// File: contracts/Swapper.sol



// SPDX-License-Identifier: Apache-2.0
pragma solidity 0.8.7;


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

interface IBaseToken {
    function burn(uint256 tokenId) external;
    function ownerOf(uint256 tokenId) external returns (address);
    function mint(address to) external;
}

contract Swapper is Ownable, Provenance {

    address public tokenToBurn;
    address public tokenToMint;
    uint256 public batchSize;
    uint256 public keyDeadline;

    /* ------------------------------- Constructor ------------------------------ */

    constructor(
        address _tokenToBurn,
        address _tokenToMint,
        uint256 _batchSize,
        uint256 _keyDeadline,
        bytes32 _provenanceHash
    ) {
        require(_tokenToBurn != address(0), "Swapper: tokenToBurn cannot be zer0 address");
        require(_tokenToMint != address(0), "Swapper: tokenToMint cannot be zer0 address");
        require(_keyDeadline > block.timestamp, "Swapper: keyDeadline must be later than now");
        require(_batchSize != 0, "Swapper: batchSize cannot be 0");

        tokenToBurn = _tokenToBurn;
        tokenToMint = _tokenToMint;
        batchSize = _batchSize;
        keyDeadline = _keyDeadline;

        _setProvenance(_provenanceHash);

    }


    /* ------------------------------ Owner Methods ----------------------------- */

    function withdraw() public onlyOwner {
        uint balance = address(this).balance;
        payable(msg.sender).transfer(balance);
    }

    function sweep(address token, address to, uint256 amount)
        external
        onlyOwner
        returns (bool)
    {    
        return IERC20(token).transfer(to, amount);
    }


    /* ----------------------------- Public Methods ----------------------------- */

    function swap(uint256 tokenId)
        public
    {
        require(IBaseToken(tokenToBurn).ownerOf(tokenId) == msg.sender, "Swapper: only current owner may swap");
        require(keyDeadline >= block.timestamp, "Swapper: redemption deadline passed");
        
        IBaseToken(tokenToBurn).burn(tokenId);
        IBaseToken(tokenToMint).mint(msg.sender);

        // First swap sets offset.
        _setStartingBlock(1, 1);

    }

    function finalizeReveal() public {
        require(batchSize != 0, "Swapper: set batch size first");
        _finalizeStartingIndex(batchSize);
    }
}
// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

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() {
        _setOwner(_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 {
        _setOwner(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");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

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



// SPDX-License-Identifier: MIT

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: contracts/Provenance.sol



// SPDX-License-Identifier: Apache-2.0
pragma solidity 0.8.7;


contract Provenance {

    // Provenance hash for metadata.
    bytes32 public provenance;
    uint256 public startingIndex;
    uint256 public startingIndexBlock;
    uint256 public revealTimestamp;


    /* ------------------------------ Internal Methods ----------------------------- */

    function _setProvenance(bytes32 provenanceHash) internal {
        provenance = provenanceHash;
    }

    function _setRevealTime(uint256 timestamp) internal {
        revealTimestamp = timestamp;
    }

    function _finalizeStartingIndex(uint256 maxSupply) internal {
        require(startingIndex == 0, "Starting index is already set");
        require(startingIndexBlock != 0, "Starting index block must be set");
        
        startingIndex = (uint(blockhash(startingIndexBlock)) % maxSupply) + 1;
        // Just a sanity case in the worst case if this function is called late (EVM only stores last 256 block hashes)
        if (block.number - startingIndexBlock > 255) {
            startingIndex = (uint(blockhash(block.number-1)) % maxSupply) + 1;
        }
        // Prevent default sequence
        if (startingIndex == 1) {
            startingIndex = startingIndex + 1;
        }
    }

    function _setStartingBlock(uint256 currentCount, uint256 maxSupply) internal {
        /**
         * Source of randomness. Theoretical miner withhold manipulation possible but should be sufficient in a pragmatic sense
         */
        if (startingIndexBlock == 0 && (currentCount == maxSupply || block.timestamp >= revealTimestamp)) {
            startingIndexBlock = block.number;
        }
    }

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



// SPDX-License-Identifier: MIT

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;
    }
}