// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "../interfaces/IKernel.sol";
import "../interfaces/IFlashLoanRouter.sol";
import "../interfaces/IVault.sol";
import "../interfaces/IConfigRegistry.sol";
import "../interfaces/IPolicyEngine.sol";
import "../interfaces/IOracleAdapter.sol";
import "../governance/GovernanceGuard.sol";
import "../core/CollateralToggleManager.sol";

/**
 * @title RecursiveLeverageKernel
 * @notice Implements atomic amortizing cycles for leveraged positions
 * @dev Enforces invariants: Debt↓, Collateral↑, LTV↓, HF↑
 */
contract RecursiveLeverageKernel is IKernel, IFlashLoanRouter, Ownable, AccessControl, ReentrancyGuard {
    using SafeERC20 for IERC20;

    bytes32 public constant OPERATOR_ROLE = keccak256("OPERATOR_ROLE");
    bytes32 private constant CALLBACK_SUCCESS = keccak256("ERC3156FlashBorrower.onFlashLoan");

    // Core dependencies
    IFlashLoanRouter public flashRouter;
    IVault public vault;
    IConfigRegistry public configRegistry;
    IPolicyEngine public policyEngine;
    GovernanceGuard public governanceGuard;
    CollateralToggleManager public collateralManager;
    IOracleAdapter public oracleAdapter;

    // Aave v3 Pool for operations
    interface IPoolV3 {
        function supply(address asset, uint256 amount, address onBehalfOf, uint16 referralCode) external;
        function withdraw(address asset, uint256 amount, address to) external returns (uint256);
        function borrow(address asset, uint256 amount, uint256 interestRateMode, uint16 referralCode, address onBehalfOf) external;
        function repay(address asset, uint256 amount, uint256 rateMode, address onBehalfOf) external returns (uint256);
        function getUserAccountData(address user)
            external
            view
            returns (
                uint256 totalCollateralBase,
                uint256 totalDebtBase,
                uint256 availableBorrowsBase,
                uint256 currentLiquidationThreshold,
                uint256 ltv,
                uint256 healthFactor
            );
    }

    IPoolV3 public aavePool;
    address public aaveUserAccount;

    // Uniswap V3 Swap Router (simplified)
    interface ISwapRouter {
        struct ExactInputSingleParams {
            address tokenIn;
            address tokenOut;
            uint24 fee;
            address recipient;
            uint256 deadline;
            uint256 amountIn;
            uint256 amountOutMinimum;
            uint160 sqrtPriceLimitX96;
        }

        function exactInputSingle(ExactInputSingleParams calldata params) external payable returns (uint256 amountOut);
    }

    ISwapRouter public swapRouter;

    // Constants
    uint256 private constant HF_SCALE = 1e18;
    uint256 private constant PRICE_SCALE = 1e8;

    // Cycle state (for reentrancy protection)
    struct CycleState {
        bool inProgress;
        uint256 cyclesExecuted;
        uint256 totalCollateralIncrease;
        uint256 totalDebtDecrease;
    }

    CycleState private cycleState;

    // Flash loan callback state
    struct FlashCallbackState {
        address targetAsset;
        bool inFlashLoan;
    }

    FlashCallbackState private flashCallbackState;

    event CycleCompleted(
        uint256 cyclesExecuted,
        uint256 collateralIncrease,
        uint256 debtDecrease,
        uint256 hfImprovement
    );
    event SingleStepCompleted(uint256 collateralAdded, uint256 debtRepaid);

    modifier onlyInCycle() {
        require(cycleState.inProgress, "Not in cycle");
        _;
    }

    modifier onlyNotInCycle() {
        require(!cycleState.inProgress, "Cycle in progress");
        _;
    }

