# Order types

Element NFT market is built on off-chain order book and on-chain matching system. off-chain order with EIP-712 signatures are called <mark style="color:green;">Maker Orders</mark>.  The paramters against a maker order are called <mark style="color:green;">Taker Param</mark>.

A maker order is stored at off-chain order book (a special order service for query and storage orders),  maker order is passive, it can only be executed by a taker(EOA or smart contract) to execute transaction on chain, so the gas fees are paid by taker.

## Maker Order

### ERC721 SellOrder

A sell order means that the maker wants to sell the NFT.  "Listing" action will make a sell order.

```
  struct NFTSellOrder {
        address maker; 
        address taker; 
        uint256 expiry;
        uint256 nonce;
        IERC20 erc20Token; 
        uint256 erc20TokenAmount;
        Fee[] fees;
        address nft;
        uint256 nftId;
    }
    
    struct Fee {
        address recipient;
        uint256 amount;
        bytes feeData;
    }
    
    struct Signature {
        SignatureType signatureType; 
        uint8 v;
        bytes32 r;
        bytes32 s;
    }
```

Params descriptions:

* **maker** - the address of the signer of this maker order
* **taker** - the address of the taker who can take this order if specified, or keep null
* **expiry** - the  time when this order expired (second)
* nonce - the unique id of this order, use a auto increment id will save gas
* **erc20Token** - the payment token address,  0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE represent native token   &#x20;
* **erc20TokenAmount** - the amount of the payment token
* **fees** - the fees of this order
* **nft** - the collection address of the NFT
* **nftId** - the tokenId of this collection address
* **signatureType** - 0 EIP721, 1 PRESIGNED
* **v、r、s** - Ethereum uses ECDSA signatures.

### ERC721 BuyOrder

A buy order means that the maker wants to buy an NFT.  "Make Offer" action will make a buy order.

```
```

```
 struct NFTBuyOrder {
        address maker;
        address taker;
        uint256 expiry;
        uint256 nonce;
        IERC20 erc20Token;
        uint256 erc20TokenAmount;
        Fee[] fees;
        address nft;
        uint256 nftId;
        Property[] nftProperties;
    }
    
    struct Property {
        IPropertyValidator propertyValidator;
        bytes propertyData;
    }

    struct Fee {
        address recipient;
        uint256 amount;
        bytes feeData;
    }

```

Params descriptions:

* **maker、taker、expiry、nonce、erc20Token、erc20TokenAmount、fees、nft、nftId、signatureType、v、r、s  -** same as SellOrder
* **nftProperties** - used for collection order if push a  Property.propertyValidator = address(0) to the array&#x20;

### ERC1155 SellOrder

```
  struct ERC1155SellOrder {
        address maker;
        address taker;
        uint256 expiry;
        uint256 nonce;
        IERC20 erc20Token;
        uint256 erc20TokenAmount;
        Fee[] fees;
        address erc1155Token;
        uint256 erc1155TokenId;
        // End of fields shared with NFTOrder
        uint128 erc1155TokenAmount;
    }

```

* **maker、taker、expiry、nonce、erc20Token、erc20TokenAmount、fees 、signatureType、v、r、s-** same as ERC721 SellOrder
* **erc1155Token** - the collection address of ERC1155,  same as ER721 nft
* **erc1155TokenId** - the tokenId of this collection, same as ERC721 nftId
* **erc1155TokenAmount** - the amount of this tokenId

### **ERC1155 BuyOrder**

```
   struct ERC1155BuyOrder {
        address maker;
        address taker;
        uint256 expiry;
        uint256 nonce;
        IERC20 erc20Token;
        uint256 erc20TokenAmount;
        Fee[] fees;
        address erc1155Token;
        uint256 erc1155TokenId;
        Property[] erc1155TokenProperties;
        // End of fields shared with NFTOrder
        uint128 erc1155TokenAmount;
    }

```

* **maker、taker、expiry、nonce、erc20Token、erc20TokenAmount、fees、signatureType、v、r、s、erc1155Token、erc1155TokenId、erc1155TokenAmount -** same as ERC1155 SellOrder
* **erc1155TokenProperties** - same as ERC721 nftProperties

## Taker Param

Take param used to call smart contract functions to match against a maker order.

### buyERC721

Buys an ERC721 asset by filling the given sell order.

```
function buyERC721(
    LibNFTOrder.NFTSellOrder memory sellOrder, 
    LibSignature.Signature memory signature
) public override payable 
```

* **sellOrder** - the sell order struct params
* **signature** - the signature of the sell order

### buyERC721Ex

Advance version of buyERC721 with more feature: mix payment with ETH+WETH、specify taker and callback.

```
  function buyERC721Ex(
        LibNFTOrder.NFTSellOrder memory sellOrder,
        LibSignature.Signature memory signature,
        address taker,
        bytes memory callbackData
    ) public override payable
```

* **sellOrder、signature** - same as buyERC721
* **taker** - the taker of order,  msg.sender or the real buyer behind a aggregator like gem.xyz/genie.xyz
* **callbackData** - call back function to the taker address if needed

### sellERC721

Sells an ERC721 asset to fill the given order.

```
function sellERC721(
        LibNFTOrder.NFTBuyOrder memory buyOrder,
        LibSignature.Signature memory signature,
        uint256 erc721TokenId,
        bool unwrapNativeToken,
        bytes memory callbackData
    ) 
```

* **buyOrder -** the erc721 buy order&#x20;
* **signature** - the signature of the buy order
* **erc721TokenId** - The ID of the ERC721 asset being sold. If the given order specifies properties,the asset must satisfy those properties. Otherwise, it must equal the tokenId in the order.
* **unwrapNativeToken** - If this parameter is true and the ERC20 token of the order is e.g. WETH, unwraps the token before transferring it to the taker.
* **callbackData -** callbackData If this parameter is non-zero, invokes `zeroExERC721OrderCallback` on `msg.sender` after the ERC20 tokens have been transferred to `msg.sender` but before transferring the ERC721 asset to the buyer.

### buyERC1155

Same as buyERC721.

```
   function buyERC1155(
        LibNFTOrder.ERC1155SellOrder memory sellOrder,
        LibSignature.Signature memory signature,
        uint128 erc1155BuyAmount
    ) public override payable
```

* **erc1155BuyAmount** - the number want to buy

### buyERC1155Ex

Advance version of buyERC1155 with more feature: mix payment with ETH+WETH、specify taker and callback.

```
```

```
  function buyERC1155Ex(
        LibNFTOrder.ERC1155SellOrder memory sellOrder,
        LibSignature.Signature memory signature,
        address taker,
        uint128 erc1155BuyAmount,
        bytes memory callbackData
    )
```

### sellERC1155

same as sellERC721

```
   function sellERC1155(
        LibNFTOrder.ERC1155BuyOrder memory buyOrder,
        LibSignature.Signature memory signature,
        uint256 erc1155TokenId,
        uint128 erc1155SellAmount,
        bool unwrapNativeToken,
        bytes memory callbackData
    )
```

* **erc1155SellAmount** - the number want to sell