add transfer validator to v2

config/.solhintignore

@@ -3,8 +3,10 @@ node_modules/
 src/clones
 src/test/
 src/shim/
-src/interfaces/IDelegationRegistry.sol
 src/lib/ERC1155.sol
 
+src/interfaces/IDelegationRegistry.sol
+src/interfaces/ITransferValidator.sol
+
 test/
 lib/

src/clones/ERC1155ContractMetadataCloneable.sol

@@ -9,6 +9,10 @@ import {
     ERC1155ConduitPreapproved
 } from "../lib/ERC1155ConduitPreapproved.sol";
 
+import { ITransferValidator } from "../interfaces/ITransferValidator.sol";
+
+import { TokenTransferValidator } from "../lib/TokenTransferValidator.sol";
+
 import { ERC1155 } from "solady/src/tokens/ERC1155.sol";
 
 import { ERC2981 } from "solady/src/tokens/ERC2981.sol";
@@ -30,6 +34,7 @@ import {
  */
 contract ERC1155ContractMetadataCloneable is
     ERC1155ConduitPreapproved,
+    TokenTransferValidator,
     ERC2981,
     Ownable,
     IERC1155ContractMetadata,
@@ -306,6 +311,38 @@ contract ERC1155ContractMetadataCloneable is
         return _baseURI;
     }
 
+    /// @dev Override this function to return true if `_beforeTokenTransfer` is used.
+    function _useBeforeTokenTransfer() internal view virtual override returns (bool) {
+        return true;
+    }
+
+    /**
+     * @dev Hook that is called before any token transfer.
+     *      This includes minting and burning.
+     */
+    function _beforeTokenTransfer(
+        address from,
+        address to,
+        uint256[] memory ids,
+        uint256[] memory amounts,
+        bytes memory /* data */
+    ) internal virtual override {
+        if (from != address(0) && to != address(0)) {
+            // Call the transfer validator if one is set.
+            if (_transferValidator != address(0)) {
+                for (uint256 i = 0; i < ids.length; i++) {
+                    ITransferValidator(_transferValidator).validateTransfer(
+                        msg.sender,
+                        from,
+                        to,
+                        ids[i],
+                        amounts[i]
+                    );
+                }
+            }
+        }
+    }
+
     /**
      * @notice Returns whether the interface is supported.
      *

src/clones/ERC1155SeaDropCloneable.sol

@@ -45,42 +45,6 @@ contract ERC1155SeaDropCloneable is ERC1155SeaDropContractOffererCloneable {
         );
     }
 
-    /**
-     * @dev Auto-approve the conduit after mint or transfer.
-     *
-     * @custom:param from    The address to transfer from.
-     * @param        to      The address to transfer to.
-     * @custom:param ids     The token ids to transfer.
-     * @custom:param amounts The quantities to transfer.
-     * @custom:param data    The data to pass if receiver is a contract.
-     */
-    function _afterTokenTransfer(
-        address /* from */,
-        address to,
-        uint256[] memory /* ids */,
-        uint256[] memory /* amounts */,
-        bytes memory /* data */
-    ) internal virtual override {
-        // Auto-approve the conduit.
-        if (to != address(0) && !isApprovedForAll(to, _CONDUIT)) {
-            _setApprovalForAll(to, _CONDUIT, true);
-        }
-    }
-
-    /**
-     * @dev Override this function to return true if `_afterTokenTransfer` is
-     *      used. The is to help the compiler avoid producing dead bytecode.
-     */
-    function _useAfterTokenTransfer()
-        internal
-        view
-        virtual
-        override
-        returns (bool)
-    {
-        return true;
-    }
-
     /**
      * @notice Burns a token, restricted to the owner or approved operator,
      *         and must have sufficient balance.

src/interfaces/ITransferValidator.sol

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.17;
+
+interface ITransferValidator {
+    /// @notice Ensure that a transfer has been authorized for a specific tokenId.
+    function validateTransfer(
+        address caller,
+        address from,
+        address to,
+        uint256 tokenId
+    ) external view;
+
+    /// @notice Ensure that a transfer has been authorized for a specific amount of
+    ///         a specific tokenId, and reduce the transferable amount remaining.
+    function validateTransfer(
+        address caller,
+        address from,
+        address to,
+        uint256 tokenId,
+        uint256 amount
+    ) external;
+}

src/lib/ERC1155ContractMetadata.sol

@@ -9,6 +9,10 @@ import {
     ERC1155ConduitPreapproved
 } from "../lib/ERC1155ConduitPreapproved.sol";
 
+import { ITransferValidator } from "../interfaces/ITransferValidator.sol";
+
+import { TokenTransferValidator } from "./TokenTransferValidator.sol";
+
 import { ERC1155 } from "solady/src/tokens/ERC1155.sol";
 
 import { ERC2981 } from "solady/src/tokens/ERC2981.sol";
@@ -26,6 +30,7 @@ import { Ownable } from "solady/src/auth/Ownable.sol";
  */
 contract ERC1155ContractMetadata is
     ERC1155ConduitPreapproved,
+    TokenTransferValidator,
     ERC2981,
     Ownable,
     IERC1155ContractMetadata
@@ -304,6 +309,46 @@ contract ERC1155ContractMetadata is
         return _baseURI;
     }
 
