// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

import { OrderParameters } from "./ConsiderationStructs.sol";

import { ConsiderationBase } from "./ConsiderationBase.sol";

import "./ConsiderationConstants.sol";

contract GettersAndDerivers is ConsiderationBase {

    constructor(address conduitController)
        ConsiderationBase(conduitController)
    {}

    function _deriveOrderHash(
        OrderParameters memory orderParameters,
        uint256 counter
    ) internal view returns (bytes32 orderHash) {
        bytes32 typeHash = _ORDER_TYPEHASH;

        assembly {
            let typeHashPtr := sub(orderParameters, OneWord)

            let previousValue := mload(typeHashPtr)

            mstore(typeHashPtr, typeHash)

            let counterPtr := add(
                orderParameters,
                OrderParameters_counter_offset
            )

            let counterDataPtr := mload(counterPtr)

            mstore(counterPtr, counter)

            orderHash := keccak256(typeHashPtr, EIP712_Order_size)

            mstore(typeHashPtr, previousValue)

            mstore(counterPtr, counterDataPtr)
        }
    }

    function _deriveConduit(bytes32 conduitKey)
        internal
        view
        returns (address conduit)
    {
        // Read conduit controller address from runtime and place on the stack.
        address conduitController = address(_CONDUIT_CONTROLLER);

        // Read conduit creation code hash from runtime and place on the stack.
        bytes32 conduitCreationCodeHash = _CONDUIT_CREATION_CODE_HASH;

        // Leverage scratch space to perform an efficient hash.
        assembly {
            // Retrieve the free memory pointer; it will be replaced afterwards.
            let freeMemoryPointer := mload(FreeMemoryPointerSlot)

            // Place the control character and the conduit controller in scratch
            // space; note that eleven bytes at the beginning are left unused.
            mstore(0, or(MaskOverByteTwelve, conduitController))

            // Place the conduit key in the next region of scratch space.
            mstore(OneWord, conduitKey)

            // Place conduit creation code hash in free memory pointer location.
            mstore(TwoWords, conduitCreationCodeHash)

            // Derive conduit by hashing and applying a mask over last 20 bytes.
            conduit := and(
                // Hash the relevant region.
                keccak256(
                    // The region starts at memory pointer 11.
                    Create2AddressDerivation_ptr,
                    // The region is 85 bytes long (1 + 20 + 32 + 32).
                    Create2AddressDerivation_length
                ),
                // The address equals the last twenty bytes of the hash.
                MaskOverLastTwentyBytes
            )

            // Restore the free memory pointer.
            mstore(FreeMemoryPointerSlot, freeMemoryPointer)
        }
    }

    /**
     * @dev Internal view function to get the EIP-712 domain separator. If the
     *      chainId matches the chainId set on deployment, the cached domain
     *      separator will be returned; otherwise, it will be derived from
     *      scratch.
     *
     * @return The domain separator.
     */
    function _domainSeparator() internal view returns (bytes32) {
        // prettier-ignore
        return block.chainid == _CHAIN_ID
            ? _DOMAIN_SEPARATOR
            : _deriveDomainSeparator();
    }

    /**
     * @dev Internal view function to retrieve configuration information for
     *      this contract.
     *
     * @return version           The contract version.
     * @return domainSeparator   The domain separator for this contract.
     * @return conduitController The conduit Controller set for this contract.
     */
    function _information()
        internal
        view
        returns (
            string memory version,
            bytes32 domainSeparator,
            address conduitController
        )
    {
        // Derive the domain separator.
        domainSeparator = _domainSeparator();

        // Declare variable as immutables cannot be accessed within assembly.
        conduitController = address(_CONDUIT_CONTROLLER);

        // Allocate a string with the intended length.
        version = new string(Version_length);

        // Set the version as data on the newly allocated string.
        assembly {
            mstore(add(version, OneWord), shl(Version_shift, Version))
        }
    }

    /**
     * @dev Internal pure function to efficiently derive an digest to sign for
     *      an order in accordance with EIP-712.
     *
     * @param domainSeparator The domain separator.
     * @param orderHash       The order hash.
     *
     * @return value The hash.
     */
    function _deriveEIP712Digest(bytes32 domainSeparator, bytes32 orderHash)
        internal
        pure
        returns (bytes32 value)
    {
        // Leverage scratch space to perform an efficient hash.
        assembly {
            // Place the EIP-712 prefix at the start of scratch space.
            mstore(0, EIP_712_PREFIX)

            // Place the domain separator in the next region of scratch space.
            mstore(EIP712_DomainSeparator_offset, domainSeparator)

            // Place the order hash in scratch space, spilling into the first
            // two bytes of the free memory pointer — this should never be set
            // as memory cannot be expanded to that size, and will be zeroed out
            // after the hash is performed.
            mstore(EIP712_OrderHash_offset, orderHash)

            // Hash the relevant region (65 bytes).
            value := keccak256(0, EIP712_DigestPayload_size)

            // Clear out the dirtied bits in the memory pointer.
            mstore(EIP712_OrderHash_offset, 0)
        }
    }
}