// SPDX-License-Identifier: AGPL-3.0-or-later
pragma solidity 0.7.5;

library SafeMath {
  /**
   * @dev Returns the addition of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `+` operator.
   *
   * Requirements:
   *
   * - Addition cannot overflow.
   */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, "SafeMath: addition overflow");

    return c;
  }

  function add32(uint32 a, uint32 b) internal pure returns (uint32) {
    uint32 c = a + b;
    require(c >= a, "SafeMath: addition overflow");

    return c;
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   *
   * - Subtraction cannot overflow.
   */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    return sub(a, b, "SafeMath: subtraction overflow");
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   *
   * - Subtraction cannot overflow.
   */
  function sub(
    uint256 a,
    uint256 b,
    string memory errorMessage
  ) internal pure returns (uint256) {
    require(b <= a, errorMessage);
    uint256 c = a - b;

    return c;
  }

  /**
   * @dev Returns the multiplication of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `*` operator.
   *
   * Requirements:
   *
   * - Multiplication cannot overflow.
   */
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b, "SafeMath: multiplication overflow");

    return c;
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   *
   * - The divisor cannot be zero.
   */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    return div(a, b, "SafeMath: division by zero");
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   *
   * - The divisor cannot be zero.
   */
  function div(
    uint256 a,
    uint256 b,
    string memory errorMessage
  ) internal pure returns (uint256) {
    require(b > 0, errorMessage);
    uint256 c = a / b;
    assert(a == b * c + (a % b)); // There is no case in which this doesn't hold

    return c;
  }
}

interface IERC20 {
  function decimals() external view returns (uint8);

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

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

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

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

  /**
   * @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);
}

library Address {
  /**
   * @dev Returns true if `account` is a contract.
   *
   * [IMPORTANT]
   * ====
   * It is unsafe to assume that an address for which this function returns
   * false is an externally-owned account (EOA) and not a contract.
   *
   * Among others, `isContract` will return false for the following
   * types of addresses:
   *
   *  - an externally-owned account
   *  - a contract in construction
   *  - an address where a contract will be created
   *  - an address where a contract lived, but was destroyed
   * ====
   */
  function isContract(address account) internal view returns (bool) {
    // This method relies in extcodesize, which returns 0 for contracts in
    // construction, since the code is only stored at the end of the
    // constructor execution.

    uint256 size;
    // solhint-disable-next-line no-inline-assembly
    assembly {
      size := extcodesize(account)
    }
    return size > 0;
  }

  /**
   * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
   * `recipient`, forwarding all available gas and reverting on errors.
   *
   * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
   * of certain opcodes, possibly making contracts go over the 2300 gas limit
   * imposed by `transfer`, making them unable to receive funds via
   * `transfer`. {sendValue} removes this limitation.
   *
   * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
   *
   * IMPORTANT: because control is transferred to `recipient`, care must be
   * taken to not create reentrancy vulnerabilities. Consider using
   * {ReentrancyGuard}
   */
  function sendValue(address payable recipient, uint256 amount) internal {
    require(address(this).balance >= amount, "Address: insufficient balance");

    // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
    (bool success, ) = recipient.call{ value: amount }("");
    require(
      success,
      "Address: unable to send value, recipient may have reverted"
    );
  }

  /**
   * @dev Performs a Solidity function call using a low level `call`. A
   * plain`call` is an unsafe replacement for a function call: use this
   * function instead.
   *
   * If `target` reverts with a revert reason, it is bubbled up by this
   * function (like regular Solidity function calls).
   *
   * Returns the raw returned data. To convert to the expected return value,
   * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
   *
   * Requirements:
   *
   * - `target` must be a contract.
   * - calling `target` with `data` must not revert.
   *
   * _Available since v3.1._
   */
  function functionCall(address target, bytes memory data)
    internal
    returns (bytes memory)
  {
    return functionCall(target, data, "Address: low-level call failed");
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
   * `errorMessage` as a fallback revert reason when `target` reverts.
   *
   * _Available since v3.1._
   */
  function functionCall(
    address target,
    bytes memory data,
    string memory errorMessage
  ) internal returns (bytes memory) {
    return _functionCallWithValue(target, data, 0, errorMessage);
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
   * but also transferring `value` wei to `target`.
   *
   * Requirements:
   *
   * - the calling contract must have an ETH balance of at least `value`.
   * - the called Solidity function must be `payable`.
   *
   * _Available since v3.1._
   */
  function functionCallWithValue(
    address target,
    bytes memory data,
    uint256 value
  ) internal returns (bytes memory) {
    return
      functionCallWithValue(
        target,
        data,
        value,
        "Address: low-level call with value failed"
      );
  }

