pragma solidity ^0.5.0;

import "./IERC1155.sol";
import "./IERC1155TokenReceiver.sol";
import "openzeppelin-solidity/contracts/math/SafeMath.sol";
import "openzeppelin-solidity/contracts/utils/Address.sol";
import "openzeppelin-solidity/contracts/introspection/ERC165.sol";

/**
 * @title Standard ERC1155 token
 *
 * @dev Implementation of the basic standard multi-token.
 * See https://eips.ethereum.org/EIPS/eip-1155
 * Originally based on code by Enjin: https://github.com/enjin/erc-1155
 */
contract ERC1155 is ERC165, IERC1155
{
    using SafeMath for uint256;
    using Address for address;

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

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

    constructor()
        public
    {
        _registerInterface(
            ERC1155(0).safeTransferFrom.selector ^
            ERC1155(0).safeBatchTransferFrom.selector ^
            ERC1155(0).balanceOf.selector ^
            ERC1155(0).balanceOfBatch.selector ^
            ERC1155(0).setApprovalForAll.selector ^
            ERC1155(0).isApprovedForAll.selector
        );
    }

    /**
        @dev Get the specified address' balance for token with specified ID.
        @param owner The address of the token holder
        @param id ID of the token
        @return The owner's balance of the token type requested
     */
    function balanceOf(address owner, uint256 id) public view returns (uint256) {
        require(owner != address(0), "ERC1155: balance query for the zero address");
        return _balances[id][owner];
    }

    /**
        @dev Get the balance of multiple account/token pairs
        @param owners The addresses of the token holders
        @param ids IDs of the tokens
        @return Balances for each owner and token id pair
     */
    function balanceOfBatch(
        address[] memory owners,
        uint256[] memory ids
    )
        public
        view
        returns (uint256[] memory)
    {
        require(owners.length == ids.length, "ERC1155: owners and IDs must have same lengths");

        uint256[] memory batchBalances = new uint256[](owners.length);

        for (uint256 i = 0; i < owners.length; ++i) {
            require(owners[i] != address(0), "ERC1155: some address in batch balance query is zero");
            batchBalances[i] = _balances[ids[i]][owners[i]];
        }

        return batchBalances;
    }

    /**
     * @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 operator address to set the approval
     * @param approved representing the status of the approval to be set
     */
    function setApprovalForAll(address operator, bool approved) external {
        _operatorApprovals[msg.sender][operator] = approved;
        emit ApprovalForAll(msg.sender, operator, approved);
    }

    /**
        @notice Queries the approval status of an operator for a given owner.
        @param owner     The owner of the Tokens
        @param operator  Address of authorized operator
        @return           True if the operator is approved, false if not
    */
    function isApprovedForAll(address owner, address operator) external view returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
        @dev Transfers `value` amount of an `id` from the `from` address to the `to` address specified.
        Caller must be approved to manage the tokens being transferred out of the `from` account.
        If `to` is a smart contract, will call `onERC1155Received` on `to` and act appropriately.
        @param from Source address
        @param to Target address
        @param id ID of the token type
        @param value Transfer amount
        @param data Data forwarded to `onERC1155Received` if `to` is a contract receiver
    */
    function safeTransferFrom(
        address from,
        address to,
        uint256 id,
        uint256 value,
        bytes calldata data
    )
        external
    {
        require(to != address(0), "ERC1155: target address must be non-zero");
        require(
            from == msg.sender || _operatorApprovals[from][msg.sender] == true,
            "ERC1155: need operator approval for 3rd party transfers."
        );

        _balances[id][from] = _balances[id][from].sub(value);
        _balances[id][to] = value.add(_balances[id][to]);

        emit TransferSingle(msg.sender, from, to, id, value);

        _doSafeTransferAcceptanceCheck(msg.sender, from, to, id, value, data);
    }

    /**
        @dev Transfers `values` amount(s) of `ids` from the `from` address to the
        `to` address specified. Caller must be approved to manage the tokens being
        transferred out of the `from` account. If `to` is a smart contract, will
        call `onERC1155BatchReceived` on `to` and act appropriately.
        @param from Source address
        @param to Target address
        @param ids IDs of each token type
        @param values Transfer amounts per token type
        @param data Data forwarded to `onERC1155Received` if `to` is a contract receiver
    */
    function safeBatchTransferFrom(
        address from,
        address to,
        uint256[] calldata ids,
        uint256[] calldata values,
        bytes calldata data
    )
        external
    {
        require(ids.length == values.length, "ERC1155: IDs and values must have same lengths");
        require(to != address(0), "ERC1155: target address must be non-zero");
        require(
            from == msg.sender || _operatorApprovals[from][msg.sender] == true,
            "ERC1155: need operator approval for 3rd party transfers."
        );

        for (uint256 i = 0; i < ids.length; ++i) {
            uint256 id = ids[i];
            uint256 value = values[i];

            _balances[id][from] = _balances[id][from].sub(value);
            _balances[id][to] = value.add(_balances[id][to]);
        }

        emit TransferBatch(msg.sender, from, to, ids, values);

        _doSafeBatchTransferAcceptanceCheck(msg.sender, from, to, ids, values, data);
    }

    /**
     * @dev Internal function to mint an amount of a token with the given ID
     * @param to The address that will own the minted token
     * @param id ID of the token to be minted
     * @param value Amount of the token to be minted
     * @param data Data forwarded to `onERC1155Received` if `to` is a contract receiver
     */
    function _mint(address to, uint256 id, uint256 value, bytes memory data) internal {
        require(to != address(0), "ERC1155: mint to the zero address");

        _balances[id][to] = value.add(_balances[id][to]);
        emit TransferSingle(msg.sender, address(0), to, id, value);

        _doSafeTransferAcceptanceCheck(msg.sender, address(0), to, id, value, data);
    }

    /**
     * @dev Internal function to burn an amount of a token with the given ID
     * @param owner Account which owns the token to be burnt
     * @param id ID of the token to be burnt
     * @param value Amount of the token to be burnt
     */
    function _burn(address owner, uint256 id, uint256 value) internal {
        _balances[id][owner] = _balances[id][owner].sub(value);
        emit TransferSingle(msg.sender, owner, address(0), id, value);
    }

    function _doSafeTransferAcceptanceCheck(
        address operator,
        address from,
        address to,
        uint256 id,
        uint256 value,
        bytes memory data
    )
        internal
    {
        if(to.isContract()) {
            require(
                IERC1155TokenReceiver(to).onERC1155Received(operator, from, id, value, data) ==
                    IERC1155TokenReceiver(to).onERC1155Received.selector,
                "ERC1155: got unknown value from onERC1155Received"
            );
        }
    }

    function _doSafeBatchTransferAcceptanceCheck(
        address operator,
        address from,
        address to,
        uint256[] memory ids,
        uint256[] memory values,
        bytes memory data
    )
        internal
    {
        if(to.isContract()) {
            require(
                IERC1155TokenReceiver(to).onERC1155BatchReceived(operator, from, ids, values, data) == IERC1155TokenReceiver(to).onERC1155BatchReceived.selector,
                "ERC1155: got unknown value from onERC1155BatchReceived"
            );
        }
    }
}