npm package: @rarible/auction
Description: Auction House implements English auction with fixed step
Latest version: 0.8.6

# Auction House
Auction House implements English auction with fixed step

For now there are two AuctionHouse contracts, the main difference between them is the type of sell asset:
  - `AuctionHouse721`
    - sell asset = ERC721
    - buy asset = ETH or ERC20
  - `AuctionHouse1155`
    - sell asset = ERC1155
    - buy asset = ETH or ERC20

There are two parameters of AuctionHouse that are the same for all autions and can be changed by AuctionHouse owner:
  - `minimalDuration`
    - defines the minimal duration of auctions
  - `minimalStepBasePoint`
    - is the minimal persentage increase between bids (in base points)
    - e.g. minimalStepBasePoint = 300 = 3%, first bid is 100 ETH, the second one should be not less than (100 + 100*3% =) 103

ERC721 Auction supports party bid
## Features
### Time frame
Auction time frame is decided by 2 parameters
  - `duration`
    - mandatory parameter, that defines the duration of auction in seconds
    - it must be between `minimalDuration`(default value is 15 days) and `1000 days` (constant)
  - `startTime`
    - optional parameter that defines the start time an auction
    - unix timestamp, can't be less than the time of creation of the auction

So there are two cases of how the auction time frame can work:
  - if `startTime` is 0, then then the auction starts at the first bid that satisfies `minimalPrice`. Then the `endTime` is calculated at the moment of the first bid as well (`now` + `duration`)
  - if `startTime` is set, then the `endTime` is calculated at the creation of an auction (`startTime` + `duration`)

If a new bid is put when auction has less than `minimalDuration` left till `endTime`, then `endTime` = `now` + `minimalDuration`

## Data model
### `Auction` (ERC721):
- **address sellToken** - sell asset contract address
- **uint sellTokenId** - sell asset tokenId
- **address buyAsset** - buy asset contract address if ERC20 (address(0) if buy asset = ETH)
- **uint96 endTime** - auction end time in unix timestamp
- **Bid lastBid** - last successful `Bid`
- **address payable seller** - seller address
- **uint96 minimalPrice** - minimal amount of the first bid
- **address payable buyer** - last successful bidder
- **uint64 protocolFee** - protocolFee at the time of auction creation
- **bytes4 dataType** - version of `data` field 
- **bytes data** - encoded additional data, V1 fields :
  - **uint originFee** - auction origin fee in one uint slot (first 12 bytes store value, last 20 bytes store recipient)
  - **uint duration** - auction duration
  - **uint startTime** - auction start time 
  - **uint buyOutPrice** - auction buyOut price (if bid amout > buyout price, then auction finishes and all transfers are done )

### `Auction` (ERC1155, the main difference from struct Auction ERC721 is the additional field **uint96 sellTokenValue**):
- **address sellToken** - sell asset contract address
- **uint96 sellTokenValue** - sell asset value
- **uint sellTokenId** - sell asset tokenId
- **address buyAsset** - buy asset contract address if ERC20 (address(0) if buy asset = ETH)
- **uint96 endTime** - auction end time in unix timestamp
- **Bid lastBid** - last successful `Bid`
- **address payable seller** - seller address
- **uint96 minimalPrice** - minimal amount of the first bid
- **address payable buyer** - last successful bidder
- **uint64 protocolFee** - protocolFee at the time of auction creation
- **bytes4 dataType** - version of `data` field 
- **bytes data** - encoded additional data, V1 fields :
  - **uint originFee** - auction origin fee in one uint slot (first 12 bytes store value, last 20 bytes store recipient)
  - **uint duration** - auction duration
  - **uint startTime** - auction start time 
  - **uint buyOutPrice** - auction buyOut price (if bid amout > buyout price, then auction finishes and all transfers are done )

#### Bid:
- **amount** - `bid` amount
- **dataType** - version of `data` field 
- **data** - encoded additional data, V1 fields :
  - **uint originFee** - bid origin fee in one uint slot (first 12 bytes store value, last 20 bytes store recipient)
### Main functions
#### **startAuction** - 
- start new auction 
- emits event `AuctionCreated(uint indexed auctionId, address seller, uint128 endTime)`
- can be called from anyone
- arguments for ERC721 Auction:
  - **address _sellToken** - sell token address
  - **uint _sellTokenId** - sell token Id
  - **address _buyAsset** - buy asset address (0 if ETH)
  - **uint96 minimalPrice** - minimal first bid price
  - **bytes4 dataType** - data field type
  - **bytes memory data** - additional Data
- arguments for ERC1155 Auction (1 additional field uint96 _sellTokenValue):
  - **address _sellToken** - sell token address
  - **uint96 _sellTokenValue** - sell token value
  - **uint _sellTokenId** - sell token Id
  - **address _buyAsset** - buy asset address (0 if ETH)
  - **uint96 minimalPrice** - minimal first bid price
  - **bytes4 dataType** - data field type
  - **bytes memory data** - additional Data

#### **putBid** - 
- puts bid on specific auction
- emits event `BidPlaced(uint indexed auctionId, address seller, uint128 endTime)`
- can be called from anyone
- arguments:
  - **_auctionId** - auction Id
  - **bid** - bid struct
#### **finishAuction** - 
- finishes auction if it's ended(now > endTime) and has at least 1 bid
- emits event `AuctionFinished(_auctionId)`
- can be called from anyone
- arguments:
  - **_auctionId** - auction Id

#### **buyOut** - 
- buy out the sell item and finishes the auction
- emits event `AuctionBuyOut(uint indexed auctionId, address buyer)`
- emits event `AuctionFinished(_auctionId)`
- can be called from anyone
- arguments:
  - **_auctionId** - auction Id
  - **bid** - bid struct
  
#### **finishAuction** - 
- finishes auction if it's not started and has no bids
- emits event `AuctionCancelled(uint indexed auctionId)`
- emits event `AuctionFinished(_auctionId)`
- can be called from auction creator
- arguments:
  - **_auctionId** - auction Id