//JDCoin ICO

pragma solidity ^0.4.0;

contract jdcoin_ico {

    // Maximum number of JDCoins
    uint public max_jdcoins = 1000000;

    // The USD to JDCoin Conversion Rate
    uint public usd_to_jdcoins = 1000;

    // Total No. of JDCoins to be held by investors
    uint public total_jdcoins_bought = 0;

    // Mapping from the investor address to its equity in JDCoins and USD
    mapping(address => uint) equity_jdcoins;
    mapping(address => uint) equity_usd;

    // Check if an investor can buy JDCoins
    modifier can_buy_jdcoins(uint usd_invested) {
        require(usd_invested * usd_to_jdcoins + total_jdcoins_bought <= max_jdcoins);
        _;
    }

    // Check if an investor can sell JDCoins
    modifier can_sell_jdcoins(uint jdcoins_sold) {
        require(jdcoins_sold <= total_jdcoins_bought);
        _;
    }

    // Get the equity in JDCoins of an investor
    function equity_in_jdcoins(address investor) external constant returns(uint) {
        return equity_jdcoins[investor];
    }

    // Get the equity in USD of an investor
    function equity_in_usd(address investor) external constant returns(uint) {
        return equity_usd[investor];
    }

    // Buy JDCoin - No return value from this function
    function buy_jdcoins(address investor, uint usd_invested) external
    can_buy_jdcoins(usd_invested) {
        uint jdcoins_bought = usd_invested * usd_to_jdcoins;
        equity_jdcoins[investor] += jdcoins_bought;
        equity_usd[investor] = equity_jdcoins[investor] / usd_to_jdcoins;
        total_jdcoins_bought += jdcoins_bought;
    }

    // Sell JDCoin
    function sell_jdcoins(address investor, uint jdcoins_sold) external
    can_sell_jdcoins(jdcoins_sold) {
        equity_jdcoins[investor] -= jdcoins_sold;
        equity_usd[investor] = equity_jdcoins[investor] / usd_to_jdcoins;
        total_jdcoins_bought -= jdcoins_sold;
    }
}