ciga-dapp/contracts/ShowTrader.sol

pragma solidity ^0.4.23;

import "./ShowOwnership.sol";

contract ShowTrader is ShowOwnership {
    event Sell(uint id, uint price);
    event Buy(uint id);

    mapping (uint=>uint) public showToPrice;
    uint productsCount;

    constructor () public {
        productsCount = 0;
    }

    function sell(uint id, uint price) external onlyOwnerOf(id) {
        require(price != 0); // 0 means not for sale
        productsCount = productsCount.add(1);
        _sell(id, price);
    }

    function buy(uint id) external payable {
        require(msg.value >= showToPrice[id]);
        msg.sender.transfer(msg.value.sub(showToPrice[id])); // Take charge
        ownerOf(id).transfer(showToPrice[id]);
        transfer(msg.sender, id);
        productsCount = productsCount.sub(1);
    }

    function getShowsForSale() external view returns (uint[]) {
        uint[] memory result = new uint[](productsCount);
        uint counter = 0;
        for (uint id = 0; id < shows.length; id++) {
            if (showToPrice[id] != 0) {
                result[counter] = id;
                counter++;
            }
        }
        return result;
    }

    function _sell(uint id, uint price) private {
        showToPrice[id] = price;
        emit Sell(id, price);
    }
}