  /**
   * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
   * with `errorMessage` as a fallback revert reason when `target` reverts.
   *
   * _Available since v3.1._
   */
  function functionCallWithValue(
    address target,
    bytes memory data,
    uint256 value,
    string memory errorMessage
  ) internal returns (bytes memory) {
    require(
      address(this).balance >= value,
      "Address: insufficient balance for call"
    );
    require(isContract(target), "Address: call to non-contract");

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory returndata) = target.call{ value: value }(data);
    return _verifyCallResult(success, returndata, errorMessage);
  }

  function _functionCallWithValue(
    address target,
    bytes memory data,
    uint256 weiValue,
    string memory errorMessage
  ) private returns (bytes memory) {
    require(isContract(target), "Address: call to non-contract");

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory returndata) = target.call{ value: weiValue }(
      data
    );
    if (success) {
      return returndata;
    } else {
      // Look for revert reason and bubble it up if present
      if (returndata.length > 0) {
        // The easiest way to bubble the revert reason is using memory via assembly

        // solhint-disable-next-line no-inline-assembly
        assembly {
          let returndata_size := mload(returndata)
          revert(add(32, returndata), returndata_size)
        }
      } else {
        revert(errorMessage);
      }
    }
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
   * but performing a static call.
   *
   * _Available since v3.3._
   */
  function functionStaticCall(address target, bytes memory data)
    internal
    view
    returns (bytes memory)
  {
    return
      functionStaticCall(target, data, "Address: low-level static call failed");
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
   * but performing a static call.
   *
   * _Available since v3.3._
   */
  function functionStaticCall(
    address target,
    bytes memory data,
    string memory errorMessage
  ) internal view returns (bytes memory) {
    require(isContract(target), "Address: static call to non-contract");

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory returndata) = target.staticcall(data);
    return _verifyCallResult(success, returndata, errorMessage);
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
   * but performing a delegate call.
   *
   * _Available since v3.3._
   */
  function functionDelegateCall(address target, bytes memory data)
    internal
    returns (bytes memory)
  {
    return
      functionDelegateCall(
        target,
        data,
        "Address: low-level delegate call failed"
      );
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
   * but performing a delegate call.
   *
   * _Available since v3.3._
   */
  function functionDelegateCall(
    address target,
    bytes memory data,
    string memory errorMessage
  ) internal returns (bytes memory) {
    require(isContract(target), "Address: delegate call to non-contract");

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory returndata) = target.delegatecall(data);
    return _verifyCallResult(success, returndata, errorMessage);
  }

  function _verifyCallResult(
    bool success,
    bytes memory returndata,
    string memory errorMessage
  ) private pure returns (bytes memory) {
    if (success) {
      return returndata;
    } else {
      // Look for revert reason and bubble it up if present
      if (returndata.length > 0) {
        // The easiest way to bubble the revert reason is using memory via assembly

        // solhint-disable-next-line no-inline-assembly
        assembly {
          let returndata_size := mload(returndata)
          revert(add(32, returndata), returndata_size)
        }
      } else {
        revert(errorMessage);
      }
    }
  }

  function addressToString(address _address)
    internal
    pure
    returns (string memory)
  {
    bytes32 _bytes = bytes32(uint256(_address));
    bytes memory HEX = "0123456789abcdef";
    bytes memory _addr = new bytes(42);

    _addr[0] = "0";
    _addr[1] = "x";

    for (uint256 i = 0; i < 20; i++) {
      _addr[2 + i * 2] = HEX[uint8(_bytes[i + 12] >> 4)];
      _addr[3 + i * 2] = HEX[uint8(_bytes[i + 12] & 0x0f)];
    }

    return string(_addr);
  }
}

library SafeERC20 {
  using SafeMath for uint256;
  using Address for address;

  function safeTransfer(
    IERC20 token,
    address to,
    uint256 value
  ) internal {
    _callOptionalReturn(
      token,
      abi.encodeWithSelector(token.transfer.selector, to, value)
    );
  }

  function safeTransferFrom(
    IERC20 token,
    address from,
    address to,
    uint256 value
  ) internal {
    _callOptionalReturn(
      token,
      abi.encodeWithSelector(token.transferFrom.selector, from, to, value)
    );
  }

