posm: add staking through subscribers

.forge-snapshots/PositionManager_burn_empty.snap

@@ -1 +1 @@
-47040
+47168

.forge-snapshots/PositionManager_burn_empty_native.snap

@@ -1 +1 @@
-46858
+46986

.forge-snapshots/PositionManager_burn_nonEmpty.snap

@@ -1 +1 @@
-129816
+130119

.forge-snapshots/PositionManager_burn_nonEmpty_native.snap

@@ -1 +1 @@
-122737
+123040

.forge-snapshots/PositionManager_collect.snap

@@ -1 +1 @@
-149962
+150258

.forge-snapshots/PositionManager_collect_native.snap

@@ -1 +1 @@
-141114
+141410

.forge-snapshots/PositionManager_collect_sameRange.snap

@@ -1 +1 @@
-149962
+150258

.forge-snapshots/PositionManager_decreaseLiquidity.snap

@@ -1 +1 @@
-115505
+115801

.forge-snapshots/PositionManager_decreaseLiquidity_native.snap

@@ -1 +1 @@
-108366
+108603

.forge-snapshots/PositionManager_decrease_burnEmpty.snap

@@ -1 +1 @@
-133849
+134178

.forge-snapshots/PositionManager_decrease_burnEmpty_native.snap

@@ -1 +1 @@
-126588
+126917

.forge-snapshots/PositionManager_decrease_sameRange_allLiquidity.snap

@@ -1 +1 @@
-128221
+128517

.forge-snapshots/PositionManager_increaseLiquidity_erc20.snap

@@ -1 +1 @@
-152100
+152364

.forge-snapshots/PositionManager_increaseLiquidity_native.snap

@@ -1 +1 @@
-133900
+134164

.forge-snapshots/PositionManager_increase_autocompoundExactUnclaimedFees.snap

@@ -1 +1 @@
-134581
+134845

.forge-snapshots/PositionManager_increase_autocompoundExcessFeesCredit.snap

@@ -1 +1 @@
-170737
+171023

.forge-snapshots/PositionManager_mint.snap

@@ -1 +1 @@
-372012
+372160

.forge-snapshots/PositionManager_mint_native.snap

@@ -1 +1 @@
-336712
+336860

.forge-snapshots/PositionManager_mint_nativeWithSweep.snap

@@ -1 +1 @@
-345221
+345369

.forge-snapshots/PositionManager_mint_onSameTickLower.snap

@@ -1 +1 @@
-314694
+314842

.forge-snapshots/PositionManager_mint_onSameTickUpper.snap

@@ -1 +1 @@
-315336
+315484

.forge-snapshots/PositionManager_mint_sameRange.snap

@@ -1 +1 @@
-240918
+241066

.forge-snapshots/PositionManager_mint_settleWithBalance_sweep.snap

@@ -1 +1 @@
-369926
+370074

.forge-snapshots/PositionManager_mint_warmedPool_differentRange.snap

@@ -1 +1 @@
-320712
+320860

.forge-snapshots/PositionManager_multicall_initialize_mint.snap

@@ -1 +1 @@
-416388
+416602

foundry.toml

@@ -11,4 +11,7 @@ fuzz_runs = 10_000
 [profile.ci]
 fuzz_runs = 100_000
 
+[profile.gas]
+gas_limit=30_000_000
+
 # See more config options https://github.com/foundry-rs/foundry/tree/master/config

src/PositionManager.sol

@@ -24,7 +24,9 @@ import {DeltaResolver} from "./base/DeltaResolver.sol";
 import {PositionConfig, PositionConfigLibrary} from "./libraries/PositionConfig.sol";
 import {BaseActionsRouter} from "./base/BaseActionsRouter.sol";
 import {Actions} from "./libraries/Actions.sol";
+import {Notifier} from "./base/Notifier.sol";
 import {CalldataDecoder} from "./libraries/CalldataDecoder.sol";
+import {INotifier} from "./interfaces/INotifier.sol";
 import {SlippageCheckLibrary} from "./libraries/SlippageCheck.sol";
 
