Add LBPool (#1001)

pkg/pool-weighted/contracts/WeightedPool.sol

@@ -52,7 +52,7 @@ contract WeightedPool is IWeightedPool, BalancerPoolToken, PoolInfo, Version {
 
     // A minimum normalized weight imposes a maximum weight ratio. We need this due to limitations in the
     // implementation of the fixed point power function, as these ratios are often exponents.
-    uint256 private constant _MIN_WEIGHT = 1e16; // 1%
+    uint256 internal constant _MIN_WEIGHT = 1e16; // 1%
 
     uint256 private immutable _totalTokens;
 
@@ -147,7 +147,7 @@ contract WeightedPool is IWeightedPool, BalancerPoolToken, PoolInfo, Version {
     }
 
     /// @inheritdoc IBasePool
-    function onSwap(PoolSwapParams memory request) public view onlyVault returns (uint256) {
+    function onSwap(PoolSwapParams memory request) public view virtual onlyVault returns (uint256) {
         uint256 balanceTokenInScaled18 = request.balancesScaled18[request.indexIn];
         uint256 balanceTokenOutScaled18 = request.balancesScaled18[request.indexOut];
 

pkg/pool-weighted/contracts/WeightedPoolFactory.sol

@@ -20,8 +20,6 @@ import { WeightedPool } from "./WeightedPool.sol";
  * @dev This is the most general factory, which allows up to eight tokens and arbitrary weights.
  */
 contract WeightedPoolFactory is IPoolVersion, BasePoolFactory, Version {
-    // solhint-disable not-rely-on-time
-
     string private _poolVersion;
 
