// SPDX-License-Identifier: MIT
pragma solidity 0.8.30;

import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
import {Ownable2Step} from "@openzeppelin/contracts/access/Ownable2Step.sol";
import {ReentrancyGuard} from "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import {Pausable} from "@openzeppelin/contracts/utils/Pausable.sol";
import {MerkleProof} from "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
import {Math} from "@openzeppelin/contracts/utils/math/Math.sol";
import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";

interface IArbSysBlockNumber {
    function arbBlockNumber() external view returns (uint256);
}

interface IV2BuybackRouter {
    function WETH() external view returns (address);
    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable;
}

/// @notice Fully funded daily ETH allocations; reporter-trusted accounting and snapshots.
/// @dev No token issuance, custody of holder tokens, upgrade proxy, or reserve withdrawal.
contract VellinDistributor is Ownable2Step, ReentrancyGuard, Pausable {
    uint256 public constant HOLDER_PERCENT = 30;
    uint256 public constant BURN_PERCENT = 30;
    uint256 public constant MAX_BATCH = 50;
    uint256 public constant PUSH_GAS = 50_000;
    uint256 public constant AUTO_RETRY_DELAY = 1 hours;
    address public constant BURN_ADDRESS = 0x000000000000000000000000000000000000dEaD;

    IERC20 public immutable token;
    IV2BuybackRouter public immutable router;
    address public immutable team;
    bytes32 public immutable policyHash;
    address public keeper;
    address[] private buybackPath;

    struct Epoch {
        bytes32 root;
        bytes32 reportHash;
        bytes32 snapshotHash;
        uint64 snapshotBlock;
        bool funded;
        uint256 netProfit;
        uint256 holderPool;
        uint256 remaining;
    }

    struct Report {
        uint64 day;
        uint64 snapshotBlock;
        bytes32 snapshotHash;
        bytes32 root;
        bytes32 reportHash;
        int256 realisedPnl;
        uint256 tradingFees;
        uint256 infrastructureCosts;
    }

    struct Payment {
        address account;
        uint256 amount;
        bytes32[] proof;
    }

    mapping(uint64 => Epoch) public epochs;
    mapping(uint64 => mapping(address => bool)) public processed;
    mapping(address => uint256) public credit;
    mapping(address => uint256) public lastPaymentAttempt;
    uint64 public lastDay;
    uint64 public lastSnapshotBlock;
    bool public hasEpoch;
    uint256 public holderReserve;
    uint256 public buybackReserve;
    uint256 public creditReserve;

    error InvalidConfiguration();
    error InvalidEpoch();
    error InvalidFunding();
    error InvalidProof();
    error AlreadyProcessed();
    error InvalidBatch();
    error InvalidPayment();
    error UnauthorizedKeeper();
    error InvalidBuyback();
    error DirectTransferDisabled();
    error RenounceDisabled();

    event EpochFunded(
        uint64 indexed day,
        bytes32 root,
        uint64 snapshotBlock,
        bytes32 snapshotHash,
        bytes32 reportHash,
        int256 realisedPnl,
        uint256 tradingFees,
        uint256 infrastructureCosts,
        uint256 netProfit,
        uint256 holders,
        uint256 buyback,
        uint256 teamAmount
    );
    event HolderProcessed(uint64 indexed day, address indexed account, uint256 amount);
    event PaymentSent(address indexed beneficiary, address indexed destination, uint256 amount);
    event PaymentDeferred(address indexed beneficiary, uint256 amount);
    event BuybackBurned(uint256 ethSpent, uint256 tokensSentToBurn, uint256 minimumOut);
    event KeeperUpdated(address indexed keeper);

    constructor(
        address initialOwner,
        address token_,
        address router_,
        address team_,
        address keeper_,
        address[] memory path_,
        bytes32 policyHash_
    ) Ownable(initialOwner) {
        if (
            token_.code.length == 0 || router_.code.length == 0 || team_ == address(0) || team_ == BURN_ADDRESS
                || keeper_ == address(0) || policyHash_ == bytes32(0) || path_.length < 2 || path_.length > 5
                || path_[path_.length - 1] != token_ || path_[0] != IV2BuybackRouter(router_).WETH()
        ) revert InvalidConfiguration();
        for (uint256 i; i < path_.length; ++i) {
            if (path_[i] == address(0)) revert InvalidConfiguration();
        }
        token = IERC20(token_);
        router = IV2BuybackRouter(router_);
        team = team_;
        keeper = keeper_;
        buybackPath = path_;
        policyHash = policyHash_;
    }

