRACT DESCRIPTION
-----------------------------------------------------------------

An Owned contract, to be inherited by other contracts.
Requires its owner to be explicitly set in the constructor.
Provides an onlyOwner access modifier.

To change owner, the current owner must nominate the next owner,
who then has to accept the nomination. The nomination can be
cancelled before it is accepted by the new owner by having the
previous owner change the nomination (setting it to 0).
-----------------------------------------------------------------
*/

pragma solidity ^0.4.20;

contract Owned {
    address public owner;
    address public nominatedOwner;

    function Owned(address _owner)
        public
    {
        owner = _owner;
    }

    function nominateOwner(address _owner)
        external
        onlyOwner
    {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

    function acceptOwnership()
        external
    {
        require(msg.sender == nominatedOwner);
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    modifier onlyOwner
    {
        require(msg.sender == owner);
        _;
    }

    event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}

/*
-----------------------------------------------------------------
CONTRACT DESCRIPTION
-----------------------------------------------------------------

A contract that holds the state of an ERC20 compliant token.

This contract is used side by side with external state token
contracts, such as Havven and EtherNomin.
It provides an easy way to upgrade contract logic while
maintaining all user balances and allowances. This is designed
to to make the changeover as easy as possible, since mappings
are not so cheap or straightforward to migrate.

The first deployed contract would create this state contract,
using it as its store of balances.
When a new contract is deployed, it links to the existing
state contract, whose owner would then change its associated
contract to the new one.

-----------------------------------------------------------------
*/

contract TokenState is Owned {

    // the address of the contract that can modify balances and allowances
    // this can only be changed by the owner of this contract
    address public associatedContract;

    // ERC20 fields.
    mapping(address => uint) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    function TokenState(address _owner, address _associatedContract)
        Owned(_owner)
        public
    {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    /* ========== SETTERS ========== */

    // Change the associated contract to a new address
    function setAssociatedContract(address _associatedContract)
        external
        onlyOwner
    {
        associatedContract = _associatedContract;
        emit AssociatedContractUpdated(_associatedContract);
    }

    function setAllowance(address tokenOwner, address spender, uint value)
        external
        onlyAssociatedContract
    {
        allowance[tokenOwner][spender] = value;
    }

    function setBalanceOf(address account, uint value)
        external
        onlyAssociatedContract
    {
        balanceOf[account] = value;
    }


    /* ========== MODIFIERS ========== */

    modifier onlyAssociatedContract
    {
        require(msg.sender == associatedContract);
        _;
    }

    /* ========== EVENTS ========== */

    event AssociatedContractUpdated(address _associatedContract);
}

/*
MIT License

Copyright (c) 2018 Havven

Permission is hereby granted, free of charge, 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.

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.
*/