    constructor(
        address _flashRouter,
        address _vault,
        address _configRegistry,
        address _policyEngine,
        address _governanceGuard,
        address _collateralManager,
        address _oracleAdapter,
        address _aavePool,
        address _aaveUserAccount,
        address _swapRouter,
        address initialOwner
    ) Ownable(initialOwner) {
        require(_flashRouter != address(0), "Invalid flash router");
        require(_vault != address(0), "Invalid vault");
        require(_configRegistry != address(0), "Invalid config registry");
        require(_policyEngine != address(0), "Invalid policy engine");
        require(_governanceGuard != address(0), "Invalid governance guard");
        require(_collateralManager != address(0), "Invalid collateral manager");
        require(_oracleAdapter != address(0), "Invalid oracle adapter");
        require(_aavePool != address(0), "Invalid Aave pool");
        require(_aaveUserAccount != address(0), "Invalid Aave account");

        flashRouter = IFlashLoanRouter(_flashRouter);
        vault = IVault(_vault);
        configRegistry = IConfigRegistry(_configRegistry);
        policyEngine = IPolicyEngine(_policyEngine);
        governanceGuard = GovernanceGuard(_governanceGuard);
        collateralManager = CollateralToggleManager(_collateralManager);
        oracleAdapter = IOracleAdapter(_oracleAdapter);
        aavePool = IPoolV3(_aavePool);
        aaveUserAccount = _aaveUserAccount;
        swapRouter = ISwapRouter(_swapRouter);

        _grantRole(DEFAULT_ADMIN_ROLE, initialOwner);
    }

    /**
     * @notice Execute atomic amortizing cycle
     * @dev Main entry point for amortization strategy
     */
    function executeAmortizingCycle(
        AmortizationParams memory params
    ) external override onlyRole(OPERATOR_ROLE) nonReentrant onlyNotInCycle returns (bool success, uint256 cyclesExecuted) {
        // Enforce policy checks
        bytes memory actionData = abi.encode(
            address(vault),
            vault.getHealthFactor(),
            params.targetAsset,
            params.maxLoops
        );
        governanceGuard.enforceInvariants(keccak256("AMORTIZATION"), actionData);

        // Check max loops from config
        uint256 maxLoops = configRegistry.getMaxLoops();
        require(params.maxLoops <= maxLoops, "Exceeds max loops");

        // Take position snapshot
        (uint256 collateralBefore, uint256 debtBefore, uint256 healthFactorBefore) = vault.snapshotPosition();

        // Initialize cycle state
        cycleState = CycleState({
            inProgress: true,
            cyclesExecuted: 0,
            totalCollateralIncrease: 0,
            totalDebtDecrease: 0
        });

        // Execute cycles up to maxLoops
        uint256 actualLoops = params.maxLoops;
        for (uint256 i = 0; i < params.maxLoops; i++) {
            // Calculate optimal flash loan amount (simplified)
            uint256 flashAmount = _calculateOptimalFlashAmount();
            
            if (flashAmount == 0) {
                actualLoops = i;
                break;
            }

            // Execute single step
            (uint256 collateralAdded, uint256 debtRepaid) = _executeSingleStepInternal(
                flashAmount,
                params.targetAsset
            );

            if (collateralAdded == 0 && debtRepaid == 0) {
                actualLoops = i;
                break; // No improvement possible
            }

            cycleState.cyclesExecuted++;
            cycleState.totalCollateralIncrease += collateralAdded;
            cycleState.totalDebtDecrease += debtRepaid;

            // Check if minimum HF improvement achieved
            uint256 currentHF = vault.getHealthFactor();
            if (currentHF >= healthFactorBefore + params.minHFImprovement) {
                break; // Early exit if target achieved
            }
        }

        // Verify invariants
        (bool invariantSuccess, string memory reason) = verifyInvariants(
            collateralBefore,
            debtBefore,
            healthFactorBefore
        );

        if (!invariantSuccess) {
            emit InvariantFail(reason);
            revert(reason);
        }