    function path() external view returns (address[] memory) {
        return buybackPath;
    }

    function split(int256 realisedPnl, uint256 tradingFees, uint256 infrastructureCosts)
        public
        pure
        returns (uint256 net, uint256 holders, uint256 burn, uint256 teamAmount)
    {
        uint256 costs = tradingFees + infrastructureCosts;
        if (realisedPnl <= 0 || uint256(realisedPnl) <= costs) return (0, 0, 0, 0);
        net = uint256(realisedPnl) - costs;
        holders = Math.mulDiv(net, HOLDER_PERCENT, 100);
        burn = Math.mulDiv(net, BURN_PERCENT, 100);
        teamAmount = net - holders - burn; // At most two wei of split rounding.
    }

    /// @dev Nitro's NUMBER opcode is a parent-chain height; snapshots use L2 RPC block numbers.
    function _currentChainBlock() private view returns (uint256) {
        if (block.chainid == 4663 || block.chainid == 46630) {
            // Fail closed if the required Robinhood/Arbitrum system precompile is unavailable.
            return IArbSysBlockNumber(address(100)).arbBlockNumber();
        }
        return block.number;
    }

    /// @notice Developer deposits exactly the positive, approved daily net result.
    /// @dev Report contents and end-of-day snapshot accuracy remain operator-attested.
    function fundEpoch(Report calldata r) external payable nonReentrant onlyOwner whenNotPaused {
        if (
            r.day >= block.timestamp / 1 days || (hasEpoch && r.day <= lastDay) || epochs[r.day].funded
                || r.snapshotBlock >= _currentChainBlock() || r.snapshotBlock == 0
                || (hasEpoch && r.snapshotBlock <= lastSnapshotBlock) || r.snapshotHash == bytes32(0)
                || r.reportHash == bytes32(0)
        ) revert InvalidEpoch();
        (uint256 net, uint256 holders, uint256 burn, uint256 teamAmount) =
            split(r.realisedPnl, r.tradingFees, r.infrastructureCosts);
        if (msg.value != net || (holders == 0) != (r.root == bytes32(0))) revert InvalidFunding();
        epochs[r.day] = Epoch(r.root, r.reportHash, r.snapshotHash, r.snapshotBlock, true, net, holders, holders);
        lastDay = r.day;
        lastSnapshotBlock = r.snapshotBlock;
        hasEpoch = true;
        holderReserve += holders;
        buybackReserve += burn;
        credit[team] += teamAmount;
        creditReserve += teamAmount;
        emit EpochFunded(
            r.day,
            r.root,
            r.snapshotBlock,
            r.snapshotHash,
            r.reportHash,
            r.realisedPnl,
            r.tradingFees,
            r.infrastructureCosts,
            net,
            holders,
            burn,
            teamAmount
        );
        _pushCredit(team);
    }

    /// @notice Anyone can deliver valid payments to their fixed beneficiaries. Replays skip.
    function distribute(uint64 day, Payment[] calldata payments) external nonReentrant {
        if (payments.length == 0 || payments.length > MAX_BATCH) revert InvalidBatch();
        for (uint256 i; i < payments.length; ++i) {
            Payment calldata p = payments[i];
            if (processed[day][p.account]) continue;
            _creditHolder(day, p.account, p.amount, p.proof);
            _pushCredit(p.account);
        }
    }

    /// @notice Holder fallback, including contracts that cannot accept the bounded push.
    function claim(uint64 day, uint256 amount, bytes32[] calldata proof, address payable destination)
        external
        nonReentrant
    {
        if (processed[day][msg.sender]) revert AlreadyProcessed();
        _creditHolder(day, msg.sender, amount, proof);
        _withdrawCredit(msg.sender, destination);
    }

    function retryPayment(address account) external nonReentrant {
        _pushCredit(account);
    }

