// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;

/**
 * @dev Collection of functions related to the address type
 */
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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 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} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (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");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, 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");

        (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 v3.4._
     */
    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 v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal 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
                /// @solidity memory-safe-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

/**
 * @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 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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, 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 `from` to `to` 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 from,
        address to,
        uint256 amount
    ) external returns (bool);
}

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    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'
        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) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

/**
 * @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;

    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() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

/**
 * @title Interface of Vesting Escrow
 */
interface IBase_VestingEscrow_V1 {
    event Fund(address indexed recipient, uint256 amount);
    event Claim(address indexed recipient, uint256 claimed);
    event CommitOwnership(address admin);
    event AcceptOwnership(address admin);

    function add_tokens(uint256 _amount) external;
    function fund(address[] memory _recipients, uint256[] memory _amounts) external;
    function vestedSupply() external view returns(uint256);
    function lockedSupply() external view returns(uint256);
    function vestedOf(address _recipient) external view returns(uint256);
    function balanceOf(address _recipient) external view returns(uint256);
    function lockedOf(address _recipient) external view returns(uint256);
    function claim(address addr) external;
    function commit_transfer_ownership(address addr) external returns(bool);
    function accept_transfer_ownership() external;
}

/**
 * @title Vesting Escrow
 */
contract Base_VestingEscrow_V1 is IBase_VestingEscrow_V1, ReentrancyGuard {
    using SafeERC20 for IERC20;

    uint8 constant ONE_QUARTER = 25;
    uint8 constant ONE_HARF = 50;
    uint8 constant THREE_QUARTER = 75;

    address public token;

    uint256 public start_time;
    uint256 public one_quarter_time;
    uint256 public one_harf_time;
    uint256 public three_quarter_time;
    uint256 public end_time;

    mapping(address => uint256) public initial_locked;
    mapping(address => uint256) public total_claimed;

    uint256 public initial_locked_supply;
    uint256 public unallocated_supply;

    address public admin;
    address public future_admin;

    modifier onlyOwner() {
        require(msg.sender == admin);
        _;
    }

    /**
     * @param _token Address of the ERC20 token being distributed (ZENI)
     * @param _start_time Timestamp at which the distribution starts. Should be in
     *    the future, so that we have enough time to VoteLock everyone
     * @param _end_time Time until everything should be vested
     */
    constructor(
        address _token,
        uint256 _start_time,
        uint256 _one_quarter_time,
        uint256 _one_harf_time,
        uint256 _three_quarter_time,
        uint256 _end_time
    ) {
        require(_start_time >= block.timestamp);
        require(_end_time > _start_time);

        admin = msg.sender;
        token = _token;

        start_time = _start_time;
        one_quarter_time = _one_quarter_time;
        one_harf_time = _one_harf_time;
        three_quarter_time = _three_quarter_time;
        end_time = _end_time;
    }

    /***
     * @notice Transfer vestable tokens into the contract
     * @dev Handled separate from `fund` to reduce transaction count when using funding admins
     * @param _amount Number of tokens to transfer
     */
    function add_tokens(uint256 _amount) external onlyOwner {
        IERC20(token).safeTransferFrom(msg.sender, address(this), _amount);
        unallocated_supply += _amount;
    }

    /***
     * @notice Vest tokens for multiple recipients.
     * @param _recipients List of addresses to fund
     * @param _amounts Amount of vested tokens for each address
     */
    function fund(address[] memory _recipients, uint256[] memory _amounts) external nonReentrant onlyOwner {
        require(_recipients.length == _amounts.length);
        uint256 _total_amount = 0;

        uint256 _length = _recipients.length;
        for (uint256 i; i < _length; i++) {
            uint256 amount = _amounts[i];
            address recipient = _recipients[i];
            if (recipient == address(0)) {
                break;
            }
            _total_amount += amount;
            initial_locked[recipient] += amount;
            emit Fund(recipient, amount);
        }

        initial_locked_supply += _total_amount;
        unallocated_supply -= _total_amount;
    }

