Pack: using Chainlink VRF v2 (Direct Funding Method) (#296)

* add chainlink contracts package

* Create PackVRFDirect: VRF with Direct payment

* Burn packs in the claimRewards function instead

* Remove addPackContents to bring down size

* Change contract type Pack - Pack_VRF

* Move pack test to dir

* Bug fix: expect randomWords to initially be empty.

* Move PackVRFDirect events to interface

* Tests for PackVRFDirect

* PackVRFDirect: Update docs

* Add benchmark test: fulfillRandomness

* Make openerToReqId public

* Offer convenience public fn canClaimRewards

* pkg update

* fix canClaimRewards

* pkg release

* Add openPackAdnClaimRewards

* pkg release

* Add tests for openPackAndClaimRewards

* allow VRF wrapper to call claim rewards

* prevent calling open twice while in flight

* Add openPackAndClaim to interface

* pkg release

* Add tests for not being able to open pack while repvious req is in flight

* fulfillRandomWords: low gas failsafe

* add WIP comment

Co-authored-by: Joaquim Verges <joaquim.verges@gmail.com>
Co-authored-by: Yash <kumaryashcse@gmail.com>

Author: 3 people

contracts/interfaces/IPackVRFDirect.sol

@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.11;
+
+import "../extension/interface/ITokenBundle.sol";
+
+/**
+ *  The thirdweb `Pack` contract is a lootbox mechanism. An account can bundle up arbitrary ERC20, ERC721 and ERC1155 tokens into
+ *  a set of packs. A pack can then be opened in return for a selection of the tokens in the pack. The selection of tokens distributed
+ *  on opening a pack depends on the relative supply of all tokens in the packs.
+ */
+
+interface IPackVRFDirect is ITokenBundle {
+    /**
+     *  @notice All info relevant to packs.
+     *
+     *  @param perUnitAmounts           Mapping from a UID -> to the per-unit amount of that asset i.e. `Token` at that index.
+     *  @param openStartTimestamp       The timestamp after which packs can be opened.
+     *  @param amountDistributedPerOpen The number of reward units distributed per open.
+     */
+    struct PackInfo {
+        uint256[] perUnitAmounts;
+        uint128 openStartTimestamp;
+        uint128 amountDistributedPerOpen;
+    }
+
+    /// @notice Emitted when a set of packs is created.
+    event PackCreated(uint256 indexed packId, address recipient, uint256 totalPacksCreated);
+
+    /// @notice Emitted when the opening of a pack is requested.
+    event PackOpenRequested(address indexed opener, uint256 indexed packId, uint256 amountToOpen, uint256 requestId);
+
+    /// @notice Emitted when Chainlink VRF fulfills a random number request.
+    event PackRandomnessFulfilled(uint256 indexed packId, uint256 indexed requestId);
+
+    /// @notice Emitted when a pack is opened.
+    event PackOpened(
+        uint256 indexed packId,
+        address indexed opener,
+        uint256 numOfPacksOpened,
+        Token[] rewardUnitsDistributed
+    );
+
+    /**
+     *  @notice Creates a pack with the stated contents.
+     *
+     *  @param contents                 The reward units to pack in the packs.
+     *  @param numOfRewardUnits         The number of reward units to create, for each asset specified in `contents`.
+     *  @param packUri                  The (metadata) URI assigned to the packs created.
+     *  @param openStartTimestamp       The timestamp after which packs can be opened.
+     *  @param amountDistributedPerOpen The number of reward units distributed per open.
+     *  @param recipient                The recipient of the packs created.
+     *
+     *  @return packId The unique identifer of the created set of packs.
+     *  @return packTotalSupply The total number of packs created.
+     */
+    function createPack(
+        Token[] calldata contents,
+        uint256[] calldata numOfRewardUnits,
+        string calldata packUri,
+        uint128 openStartTimestamp,
+        uint128 amountDistributedPerOpen,
+        address recipient
+    ) external payable returns (uint256 packId, uint256 packTotalSupply);
+
+    /**
+     *  @notice Lets a pack owner request to open a pack.
+     *
+     *  @param packId       The identifier of the pack to open.
+     *  @param amountToOpen The number of packs to open at once.
+     */
+    function openPack(uint256 packId, uint256 amountToOpen) external returns (uint256 requestId);
+
+    /// @notice Called by a pack opener to claim rewards from the opened pack.
+    function claimRewards() external returns (Token[] memory rewardUnits);
+
+    /// @notice Called by a pack opener to open a pack in a single transaction, instead of calling openPack and claimRewards separately.
+    function openPackAndClaimRewards(
+        uint256 _packId,
+        uint256 _amountToOpen,
+        uint32 _callBackGasLimit
+    ) external returns (uint256);
+
+    /// @notice Returns whether a pack opener is ready to call `claimRewards`.
+    function canClaimRewards(address _opener) external view returns (bool);
+}