  /**
   * @dev Deprecated. This function has issues similar to the ones found in
   * {IERC20-approve}, and its usage is discouraged.
   *
   * Whenever possible, use {safeIncreaseAllowance} and
   * {safeDecreaseAllowance} instead.
   */
  function safeApprove(
    IERC20 token,
    address spender,
    uint256 value
  ) internal {
    // safeApprove should only be called when setting an initial allowance,
    // or when resetting it to zero. To increase and decrease it, use
    // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
    // solhint-disable-next-line max-line-length
    require(
      (value == 0) || (token.allowance(address(this), spender) == 0),
      "SafeERC20: approve from non-zero to non-zero allowance"
    );
    _callOptionalReturn(
      token,
      abi.encodeWithSelector(token.approve.selector, spender, value)
    );
  }

  function safeIncreaseAllowance(
    IERC20 token,
    address spender,
    uint256 value
  ) internal {
    uint256 newAllowance = token.allowance(address(this), spender).add(value);
    _callOptionalReturn(
      token,
      abi.encodeWithSelector(token.approve.selector, spender, newAllowance)
    );
  }

  function safeDecreaseAllowance(
    IERC20 token,
    address spender,
    uint256 value
  ) internal {
    uint256 newAllowance = token.allowance(address(this), spender).sub(
      value,
      "SafeERC20: decreased allowance below zero"
    );
    _callOptionalReturn(
      token,
      abi.encodeWithSelector(token.approve.selector, spender, newAllowance)
    );
  }

  /**
   * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
   * on the return value: the return value is optional (but if data is returned, it must not be false).
   * @param token The token targeted by the call.
   * @param data The call data (encoded using abi.encode or one of its variants).
   */
  function _callOptionalReturn(IERC20 token, bytes memory data) private {
    // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
    // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
    // the target address contains contract code and also asserts for success in the low-level call.

    bytes memory returndata = address(token).functionCall(
      data,
      "SafeERC20: low-level call failed"
    );
    if (returndata.length > 0) {
      // Return data is optional
      // solhint-disable-next-line max-line-length
      require(
        abi.decode(returndata, (bool)),
        "SafeERC20: ERC20 operation did not succeed"
      );
    }
  }
}

interface IOwnable {
  function manager() external view returns (address);

  function renounceManagement() external;

  function pushManagement(address newOwner_) external;

  function pullManagement() external;
}

contract Ownable is IOwnable {
  address internal _owner;
  address internal _newOwner;

  event OwnershipPushed(
    address indexed previousOwner,
    address indexed newOwner
  );
  event OwnershipPulled(
    address indexed previousOwner,
    address indexed newOwner
  );

  constructor() {
    _owner = msg.sender;
    emit OwnershipPushed(address(0), _owner);
  }

  function manager() public view override returns (address) {
    return _owner;
  }

  modifier onlyManager() {
    require(_owner == msg.sender, "Ownable: caller is not the owner");
    _;
  }

  function renounceManagement() public virtual override onlyManager {
    emit OwnershipPushed(_owner, address(0));
    _owner = address(0);
  }

  function pushManagement(address newOwner_)
    public
    virtual
    override
    onlyManager
  {
    require(newOwner_ != address(0), "Ownable: new owner is the zero address");
    emit OwnershipPushed(_owner, newOwner_);
    _newOwner = newOwner_;
  }

  function pullManagement() public virtual override {
    require(msg.sender == _newOwner, "Ownable: must be new owner to pull");
    emit OwnershipPulled(_owner, _newOwner);
    _owner = _newOwner;
  }
}

interface IsIMMO {
  function rebase(uint256 profit_, uint256 epoch_) external returns (uint256);

  function circulatingSupply() external view returns (uint256);

  function balanceOf(address who) external view returns (uint256);

  function gonsForBalance(uint256 amount) external view returns (uint256);

  function balanceForGons(uint256 gons) external view returns (uint256);

  function index() external view returns (uint256);
}

interface IWarmup {
  function retrieve(address staker_, uint256 amount_) external;
}

interface IDistributor {
  function distribute() external returns (bool);
}

contract ImmortalStaking is Ownable {
  using SafeMath for uint256;
  using SafeMath for uint32;
  using SafeERC20 for IERC20;

  address public immutable IMMO;
  address public immutable sIMMO;

  struct Epoch {
    uint256 number;
    uint256 distribute;
    uint32 length;
    uint32 endTime;
  }
  Epoch public epoch;

  address public distributor;

  address public locker;
  uint256 public totalBonus;

  address public warmupContract;
  uint256 public warmupPeriod;

  constructor(
    address _IMMO,
    address _sIMMO,
    uint32 _epochLength,
    uint256 _firstEpochNumber,
    uint32 _firstEpochTime
  ) {
    require(_IMMO != address(0));
    IMMO = _IMMO;
    require(_sIMMO != address(0));
    sIMMO = _sIMMO;

    epoch = Epoch({
      length: _epochLength,
      number: _firstEpochNumber,
      endTime: _firstEpochTime,
      distribute: 0
    });
  }

  struct Claim {
    uint256 deposit;
    uint256 gons;
    uint256 expiry;
    bool lock; // prevents malicious delays
  }
  mapping(address => Claim) public warmupInfo;

  /**
        @notice stake IMMO to enter warmup
        @param _amount uint
        @return bool
     */
  function stake(uint256 _amount, address _recipient) external returns (bool) {
    rebase();

