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/**
 * SPDX-License-Identifier: MIT
 *
 * Copyright (c) 2018 zOS Global Limited.
 *
 * 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
 * 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.
 */

// File: contracts/upgradeability/Proxy.sol

pragma solidity ^0.8.0;

/**
 * @notice Implements delegation of calls to other contracts, with proper
 * forwarding of return values and bubbling of failures.
 * It defines a fallback function that delegates all calls to the address
 * returned by the abstract _implementation() internal function.
 * @dev Forked from https://github.com/zeppelinos/zos-lib/blob/8a16ef3ad17ec7430e3a9d2b5e3f39b8204f8c8d/contracts/upgradeability/Proxy.sol
 * Modifications:
 * 1. Reformat and conform to Solidity 0.6 syntax (5/13/20)
 */
abstract contract Proxy {
    /**
     * @dev Fallback function.
     * Implemented entirely in `_fallback`.
     */
    fallback() external payable {
        _fallback();
    }

/**
     * @return The Address of the implementation.
     */
    function _implementation() internal virtual view returns (address);

/**
     * @dev Delegates execution to an implementation contract.
     * This is a low level function that doesn't return to its internal call site.
     * It will return to the external caller whatever the implementation returns.
     * @param implementation Address to delegate.
     */
    function _delegate(address implementation) internal {
        assembly {
            // Copy msg.data. We take full control of memory in this inline assembly
            // block because it will not return to Solidity code. We overwrite the
            // Solidity scratch pad at memory position 0.
            calldatacopy(0, 0, calldatasize())

// Call the implementation.
            // out and outsize are 0 because we don't know the size yet.
            let result := delegatecall(
                gas(),
                implementation,
                0,
                calldatasize(),
                0,
                0
            )

// Copy the returned data.
            returndatacopy(0, 0, returndatasize())

switch result
                // delegatecall returns 0 on error.
                case 0 {
                    revert(0, returndatasize())
                }
                default {
                    return(0, returndatasize())
                }
        }
    }

/**
     * @dev Function that is run as the first thing in the fallback function.
     * Can be redefined in derived contracts to add functionality.
     * Redefinitions must call super._willFallback().
     */
    function _willFallback() internal virtual {}

/**
     * @dev fallback implementation.
     * Extracted to enable manual triggering.
     */
    function _fallback() internal {
        _willFallback();
        _delegate(_implementation());
    }
}

// File: @openzeppelin/contracts/utils/Address.sol

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }
}

// File: contracts/upgradeability/UpgradeabilityProxy.sol

/**
 * @notice This contract implements a proxy that allows to change the
 * implementation address to which it will delegate.
 * Such a change is called an implementation upgrade.
 * @dev Forked from https://github.com/zeppelinos/zos-lib/blob/8a16ef3ad17ec7430e3a9d2b5e3f39b8204f8c8d/contracts/upgradeability/UpgradeabilityProxy.sol
 * Modifications:
 * 1. Reformat, conform to Solidity 0.6 syntax, and add error messages (5/13/20)
 * 2. Use Address utility library from the latest OpenZeppelin (5/13/20)
 */
contract UpgradeabilityProxy is Proxy {
    /**
     * @dev Emitted when the implementation is upgraded.
     * @param implementation Address of the new implementation.
     */
    event Upgraded(address implementation);

/**
     * @dev Storage slot with the address of the current implementation.
     * This is the keccak-256 hash of "org.zeppelinos.proxy.implementation", and is
     * validated in the constructor.
     */
    bytes32
        private constant IMPLEMENTATION_SLOT = 0x7050c9e0f4ca769c69bd3a8ef740bc37934f8e2c036e5a723fd8ee048ed3f8c3;

/**
     * @dev Contract constructor.
     * @param implementationContract Address of the initial implementation.
     */
    constructor(address implementationContract) public {
        assert(
            IMPLEMENTATION_SLOT ==
                keccak256("org.zeppelinos.proxy.implementation")
        );

_setImplementation(implementationContract);
    }

/**
     * @dev Returns the current implementation.
     * @return impl Address of the current implementation
     */
    function _implementation() internal override view returns (address impl) {
        bytes32 slot = IMPLEMENTATION_SLOT;
        assembly {
            impl := sload(slot)
        }
    }

/**
     * @dev Upgrades the proxy to a new implementation.
     * @param newImplementation Address of the new implementation.
     */
    function _upgradeTo(address newImplementation) internal {
        _setImplementation(newImplementation);
        emit Upgraded(newImplementation);
    }