 contract PositionManager is
@@ -34,12 +36,13 @@ contract PositionManager is
     Multicall,
     DeltaResolver,
     ReentrancyLock,
-    BaseActionsRouter
+    BaseActionsRouter,
+    Notifier
 {
     using SafeTransferLib for *;
     using CurrencyLibrary for Currency;
     using PoolIdLibrary for PoolKey;
-    using PositionConfigLibrary for PositionConfig;
+    using PositionConfigLibrary for *;
     using StateLibrary for IPoolManager;
     using TransientStateLibrary for IPoolManager;
     using SafeCast for uint256;
@@ -50,7 +53,7 @@ contract PositionManager is
     uint256 public nextTokenId = 1;
 
     /// @inheritdoc IPositionManager
-    mapping(uint256 tokenId => bytes32 configId) public positionConfigs;
+    mapping(uint256 tokenId => bytes32 config) public positionConfigs;
 
     IAllowanceTransfer public immutable permit2;
 
@@ -61,11 +64,31 @@ contract PositionManager is
         permit2 = _permit2;
     }
 
+    /// @notice Reverts if the deadline has passed
+    /// @param deadline The timestamp at which the call is no longer valid, passed in by the caller
     modifier checkDeadline(uint256 deadline) {
         if (block.timestamp > deadline) revert DeadlinePassed();
         _;
     }
 
+    /// @notice Reverts if the caller is not the owner or approved for the ERC721 token
+    /// @param sender The address of the caller
+    /// @param tokenId the unique identifier of the ERC721 token
+    /// @dev either msg.sender or _msgSender() is passed in as the sender
+    /// _msgSender() should ONLY be used if this is being called from within the unlockCallback
+    modifier onlyIfApproved(address sender, uint256 tokenId) {
+        if (!_isApprovedOrOwner(sender, tokenId)) revert NotApproved(sender);
+        _;
+    }
+
+    /// @notice Reverts if the hash of the config does not equal the saved hash
+    /// @param tokenId the unique identifier of the ERC721 token
+    /// @param config the PositionConfig to check against
+    modifier onlyValidConfig(uint256 tokenId, PositionConfig calldata config) {
+        if (positionConfigs.getConfigId(tokenId) != config.toId()) revert IncorrectPositionConfigForTokenId(tokenId);
+        _;
+    }
+
     /// @param unlockData is an encoding of actions, params, and currencies
     /// @param deadline is the timestamp at which the unlockData will no longer be valid
     function modifyLiquidities(bytes calldata unlockData, uint256 deadline)
@@ -77,6 +100,28 @@ contract PositionManager is
         _executeActions(unlockData);
     }
 
