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



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @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: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: 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
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

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



// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// File: contracts/implements/MerkleRedeem.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";

import "../interfaces/IEmergency.sol";

import "./Ownable.sol";
import "../utils/MerkleProof.sol";

contract MerkleRedeem is Ownable, ReentrancyGuard, IEmergency {
    using SafeMath for uint256;

    struct Claim {
        uint256 period;
        uint256 balance;
        bytes32[] proof;
    }

    IERC20 public rewardsToken;
    address public emergencyRecipient;

    // Recorded periods
    mapping(uint256 => bytes32) public periodMerkleRoots;
    mapping(uint256 => mapping(address => bool)) public claimed;

    /*==== PUBLIC FUNCTIONS =====*/
    constructor(address _owner, IERC20 _rewardsToken, address _emergencyRecipient) Ownable(_owner) {
       emergencyRecipient = _emergencyRecipient;
       rewardsToken = _rewardsToken;
    }

    function claimPeriod(address recipient, uint256 period, uint256 balance, bytes32[] memory proof) external nonReentrant {
        require(!claimed[period][recipient]);
        require(verifyClaim(recipient, period, balance, proof), "incorrect merkle proof");

        claimed[period][recipient] = true;
        _disburse(recipient, balance);
    }

    function verifyClaim(address recipient, uint256 period, uint256 balance, bytes32[] memory proof) public view returns (bool) {
        bytes32 leaf = keccak256(abi.encodePacked(recipient, balance));
        return MerkleProof.verify(proof, periodMerkleRoots[period], leaf);
    }

    function claimPeriods(address recipient, Claim[] memory claims) external nonReentrant {
        uint256 totalBalance = 0;
        Claim memory claim ;

        for(uint256 i = 0; i < claims.length; i++) {
            claim = claims[i];

            require(!claimed[claim.period][recipient]);
            require(verifyClaim(recipient, claim.period, claim.balance, claim.proof), "incorrect merkle proof");

            totalBalance = totalBalance.add(claim.balance);
            claimed[claim.period][recipient] = true;
        }

        _disburse(recipient, totalBalance);
    }

    function claimStatus(address recipient, uint256 begin, uint256 end) external view returns (bool[] memory) {
        uint256 size = 1 + end - begin;
        bool[] memory arr = new bool[](size);
        for(uint256 i = 0; i < size; i++) {
            arr[i] = claimed[begin + i][recipient];
        }
        return arr;
    }

    function merkleRoots(uint256 begin, uint256 end) external view returns (bytes32[] memory) {
        uint256 size = 1 + end - begin;
        bytes32[] memory arr = new bytes32[](size);
        for(uint256 i = 0; i < size; i++) {
            arr[i] = periodMerkleRoots[begin + i];
        }
        return arr;
    }

    function emergencyWithdraw(IERC20 token) external override {
      require(token != rewardsToken, "forbidden token");

      token.transfer(emergencyRecipient, token.balanceOf(address(this)));
    }

    function seedAllocations(uint256 period, bytes32 merkleRoot, uint256 totalAllocation) external onlyOwner {
        require(periodMerkleRoots[period] == bytes32(0), "already seed");

        periodMerkleRoots[period] = merkleRoot;
        require(rewardsToken.transferFrom(msg.sender, address(this), totalAllocation), "transfer failed");
    }

    function _disburse(address recipient, uint256 balance) private {
        if (balance > 0) {
            rewardsToken.transfer(recipient, balance);
            emit Claimed(recipient, balance);
        }
    }

    /*==== EVENTS ====*/
    event Claimed(address indexed recipient, uint256 balance);
}

// File: contracts/implements/Ownable.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;

abstract contract Ownable {
    address public owner;
    address public nominatedOwner;

    constructor(address _owner) {
        owner = _owner;
    }

    function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "not nominated");
        emit OwnerChanged(owner, nominatedOwner);

        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

    function renounceOwnership() external onlyOwner {
        emit OwnerChanged(owner, address(0));
        owner = address(0);
    }

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

    modifier onlyOwner {
        require(msg.sender == owner, "not owner");
        _;
    }

    event OwnerNominated(address indexed newOwner);
    event OwnerChanged(address indexed oldOwner, address indexed newOwner);
}
// File: contracts/interfaces/IEmergency.sol



// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

interface IEmergency {
    function emergencyWithdraw(IERC20 token) external ;
}
// File: contracts/utils/MerkleProof.sol



// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev These functions deal with verification of Merkle trees (hash trees),
 */
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(bytes32[] memory proof, bytes32 root, bytes32 leaf) internal pure returns (bool) {
        bytes32 computedHash = leaf;

        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];

            if (computedHash <= proofElement) {
                // Hash(current computed hash + current element of the proof)
                computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
            } else {
                // Hash(current element of the proof + current computed hash)
                computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
            }
        }

        // Check if the computed hash (root) is equal to the provided root
        return computedHash == root;
    }
}