// File: contracts/RulerAirdrop.sol



// SPDX-License-Identifier: NONE

pragma solidity ^0.8.0;

import "./utils/MerkleProof.sol";
import "./utils/Ownable.sol";
import "./interfaces/IERC20.sol";
import "./interfaces/IDistributor.sol";

/**
 * @title Ruler Airdrop contract
 * @author crypto-pumpkin
 */
contract RulerAirdrop is IDistributor, Ownable {
  address public immutable override token;
  bytes32 public immutable override merkleRoot;

  uint256 public override totalClaimed;
  uint256 public immutable startTime;
  uint256 public constant claimWindow = 21 days;

  mapping(uint256 => uint256) private claimedBitMap;

  constructor(address token_, bytes32 merkleRoot_) {
    token = token_;
    merkleRoot = merkleRoot_;
    startTime = block.timestamp;
  }

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

  function claim(
    uint256 index,
    address account,
    uint256 amount,
    bytes32[] calldata merkleProof
  ) external override {
    require(!isClaimed(index), "RulerAirdrop: Already claimed");
    require(block.timestamp - startTime <= claimWindow, "RulerAirdrop: Too late");

    // Verify the merkle proof.
    bytes32 node = keccak256(abi.encodePacked(index, account, amount));
    require(MerkleProof.verify(merkleProof, merkleRoot, node), "RulerAirdrop: Invalid proof");

    // Mark it claimed and send the token.
    totalClaimed = totalClaimed + amount;
    _setClaimed(index);
    require(IERC20(token).transfer(account, amount), "RulerAirdrop: Transfer failed");

    emit Claimed(index, account, amount);
  }

  // collect any token send by mistake, collect target after 90 days
  function collectDust(address _token) external {
    if (_token == address(0)) { // token address(0) = ETH
      payable(owner()).transfer(address(this).balance);
    } else {
      if (_token == token) {
        require(block.timestamp > startTime + claimWindow, "RulerAirdrop: Not ready");
      }
      uint256 balance = IERC20(_token).balanceOf(address(this));
      IERC20(_token).transfer(owner(), balance);
    }
  }

  function _setClaimed(uint256 index) private {
    uint256 claimedWordIndex = index / 256;
    uint256 claimedBitIndex = index % 256;
    claimedBitMap[claimedWordIndex] = claimedBitMap[claimedWordIndex] | (1 << claimedBitIndex);
  }
}
// File: contracts/utils/MerkleProof.sol



// SPDX-License-Identifier: MIT

pragma solidity ^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;
    }
}
// File: contracts/utils/Ownable.sol



// SPDX-License-Identifier: None

pragma solidity ^0.8.0;

/**
 * @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.
 * @author crypto-pumpkin@github
 *
 * By initialization, the owner account will be the one that called initializeOwner. 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.
 */
contract Ownable {
    address private _owner;

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

    /**
     * @dev COVER: Initializes the contract setting the deployer as the initial owner.
     */
    constructor () {
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), _owner);
    }

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

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

    /**
     * @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");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}
// File: contracts/interfaces/IERC20.sol



// SPDX-License-Identifier: No License

pragma solidity ^0.8.0;

/**
 * @title Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    function balanceOf(address account) external view returns (uint256);
    function totalSupply() external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    function increaseAllowance(address spender, uint256 addedValue) external returns (bool);
    function decreaseAllowance(address spender, uint256 subtractedValue) external returns (bool);
}
// File: contracts/interfaces/IDistributor.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

// Allows anyone to claim a token if they exist in a merkle root.
interface IDistributor {
    // Returns the address of the token distributed by this contract.
    function token() external view returns (address);
    // Returns the merkle root of the merkle tree containing account balances available to claim.
    function merkleRoot() external view returns (bytes32);
    // Returns true if the index has been marked claimed.
    function isClaimed(uint256 index) external view returns (bool);
    function totalClaimed() external view returns (uint256);
    // Claim the given amount of the token to the given address. Reverts if the inputs are invalid.
    function claim(uint256 index, address account, uint256 amount, bytes32[] calldata merkleProof) external;

    // This event is triggered whenever a call to #claim succeeds.
    event Claimed(uint256 index, address account, uint256 amount);
}