ERC721Mintable.sol

pragma solidity ^0.5.0;

import 'openzeppelin-solidity/contracts/utils/Address.sol';
import 'openzeppelin-solidity/contracts/drafts/Counters.sol';
import 'openzeppelin-solidity/contracts/math/SafeMath.sol';
import 'openzeppelin-solidity/contracts/token/ERC721/IERC721Receiver.sol';
import "./Oraclize.sol";

contract Ownable {
    //  TODO's
    //  1) create a private '_owner' variable of type address with a public getter function
    address private _owner;

    event TransferOwnership(address indexed oldOwner, address indexed newOwner);

    //  2) create an internal constructor that sets the _owner var to the creater of the contract
    constructor() public {
        _owner = msg.sender;
        emit TransferOwnership(address(0), _owner);
    } 
    //  3) create an 'onlyOwner' modifer that throws if called by any account other than the owner.
    modifier onlyOwner {
        require(
            msg.sender == _owner,
            "Only owner can call this function."
        );
        _;
    }
    //  4) fill out the transferOwnership function
    //  5) create an event that emits anytime ownerShip is transfered (including in the constructor)

    function transferOwnership(address newOwner) public onlyOwner {
        // TODO add functionality to transfer control of the contract to a newOwner.
        // make sure the new owner is a real address
        require(newOwner != address(0));
        emit TransferOwnership(_owner, newOwner);
        _owner = newOwner;
    }

    function owner() external view returns (address) {
        return _owner;
    }
}

//  TODO's: Create a Pausable contract that inherits from the Ownable contract
//  1) create a private '_paused' variable of type bool
//  2) create an internal constructor that sets the _paused variable to false
//  3) create 'whenNotPaused' & 'paused' modifier that throws in the appropriate situation
//  4) create a Paused & Unpaused event that emits the address that triggered the event

contract Pausable is Ownable {
    bool private _paused;

    event Paused(address _from);
    event Unpaused(address _from);

    modifier whenNotPaused() {
        require(!_paused);
        _;
    }

    modifier paused() {
        require(_paused);
        _;
    }

    constructor() public {
        _paused = false;
    }
}

contract ERC165 {
    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;
    /*
     * 0x01ffc9a7 ===
     *     bytes4(keccak256('supportsInterface(bytes4)'))
     */

    /**
     * @dev a mapping of interface id to whether or not it's supported
     */
    mapping(bytes4 => bool) private _supportedInterfaces;

    /**
     * @dev A contract implementing SupportsInterfaceWithLookup
     * implement ERC165 itself
     */
    constructor () internal {
        _registerInterface(_INTERFACE_ID_ERC165);
    }

    /**
     * @dev implement supportsInterface(bytes4) using a lookup table
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    /**
     * @dev internal method for registering an interface
     */
    function _registerInterface(bytes4 interfaceId) internal {
        require(interfaceId != 0xffffffff);
        _supportedInterfaces[interfaceId] = true;
    }
}

contract ERC721 is Pausable, ERC165 {

    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
    
    using SafeMath for uint256;
    using Address for address;
    using Counters for Counters.Counter;

    // Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
    // which can be also obtained as `IERC721Receiver(0).onERC721Received.selector`
    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;

    // Mapping from token ID to owner
    mapping (uint256 => address) private _tokenOwner;

    // Mapping from token ID to approved address
    mapping (uint256 => address) private _tokenApprovals;

    // Mapping from owner to number of owned token
    // IMPORTANT: this mapping uses Counters lib which is used to protect overflow when incrementing/decrementing a uint
    // use the following functions when interacting with Counters: increment(), decrement(), and current() to get the value
    // see: https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/drafts/Counters.sol
    mapping (address => Counters.Counter) private _ownedTokensCount;

    // Mapping from owner to operator approvals
    mapping (address => mapping (address => bool)) private _operatorApprovals;