        // Calculate improvements
        uint256 collateralAfter = vault.getTotalCollateralValue();
        uint256 debtAfter = vault.getTotalDebtValue();
        uint256 healthFactorAfter = vault.getHealthFactor();

        uint256 hfImprovement = healthFactorAfter > healthFactorBefore
            ? healthFactorAfter - healthFactorBefore
            : 0;

        // Emit events
        emit AmortizationExecuted(
            cycleState.cyclesExecuted,
            collateralAfter > collateralBefore ? collateralAfter - collateralBefore : 0,
            debtBefore > debtAfter ? debtBefore - debtAfter : 0,
            hfImprovement
        );

        emit CycleCompleted(
            cycleState.cyclesExecuted,
            cycleState.totalCollateralIncrease,
            cycleState.totalDebtDecrease,
            hfImprovement
        );

        success = true;
        cyclesExecuted = cycleState.cyclesExecuted;

        // Clear state
        cycleState.inProgress = false;
        delete cycleState;

        return (success, cyclesExecuted);
    }

    /**
     * @notice Execute a single amortization step
     */
    function executeSingleStep(
        IFlashLoanRouter.FlashLoanParams memory flashLoanParams,
        address targetAsset
    ) external override onlyRole(OPERATOR_ROLE) nonReentrant onlyNotInCycle returns (uint256 collateralAdded, uint256 debtRepaid) {
        // Enforce policy checks
        bytes memory actionData = abi.encode(
            address(vault),
            flashLoanParams.asset,
            flashLoanParams.amount
        );
        governanceGuard.enforceInvariants(keccak256("FLASH_LOAN"), actionData);

        cycleState.inProgress = true;
        (collateralAdded, debtRepaid) = _executeSingleStepInternal(flashLoanParams.amount, targetAsset);
        cycleState.inProgress = false;
        delete cycleState;

        emit SingleStepCompleted(collateralAdded, debtRepaid);
    }

    /**
     * @notice Internal single step execution
     */
    function _executeSingleStepInternal(
        uint256 flashAmount,
        address targetAsset
    ) internal returns (uint256 collateralAdded, uint256 debtRepaid) {
        // Set up flash callback state
        flashCallbackState = FlashCallbackState({
            targetAsset: targetAsset,
            inFlashLoan: true
        });

        // Determine best flash loan provider (simplified - use Aave by default)
        IFlashLoanRouter.FlashLoanParams memory params = IFlashLoanRouter.FlashLoanParams({
            asset: targetAsset, // Would determine optimal asset in production
            amount: flashAmount,
            provider: IFlashLoanRouter.FlashLoanProvider.AAVE
        });

        bytes memory callbackData = abi.encode(targetAsset);
        
        // Execute flash loan (this will call onFlashLoan callback)
        flashRouter.flashLoan(params, callbackData);

        // Clear flash callback state
        delete flashCallbackState;

        // Calculate improvements (would track during callback)
        // For now, return placeholder
        collateralAdded = flashAmount / 2; // Simplified: 50% to collateral
        debtRepaid = flashAmount / 2; // 50% to debt repayment

        // Record in vault
        vault.recordCollateralAdded(targetAsset, collateralAdded);
        vault.recordDebtRepaid(targetAsset, debtRepaid);
    }

    /**
     * @notice Flash loan callback
     */
    function onFlashLoan(
        address asset,
        uint256 amount,
        uint256 fee,
        bytes calldata callbackData
    ) external override returns (bytes32) {
        require(msg.sender == address(flashRouter), "Invalid caller");
        require(flashCallbackState.inFlashLoan, "Not in flash loan");

        address targetAsset = flashCallbackState.targetAsset;
        if (targetAsset == address(0)) {
            (targetAsset) = abi.decode(callbackData, (address));
        }

        // 1. Harvest yield (simplified - would claim rewards from Aave/other protocols)
        uint256 yieldAmount = _harvestYield(targetAsset);

        // 2. Swap yield to target asset (if needed)
        uint256 totalAmount = amount + yieldAmount;
        if (asset != targetAsset) {
            totalAmount = _swapAsset(asset, targetAsset, totalAmount);
        }

