// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "./interfaces/IComboHandler.sol";
import "./interfaces/IAdapterRegistry.sol";
import "./interfaces/INotaryRegistry.sol";

/**
 * @title ComboHandler
 * @notice Aggregates multiple DeFi protocol calls and DLT operations into atomic transactions
 */
contract ComboHandler is IComboHandler, Ownable, ReentrancyGuard {
    IAdapterRegistry public adapterRegistry;
    INotaryRegistry public notaryRegistry;

    mapping(bytes32 => ExecutionState) public executions;

    struct ExecutionState {
        ExecutionStatus status;
        uint256 currentStep;
        Step[] steps;
        bool prepared;
    }

    event PlanExecuted(bytes32 indexed planId, bool success);
    event PlanPrepared(bytes32 indexed planId);
    event PlanCommitted(bytes32 indexed planId);
    event PlanAborted(bytes32 indexed planId);

    constructor(address _adapterRegistry, address _notaryRegistry) {
        adapterRegistry = IAdapterRegistry(_adapterRegistry);
        notaryRegistry = INotaryRegistry(_notaryRegistry);
    }

    /**
     * @notice Execute a multi-step combo plan atomically
     */
    function executeCombo(
        bytes32 planId,
        Step[] calldata steps,
        bytes calldata signature
    ) external override nonReentrant returns (bool success, StepReceipt[] memory receipts) {
        require(executions[planId].status == ExecutionStatus.PENDING, "Plan already executed");
        
        // Verify signature
        require(_verifySignature(planId, signature, msg.sender), "Invalid signature");

        // Register with notary
        notaryRegistry.registerPlan(planId, steps, msg.sender);

        executions[planId] = ExecutionState({
            status: ExecutionStatus.IN_PROGRESS,
            currentStep: 0,
            steps: steps,
            prepared: false
        });

        receipts = new StepReceipt[](steps.length);

        // Execute steps sequentially
        for (uint256 i = 0; i < steps.length; i++) {
            (bool stepSuccess, bytes memory returnData, uint256 gasUsed) = _executeStep(steps[i], i);
            
            receipts[i] = StepReceipt({
                stepIndex: i,
                success: stepSuccess,
                returnData: returnData,
                gasUsed: gasUsed
            });

            if (!stepSuccess) {
                executions[planId].status = ExecutionStatus.FAILED;
                revert("Step execution failed");
            }
        }

        executions[planId].status = ExecutionStatus.COMPLETE;
        success = true;

        emit PlanExecuted(planId, true);

        // Finalize with notary
        notaryRegistry.finalizePlan(planId, true);
    }

    /**
     * @notice Prepare phase for 2PC (two-phase commit)
     */
    function prepare(
        bytes32 planId,
        Step[] calldata steps
    ) external override returns (bool prepared) {
        require(executions[planId].status == ExecutionStatus.PENDING, "Plan not pending");

        // Validate all steps can be prepared
        for (uint256 i = 0; i < steps.length; i++) {
            require(_canPrepareStep(steps[i]), "Step cannot be prepared");
        }

        executions[planId] = ExecutionState({
            status: ExecutionStatus.IN_PROGRESS,
            currentStep: 0,
            steps: steps,
            prepared: true
        });

        emit PlanPrepared(planId);
        prepared = true;
    }

    /**
     * @notice Commit phase for 2PC
     */
    function commit(bytes32 planId) external override returns (bool committed) {
        ExecutionState storage state = executions[planId];
        require(state.prepared, "Plan not prepared");
        require(state.status == ExecutionStatus.IN_PROGRESS, "Invalid state");

        // Execute all prepared steps
        for (uint256 i = 0; i < state.steps.length; i++) {
            (bool success, , ) = _executeStep(state.steps[i], i);
            require(success, "Commit failed");
        }

        state.status = ExecutionStatus.COMPLETE;
        committed = true;

        emit PlanCommitted(planId);

        notaryRegistry.finalizePlan(planId, true);
    }

    /**
     * @notice Abort phase for 2PC (rollback)
     */
    function abort(bytes32 planId) external override {
        ExecutionState storage state = executions[planId];
        require(state.status == ExecutionStatus.IN_PROGRESS, "Cannot abort");

        // Release any reserved funds/collateral
        _rollbackSteps(planId);

        state.status = ExecutionStatus.ABORTED;
        
        emit PlanAborted(planId);
        
        notaryRegistry.finalizePlan(planId, false);
    }

    /**
     * @notice Get execution status for a plan
     */
    function getExecutionStatus(bytes32 planId) external view override returns (ExecutionStatus) {
        return executions[planId].status;
    }

    /**
     * @notice Execute a single step
     */
    function _executeStep(Step memory step, uint256 stepIndex) internal returns (bool success, bytes memory returnData, uint256 gasUsed) {
        // Verify adapter is whitelisted
        require(adapterRegistry.isWhitelisted(step.target), "Adapter not whitelisted");

        uint256 gasBefore = gasleft();
        
        (success, returnData) = step.target.call{value: step.value}(
            abi.encodeWithSignature("executeStep(bytes)", step.data)
        );

        gasUsed = gasBefore - gasleft();
    }

    /**
     * @notice Check if step can be prepared
     */
    function _canPrepareStep(Step memory step) internal view returns (bool) {
        // Check if adapter supports prepare phase
        return adapterRegistry.isWhitelisted(step.target);
    }

    /**
     * @notice Rollback steps on abort
     */
    function _rollbackSteps(bytes32 planId) internal {
        // Release reserved funds, unlock collateral, etc.
        // Implementation depends on specific step types
    }

    /**
     * @notice Verify user signature on plan
     */
    function _verifySignature(bytes32 planId, bytes calldata signature, address signer) internal pure returns (bool) {
        // Simplified signature verification
        // In production, use ECDSA.recover or similar
        bytes32 messageHash = keccak256(abi.encodePacked(planId, signer));
        // Verify signature matches signer
        return true; // Simplified for now
    }
}