// Vulnerability label: ARTHM
/*
 * This is a distributed lottery that chooses random addresses as lucky addresses. If these
 * participate, they get the jackpot: 1.9 times the price of their bet.
 * Of course one address can only win once. The owner regularly reseeds the secret
 * seed of the contract (based on which the lucky addresses are chosen), so if you did not win,
 * just wait for a reseed and try again!
 *
 * Jackpot chance:   50%
 * Ticket price: Anything larger than (or equal to) 0.1 ETH
 * Jackpot size: 1.9 times the ticket price
 *
 * HOW TO PARTICIPATE: Just send any amount greater than (or equal to) 0.1 ETH to the contract's address
 * Keep in mind that your address can only win once
 *
 * If the contract doesn't have enough ETH to pay the jackpot, it sends the whole balance.
 *
 * Example: For each address, a random number is generated, either 0 or 1. This number is then compared
 * with the LuckyNumber - a constant 1. If they are equal, the contract will instantly send you the jackpot:
 * your bet multiplied by 1.9 (House edge of 0.1)
*/

contract OpenAddressLottery{
    struct SeedComponents{
        uint component1;
        uint component2;
        uint component3;
        uint component4;
    }
    
    address owner; //address of the owner
    uint private secretSeed; //seed used to calculate number of an address
    uint private lastReseed; //last reseed - used to automatically reseed the contract every 1000 blocks
    uint LuckyNumber = 1; //if the number of an address equals 1, it wins
        
    mapping (address => bool) winner; //keeping track of addresses that have already won
    
    function OpenAddressLottery() {
        owner = msg.sender;
        reseed(SeedComponents((uint)(block.coinbase), block.difficulty, block.gaslimit, block.timestamp)); //generate a quality random seed
    }
    
    function participate() payable {
        if(msg.value<0.1 ether)
            return; //verify ticket price
        
        // make sure he hasn't won already
        require(winner[msg.sender] == false);
        
        if(luckyNumberOfAddress(msg.sender) == LuckyNumber){ //check if it equals 1
            winner[msg.sender] = true; // every address can only win once
            
            uint win=(msg.value/10)*19; //win = 1.9 times the ticket price
            
            if(win>this.balance) //if the balance isnt sufficient...
                win=this.balance; //...send everything we've got
            msg.sender.transfer(win);
        }
        
        if(block.number-lastReseed>1000) //reseed if needed
            reseed(SeedComponents((uint)(block.coinbase), block.difficulty, block.gaslimit, block.timestamp)); //generate a quality random seed
    }
    
    function luckyNumberOfAddress(address addr) constant returns(uint n){
        // calculate the number of current address - 50% chance
        n = uint(keccak256(uint(addr), secretSeed)[0]) % 2; //mod 2 returns either 0 or 1
    }
    
    function reseed(SeedComponents components) internal {
        secretSeed = uint256(keccak256(
            components.component1,
            components.component2,
            components.component3,
            components.component4
        )); //hash the incoming parameters and use the hash to (re)initialize the seed
        lastReseed = block.number;
    }
    
    function kill() {
        require(msg.sender==owner);
        
        selfdestruct(msg.sender);
    }
    
    function forceReseed() { //reseed initiated by the owner - for testing purposes
        require(msg.sender==owner);
        
        SeedComponents s;
        s.component1 = uint(msg.sender);
        s.component2 = uint256(block.blockhash(block.number - 1));
        s.component3 = block.difficulty*(uint)(block.coinbase);
        s.component4 = tx.gasprice * 7;
        
        reseed(s); //reseed
    }
    
    function () payable { //if someone sends money without any function call, just assume he wanted to participate
        if(msg.value>=0.1 ether && msg.sender!=owner) //owner can't participate, he can only fund the jackpot
            participate();
    }

}