        // 3. Split: repay debt + add collateral
        uint256 repayAmount = totalAmount / 2;
        uint256 collateralAmount = totalAmount - repayAmount;

        // Repay debt
        _repayDebt(targetAsset, repayAmount);

        // Add collateral
        _addCollateral(targetAsset, collateralAmount);

        // Repay flash loan
        uint256 repaymentAmount = amount + fee;
        IERC20(asset).safeApprove(address(flashRouter), repaymentAmount);

        return CALLBACK_SUCCESS;
    }

    /**
     * @notice Harvest yield from protocols
     */
    function _harvestYield(address asset) internal returns (uint256 yieldAmount) {
        // Simplified: would claim rewards from Aave, compound, etc.
        // For now, return 0
        return 0;
    }

    /**
     * @notice Swap asset using Uniswap V3
     */
    function _swapAsset(
        address tokenIn,
        address tokenOut,
        uint256 amountIn
    ) internal returns (uint256 amountOut) {
        // Approve router
        IERC20(tokenIn).safeApprove(address(swapRouter), amountIn);

        // Execute swap (simplified - would use proper fee tier and price limits)
        ISwapRouter.ExactInputSingleParams memory params = ISwapRouter.ExactInputSingleParams({
            tokenIn: tokenIn,
            tokenOut: tokenOut,
            fee: 3000, // 0.3% fee tier
            recipient: address(this),
            deadline: block.timestamp + 300,
            amountIn: amountIn,
            amountOutMinimum: 0, // Would calculate in production
            sqrtPriceLimitX96: 0
        });

        return swapRouter.exactInputSingle(params);
    }

    /**
     * @notice Repay debt
     */
    function _repayDebt(address asset, uint256 amount) internal {
        // Approve Aave
        IERC20(asset).safeApprove(address(aavePool), amount);

        // Repay (variable rate mode = 2)
        aavePool.repay(asset, amount, 2, aaveUserAccount);
    }

    /**
     * @notice Add collateral
     */
    function _addCollateral(address asset, uint256 amount) internal {
        // Approve Aave
        IERC20(asset).safeApprove(address(aavePool), amount);

        // Supply as collateral
        aavePool.supply(asset, amount, aaveUserAccount, 0);
    }

    /**
     * @notice Verify invariants
     */
    function verifyInvariants(
        uint256 collateralBefore,
        uint256 debtBefore,
        uint256 healthFactorBefore
    ) public view override returns (bool success, string memory reason) {
        return vault.verifyPositionImproved(collateralBefore, debtBefore, healthFactorBefore)
            ? (true, "")
            : (false, "Position did not improve");
    }

    /**
     * @notice Calculate optimal flash loan amount
     */
    function _calculateOptimalFlashAmount() internal view returns (uint256) {
        // Simplified: use a percentage of available borrow capacity
        try aavePool.getUserAccountData(aaveUserAccount) returns (
            uint256,
            uint256,
            uint256 availableBorrowsBase,
            uint256,
            uint256,
            uint256
        ) {
            // Use 50% of available borrows
            return availableBorrowsBase / 2;
        } catch {
            return 0;
        }
    }

    /**
     * @notice Update dependencies
     */
    function setFlashRouter(address newRouter) external onlyOwner {
        require(newRouter != address(0), "Invalid router");
        flashRouter = IFlashLoanRouter(newRouter);
    }

    function setConfigRegistry(address newRegistry) external onlyOwner {
        require(newRegistry != address(0), "Invalid registry");
        configRegistry = IConfigRegistry(newRegistry);
    }

    function setPolicyEngine(address newEngine) external onlyOwner {
        require(newEngine != address(0), "Invalid engine");
        policyEngine = IPolicyEngine(newEngine);
    }

    function setGovernanceGuard(address newGuard) external onlyOwner {
        require(newGuard != address(0), "Invalid guard");
        governanceGuard = GovernanceGuard(newGuard);
    }
}