    /// @notice Bounded keeper recovery; persistently rejecting wallets are retried at most hourly.
    /// @dev Holder withdrawals and individual caller-funded retries remain immediately accessible.
    function retryPayments(address[] calldata accounts) external nonReentrant {
        if (accounts.length == 0 || accounts.length > MAX_BATCH) revert InvalidBatch();
        for (uint256 i; i < accounts.length; ++i) {
            address account = accounts[i];
            if (credit[account] != 0 && block.timestamp >= lastPaymentAttempt[account] + AUTO_RETRY_DELAY) {
                _pushCredit(account);
            }
        }
    }

    function withdrawCredit(address payable destination) external nonReentrant {
        _withdrawCredit(msg.sender, destination);
    }

    function _creditHolder(uint64 day, address account, uint256 amount, bytes32[] calldata proof) private {
        Epoch storage e = epochs[day];
        if (
            !e.funded || account == address(0) || account == BURN_ADDRESS || account == address(this) || amount == 0
                || amount > e.remaining || !MerkleProof.verifyCalldata(proof, e.root, leaf(day, account, amount))
        ) revert InvalidProof();
        processed[day][account] = true;
        e.remaining -= amount;
        holderReserve -= amount;
        credit[account] += amount;
        creditReserve += amount;
        emit HolderProcessed(day, account, amount);
    }

    function leaf(uint64 day, address account, uint256 amount) public view returns (bytes32) {
        // OpenZeppelin StandardMerkleTree double-hashed ABI encoding; domain-bound.
        return keccak256(bytes.concat(keccak256(abi.encode(block.chainid, address(this), day, account, amount))));
    }

    function _pushCredit(address account) private {
        uint256 amount = credit[account];
        if (amount == 0) return;
        lastPaymentAttempt[account] = block.timestamp;
        credit[account] = 0;
        creditReserve -= amount;
        bool sent;
        // No returndata copy: even a hostile receiver cannot return-bomb the batch.
        assembly ("memory-safe") { sent := call(50000, account, amount, 0, 0, 0, 0) }
        if (sent) {
            emit PaymentSent(account, account, amount);
        } else {
            credit[account] = amount;
            creditReserve += amount;
            emit PaymentDeferred(account, amount);
        }
    }

    function _withdrawCredit(address account, address payable destination) private {
        uint256 amount = credit[account];
        if (amount == 0 || destination == address(0) || destination == BURN_ADDRESS || destination == address(this)) {
            revert InvalidPayment();
        }
        credit[account] = 0;
        creditReserve -= amount;
        (bool sent,) = destination.call{value: amount}("");
        if (!sent) revert InvalidPayment();
        emit PaymentSent(account, destination, amount);
    }

    /// @notice Uses only the 30% burn reserve; swap failure leaves holder payments available.
    /// @dev Target V2 router/path must be verified for the actual launch market before deployment.
    function executeBuyback(uint256 ethAmount, uint256 minimumTokens, uint256 deadline)
        external
        nonReentrant
        whenNotPaused
    {
        if (msg.sender != keeper && msg.sender != owner()) revert UnauthorizedKeeper();
        if (
            ethAmount == 0 || ethAmount > buybackReserve || minimumTokens == 0 || deadline < block.timestamp
                || deadline > block.timestamp + 10 minutes
        ) revert InvalidBuyback();
        buybackReserve -= ethAmount;
        uint256 beforeBurn = token.balanceOf(BURN_ADDRESS);
        router.swapExactETHForTokensSupportingFeeOnTransferTokens{value: ethAmount}(
            minimumTokens, buybackPath, BURN_ADDRESS, deadline
        );
        uint256 burned = token.balanceOf(BURN_ADDRESS) - beforeBurn;
        if (burned < minimumTokens) revert InvalidBuyback();
        emit BuybackBurned(ethAmount, burned, minimumTokens);
    }

    function reserved() public view returns (uint256) {
        return holderReserve + buybackReserve + creditReserve;
    }

    function setKeeper(address next) external onlyOwner {
        if (next == address(0)) revert InvalidConfiguration();
        keeper = next;
        emit KeeperUpdated(next);
    }

    // Pause new reports and buybacks; funded holder claims/credits remain accessible.
    function pause() external onlyOwner {
        _pause();
    }

    function unpause() external onlyOwner {
        _unpause();
    }

    function renounceOwnership() public view override onlyOwner {
        revert RenounceDisabled();
    }

    receive() external payable {
        revert DirectTransferDisabled();
    }
}