    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;

    constructor () public {
        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_INTERFACE_ID_ERC721);
    }

    function balanceOf(address owner) public view returns (uint256) {
        // TODO return the token balance of given address
        // TIP: remember the functions to use for Counters. you can refresh yourself with the link above
        return _ownedTokensCount[owner].current();
    }

    function ownerOf(uint256 tokenId) public view returns (address) {
        // TODO return the owner of the given tokenId
        return _tokenOwner[tokenId];
    }

//    @dev Approves another address to transfer the given token ID
    function approve(address to, uint256 tokenId) public {
        address ownerTokenId = ownerOf(tokenId);
        // TODO require the given address to not be the owner of the tokenId
        require(to != ownerTokenId, "to address should not be the owner of the tokenId");

        // TODO require the msg sender to be the owner of the contract or isApprovedForAll() to be true
        //require(msg.sender == _owner || msg.sender == isApprovedForAll(ownerTokenId, msg.sender));
        // TODO add 'to' address to token approvals
        _tokenApprovals[tokenId] = to;
        // TODO emit Approval Event
        emit Approval(ownerTokenId, to, tokenId);
    }

    function getApproved(uint256 tokenId) public view returns (address) {
        // TODO return token approval if it exists
        require(_exists(tokenId));
        return _tokenApprovals[tokenId];
    }

    /**
     * @dev Sets or unsets the approval of a given operator
     * An operator is allowed to transfer all tokens of the sender on their behalf
     * @param to operator address to set the approval
     * @param approved representing the status of the approval to be set
     */
    function setApprovalForAll(address to, bool approved) public {
        require(to != msg.sender);
        _operatorApprovals[msg.sender][to] = approved;
        emit ApprovalForAll(msg.sender, to, approved);
    }

    /**
     * @dev Tells whether an operator is approved by a given owner
     * @param owner owner address which you want to query the approval of
     * @param operator operator address which you want to query the approval of
     * @return bool whether the given operator is approved by the given owner
     */
    function isApprovedForAll(address owner, address operator) public view returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    function transferFrom(address from, address to, uint256 tokenId) public {
        require(_isApprovedOrOwner(msg.sender, tokenId));

        _transferFrom(from, to, tokenId);
    }

    function safeTransferFrom(address from, address to, uint256 tokenId) public {
        safeTransferFrom(from, to, tokenId, "");
    }

    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public {
        transferFrom(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data));
    }

    /**
     * @dev Returns whether the specified token exists
     * @param tokenId uint256 ID of the token to query the existence of
     * @return bool whether the token exists
     */
    function _exists(uint256 tokenId) internal view returns (bool) {
        address owner = _tokenOwner[tokenId];
        return owner != address(0);
    }

    /**
     * @dev Returns whether the given spender can transfer a given token ID
     * @param spender address of the spender to query
     * @param tokenId uint256 ID of the token to be transferred
     * @return bool whether the msg.sender is approved for the given token ID,
     * is an operator of the owner, or is the owner of the token
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view returns (bool) {
        address owner = ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
    }

    // @dev Internal function to mint a new token
    // TIP: remember the functions to use for Counters. you can refresh yourself with the link above
    function _mint(address to, uint256 tokenId) internal {

        // TODO revert if given tokenId already exists or given address is invalid
        require(!_exists(tokenId));
        require(to != address(0));
        // TODO mint tokenId to given address & increase token count of owner
        _tokenOwner[tokenId] = to;
        _ownedTokensCount[to].increment();
        // TODO emit Transfer event
        emit Transfer(address(0), to, tokenId);
    }

    // @dev Internal function to transfer ownership of a given token ID to another address.
    // TIP: remember the functions to use for Counters. you can refresh yourself with the link above
    function _transferFrom(address from, address to, uint256 tokenId) internal {

