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pragma solidity ^0.5.10; // Imports symbols from other files into the current contract. // In this case, a series of helper contracts from OpenZeppelin. // Learn more: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#importing-other-source-files import "../node_modules/@openzeppelin/contracts/token/ERC721/IERC721.sol"; import "../node_modules/@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol"; import "../node_modules/@openzeppelin/contracts/introspection/ERC165.sol"; import "../node_modules/@openzeppelin/contracts/math/SafeMath.sol"; // The `is` keyword is used to inherit functions and keywords from external contracts. // In this case, `CryptoPizza` inherits from the `IERC721` and `ERC165` contracts. // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#inheritance contract CryptoPizza is IERC721, ERC165 { // Uses OpenZeppelin's SafeMath library to perform arithmetic operations safely. // Learn more: https://docs.openzeppelin.com/contracts/2.x/api/math#SafeMath using SafeMath for uint256; // Constant state variables in Solidity are similar to other languages // but you must assign from an expression which is constant at compile time. // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constant-state-variables uint256 constant dnaDigits = 10; uint256 constant dnaModulus = 10 ** dnaDigits; bytes4 private constant _ERC721_RECEIVED = 0x150b7a02; // Struct types let you define your own type // Learn more: https://solidity.readthedocs.io/en/v0.5.10/types.html#structs struct Pizza { string name; uint256 dna; } // Creates an empty array of Pizza structs Pizza[] public pizzas; // Mapping from pizza ID to its owner's address mapping(uint256 => address) public pizzaToOwner; // Mapping from owner's address to number of owned token mapping(address => uint256) public ownerPizzaCount; // Mapping from token ID to approved address mapping(uint256 => address) pizzaApprovals; // You can nest mappings, this example maps owner to operator approvals mapping(address => mapping(address => bool)) private operatorApprovals; // Internal function to create a random Pizza from string (name) and DNA function _createPizza(string memory _name, uint256 _dna) // The `internal` keyword means this function is only visible // within this contract and contracts that derive this contract // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#visibility-and-getters internal // `isUnique` is a function modifier that checks if the pizza already exists // Learn more: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html#function-modifiers isUnique(_name, _dna) { // Adds Pizza to array of Pizzas and get id uint256 id = SafeMath.sub(pizzas.push(Pizza(_name, _dna)), 1); // Checks that Pizza owner is the same as current user // Learn more: https://solidity.readthedocs.io/en/v0.5.10/control-structures.html#error-handling-assert-require-revert-and-exceptions // note that address(0) is the zero address, // indicating that pizza[id] is not yet allocated to a particular user. assert(pizzaToOwner[id] == address(0)); // Maps the Pizza to the owner pizzaToOwner[id] = msg.sender; ownerPizzaCount[msg.sender] = SafeMath.add( ownerPizzaCount[msg.sender], 1 ); } // Creates a random Pizza from string (name) function createRandomPizza(string memory _name) public { uint256 randDna = generateRandomDna(_name, msg.sender); _createPizza(_name, randDna); } // Generates random DNA from string (name) and address of the owner (creator) function generateRandomDna(string memory _str, address _owner) public // Functions marked as `pure` promise not to read from or modify the state // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#pure-functions pure returns (uint256) { // Generates random uint from string (name) + address (owner) uint256 rand = uint256(keccak256(abi.encodePacked(_str))) + uint256(_owner); rand = rand % dnaModulus; return rand; } // Returns array of Pizzas found by owner function getPizzasByOwner(address _owner) public // Functions marked as `view` promise not to modify state // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#view-functions view returns (uint256[] memory) { // Uses the `memory` storage location to store values only for the // lifecycle of this function call. // Learn more: https://solidity.readthedocs.io/en/v0.5.10/introduction-to-smart-contracts.html#storage-memory-and-the-stack uint256[] memory result = new uint256[](ownerPizzaCount[_owner]); uint256 counter = 0; for (uint256 i = 0; i < pizzas.length; i++) { if (pizzaToOwner[i] == _owner) { result[counter] = i; counter++; } } return result; } // Transfers Pizza and ownership to other address function transferFrom(address _from, address _to, uint256 _pizzaId) public { require(_from != address(0) && _to != address(0), "Invalid address."); require(_exists(_pizzaId), "Pizza does not exist."); require(_from != _to, "Cannot transfer to the same address."); require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved."); ownerPizzaCount[_to] = SafeMath.add(ownerPizzaCount[_to], 1); ownerPizzaCount[_from] = SafeMath.sub(ownerPizzaCount[_from], 1); pizzaToOwner[_pizzaId] = _to; // Emits event defined in the imported IERC721 contract emit Transfer(_from, _to, _pizzaId); _clearApproval(_to, _pizzaId); } /** * Safely transfers the ownership of a given token ID to another address * If the target address is a contract, it must implement `onERC721Received`, * which