// File: contracts/EPriceOracleEL.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.7.4;

import "@openzeppelin/contracts/math/SafeMath.sol";
import "./IEPriceOracle.sol";
import "./Library.sol";

/**
 * @title Elysia's price feed
 * @notice Elysia server set EL Price regularlry
 * @author Elysia
 */
contract EPriceOracleEL is IEPriceOracle {

    /// @notice Emitted when el Price is changed
    event NewElPrice(uint256 newElPrice);

    // USD per Elysia token
    // decimals: 18
    uint256 private _elPrice;

    address public admin;

    constructor() {
        admin = msg.sender;
    }

    function getPrice() external view override returns (uint256) {
        return _elPrice;
    }

    function setElPrice(uint256 elPrice_) external returns (bool) {
        require(msg.sender == admin, "Restricted to admin.");

        _elPrice = elPrice_;
        emit NewElPrice(elPrice_);

        return true;
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

        return c;
    }

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

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

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

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

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

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

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

// File: contracts/IEPriceOracle.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.7.4;

interface IEPriceOracle {
    function getPrice() external view returns (uint256);
}

// File: contracts/Library.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.7.4;

import "@openzeppelin/contracts/math/SafeMath.sol";

struct RewardLocalVars {
    uint256 newReward;
    uint256 accountReward;
    uint256 accountBalance;
    uint256 rewardBlockNumber;
    uint256 blockNumber;
    uint256 diffBlock;
    uint256 rewardPerBlock;
    uint256 totalSupply;
}

struct ExchangeLocalVars {
    uint256 currencyPrice;
    uint256 assetTokenPrice;
}

library AssetTokenLibrary {
    using SafeMath for uint256;

    function getReward(RewardLocalVars memory self)
        internal
        pure
        returns (uint256)
    {
        if (
            self.rewardBlockNumber != 0 &&
            self.blockNumber > self.rewardBlockNumber
        ) {
            self.diffBlock = self.blockNumber.sub(self.rewardBlockNumber);
            self.newReward = self
                .accountBalance
                .mul(self.diffBlock)
                .mul(self.rewardPerBlock)
                .div(self.totalSupply);
        }
        return self.accountReward.add(self.newReward);
    }

    function mulPrice(ExchangeLocalVars memory self)
        internal
        pure
        returns (uint)
    {
        return self.assetTokenPrice.mul(1e18).div(self.currencyPrice);
    }
}