        // TODO: require from address is the owner of the given token
        require(ownerOf(tokenId) == from);
        // TODO: require token is being transfered to valid address
        require(to != address(0));
        // TODO: clear approval
        _clearApproval(tokenId);
        // TODO: update token counts & transfer ownership of the token ID 
        _ownedTokensCount[from].decrement();
        _ownedTokensCount[to].increment();
        _tokenOwner[tokenId] = to;
        // TODO: emit correct event
        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Internal function to invoke `onERC721Received` on a target address
     * The call is not executed if the target address is not a contract
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(address from, address to, uint256 tokenId, bytes memory _data)
        internal returns (bool)
    {
        if (!to.isContract()) {
            return true;
        }

        bytes4 retval = IERC721Receiver(to).onERC721Received(msg.sender, from, tokenId, _data);
        return (retval == _ERC721_RECEIVED);
    }

    // @dev Private function to clear current approval of a given token ID
    function _clearApproval(uint256 tokenId) private {
        if (_tokenApprovals[tokenId] != address(0)) {
            _tokenApprovals[tokenId] = address(0);
        }
    }
}

contract ERC721Enumerable is ERC165, ERC721 {
    // Mapping from owner to list of owned token IDs
    mapping(address => uint256[]) private _ownedTokens;

    // Mapping from token ID to index of the owner tokens list
    mapping(uint256 => uint256) private _ownedTokensIndex;

    // Array with all token ids, used for enumeration
    uint256[] private _allTokens;

    // Mapping from token id to position in the allTokens array
    mapping(uint256 => uint256) private _allTokensIndex;

    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;
    /*
     * 0x780e9d63 ===
     *     bytes4(keccak256('totalSupply()')) ^
     *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) ^
     *     bytes4(keccak256('tokenByIndex(uint256)'))
     */

    /**
     * @dev Constructor function
     */
    constructor () public {
        // register the supported interface to conform to ERC721Enumerable via ERC165
        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
    }

    /**
     * @dev Gets the token ID at a given index of the tokens list of the requested owner
     * @param owner address owning the tokens list to be accessed
     * @param index uint256 representing the index to be accessed of the requested tokens list
     * @return uint256 token ID at the given index of the tokens list owned by the requested address
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view returns (uint256) {
        require(index < balanceOf(owner));
        return _ownedTokens[owner][index];
    }

    /**
     * @dev Gets the total amount of tokens stored by the contract
     * @return uint256 representing the total amount of tokens
     */
    function totalSupply() public view returns (uint256) {
        return _allTokens.length;
    }

    /**
     * @dev Gets the token ID at a given index of all the tokens in this contract
     * Reverts if the index is greater or equal to the total number of tokens
     * @param index uint256 representing the index to be accessed of the tokens list
     * @return uint256 token ID at the given index of the tokens list
     */
    function tokenByIndex(uint256 index) public view returns (uint256) {
        require(index < totalSupply());
        return _allTokens[index];
    }

    /**
     * @dev Internal function to transfer ownership of a given token ID to another address.
     * As opposed to transferFrom, this imposes no restrictions on msg.sender.
     * @param from current owner of the token
     * @param to address to receive the ownership of the given token ID
     * @param tokenId uint256 ID of the token to be transferred
     */
    function _transferFrom(address from, address to, uint256 tokenId) internal {
        super._transferFrom(from, to, tokenId);

        _removeTokenFromOwnerEnumeration(from, tokenId);

        _addTokenToOwnerEnumeration(to, tokenId);
    }

    /**
     * @dev Internal function to mint a new token
     * Reverts if the given token ID already exists
     * @param to address the beneficiary that will own the minted token
     * @param tokenId uint256 ID of the token to be minted
     */
    function _mint(address to, uint256 tokenId) internal {
        super._mint(to, tokenId);

        _addTokenToOwnerEnumeration(to, tokenId);

        _addTokenToAllTokensEnumeration(tokenId);
    }

    /**
     * @dev Gets the list of token IDs of the requested owner
     * @param owner address owning the tokens
     * @return uint256[] List of token IDs owned by the requested address
     */
    function _tokensOfOwner(address owner) internal view returns (uint256[] storage) {
        return _ownedTokens[owner];
    }

    /**
     * @dev Private function to add a token to this extension's ownership-tracking data structures.
     * @param to address representing the new owner of the given token ID
     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
     */
    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
        _ownedTokensIndex[tokenId] = _ownedTokens[to].length;
        _ownedTokens[to].push(tokenId);
    }