     constructor(

pkg/pool-weighted/contracts/lbp/LBPool.sol

@@ -0,0 +1,304 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+pragma solidity ^0.8.24;
+
+import { SafeCast } from "@openzeppelin/contracts/utils/math/SafeCast.sol";
+import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
+import { Ownable2Step } from "@openzeppelin/contracts/access/Ownable2Step.sol";
+
+import { IBasePoolFactory } from "@balancer-labs/v3-interfaces/contracts/vault/IBasePoolFactory.sol";
+import { IRouterCommon } from "@balancer-labs/v3-interfaces/contracts/vault/IRouterCommon.sol";
+import { IVaultErrors } from "@balancer-labs/v3-interfaces/contracts/vault/IVaultErrors.sol";
+import { IVault } from "@balancer-labs/v3-interfaces/contracts/vault/IVault.sol";
+import "@balancer-labs/v3-interfaces/contracts/vault/VaultTypes.sol";
+
+import { InputHelpers } from "@balancer-labs/v3-solidity-utils/contracts/helpers/InputHelpers.sol";
+import { FixedPoint } from "@balancer-labs/v3-solidity-utils/contracts/math/FixedPoint.sol";
+import { BaseHooks } from "@balancer-labs/v3-vault/contracts/BaseHooks.sol";
+
+import { GradualValueChange } from "../lib/GradualValueChange.sol";
+import { WeightedPool } from "../WeightedPool.sol";
+
+/**
+ * @notice Weighted Pool with mutable weights, designed to support v3 Liquidity Bootstrapping.
+ * @dev Inheriting from WeightedPool is only slightly wasteful (setting 2 immutable weights and `_totalTokens`,
+ * which will not be used later), and it is tremendously helpful for pool validation and any potential future
+ * base contract changes.
+ */
+contract LBPool is WeightedPool, Ownable2Step, BaseHooks {
+    using SafeCast for *;
+
+    // Since we have max 2 tokens and the weights must sum to 1, we only need to store one weight.
+    // Weights are 18 decimal floating point values, which fit in less than 64 bits. Store smaller numeric values
+    // to ensure the PoolState fits in a single slot. All timestamps in the system are uint32, enforced through
+    // SafeCast.
+    struct PoolState {
+        uint32 startTime;
+        uint32 endTime;
+        uint64 startWeight0;
+        uint64 endWeight0;
+        bool swapEnabled;
+    }
+
+    // LBPs are constrained to two tokens.
+    uint256 private constant _NUM_TOKENS = 2;
+
+    // LBPools are deployed with the Balancer standard router address, which we know reliably reports the true
+    // originating account on operations. This is important for liquidity operations, as these are permissioned
+    // operations that can only be performed by the owner of the pool. Without this check, a malicious router
+    // could spoof the address of the owner, allowing anyone to call permissioned functions.
+    //
+    // Since the initialization mechanism does not allow verification of the router, it is technically possible
+    // to front-run `initialize`. This should not be a concern in the typical LBP use case of a new token launch,
+    // where there is no existing liquidity. In the unlikely event it is a concern, `LBPoolFactory` provides the
+    // `createAndInitialize` function, which does both operations in a single step.
+
+    // solhint-disable-next-line var-name-mixedcase
+    address private immutable _trustedRouter;
+
+    PoolState private _poolState;
+
+    /**
+     * @notice Emitted when the owner enables or disables swaps.
+     * @param swapEnabled True if we are enabling swaps
+     */
+    event SwapEnabledSet(bool swapEnabled);
+
+    /**
+     * @notice Emitted when the owner initiates a gradual weight change (e.g., at the start of the sale).
+     * @dev Also emitted on deployment, recording the initial state.
+     * @param startTime The starting timestamp of the update
+     * @param endTime  The ending timestamp of the update
+     * @param startWeights The weights at the start of the update
+     * @param endWeights The final weights after the update is completed
+     */
+    event GradualWeightUpdateScheduled(
+        uint256 startTime,
+        uint256 endTime,
+        uint256[] startWeights,
+        uint256[] endWeights
+    );
+
+    /// @dev Indicates that the router that called the Vault is not trusted, so liquidity operations should revert.
+    error RouterNotTrusted();
+
+    /// @dev Indicates that the `owner` has disabled swaps.
+    error SwapsDisabled();
+
+    constructor(
+        NewPoolParams memory params,
+        IVault vault,
+        address owner,
+        bool swapEnabledOnStart,
+        address trustedRouter
+    ) WeightedPool(params, vault) Ownable(owner) {
+        // WeightedPool validates `numTokens == normalizedWeights.length`, and ensures valid weights.
+        // Here we additionally enforce that LBPs must be two-token pools.
+        InputHelpers.ensureInputLengthMatch(_NUM_TOKENS, params.numTokens);
+
+        // Set the trusted router (passed down from the factory).
+        _trustedRouter = trustedRouter;
+
+        // solhint-disable-next-line not-rely-on-time
+        uint32 currentTime = block.timestamp.toUint32();
+        _startGradualWeightChange(currentTime, currentTime, params.normalizedWeights, params.normalizedWeights);
+        _setSwapEnabled(swapEnabledOnStart);
+    }
+
+    /// @notice Returns the trusted router, which is the gateway to add liquidity to the pool.
+    function getTrustedRouter() external view returns (address) {
+        return _trustedRouter;
+    }
+
+    /**
+     * @notice Return start time, end time, and endWeights as an array.
+     * @dev Current weights should be retrieved via `getNormalizedWeights()`.
+     * @return startTime The starting timestamp of any ongoing weight change
+     * @return endTime The ending timestamp of any ongoing weight change
+     * @return endWeights The "destination" weights, sorted in token registration order
+     */
+    function getGradualWeightUpdateParams()
+        external
+        view
+        returns (uint256 startTime, uint256 endTime, uint256[] memory endWeights)
+    {
+        PoolState memory poolState = _poolState;
+
+        startTime = poolState.startTime;
+        endTime = poolState.endTime;
+
+        endWeights = new uint256[](_NUM_TOKENS);
+        endWeights[0] = poolState.endWeight0;
+        endWeights[1] = FixedPoint.ONE - poolState.endWeight0;
+    }
+
+    /**
+     * @notice Indicate whether swaps are enabled or not for the given pool.
+     * @return swapEnabled True if trading is enabled
+     */
+    function getSwapEnabled() external view returns (bool) {
+        return _getPoolSwapEnabled();