+    /**
+     * @notice Set the transfer validator. Only callable by the token owner.
+     */
+    function setTransferValidator(address newValidator) external onlyOwner {
+        // Set the new transfer validator.
+        _setTransferValidator(newValidator);
+    }
+
+    /// @dev Override this function to return true if `_beforeTokenTransfer` is used.
+    function _useBeforeTokenTransfer() internal view virtual override returns (bool) {
+        return true;
+    }
+
+    /**
+     * @dev Hook that is called before any token transfer.
+     *      This includes minting and burning.
+     */
+    function _beforeTokenTransfer(
+        address from,
+        address to,
+        uint256[] memory ids,
+        uint256[] memory amounts,
+        bytes memory /* data */
+    ) internal virtual override {
+        if (from != address(0) && to != address(0)) {
+            // Call the transfer validator if one is set.
+            if (_transferValidator != address(0)) {
+                for (uint256 i = 0; i < ids.length; i++) {
+                    ITransferValidator(_transferValidator).validateTransfer(
+                        msg.sender,
+                        from,
+                        to,
+                        ids[i],
+                        amounts[i]
+                    );
+                }
+            }
+        }
+    }
+
     /**
      * @notice Returns whether the interface is supported.
      *

src/lib/ERC721ContractMetadata.sol

@@ -7,6 +7,10 @@ import {
 
 import { ERC721AConduitPreapproved } from "./ERC721AConduitPreapproved.sol";
 
+import { ITransferValidator } from "../interfaces/ITransferValidator.sol";
+
+import { TokenTransferValidator } from "./TokenTransferValidator.sol";
+
 import { ERC721A } from "ERC721A/ERC721A.sol";
 
 import { Ownable } from "solady/src/auth/Ownable.sol";
@@ -24,6 +28,7 @@ import { ERC2981 } from "solady/src/tokens/ERC2981.sol";
  */
 contract ERC721ContractMetadata is
     ERC721AConduitPreapproved,
+    TokenTransferValidator,
     ERC2981,
     Ownable,
     IERC721ContractMetadata
@@ -272,6 +277,37 @@ contract ERC721ContractMetadata is
         return string.concat(theBaseURI, _toString(tokenId));
     }
 
+    /**
+     * @notice Set the transfer validator. Only callable by the token owner.
+     */
+    function setTransferValidator(address newValidator) external onlyOwner {
+        // Set the new transfer validator.
+        _setTransferValidator(newValidator);
+    }
+
+    /**
+     * @dev Hook that is called before any token transfer.
+     *      This includes minting and burning.
+     */
+    function _beforeTokenTransfers(
+        address from,
+        address to,
+        uint256 startTokenId,
+        uint256 /* quantity */
+    ) internal virtual override {
+        if (from != address(0) && to != address(0)) {
+            // Call the transfer validator if one is set.
+            if (_transferValidator != address(0)) {
+                ITransferValidator(_transferValidator).validateTransfer(
+                    msg.sender,
+                    from,
+                    to,
+                    startTokenId
+                );
+            }
+        }
+    }
+
     /**
      * @notice Returns whether the interface is supported.
      *

src/lib/TokenTransferValidator.sol

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.17;
+
+/**
+ * @title  TokenTransferValidator
+ * @notice Functionality to use a transfer validator.
+ */
+contract TokenTransferValidator {
+    /// @dev Store the transfer validator. The null address means no transfer validator is set.
+    address internal _transferValidator;
+
+    /// @notice Emit an event when the transfer validator is updated.
+    event TransferValidatorUpdated(address oldValidator, address newValidator);
+
+    /// @notice Revert with an error if the transfer validator is being set to the same address.
+    error SameTransferValidator();
+
+    /// @notice Returns the currently active transfer validator.
+    ///         The null address means no transfer validator is set.
+    function getTransferValidator() external view returns (address) {
+        return _transferValidator;
+    }
+
+    /// @notice Set the transfer validator.
+    ///         The external method that uses this must include access control.
+    function _setTransferValidator(address newValidator) internal {
+        address oldValidator = _transferValidator;
+        if (oldValidator == newValidator) {
+            revert SameTransferValidator();
+        }
+        _transferValidator = newValidator;
+        emit TransferValidatorUpdated(oldValidator, newValidator);
+    }
+}

src/test/MockTransferValidator.sol

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: Unlicense
+pragma solidity ^0.8.17;
+
+import { ITransferValidator } from "../interfaces/ITransferValidator.sol";
+
+contract MockTransferValidator is ITransferValidator {
+    bool internal _revertOnValidate;
+
+    constructor(bool revertOnValidate) {
+        _revertOnValidate = revertOnValidate;
+    }
+
+    function validateTransfer(
+        address,
+        /* caller */
+        address,
+        /* from */
+        address,
+        /* to */
+        uint256 /* tokenId */
+    ) external view {
+        if (_revertOnValidate) {
+            revert("MockTransferValidator: always reverts");
+        }
+    }
+
+    function validateTransfer(
+        address, /* caller */
+        address, /* from */
+        address, /* to */
+        uint256, /* tokenId */
+        uint256 /* amount */
+    ) external view {
+        if (_revertOnValidate) {
+            revert("MockTransferValidator: always reverts");
+        }
+    }
+}