ERC721Example.sol

ERC721Example.sol

pragma solidity ^0.4.23;

import '../node_modules/openzeppelin-solidity/contracts/token/ERC721/ERC721.sol';

contract StarNotary is ERC721 { 

    struct Star { 
        string name;
        uint256 id;
        string story;
        string dec;
        string mag;
        string cent;
    }

    mapping(uint256 => Star) public tokenIdToStarInfo; 
    mapping(uint256 => uint256) public starsForSale;
    mapping(bytes32 => uint256) public uniqueness;

    event starClaimed(string name, string story, string ra, string dec, string mag);

    function checkIfStarExist(bytes32 _coordHash) public returns(bool) {
        return uniqueness[_coordHash] != 0;
    }

    function tokenIdToStarInfo(uint256 _tokenId) view public returns (string name, string story, string cent, string dec, string mag) {
        Star memory info = tokenIdToStarInfo[_tokenId];
        return (info.name, info.story, info.cent, info.dec, info.mag);
    }


    function createStar(string _name, string _story, string _cent, string _dec, string _mag, uint256 _tokenId) public { 
        require(_tokenId != 0);
        bytes32 coordHash = keccak256(_dec, _mag, _cent);
        require(checkIfStarExist(coordHash) != true, "Star already registered");
        Star memory newStar = Star(_name, _tokenId, _story, _dec, _mag, _cent);
        tokenIdToStarInfo[_tokenId] = newStar;
        uniqueness[coordHash] = _tokenId;
        _mint(msg.sender, _tokenId);
        emit staarClaimed(_name, _story, _cent, _dec, _mag);
    }

    function putStarUpForSale(uint256 _tokenId, uint256 _price) public { 
        require(this.ownerOf(_tokenId) == msg.sender, "You are not the owner of this star");

        starsForSale[_tokenId] = _price;
    }


    function buyStar(uint256 _tokenId) public payable { 
        require(starsForSale[_tokenId] > 0);
        
        uint256 starCost = starsForSale[_tokenId];
        address starOwner = this.ownerOf(_tokenId);
        require(msg.value >= starCost);

        _removeTokenFrom(starOwner, _tokenId);
        _addTokenTo(msg.sender, _tokenId);
        
        starOwner.transfer(starCost);

        if(msg.value > starCost) { 
            msg.sender.transfer(msg.value - starCost);
        }

        
    }

    function mint(uint256 tokenId) public {
        super._mint(msg.sender, tokenId);
    }
}