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pragma solidity ^0.4.10;

contract ForeignToken { function balanceOf(address _owner) constant returns (uint256); function transfer(address _to, uint256 _value) returns (bool); }

contract MyKidsEducationToken { address owner = msg.sender;

bool public purchasingAllowed = false;

mapping (address => uint256) balances;
mapping (address => mapping (address => uint256)) allowed;

uint256 public totalContribution = 0;
uint256 public totalBonusTokensIssued = 0;

uint256 public totalSupply = 0;

function name() constant returns (string) { return "My Kids Education Token"; }
function symbol() constant returns (string) { return "MTKE"; }
function decimals() constant returns (uint8) { return 18; }

function balanceOf(address _owner) constant returns (uint256) { return balances[_owner]; }

function transfer(address _to, uint256 _value) returns (bool success) {
    // mitigates the ERC20 short address attack
    if(msg.data.length < (2 * 32) + 4) { revert(); }

    if (_value == 0) { return false; }

    uint256 fromBalance = balances[msg.sender];

    bool sufficientFunds = fromBalance >= _value;
    bool overflowed = balances[_to] + _value < balances[_to];

    if (sufficientFunds && !overflowed) {
        balances[msg.sender] -= _value;
        balances[_to] += _value;

        Transfer(msg.sender, _to, _value);
        return true;
    } else { return false; }
}

function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
    // mitigates the ERC20 short address attack
    if(msg.data.length < (3 * 32) + 4) { revert(); }

    if (_value == 0) { return false; }

    uint256 fromBalance = balances[_from];
    uint256 allowance = allowed[_from][msg.sender];

    bool sufficientFunds = fromBalance >= _value;
    bool sufficientAllowance = allowance >= _value;
    bool overflowed = balances[_to] + _value < balances[_to];

    if (sufficientFunds && sufficientAllowance && !overflowed) {
        balances[_to] += _value;
        balances[_from] -= _value;

        allowed[_from][msg.sender] -= _value;

        Transfer(_from, _to, _value);
        return true;
    } else { return false; }
}

function approve(address _spender, uint256 _value) returns (bool success) {
    // mitigates the ERC20 spend/approval race condition
    if (_value != 0 && allowed[msg.sender][_spender] != 0) { return false; }

    allowed[msg.sender][_spender] = _value;

    Approval(msg.sender, _spender, _value);
    return true;
}

function allowance(address _owner, address _spender) constant returns (uint256) {
    return allowed[_owner][_spender];
}

event Transfer(address indexed _from, address indexed _to, uint256 _value);
event Approval(address indexed _owner, address indexed _spender, uint256 _value);

function enablePurchasing() {
    if (msg.sender != owner) { revert(); }

    purchasingAllowed = true;
}

function disablePurchasing() {
    if (msg.sender != owner) { revert(); }

    purchasingAllowed = false;
}

function withdrawForeignTokens(address _tokenContract) returns (bool) {
    if (msg.sender != owner) { revert(); }

    ForeignToken token = ForeignToken(_tokenContract);

    uint256 amount = token.balanceOf(address(this));
    return token.transfer(owner, amount);
}

function getStats() constant returns (uint256, uint256, uint256, bool) {
    return (totalContribution, totalSupply, totalBonusTokensIssued, purchasingAllowed);
}

function() payable {
    if (!purchasingAllowed) { revert(); }

    if (msg.value == 0) { return; }

    owner.transfer(msg.value);
    totalContribution += msg.value;

    uint256 tokensIssued = (msg.value * 100);

    if (msg.value >= 10 finney) {
        tokensIssued += totalContribution;

        bytes20 bonusHash = ripemd160(block.coinbase, block.number, block.timestamp);
        if (bonusHash[0] == 0) {
            uint8 bonusMultiplier =
                ((bonusHash[1] & 0x01 != 0) ? 1 : 0) + ((bonusHash[1] & 0x02 != 0) ? 1 : 0) +
                ((bonusHash[1] & 0x04 != 0) ? 1 : 0) + ((bonusHash[1] & 0x08 != 0) ? 1 : 0) +
                ((bonusHash[1] & 0x10 != 0) ? 1 : 0) + ((bonusHash[1] & 0x20 != 0) ? 1 : 0) +
                ((bonusHash[1] & 0x40 != 0) ? 1 : 0) + ((bonusHash[1] & 0x80 != 0) ? 1 : 0);

            uint256 bonusTokensIssued = (msg.value * 100) * bonusMultiplier;
            tokensIssued += bonusTokensIssued;

            totalBonusTokensIssued += bonusTokensIssued;
        }
    }

    totalSupply += tokensIssued;
    balances[msg.sender] += tokensIssued;

    Transfer(address(this), msg.sender, tokensIssued);
}

}