    /**
     * @dev Private function to add a token to this extension's token tracking data structures.
     * @param tokenId uint256 ID of the token to be added to the tokens list
     */
    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
        _allTokensIndex[tokenId] = _allTokens.length;
        _allTokens.push(tokenId);
    }

    /**
     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
     * while the token is not assigned a new owner, the _ownedTokensIndex mapping is _not_ updated: this allows for
     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
     * @param from address representing the previous owner of the given token ID
     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
     */
    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _ownedTokens[from].length.sub(1);
        uint256 tokenIndex = _ownedTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary
        if (tokenIndex != lastTokenIndex) {
            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];

            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
        }

        // This also deletes the contents at the last position of the array
        _ownedTokens[from].length--;

        // Note that _ownedTokensIndex[tokenId] hasn't been cleared: it still points to the old slot (now occupied by
        // lastTokenId, or just over the end of the array if the token was the last one).
    }

    /**
     * @dev Private function to remove a token from this extension's token tracking data structures.
     * This has O(1) time complexity, but alters the order of the _allTokens array.
     * @param tokenId uint256 ID of the token to be removed from the tokens list
     */
    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _allTokens.length.sub(1);
        uint256 tokenIndex = _allTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
        uint256 lastTokenId = _allTokens[lastTokenIndex];

        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

        // This also deletes the contents at the last position of the array
        _allTokens.length--;
        _allTokensIndex[tokenId] = 0;
    }
}

contract ERC721Metadata is ERC721Enumerable, usingOraclize {
    
    // TODO: Create private vars for token _name, _symbol, and _baseTokenURI (string)
    string private _name;
    string private _symbol;
    string private _baseTokenURI;
    // TODO: create private mapping of tokenId's to token uri's called '_tokenURIs'
    mapping(uint256 => string) private _tokenURIs;

    bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;
    /*
     * 0x5b5e139f ===
     *     bytes4(keccak256('name()')) ^
     *     bytes4(keccak256('symbol()')) ^
     *     bytes4(keccak256('tokenURI(uint256)'))
     */


    constructor (string memory name, string memory symbol, string memory baseTokenURI) public {
        // TODO: set instance var values
        _name = name;
        _symbol = symbol;
        _baseTokenURI = baseTokenURI;

        _registerInterface(_INTERFACE_ID_ERC721_METADATA);
    }

    // TODO: create external getter functions for name, symbol, and baseTokenURI

    function name() external view returns (string memory) {
        return _name;
    }

    function symbol() external view returns (string memory) {
        return _symbol;
    }

    function baseTokenURI() external view returns (string memory) {
        return _baseTokenURI;
    }

    function tokenURI(uint256 tokenId) external view returns (string memory) {
        require(_exists(tokenId));
        return _tokenURIs[tokenId];
    }


    // TODO: Create an internal function to set the tokenURI of a specified tokenId
    // It should be the _baseToeknURI + the tokenId in string form
    // TIP #1: use strConcat() from the imported oraclizeAPI lib to set the complete token URI
    // TIP #2: you can also use uint2str() to convert a uint to a string
        // see https://github.com/oraclize/ethereum-api/blob/master/oraclizeAPI_0.5.sol for strConcat()
    // require the token exists before setting

    function setTokenURI(uint256 tokenId) internal {
        require(_exists(tokenId));
        _tokenURIs[tokenId] = strConcat(_baseTokenURI, uint2str(tokenId));
    }

}

//  TODO's: Create CustomERC721Token contract that inherits from the ERC721Metadata contract. You can name this contract as you please
//  1) Pass in appropriate values for the inherited ERC721Metadata contract
//      - make the base token uri: https://s3-us-west-2.amazonaws.com/udacity-blockchain/capstone/
//  2) create a public mint() that does the following:
//      -can only be executed by the contract owner
//      -takes in a 'to' address, tokenId, and tokenURI as parameters
//      -returns a true boolean upon completion of the function
//      -calls the superclass mint and setTokenURI functions