    IERC20(IMMO).safeTransferFrom(msg.sender, address(this), _amount);

    Claim memory info = warmupInfo[_recipient];
    require(!info.lock, "Deposits for account are locked");

    warmupInfo[_recipient] = Claim({
      deposit: info.deposit.add(_amount),
      gons: info.gons.add(IsIMMO(sIMMO).gonsForBalance(_amount)),
      expiry: epoch.number.add(warmupPeriod),
      lock: false
    });

    IERC20(sIMMO).safeTransfer(warmupContract, _amount);
    return true;
  }

  /**
        @notice retrieve sIMMO from warmup
        @param _recipient address
     */
  function claim(address _recipient) public {
    Claim memory info = warmupInfo[_recipient];
    if (epoch.number >= info.expiry && info.expiry != 0) {
      delete warmupInfo[_recipient];
      IWarmup(warmupContract).retrieve(
        _recipient,
        IsIMMO(sIMMO).balanceForGons(info.gons)
      );
    }
  }

  /**
        @notice forfeit sIMMO in warmup and retrieve IMMO
     */
  function forfeit() external {
    Claim memory info = warmupInfo[msg.sender];
    delete warmupInfo[msg.sender];

    IWarmup(warmupContract).retrieve(
      address(this),
      IsIMMO(sIMMO).balanceForGons(info.gons)
    );
    IERC20(IMMO).safeTransfer(msg.sender, info.deposit);
  }

  /**
        @notice prevent new deposits to address (protection from malicious activity)
     */
  function toggleDepositLock() external {
    warmupInfo[msg.sender].lock = !warmupInfo[msg.sender].lock;
  }

  /**
        @notice redeem sIMMO for IMMO
        @param _amount uint
        @param _trigger bool
     */
  function unstake(uint256 _amount, bool _trigger) external {
    if (_trigger) {
      rebase();
    }
    IERC20(sIMMO).safeTransferFrom(msg.sender, address(this), _amount);
    IERC20(IMMO).safeTransfer(msg.sender, _amount);
  }

  /**
        @notice returns the sIMMO index, which tracks rebase growth
        @return uint
     */
  function index() public view returns (uint256) {
    return IsIMMO(sIMMO).index();
  }

  /**
        @notice trigger rebase if epoch over
     */
  function rebase() public {
    if (epoch.endTime <= uint32(block.timestamp)) {
      IsIMMO(sIMMO).rebase(epoch.distribute, epoch.number);

      epoch.endTime = epoch.endTime.add32(epoch.length);
      epoch.number++;

      if (distributor != address(0)) {
        IDistributor(distributor).distribute();
      }

      uint256 balance = contractBalance();
      uint256 staked = IsIMMO(sIMMO).circulatingSupply();

      if (balance <= staked) {
        epoch.distribute = 0;
      } else {
        epoch.distribute = balance.sub(staked);
      }
    }
  }

  /**
        @notice returns contract IMMO holdings, including bonuses provided
        @return uint
     */
  function contractBalance() public view returns (uint256) {
    return IERC20(IMMO).balanceOf(address(this)).add(totalBonus);
  }

  /**
        @notice provide bonus to locked staking contract
        @param _amount uint
     */
  function giveLockBonus(uint256 _amount) external {
    require(msg.sender == locker);
    totalBonus = totalBonus.add(_amount);
    IERC20(sIMMO).safeTransfer(locker, _amount);
  }

  /**
        @notice reclaim bonus from locked staking contract
        @param _amount uint
     */
  function returnLockBonus(uint256 _amount) external {
    require(msg.sender == locker);
    totalBonus = totalBonus.sub(_amount);
    IERC20(sIMMO).safeTransferFrom(locker, address(this), _amount);
  }

  enum CONTRACTS {
    DISTRIBUTOR,
    WARMUP,
    LOCKER
  }

  /**
        @notice sets the contract address for LP staking
        @param _contract address
     */
  function setContract(CONTRACTS _contract, address _address)
    external
    onlyManager
  {
    if (_contract == CONTRACTS.DISTRIBUTOR) {
      // 0
      distributor = _address;
    } else if (_contract == CONTRACTS.WARMUP) {
      // 1
      require(
        warmupContract == address(0),
        "Warmup cannot be set more than once"
      );
      warmupContract = _address;
    } else if (_contract == CONTRACTS.LOCKER) {
      // 2
      require(locker == address(0), "Locker cannot be set more than once");
      locker = _address;
    }
  }

  /**
   * @notice set warmup period in epoch number for new stakers
   * @param _warmupPeriod uint
   */
  function setWarmup(uint256 _warmupPeriod) external onlyManager {
    warmupPeriod = _warmupPeriod;
  }
}