// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/OffchainLabs/nitro-contracts/blob/main/LICENSE
// SPDX-License-Identifier: BUSL-1.1

pragma solidity ^0.8.0;

import "../state/GlobalState.sol";
import "../state/Machine.sol";

struct ExecutionState {
    GlobalState globalState;
    MachineStatus machineStatus;
}

struct Assertion {
    ExecutionState beforeState;
    ExecutionState afterState;
    uint64 numBlocks;
}

struct Node {
    // Hash of the state of the chain as of this node
    bytes32 stateHash;
    // Hash of the data that can be challenged
    bytes32 challengeHash;
    // Hash of the data that will be committed if this node is confirmed
    bytes32 confirmData;
    // Index of the node previous to this one
    uint64 prevNum;
    // Deadline at which this node can be confirmed
    uint64 deadlineBlock;
    // Deadline at which a child of this node can be confirmed
    uint64 noChildConfirmedBeforeBlock;
    // Number of stakers staked on this node. This includes real stakers and zombies
    uint64 stakerCount;
    // Number of stakers staked on a child node. This includes real stakers and zombies
    uint64 childStakerCount;
    // This value starts at zero and is set to a value when the first child is created. After that it is constant until the node is destroyed or the owner destroys pending nodes
    uint64 firstChildBlock;
    // The number of the latest child of this node to be created
    uint64 latestChildNumber;
    // The block number when this node was created
    uint64 createdAtBlock;
    // A hash of all the data needed to determine this node's validity, to protect against reorgs
    bytes32 nodeHash;
}

/**
 * @notice Utility functions for Node
 */
library NodeLib {
    /**
     * @notice Initialize a Node
     * @param _stateHash Initial value of stateHash
     * @param _challengeHash Initial value of challengeHash
     * @param _confirmData Initial value of confirmData
     * @param _prevNum Initial value of prevNum
     * @param _deadlineBlock Initial value of deadlineBlock
     * @param _nodeHash Initial value of nodeHash
     */
    function createNode(
        bytes32 _stateHash,
        bytes32 _challengeHash,
        bytes32 _confirmData,
        uint64 _prevNum,
        uint64 _deadlineBlock,
        bytes32 _nodeHash
    ) internal view returns (Node memory) {
        Node memory node;
        node.stateHash = _stateHash;
        node.challengeHash = _challengeHash;
        node.confirmData = _confirmData;
        node.prevNum = _prevNum;
        node.deadlineBlock = _deadlineBlock;
        node.noChildConfirmedBeforeBlock = _deadlineBlock;
        node.createdAtBlock = uint64(block.number);
        node.nodeHash = _nodeHash;
        return node;
    }

    /**
     * @notice Update child properties
     * @param number The child number to set
     */
    function childCreated(Node storage self, uint64 number) internal {
        if (self.firstChildBlock == 0) {
            self.firstChildBlock = uint64(block.number);
        }
        self.latestChildNumber = number;
    }

    /**
     * @notice Update the child confirmed deadline
     * @param deadline The new deadline to set
     */
    function newChildConfirmDeadline(Node storage self, uint64 deadline) internal {
        self.noChildConfirmedBeforeBlock = deadline;
    }

    /**
     * @notice Check whether the current block number has met or passed the node's deadline
     */
    function requirePastDeadline(Node memory self) internal view {
        require(block.number >= self.deadlineBlock, "BEFORE_DEADLINE");
    }

    /**
     * @notice Check whether the current block number has met or passed deadline for children of this node to be confirmed
     */
    function requirePastChildConfirmDeadline(Node memory self) internal view {
        require(block.number >= self.noChildConfirmedBeforeBlock, "CHILD_TOO_RECENT");
    }
}