/**
     * @dev Sets the implementation address of the proxy.
     * @param newImplementation Address of the new implementation.
     */
    function _setImplementation(address newImplementation) private {
        require(
            Address.isContract(newImplementation),
            "Cannot set a proxy implementation to a non-contract address"
        );

bytes32 slot = IMPLEMENTATION_SLOT;

assembly {
            sstore(slot, newImplementation)
        }
    }
}

// File: contracts/upgradeability/AdminUpgradeabilityProxy.sol

/**
 * @notice This contract combines an upgradeability proxy with an authorization
 * mechanism for administrative tasks.
 * @dev Forked from https://github.com/zeppelinos/zos-lib/blob/8a16ef3ad17ec7430e3a9d2b5e3f39b8204f8c8d/contracts/upgradeability/AdminUpgradeabilityProxy.sol
 * Modifications:
 * 1. Reformat, conform to Solidity 0.6 syntax, and add error messages (5/13/20)
 * 2. Remove ifAdmin modifier from admin() and implementation() (5/13/20)
 */
contract AdminUpgradeabilityProxy is UpgradeabilityProxy {
    /**
     * @dev Emitted when the administration has been transferred.
     * @param previousAdmin Address of the previous admin.
     * @param newAdmin Address of the new admin.
     */
    event AdminChanged(address previousAdmin, address newAdmin);

/**
     * @dev Storage slot with the admin of the contract.
     * This is the keccak-256 hash of "org.zeppelinos.proxy.admin", and is
     * validated in the constructor.
     */
    bytes32
        private constant ADMIN_SLOT = 0x10d6a54a4754c8869d6886b5f5d7fbfa5b4522237ea5c60d11bc4e7a1ff9390b;

/**
     * @dev Modifier to check whether the `msg.sender` is the admin.
     * If it is, it will run the function. Otherwise, it will delegate the call
     * to the implementation.
     */
    modifier ifAdmin() {
        if (msg.sender == _admin()) {
            _;
        } else {
            _fallback();
        }
    }

/**
     * @dev Contract constructor.
     * It sets the `msg.sender` as the proxy administrator.
     * @param implementationContract address of the initial implementation.
     */
    constructor(address implementationContract)
        public
        UpgradeabilityProxy(implementationContract)
    {
        assert(ADMIN_SLOT == keccak256("org.zeppelinos.proxy.admin"));

_setAdmin(msg.sender);
    }

/**
     * @return The address of the proxy admin.
     */
    function admin() external view returns (address) {
        return _admin();
    }

/**
     * @return The address of the implementation.
     */
    function implementation() external view returns (address) {
        return _implementation();
    }

/**
     * @dev Changes the admin of the proxy.
     * Only the current admin can call this function.
     * @param newAdmin Address to transfer proxy administration to.
     */
    function changeAdmin(address newAdmin) external ifAdmin {
        require(
            newAdmin != address(0),
            "Cannot change the admin of a proxy to the zero address"
        );
        emit AdminChanged(_admin(), newAdmin);
        _setAdmin(newAdmin);
    }

/**
     * @dev Upgrade the backing implementation of the proxy.
     * Only the admin can call this function.
     * @param newImplementation Address of the new implementation.
     */
    function upgradeTo(address newImplementation) external ifAdmin {
        _upgradeTo(newImplementation);
    }

/**
     * @dev Upgrade the backing implementation of the proxy and call a function
     * on the new implementation.
     * This is useful to initialize the proxied contract.
     * @param newImplementation Address of the new implementation.
     * @param data Data to send as msg.data in the low level call.
     * It should include the signature and the parameters of the function to be
     * called, as described in
     * https://solidity.readthedocs.io/en/develop/abi-spec.html#function-selector-and-argument-encoding.
     */
    function upgradeToAndCall(address newImplementation, bytes calldata data)
        external
        payable
        ifAdmin
    {
        _upgradeTo(newImplementation);
        // prettier-ignore
        // solhint-disable-next-line avoid-low-level-calls
        (bool success,) = address(this).call{value: msg.value}(data);
        // solhint-disable-next-line reason-string
        require(success);
    }

/**
     * @return adm The admin slot.
     */
    function _admin() internal view returns (address adm) {
        bytes32 slot = ADMIN_SLOT;

assembly {
            adm := sload(slot)
        }
    }

/**
     * @dev Sets the address of the proxy admin.
     * @param newAdmin Address of the new proxy admin.
     */
    function _setAdmin(address newAdmin) internal {
        bytes32 slot = ADMIN_SLOT;

assembly {
            sstore(slot, newAdmin)
        }
    }

/**
     * @dev Only fall back when the sender is not the admin.
     */
    function _willFallback() internal override {
        require(
            msg.sender != _admin(),
            "Cannot call fallback function from the proxy admin"
        );
        super._willFallback();
    }
}

// File: contracts/FiatTokenProxy.sol

/**
 * @title FiatTokenProxy
 * @dev This contract proxies FiatToken calls and enables FiatToken upgrades
 */
contract FiatTokenProxy is AdminUpgradeabilityProxy {
    constructor(address implementationContract)
        public
        AdminUpgradeabilityProxy(implementationContract)
    {}
}