+    /// @inheritdoc INotifier
+    function subscribe(uint256 tokenId, PositionConfig calldata config, address subscriber)
+        external
+        payable
+        onlyIfApproved(msg.sender, tokenId)
+        onlyValidConfig(tokenId, config)
+    {
+        positionConfigs.setSubscribe(tokenId);
+        _subscribe(tokenId, config, subscriber);
+    }
+
+    /// @inheritdoc INotifier
+    function unsubscribe(uint256 tokenId, PositionConfig calldata config)
+        external
+        payable
+        onlyIfApproved(msg.sender, tokenId)
+        onlyValidConfig(tokenId, config)
+    {
+        positionConfigs.setUnsubscribe(tokenId);
+        _unsubscribe(tokenId, config);
+    }
+
     function _handleAction(uint256 action, bytes calldata params) internal virtual override {
         if (action == Actions.INCREASE_LIQUIDITY) {
             (
@@ -144,8 +189,7 @@ contract PositionManager is
         uint128 amount0Max,
         uint128 amount1Max,
         bytes calldata hookData
-    ) internal {
-        if (positionConfigs[tokenId] != config.toId()) revert IncorrectPositionConfigForTokenId(tokenId);
+    ) internal onlyValidConfig(tokenId, config) {
         // Note: The tokenId is used as the salt for this position, so every minted position has unique storage in the pool manager.
         BalanceDelta liquidityDelta = _modifyLiquidity(config, liquidity.toInt256(), bytes32(tokenId), hookData);
         liquidityDelta.validateMaxInNegative(amount0Max, amount1Max);
@@ -159,10 +203,7 @@ contract PositionManager is
         uint128 amount0Min,
         uint128 amount1Min,
         bytes calldata hookData
-    ) internal {
-        if (!_isApprovedOrOwner(_msgSender(), tokenId)) revert NotApproved(_msgSender());
-        if (positionConfigs[tokenId] != config.toId()) revert IncorrectPositionConfigForTokenId(tokenId);
-
+    ) internal onlyIfApproved(_msgSender(), tokenId) onlyValidConfig(tokenId, config) {
         // Note: the tokenId is used as the salt.
         BalanceDelta liquidityDelta = _modifyLiquidity(config, -(liquidity.toInt256()), bytes32(tokenId), hookData);
         liquidityDelta.validateMinOut(amount0Min, amount1Min);
@@ -217,9 +258,7 @@ contract PositionManager is
         uint128 amount0Min,
         uint128 amount1Min,
         bytes calldata hookData
-    ) internal {
-        if (!_isApprovedOrOwner(_msgSender(), tokenId)) revert NotApproved(_msgSender());
-        if (positionConfigs[tokenId] != config.toId()) revert IncorrectPositionConfigForTokenId(tokenId);
+    ) internal onlyIfApproved(_msgSender(), tokenId) onlyValidConfig(tokenId, config) {
         uint256 liquidity = uint256(_getPositionLiquidity(config, tokenId));
 
         BalanceDelta liquidityDelta;
@@ -250,6 +289,10 @@ contract PositionManager is
             }),
             hookData
         );
+
+        if (positionConfigs.hasSubscriber(uint256(salt))) {
+            _notifyModifyLiquidity(uint256(salt), config, liquidityChange);
+        }
     }
 
     function _getPositionLiquidity(PositionConfig calldata config, uint256 tokenId)
@@ -277,4 +320,10 @@ contract PositionManager is
             permit2.transferFrom(payer, address(poolManager), uint160(amount), Currency.unwrap(currency));
         }
     }
+
+    /// @dev overrides solmate transferFrom in case a notification to subscribers is needed
+    function transferFrom(address from, address to, uint256 id) public override {
+        super.transferFrom(from, to, id);
+        if (positionConfigs.hasSubscriber(id)) _notifyTransfer(id, from, to);
+    }
 }

src/base/Notifier.sol

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+pragma solidity ^0.8.24;
+
+import {ISubscriber} from "../interfaces/ISubscriber.sol";
+import {PositionConfig} from "../libraries/PositionConfig.sol";
+import {GasLimitCalculator} from "../libraries/GasLimitCalculator.sol";
+
+import "../interfaces/INotifier.sol";
+
+abstract contract Notifier is INotifier {
+    using GasLimitCalculator for uint256;
+
+    error SubscriberCannotBeNotified();
+    error AlreadySubscribed(address subscriber);
+
+    event Subscribed(uint256 tokenId, address subscriber);
+    event Unsubscribed(uint256 tokenId, address subscriber);
+
+    ISubscriber private constant NO_SUBSCRIBER = ISubscriber(address(0));
+
+    // a percentage of the block.gaslimit denoted in BPS, used as the gas limit for subscriber calls
+    // 100 bps is 1%
+    // at 30M gas, the limit is 300K
+    uint256 private constant BLOCK_LIMIT_BPS = 100;
+
+    mapping(uint256 tokenId => ISubscriber subscriber) public subscriber;
+
+    constructor() {}
+
+    function _subscribe(uint256 tokenId, PositionConfig memory config, address newSubscriber) internal {
+        ISubscriber _subscriber = subscriber[tokenId];
+
+        if (_subscriber != NO_SUBSCRIBER) revert AlreadySubscribed(address(_subscriber));
+        subscriber[tokenId] = ISubscriber(newSubscriber);
+
+        ISubscriber(newSubscriber).notifySubscribe(tokenId, config);
+        emit Subscribed(tokenId, address(newSubscriber));
+    }
+
+    /// @dev Must always allow a user to unsubscribe. In the case of a malicious subscriber, a user can always unsubscribe safely, ensuring liquidity is always modifiable.
+    function _unsubscribe(uint256 tokenId, PositionConfig memory config) internal {
+        ISubscriber _subscriber = subscriber[tokenId];
+
+        uint256 subscriberGasLimit = BLOCK_LIMIT_BPS.toGasLimit();
+
+        bytes memory data = abi.encodeWithSelector(ISubscriber.notifyUnsubscribe.selector, tokenId, config);
+
+        try _subscriber.notifyUnsubscribe{gas: subscriberGasLimit}(tokenId, config) {} catch {}
+
+        delete subscriber[tokenId];
+        emit Unsubscribed(tokenId, address(_subscriber));
+    }
+
+    function _notifyModifyLiquidity(uint256 tokenId, PositionConfig memory config, int256 liquidityChange) internal {
+        subscriber[tokenId].notifyModifyLiquidity(tokenId, config, liquidityChange);
+    }
+
+    function _notifyTransfer(uint256 tokenId, address previousOwner, address newOwner) internal {
+        subscriber[tokenId].notifyTransfer(tokenId, previousOwner, newOwner);
+    }
+}

