KingOfTheEtherThrone

// A chain-game contract that maintains a 'throne' which agents may pay to rule.
// (c) Kieran Elby. All rights reserved.
// v0.3.0.
// Inspired by ethereumpyramid.com and the (now-gone?) "magnificent bitcoin gem".
// Compiler: soljson-v0.2.0-nightly.2016.1.20+commit.67c855c5, optimizer OFF

contract KingOfTheEtherThrone {

    struct Monarch {
        address etherAddress;
        string name;
        uint claimPrice;
        uint coronationTimestamp;
    }

    address wizardAddress;
    uint accumulatedWizardPayments = 0;

    modifier onlywizard { if (msg.sender == wizardAddress) _ }

    uint constant startingClaimPrice = 10 finney;
    uint constant claimPriceAdjustNum = 3;
    uint constant claimPriceAdjustDen = 2;
    uint constant wizardCommissionFractionNum = 1;
    uint constant wizardCommissionFractionDen = 100;

    uint public currentClaimPrice;
    Monarch public currentMonarch;
    Monarch[] public pastMonarchs;

    function KingOfTheEtherThrone() {
        wizardAddress = msg.sender;
        currentClaimPrice = startingClaimPrice;
        currentMonarch = Monarch(
            wizardAddress,
            "[Vacant]",
            0,
            block.timestamp
        );
    }

    function numberOfMonarchs() constant returns (uint n) {
        return pastMonarchs.length;
    }

    event ThroneClaimed(
        address usurperEtherAddress,
        string usurperName,
        uint newClaimPrice
    );

    function() {
        claimThrone(string(msg.data));
    }

    function claimThrone(string name) {
        uint valuePaid = msg.value;
        if (valuePaid < currentClaimPrice) {
            msg.sender.send(valuePaid);
            return;
        }
        if (valuePaid > currentClaimPrice) {
            uint excessPaid = valuePaid - currentClaimPrice;
            msg.sender.send(excessPaid);
            valuePaid = valuePaid - excessPaid;
        }
        uint wizardCommission = (valuePaid * wizardCommissionFractionNum) / wizardCommissionFractionDen;
        accumulatedWizardPayments += wizardCommission;
        uint compensation = valuePaid - wizardCommission;
        if (currentMonarch.etherAddress != wizardAddress) {
            currentMonarch.etherAddress.send(compensation);
        } else {
            accumulatedWizardPayments += compensation;
        }
        pastMonarchs.push(currentMonarch);
        currentMonarch = Monarch(
            msg.sender,
            name,
            valuePaid,
            block.timestamp
        );
        currentClaimPrice = currentClaimPrice * claimPriceAdjustNum / claimPriceAdjustDen;
        ThroneClaimed(currentMonarch.etherAddress, currentMonarch.name, currentClaimPrice);
    }

    function sweepCommission() onlywizard {
        if (accumulatedWizardPayments == 0) {
            return;
        }
        wizardAddress.send(accumulatedWizardPayments);
        accumulatedWizardPayments = 0;
    }

}