// 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 "./Value.sol";

struct StackFrame {
    Value returnPc;
    bytes32 localsMerkleRoot;
    uint32 callerModule;
    uint32 callerModuleInternals;
}

struct StackFrameWindow {
    StackFrame[] proved;
    bytes32 remainingHash;
}

library StackFrameLib {
    using ValueLib for Value;

    function hash(StackFrame memory frame) internal pure returns (bytes32) {
        return
            keccak256(
                abi.encodePacked(
                    "Stack frame:",
                    frame.returnPc.hash(),
                    frame.localsMerkleRoot,
                    frame.callerModule,
                    frame.callerModuleInternals
                )
            );
    }

    function hash(StackFrameWindow memory window) internal pure returns (bytes32 h) {
        h = window.remainingHash;
        for (uint256 i = 0; i < window.proved.length; i++) {
            h = keccak256(abi.encodePacked("Stack frame stack:", hash(window.proved[i]), h));
        }
    }

    function peek(StackFrameWindow memory window) internal pure returns (StackFrame memory) {
        require(window.proved.length == 1, "BAD_WINDOW_LENGTH");
        return window.proved[0];
    }

    function pop(StackFrameWindow memory window) internal pure returns (StackFrame memory frame) {
        require(window.proved.length == 1, "BAD_WINDOW_LENGTH");
        frame = window.proved[0];
        window.proved = new StackFrame[](0);
    }

    function push(StackFrameWindow memory window, StackFrame memory frame) internal pure {
        StackFrame[] memory newProved = new StackFrame[](window.proved.length + 1);
        for (uint256 i = 0; i < window.proved.length; i++) {
            newProved[i] = window.proved[i];
        }
        newProved[window.proved.length] = frame;
        window.proved = newProved;
    }
}