+    }
+
+    /*******************************************************************************
+                                Permissioned Functions
+    *******************************************************************************/
+
+    /**
+     * @notice Enable/disable trading.
+     * @dev This is a permissioned function that can only be called by the owner.
+     * @param swapEnabled True if trading should be enabled
+     */
+    function setSwapEnabled(bool swapEnabled) external onlyOwner {
+        _setSwapEnabled(swapEnabled);
+    }
+
+    /**
+     * @notice Start a gradual weight change. Weights will change smoothly from current values to `endWeights`.
+     * @dev This is a permissioned function that can only be called by the owner.
+     * If the `startTime` is in the past, the weight change will begin immediately.
+     *
+     * @param startTime The timestamp when the weight change will start
+     * @param endTime  The timestamp when the weights will reach their final values
+     * @param endWeights The final values of the weights
+     */
+    function updateWeightsGradually(
+        uint256 startTime,
+        uint256 endTime,
+        uint256[] memory endWeights
+    ) external onlyOwner {
+        InputHelpers.ensureInputLengthMatch(_NUM_TOKENS, endWeights.length);
+
+        if (endWeights[0] < _MIN_WEIGHT || endWeights[1] < _MIN_WEIGHT) {
+            revert MinWeight();
+        }
+        if (endWeights[0] + endWeights[1] != FixedPoint.ONE) {
+            revert NormalizedWeightInvariant();
+        }
+
+        // Ensure startTime >= now.
+        startTime = GradualValueChange.resolveStartTime(startTime, endTime);
+
+        // The SafeCast ensures `endTime` can't overflow.
+        _startGradualWeightChange(startTime.toUint32(), endTime.toUint32(), _getNormalizedWeights(), endWeights);
+    }
+
+    /// @inheritdoc WeightedPool
+    function onSwap(PoolSwapParams memory request) public view override onlyVault returns (uint256) {
+        if (!_getPoolSwapEnabled()) {
+            revert SwapsDisabled();
+        }
+        return super.onSwap(request);
+    }
+
+    /*******************************************************************************
+                                    Hook Functions
+    *******************************************************************************/
+
+    /**
+     * @notice Hook to be executed when pool is registered.
+     * @dev Returns true if registration was successful, and false to revert the registration of the pool.
+     * @param pool Address of the pool
+     * @return success True if the hook allowed the registration, false otherwise
+     */
+    function onRegister(
+        address,
+        address pool,
+        TokenConfig[] memory tokenConfig,
+        LiquidityManagement calldata
+    ) public view override onlyVault returns (bool) {
+        InputHelpers.ensureInputLengthMatch(_NUM_TOKENS, tokenConfig.length);
+
+        return pool == address(this);
+    }
+
+    // Return HookFlags struct that indicates which hooks this contract supports
+    function getHookFlags() public pure override returns (HookFlags memory hookFlags) {
+        // Ensure the caller is the owner, as only the owner can add liquidity.
+        hookFlags.shouldCallBeforeAddLiquidity = true;
+    }
+
+    /**
+     * @notice Check that the caller who initiated the add liquidity operation is the owner.
+     * @dev We first ensure the caller is the standard router, so that we know we can trust the value it returns
+     * from `getSender`.
+     *
+     * @param router The address (usually a router contract) that initiated the add liquidity operation
+     */
+    function onBeforeAddLiquidity(
+        address router,
+        address,
+        AddLiquidityKind,
+        uint256[] memory,
+        uint256,
+        uint256[] memory,
+        bytes memory
+    ) public view override onlyVault returns (bool) {
+        if (router != _trustedRouter) {
+            revert RouterNotTrusted();
+        }
+        return IRouterCommon(router).getSender() == owner();
+    }
+
+    /*******************************************************************************
+                                  Internal Functions
+    *******************************************************************************/
+
+    // This is unused in this contract, but must be overridden from WeightedPool for consistency.
+    function _getNormalizedWeight(uint256 tokenIndex) internal view virtual override returns (uint256) {
+        if (tokenIndex < _NUM_TOKENS) {
+            return _getNormalizedWeights()[tokenIndex];
+        }
+
+        revert IVaultErrors.InvalidToken();
+    }
+
+    function _getNormalizedWeights() internal view override returns (uint256[] memory) {
+        uint256[] memory normalizedWeights = new uint256[](_NUM_TOKENS);
+        normalizedWeights[0] = _getNormalizedWeight0();
+        normalizedWeights[1] = FixedPoint.ONE - normalizedWeights[0];
+
+        return normalizedWeights;
+    }
+
+    function _getNormalizedWeight0() internal view virtual returns (uint256) {
+        PoolState memory poolState = _poolState;
+        uint256 pctProgress = GradualValueChange.calculateValueChangeProgress(poolState.startTime, poolState.endTime);
+
+        return GradualValueChange.interpolateValue(poolState.startWeight0, poolState.endWeight0, pctProgress);
+    }
+
+    function _getPoolSwapEnabled() private view returns (bool) {
+        return _poolState.swapEnabled;
+    }
+
+    function _setSwapEnabled(bool swapEnabled) private {
+        _poolState.swapEnabled = swapEnabled;
+
+        emit SwapEnabledSet(swapEnabled);
+    }
+
+    /**
+     * @dev When calling updateWeightsGradually again during an update, reset the start weights to the current weights,
+     * if necessary.
+     */
+    function _startGradualWeightChange(
+        uint32 startTime,
+        uint32 endTime,
+        uint256[] memory startWeights,
+        uint256[] memory endWeights
+    ) internal virtual {
+        PoolState memory poolState = _poolState;
+
+        poolState.startTime = startTime;
+        poolState.endTime = endTime;
+
+        // These have been validated, but SafeCast anyway out of an abundance of caution.
+        poolState.startWeight0 = startWeights[0].toUint64();
+        poolState.endWeight0 = endWeights[0].toUint64();
+
+        _poolState = poolState;
+
+        emit GradualWeightUpdateScheduled(startTime, endTime, startWeights, endWeights);
+    }
+}