contract BearBums is ERC721, Ownable {
    using SafeMath for uint256;

    string public BEAR_PROVENANCE = "";

    uint256 public startingIndexBlock;

    uint256 public startingIndex;

    uint256 public constant bearprice = 80000000000000000; //0.08 ETH

    uint public constant maxBearPurchase = 20;

    uint256 public MAX_BEAR = 10000;

    bool public saleIsActive = false;

    uint256 public REVEAL_TIMESTAMP;

    constructor(string memory name, string memory symbol, uint256 maxNftSupply, uint256 saleStart) ERC721(name, symbol) {
        MAX_BEAR = maxNftSupply;
        REVEAL_TIMESTAMP = saleStart + (86400 * 9);
    }

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

    /**
     * Set some Bear Bums aside
     */
    function reserveBear(uint256 reservingCount) public onlyOwner {        
        require(totalSupply().add(reservingCount) <= MAX_BEAR, "Purchase would exceed max supply of Bears");

        uint supply = totalSupply();
        uint i;
        for (i = 0; i < reservingCount; i++) {
            _safeMint(msg.sender, supply + i);
        }
    }

    /**
     * DM Gargamel in Discord that you're standing right behind him.
     */
    function setRevealTimestamp(uint256 revealTimeStamp) public onlyOwner {
        REVEAL_TIMESTAMP = revealTimeStamp;
    } 

    /*     
    * Set provenance once it's calculated
    */
    function setProvenanceHash(string memory provenanceHash) public onlyOwner {
        BEAR_PROVENANCE = provenanceHash;
    }

    function setBaseURI(string memory baseURI) public onlyOwner {
        _setBaseURI(baseURI);
    }

    /*
    * Pause sale if active, make active if paused
    */
    function flipSaleState() public onlyOwner {
        saleIsActive = !saleIsActive;
    }

    /**
    * Mints BearBums
    */
    function mintBear(uint numberOfTokens) public payable {
        require(saleIsActive, "Sale must be active to mint Bear");
        require(numberOfTokens <= maxBearPurchase, "Can only mint 20 tokens at a time");
        require(totalSupply().add(numberOfTokens) <= MAX_BEAR, "Purchase would exceed max supply of Bears");
        require(bearprice.mul(numberOfTokens) <= msg.value, "Ether value sent is not correct");
        
        for(uint i = 0; i < numberOfTokens; i++) {
            uint mintIndex = totalSupply();
            if (totalSupply() < MAX_BEAR) {
                _safeMint(msg.sender, mintIndex);
            }
        }

        // If we haven't set the starting index and this is either 1) the last saleable token or 2) the first token to be sold after
        // the end of pre-sale, set the starting index block
        if (startingIndexBlock == 0 && (totalSupply() == MAX_BEAR || block.timestamp >= REVEAL_TIMESTAMP)) {
            startingIndexBlock = block.number;
        } 
    }

    /**
     * Set the starting index for the collection
     */
    function setStartingIndex() public {
        require(startingIndex == 0, "Starting index is already set");
        require(startingIndexBlock != 0, "Starting index block must be set");
        
        startingIndex = uint(blockhash(startingIndexBlock)) % MAX_BEAR;
        // Just a sanity case in the worst case if this function is called late (EVM only stores last 256 block hashes)
        if (block.number.sub(startingIndexBlock) > 255) {
            startingIndex = uint(blockhash(block.number - 1)) % MAX_BEAR;
        }
        // Prevent default sequence
        if (startingIndex == 0) {
            startingIndex = startingIndex.add(1);
        }
    }

    /**
     * Set the starting index block for the collection, essentially unblocking
     * setting starting index
     
     */
    function emergencySetStartingIndexBlock() public onlyOwner {
        require(startingIndex == 0, "Starting index is already set");
        
        startingIndexBlock = block.number;
    }
}
/**
 * @title BEARBUMS contract
 * @dev Extends ERC721 Non-Fungible Token Standard basic implementation
 */
function reserveBear(uint256 reservingCount) public onlyOwner {        
        require(totalSupply().add(reservingCount) <= MAX_BEAR, "Purchase would exceed max supply of Bears");

        uint supply = totalSupply();
        uint i;
        for (i = 0; i < reservingCount; i++) {
            _safeMint(msg.sender, supply + i);
        }
    }
/**
 * Set some Bear Bums aside
 */