is called upon a safe transfer, and return the magic value * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; * otherwise, the transfer is reverted. */ function safeTransferFrom(address from, address to, uint256 pizzaId) public { // solium-disable-next-line arg-overflow this.safeTransferFrom(from, to, pizzaId, ""); } /** * Safely transfers the ownership of a given token ID to another address * If the target address is a contract, it must implement `onERC721Received`, * which is called upon a safe transfer, and return the magic value * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`; * otherwise, the transfer is reverted. */ function safeTransferFrom( address from, address to, uint256 pizzaId, bytes memory _data ) public { this.transferFrom(from, to, pizzaId); require(_checkOnERC721Received(from, to, pizzaId, _data), "Must implement onERC721Received."); } /** * Internal function to invoke `onERC721Received` on a target address * The call is not executed if the target address is not a contract */ function _checkOnERC721Received( address from, address to, uint256 pizzaId, bytes memory _data ) internal returns (bool) { if (!isContract(to)) { return true; } bytes4 retval = IERC721Receiver(to).onERC721Received( msg.sender, from, pizzaId, _data ); return (retval == _ERC721_RECEIVED); } // Burns a Pizza - destroys Token completely // The `external` function modifier means this function is // part of the contract interface and other contracts can call it function burn(uint256 _pizzaId) external { require(msg.sender != address(0), "Invalid address."); require(_exists(_pizzaId), "Pizza does not exist."); require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved."); ownerPizzaCount[msg.sender] = SafeMath.sub( ownerPizzaCount[msg.sender], 1 ); pizzaToOwner[_pizzaId] = address(0); } // Returns count of Pizzas by address function balanceOf(address _owner) public view returns (uint256 _balance) { return ownerPizzaCount[_owner]; } // Returns owner of the Pizza found by id function ownerOf(uint256 _pizzaId) public view returns (address _owner) { address owner = pizzaToOwner[_pizzaId]; require(owner != address(0), "Invalid Pizza ID."); return owner; } // Approves other address to transfer ownership of Pizza function approve(address _to, uint256 _pizzaId) public { require(msg.sender == pizzaToOwner[_pizzaId], "Must be the Pizza owner."); pizzaApprovals[_pizzaId] = _to; emit Approval(msg.sender, _to, _pizzaId); } // Returns approved address for specific Pizza function getApproved(uint256 _pizzaId) public view returns (address operator) { require(_exists(_pizzaId), "Pizza does not exist."); return pizzaApprovals[_pizzaId]; } /** * Private function to clear current approval of a given token ID * Reverts if the given address is not indeed the owner of the token */ function _clearApproval(address owner, uint256 _pizzaId) private { require(pizzaToOwner[_pizzaId] == owner, "Must be pizza owner."); require(_exists(_pizzaId), "Pizza does not exist."); if (pizzaApprovals[_pizzaId] != address(0)) { pizzaApprovals[_pizzaId] = address(0); } } /* * Sets or unsets the approval of a given operator * An operator is allowed to transfer all tokens of the sender on their behalf */ function setApprovalForAll(address to, bool approved) public { require(to != msg.sender, "Cannot approve own address"); operatorApprovals[msg.sender][to] = approved; emit ApprovalForAll(msg.sender, to, approved); } // Tells whether an operator is approved by a given owner function isApprovedForAll(address owner, address operator) public view returns (bool) { return operatorApprovals[owner][operator]; } // Takes ownership of Pizza - only for approved users function takeOwnership(uint256 _pizzaId) public { require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved."); address owner = this.ownerOf(_pizzaId); this.transferFrom(owner, msg.sender, _pizzaId); } // Checks if Pizza exists function _exists(uint256 pizzaId) internal view returns (bool) { address owner = pizzaToOwner[pizzaId]; return owner != address(0); } // Checks if address is owner or is approved to transfer Pizza function _isApprovedOrOwner(address spender, uint256 pizzaId) internal view returns (bool) { address owner = pizzaToOwner[pizzaId]; // Disable solium check because of // https://github.com/duaraghav8/Solium/issues/175 // solium-disable-next-line operator-whitespace return (spender == owner || this.getApproved(pizzaId) == spender || this.isApprovedForAll(owner, spender)); } // Check if Pizza is unique and doesn't exist yet modifier isUnique(string memory _name, uint256 _dna) { bool result = true; for (uint256 i = 0; i < pizzas.length; i++) { if ( keccak256(abi.encodePacked(pizzas[i].name)) == keccak256(abi.encodePacked(_name)) && pizzas[i].dna == _dna ) { result = false; } } require(result, "Pizza with such name already exists."); _; } // Returns whether the target address is a contract function isContract(address account) internal view returns (bool) { uint256 size; // Currently there is no better way to check if there is a contract in an address // than to check the size of the code at that address. // See https://ethereum.stackexchange.com/a/14016/36603 // for more details about how this works. // TODO Check this again before the Serenity release, because all addresses will be // contracts then. // solium-disable-next-line security/no-inline-assembly assembly { size := extcodesize(account) } return size > 0; } }