    /***
     * @notice Amount of unlocked token amount of _recipient at _time. (include claimed)
     */
    function _total_vested_of(address _recipient, uint256 _time) internal view returns(uint256) {
        uint256 start = start_time;
        uint256 locked = initial_locked[_recipient];
        if (_time < start) {
            return 0;
        }

        return _get_vested_amount(locked, _time);
    }

    function _total_vested() internal view returns(uint256) {
        uint256 start = start_time;
        uint256 locked = initial_locked_supply;

        if (block.timestamp < start) {
            return 0;
        } else {
            return _get_vested_amount(locked, block.timestamp); // when block.timestamp > end, return locked
        }
    }

    function _get_vested_amount(uint256 _locked, uint256 _time) internal view returns(uint256) {
        uint256 amount = 0;

        if (start_time <= _time && one_quarter_time > _time) {
            amount = 0;
        } else if (one_quarter_time <= _time && one_harf_time > _time) {
            amount = _locked * ONE_QUARTER / 100;
        } else if (one_harf_time <= _time && three_quarter_time > _time) {
            amount = _locked * ONE_HARF / 100;
        } else if (three_quarter_time <= _time && end_time > _time) {
            amount = _locked * THREE_QUARTER / 100;
        } else if (end_time < _time) {
            amount = _locked;
        } else {
            amount = 0;
        }

        return amount;
    }

    /***
     * @notice Get the total number of tokens which have vested, that are held by this contract
     */
    function vestedSupply() external view returns(uint256) {
        return _total_vested();
    }

    /***
     * @notice Get the total number of tokens which are still locked (have not yet vested)
     */
    function lockedSupply() external view returns(uint256) {
        return initial_locked_supply - _total_vested();
    }

    /***
     * @notice Get the number of tokens which have vested for a given address
     * @param _recipient address to check
     */
    function vestedOf(address _recipient) external view returns(uint256) {
        return _total_vested_of(_recipient, block.timestamp);
    }

    /***
     * @notice Get the number of unclaimed, vested tokens for a given address
     * @param _recipient address to check
     */
    function balanceOf(address _recipient) external view returns(uint256) {
        return _total_vested_of(_recipient, block.timestamp) - total_claimed[_recipient];
    }

    /***
     * @notice Get the number of locked tokens for a given address
     * @param _recipient address to check
     */
    function lockedOf(address _recipient) external view returns(uint256) {
        return initial_locked[_recipient] - _total_vested_of(_recipient, block.timestamp);
    }

    /***
     * @notice Claim tokens which have vested
     * @param addr Address to claim tokens for
     */
    function claim(address addr) external nonReentrant {
        uint256 claimable = _total_vested_of(addr, block.timestamp) - total_claimed[addr];

        total_claimed[addr] += claimable;
        require(IERC20(token).transfer(addr, claimable));

        emit Claim(addr, claimable);
    }

    /***
     * @notice Transfer ownership of GaugeController to `addr`
     * @param addr Address to have ownership transferred to
     */
    function commit_transfer_ownership(address addr) external onlyOwner returns(bool) {
        future_admin = addr;
        emit CommitOwnership(addr);

        return true;
    }

    /***
     * @notice Accept a transfer of ownership
     * @return bool success
     */
    function accept_transfer_ownership() external {
        address _future_admin = future_admin;
        require(address(msg.sender) == _future_admin, "onlyFutureOwner");
        admin = _future_admin;
        emit AcceptOwnership(_future_admin);
    }
}

/**
 * @title Vesting Escrow
 */
contract Koban_VestingEscrow_V1 is Base_VestingEscrow_V1 {
    /**
     * @param _token Address of the ERC20 token being distributed (ZENI)
     * @param _start_time Timestamp at which the distribution starts. Should be in
     *    the future, so that we have enough time to VoteLock everyone
     * @param _end_time Time until everything should be vested
     */
    constructor(
        address _token,
        uint256 _start_time,
        uint256 _one_quarter_time,
        uint256 _one_harf_time,
        uint256 _three_quarter_time,
        uint256 _end_time
    ) Base_VestingEscrow_V1(_token, _start_time, _one_quarter_time, _one_harf_time, _three_quarter_time, _end_time) {}
}