src/interfaces/INotifier.sol

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.24;
+
+import {PositionConfig} from "../libraries/PositionConfig.sol";
+
+/// @notice This interface is used to opt in to sending updates to external contracts about position modifications or transfers
+interface INotifier {
+    /// @notice Enables the subscriber to receive notifications for a respective position
+    /// @param tokenId the ERC721 tokenId
+    /// @param config the corresponding PositionConfig for the tokenId
+    /// @param subscriber the address to notify
+    function subscribe(uint256 tokenId, PositionConfig calldata config, address subscriber) external payable;
+
+    /// @notice Removes the subscriber from receiving notifications for a respective position
+    /// @param tokenId the ERC721 tokenId
+    /// @param config the corresponding PositionConfig for the tokenId
+    function unsubscribe(uint256 tokenId, PositionConfig calldata config) external payable;
+}

src/interfaces/IPositionManager.sol

@@ -3,15 +3,19 @@ pragma solidity ^0.8.24;
 
 import {PoolKey} from "@uniswap/v4-core/src/types/PoolKey.sol";
 
-interface IPositionManager {
+import {INotifier} from "./INotifier.sol";
+
+interface IPositionManager is INotifier {
     error NotApproved(address caller);
     error DeadlinePassed();
     error IncorrectPositionConfigForTokenId(uint256 tokenId);
 
     /// @notice Maps the ERC721 tokenId to a configId, which is a keccak256 hash of the position's pool key, and range (tickLower, tickUpper)
     /// Enforces that a minted ERC721 token is tied to one range on one pool.
     /// @param tokenId the ERC721 tokenId, assigned at mint
-    /// @return configId the hash of the position's poolkey, tickLower, and tickUpper
+    /// @return configId a truncated hash of the position's poolkey, tickLower, and tickUpper and a reserved upper bit for the isSubscribed flag
+    /// @dev the highest bit of the configId is used to signal if the position is subscribed
+    /// and the lower bits contain the truncated hash of the PositionConfig
     function positionConfigs(uint256 tokenId) external view returns (bytes32 configId);
 
     /// @notice Batches many liquidity modification calls to pool manager

src/interfaces/ISubscriber.sol

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.24;
+
+import {PositionConfig} from "../libraries/PositionConfig.sol";
+
+interface ISubscriber {
+    function notifySubscribe(uint256 tokenId, PositionConfig memory config) external;
+    function notifyUnsubscribe(uint256 tokenId, PositionConfig memory config) external;
+    function notifyModifyLiquidity(uint256 tokenId, PositionConfig memory config, int256 liquidityChange) external;
+    function notifyTransfer(uint256 tokenId, address previousOwner, address newOwner) external;
+}