// File: /contracts/MerkleDistributor.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity 0.8.10;

import "./interfaces/IMerkleDistributor.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";

contract MerkleDistributor is IMerkleDistributor, Ownable {
    address public immutable token;
    bytes32 public immutable merkleRoot;
    uint256 public immutable distributionEnd;

    // This is a packed array of booleans.
    mapping(uint256 => uint256) private claimedBitMap;

    constructor(
        address token_,
        bytes32 merkleRoot_,
        uint256 distributionDuration
    ) {
        token = token_;
        merkleRoot = merkleRoot_;
        distributionEnd = block.timestamp + distributionDuration;
    }

    function isClaimed(uint256 index) public view returns (bool) {
        uint256 claimedWordIndex = index / 256;
        uint256 claimedBitIndex = index % 256;
        uint256 claimedWord = claimedBitMap[claimedWordIndex];
        uint256 mask = (1 << claimedBitIndex);
        return claimedWord & mask == mask;
    }

    function _setClaimed(uint256 index) private {
        uint256 claimedWordIndex = index / 256;
        uint256 claimedBitIndex = index % 256;
        claimedBitMap[claimedWordIndex] = claimedBitMap[claimedWordIndex] | (1 << claimedBitIndex);
    }

    function claim(
        uint256 index,
        address account,
        uint256 amount,
        bytes32[] calldata merkleProof
    ) external {
        if (block.timestamp > distributionEnd) revert DistributionEnded(block.timestamp, distributionEnd);
        if (isClaimed(index)) revert DropClaimed();

        // Verify the merkle proof.
        bytes32 node = keccak256(abi.encodePacked(index, account, amount));
        if (!MerkleProof.verify(merkleProof, merkleRoot, node)) revert InvalidProof();

        // Mark it claimed and send the token.
        _setClaimed(index);
        if (!IERC20(token).transfer(account, amount)) revert TransferFailed(token, address(this), account);

        emit Claimed(index, account, amount);
    }

    // Allows the owner to reclaim the tokens deposited in this contract.
    function withdraw(address recipient) external onlyOwner {
        if (block.timestamp <= distributionEnd) revert DistributionOngoing(block.timestamp, distributionEnd);
        uint256 balance = IERC20(token).balanceOf(address(this));
        if (balance == 0) revert AlreadyWithdrawn();
        if (!IERC20(token).transfer(recipient, balance)) revert TransferFailed(token, address(this), recipient);
        emit Withdrawn(recipient, balance);
    }
}

// File: /contracts/interfaces/IMerkleDistributor.sol



// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.0;

/// @title Allows anyone to claim a token if they exist in a merkle root.
interface IMerkleDistributor {
    /// @notice Returns the address of the token distributed by this contract.
    function token() external view returns (address);

    /// @notice Returns the merkle root of the merkle tree containing account balances available to claim.
    function merkleRoot() external view returns (bytes32);

    /// @notice Returns the unix timestamp that marks the end of the token distribution.
    function distributionEnd() external view returns (uint256);

    /// @notice Returns true if the index has been marked claimed.
    /// @param index A value from the generated input list.
    function isClaimed(uint256 index) external view returns (bool);

    /// @notice Claim the given amount of the token to the given address. Reverts if the inputs are invalid.
    /// @param index A value from the generated input list.
    /// @param account A value from the generated input list.
    /// @param amount A value from the generated input list.
    function claim(
        uint256 index,
        address account,
        uint256 amount,
        bytes32[] calldata merkleProof
    ) external;

    /// @notice Allows the owner to reclaim the tokens after the distribution has ended.
    /// @param recipient The address receiving the tokens.
    function withdraw(address recipient) external;

    /// @notice This event is triggered whenever a call to #claim succeeds.
    /// @param index A value from the generated input list.
    /// @param account A value from the generated input list.
    /// @param amount A value from the generated input list.
    event Claimed(uint256 index, address account, uint256 amount);

    /// @notice This event is triggered whenever a call to #withdraw succeeds.
    /// @param account The address that received the tokens.
    /// @param amount The amount of tokens the address received.
    event Withdrawn(address account, uint256 amount);

    /// @notice Error thrown when there's nothing to withdraw.
    error AlreadyWithdrawn();

    /// @notice Error thrown when the distribution period ended.
    /// @param current The current timestamp.
    /// @param end The time when the distribution ended.
    error DistributionEnded(uint256 current, uint256 end);

    /// @notice Error thrown when the distribution period did not end yet.
    /// @param current The current timestamp.
    /// @param end The time when the distribution ends.
    error DistributionOngoing(uint256 current, uint256 end);

    /// @notice Error thrown when the drop is already claimed.
    error DropClaimed();

    /// @notice Error thrown when the Merkle proof is invalid.
    error InvalidProof();

    /// @notice Error thrown when a transfer failed.
    /// @param token The address of token attempted to be transferred.
    /// @param from The sender of the token.
    /// @param to The recipient of the token.
    error TransferFailed(address token, address from, address to);
}

// File: @openzeppelin/contracts/utils/cryptography/MerkleProof.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/cryptography/MerkleProof.sol)

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Trees proofs.
 *
 * The proofs can be generated using the JavaScript library
 * https://github.com/miguelmota/merkletreejs[merkletreejs].
 * Note: the hashing algorithm should be keccak256 and pair sorting should be enabled.
 *
 * See `test/utils/cryptography/MerkleProof.test.js` for some examples.
 */
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) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merklee tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     *
     * _Available since v4.4._
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        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));
            }
        }
        return computedHash;
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @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/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

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

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

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

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

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