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

import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
import "./interfaces/IToken.sol";
import "./interfaces/IManager.sol";

contract Staking is ReentrancyGuard {
    IManager private Manager;
    IToken private Token;

    uint256 public totalStaked;
    uint256 private _initialRewardPerBlock = 2 * 1e18; // 2 tokens per block
    uint256 private _accumulatedRewardPerShare;
    uint256 private _halvingInterval = 54_000; // 54k blocks - 1 week
    uint256 private _startingBlock;
    uint256 private _lastRewardBlock;

    struct Stake {
        uint256 amount;
        uint256 rewardDebt;
    }

    mapping(address => Stake) public stakes;

    constructor(address _manager) {
        Manager = IManager(_manager);
    }

    /*------------------------------------*
                    MODIFIERS
    *------------------------------------*/

    modifier onlyOwner() {
        require(msg.sender == Manager.owner(), "Not authorized");
        _;
    }

    /*------------------------------------*
                    SETTERS
    *------------------------------------*/

    function setManager(address _manager) external onlyOwner {
        Manager = IManager(_manager);
    }

    function update() external onlyOwner {
        Token = IToken(_getContract("Token"));
    }

    function start() external onlyOwner {
        _startingBlock = block.number;
    }

    /*------------------------------------*
                    FUNCTIONS
    *------------------------------------*/

    function stake(uint256 amount) external nonReentrant {
        require(amount > 0, "Amount must be greater than 0");
        address sender = msg.sender;

        uint256 rewards = pendingReward(sender);

        if (rewards > 0) {
            _claim(sender, rewards);
        }

        _updatePool();
        _stake(amount, sender);
    }

    function unstake(uint256 amount) external nonReentrant {
        address sender = msg.sender;
        require(amount > 0, "Amount must be greater than 0");
        require(stakes[sender].amount >= amount, "Insufficient balance");

        uint256 rewards = pendingReward(sender);

        if (rewards > 0) {
            _claim(sender, rewards);
        }

        _unstake(amount, sender);
        _updatePool();
    }

    function claim() external nonReentrant {
        uint256 rewards = pendingReward(msg.sender);
        require(rewards > 0, "No rewards to claim");

        _claim(msg.sender, rewards);
        _updatePool();
    }

    /*------------------------------------*
                    INTERNAL
    *------------------------------------*/

    function _stake(uint256 amount, address user) private {
        Token.transferFrom(user, address(this), amount);

        totalStaked += amount;
        stakes[user].amount += amount;
        stakes[user].rewardDebt =
            (stakes[user].amount * _accumulatedRewardPerShare) /
            1e18;
    }

    function _unstake(uint256 amount, address user) private {
        totalStaked -= amount;
        stakes[user].amount -= amount;
        stakes[user].rewardDebt =
            (stakes[user].amount * _accumulatedRewardPerShare) /
            1e18;

        Token.transfer(user, amount);
    }

    function _claim(address user, uint256 _rewards) private {
        stakes[user].rewardDebt =
            (stakes[user].amount * _accumulatedRewardPerShare) /
            1e18;

        Token.transfer(user, _rewards);
    }

    function _calculateReward(
        uint256 _from,
        uint256 _to
    ) internal view returns (uint256) {
        uint256 rewards;
        uint256 currentBlock = _from;
        uint256 __startingBlock = _startingBlock;
        uint256 __halvingInterval = _halvingInterval;
        uint256 __initialRewardPerBlock = _initialRewardPerBlock;

        for (uint256 i = 0; i < 4; i++) {
            uint256 nextHalvingBlock = __startingBlock +
                (i + 1) *
                __halvingInterval;
            if (_to <= nextHalvingBlock) {
                rewards +=
                    (_to - currentBlock) *
                    (__initialRewardPerBlock >> i);
                break;
            } else if (currentBlock < nextHalvingBlock) {
                rewards +=
                    (nextHalvingBlock - currentBlock) *
                    (__initialRewardPerBlock >> i);
                currentBlock = nextHalvingBlock;
            }
        }

        return rewards;
    }

    function _updatePool() internal {
        uint256 __lastRewardBlock = _lastRewardBlock;
        if (block.number <= __lastRewardBlock) {
            return;
        }

        uint256 reward = _calculateReward(__lastRewardBlock, block.number);

        if (totalStaked > 0) {
            _accumulatedRewardPerShare += (reward * 1e18) / totalStaked;
        }

        _lastRewardBlock = block.number;
    }

    function pendingReward(address _staker) public view returns (uint256) {
        uint256 accRewardPerShare = _accumulatedRewardPerShare;
        uint256 __lastRewardBlock = _lastRewardBlock;

        if (block.number > __lastRewardBlock && totalStaked > 0) {
            uint256 reward = _calculateReward(__lastRewardBlock, block.number);
            accRewardPerShare += (reward * 1e18) / totalStaked;
        }
        return
            (stakes[_staker].amount * accRewardPerShare) /
            1e18 -
            stakes[_staker].rewardDebt;
    }

    /*------------------------------------*
                    GETTERS
    *------------------------------------*/

    /*------------------------------------*
                    UTILS
    *------------------------------------*/

    function _getContract(
        string memory contractName
    ) internal view returns (address) {
        return Manager.getContract(contractName);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.20;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the value of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the value of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves a `value` amount of tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 value) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets a `value` amount of tokens as the allowance of `spender` over the
     * caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the
     * allowance mechanism. `value` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 value) external returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (utils/ReentrancyGuard.sol)

pragma solidity ^0.8.20;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant NOT_ENTERED = 1;
    uint256 private constant ENTERED = 2;

    uint256 private _status;

    /**
     * @dev Unauthorized reentrant call.
     */
    error ReentrancyGuardReentrantCall();

    constructor() {
        _status = NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be NOT_ENTERED
        if (_status == ENTERED) {
            revert ReentrancyGuardReentrantCall();
        }

        // Any calls to nonReentrant after this point will fail
        _status = ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = NOT_ENTERED;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == ENTERED;
    }
}

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

interface IManager {
    function getContract(string memory name) external view returns (address);
    function owner() external view returns (address);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.24;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

interface IToken is IERC20 {
    function mint(address to, uint256 value) external;
    function burnFrom(address account, uint256 value) external;
}

{
  "optimizer": {
    "enabled": true,
    "runs": 1000
  },
  "evmVersion": "paris",
  "outputSelection": {
    "*": {
      "*": [
        "evm.bytecode",
        "evm.deployedBytecode",
        "devdoc",
        "userdoc",
        "metadata",
        "abi"
      ]
    }
  },
  "libraries": {}
}

[{"inputs":[{"internalType":"address","name":"_manager","type":"address"}],"stateMutability":"nonpayable","type":"constructor"},{"inputs":[],"name":"ReentrancyGuardReentrantCall","type":"error"},{"inputs":[],"name":"claim","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"_staker","type":"address"}],"name":"pendingReward","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"_manager","type":"address"}],"name":"setManager","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"stake","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"stakes","outputs":[{"internalType":"uint256","name":"amount","type":"uint256"},{"internalType":"uint256","name":"rewardDebt","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"start","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"totalStaked","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"unstake","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"update","outputs":[],"stateMutability":"nonpayable","type":"function"}]

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