From 6e9c67a070ccac36a63de249a214fa33f0a85a06 Mon Sep 17 00:00:00 2001
From: RedVeil <leon.niesler@gmail.com>
Date: Wed, 1 Feb 2023 12:41:46 +0100
Subject: [PATCH] brought in SugarVault from storming0x

---
 packages/foundry/src/utils/SugarVault.sol | 127 ++++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 packages/foundry/src/utils/SugarVault.sol

diff --git a/packages/foundry/src/utils/SugarVault.sol b/packages/foundry/src/utils/SugarVault.sol
new file mode 100644
index 00000000..05946535
--- /dev/null
+++ b/packages/foundry/src/utils/SugarVault.sol
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-3.0
+// Docgen-SOLC: 0.8.15
+
+pragma solidity ^0.8.15;
+
+import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
+import "../interfaces/IERC4626.sol";
+
+/********************
+ *
+ *   This contract is a POC as an example of a ERC4626 integration meant for instructive purposes.
+ *   The donator assigns approves a token to Sugar Contract and can StartSharingYield with a receiver.
+ *   The receiver can claim the donated yield that's "streamed" every time yield is realized in vault.
+ *   The donator can stopSharingYield() any time and receiver won't be able to claim yield after this.
+ *
+ *
+ *   // TODO: tokenized this into an NFT or two NFT one for donator and one for receiver keeping same IDs
+ *   // TODO: add support for migrating yield source as admin. Require token matches
+ ********************* */
+
+contract SugarVault is Ownable {
+  /*//////////////////////////////////////////////////////////////
+                                 EVENTS
+    //////////////////////////////////////////////////////////////*/
+
+  event StartShare(address indexed receiver, address indexed donator, uint256 amount);
+
+  event StopShare(address indexed donator, uint256 amountReturned);
+
+  event Claimed(address indexed receiver, address indexed donator, uint256 claimed, uint256 newShareAmount);
+
+  /*//////////////////////////////////////////////////////////////
+                         METADATA STORAGE/LOGIC
+    //////////////////////////////////////////////////////////////*/
+  IERC4626 public immutable vault;
+  IERC20 public immutable token;
+  mapping(address => uint256) public tokenBalances;
+  mapping(address => uint256) public shareBalances;
+  mapping(address => address) public donatorToReceiver;
+  mapping(address => mapping(address => bool)) public receiverToDonator;
+  uint256 public dust = 1e16;
+
+  constructor(address _vault) {
+    vault = IERC4626(_vault);
+    token = IERC20(vault.asset());
+    token.approve(address(vault), type(uint256).max);
+  }
+
+  function startSharingYield(address receiver, uint256 amount) public returns (uint256 shares) {
+    require(receiver != address(0), "ADDRESS_NOT_ZERO");
+    require(receiver != msg.sender, "SELF_SHARE");
+    require(amount > 0, "AMT_NOT_ZERO");
+    require(donatorToReceiver[msg.sender] == address(0), "DONATOR_NOT_SET");
+    SafeERC20.safeTransferFrom(token, msg.sender, address(this), amount);
+    shares = vault.deposit(amount, address(this));
+    tokenBalances[msg.sender] += amount;
+    shareBalances[msg.sender] += shares;
+    // donator can only have one receiver for yield and can switch it here
+    donatorToReceiver[msg.sender] = receiver;
+    receiverToDonator[receiver][msg.sender] = true;
+
+    emit StartShare(msg.sender, receiver, amount);
+  }
+
+  function stopSharingYield() public returns (uint256 amount) {
+    uint256 _shares = shareBalances[msg.sender];
+    uint256 _tokenBalance = tokenBalances[msg.sender];
+    require(_shares > 0, "NO_SHARES");
+    require(_tokenBalance > 0, "NO_TOKEN");
+
+    shareBalances[msg.sender] = 0;
+    tokenBalances[msg.sender] = 0;
+    address _receiver = donatorToReceiver[msg.sender];
+    donatorToReceiver[msg.sender] = address(0);
+    receiverToDonator[_receiver][msg.sender] = false;
+
+    amount = vault.redeem(_shares, msg.sender, address(this));
+
+    emit StopShare(msg.sender, amount);
+
+    // TODO: add emergency exit to withdraw and realize loss in case it happens
+    require(amount >= _tokenBalance, "LOSS");
+  }
+
+  function claimYield(address _donator) public returns (uint256 claimed) {
+    require(donatorToReceiver[_donator] == msg.sender, "NOT_RECEIVER");
+    // NOTE: checks in startSharingYield ensure these values are not zero
+    uint256 _shares = shareBalances[_donator];
+    uint256 _tokenBalance = tokenBalances[_donator];
+
+    // NOTE: we add dust thresold to assure precision
+    require(vault.convertToAssets(_shares) > _tokenBalance + dust, "NO_YIELD");
+
+    uint256 _remainingShares = vault.convertToShares(_tokenBalance + dust);
+    require(_shares > _remainingShares, "LOSS");
+
+    uint256 _sharesToClaim = _shares - _remainingShares;
+
+    shareBalances[_donator] = _remainingShares;
+
+    claimed = vault.redeem(_sharesToClaim, msg.sender, address(this));
+    // NOTE: ensure donator still has deposited capital after side effect
+    require(vault.convertToAssets(_remainingShares) >= _tokenBalance, "CLAIM_EXCEED");
+
+    emit Claimed(msg.sender, _donator, claimed, _remainingShares);
+  }
+
+  function claimable(address _donator, address _receiver) external view returns (uint256 amount) {
+    if (donatorToReceiver[_donator] != _receiver) return 0;
+
+    // NOTE: checks in startSharingYield ensure these values are not zero
+    uint256 _shares = shareBalances[_donator];
+    uint256 _tokenBalance = tokenBalances[_donator];
+    if (_shares == 0 || _tokenBalance == 0) return 0;
+
+    // NOTE: we add dust thresold to assure precision
+    if (vault.convertToAssets(_shares) < _tokenBalance + dust) return 0;
+
+    uint256 _remainingShares = vault.convertToShares(_tokenBalance + dust);
+    if (_shares <= _remainingShares) return 0;
+
+    uint256 _sharesToClaim = _shares - _remainingShares;
+
+    amount = vault.previewRedeem(_sharesToClaim);
+  }
+}
\ No newline at end of file