// File: contracts/token/vesting/ERC20Vesting.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.8.6;

import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

import "./IERC20Vesting.sol";

contract ERC20Vesting is IERC20Vesting {
    using SafeERC20 for IERC20;

    address public immutable override wallet;
    IERC20 public immutable override token;
    mapping(address => VestingTerms) private vestingTerms;

    modifier onlyWallet() {
        require(msg.sender == wallet, "Only wallet is allowed to proceed");
        _;
    }

    /// @param _token Address of ERC20 token associated with this vesting contract
    /// @param _wallet Address of account that starts and stops vesting for different parties
    constructor(IERC20 _token, address _wallet) {
        require(address(_token) != address(0), "Token cannot be 0.");
        require(address(_wallet) != address(0), "Wallet cannot be 0.");

        token = _token;
        wallet = _wallet;
    }

    function getVestingTerms(address receiver) external view override returns (VestingTerms memory) {
        return vestingTerms[receiver];
    }

    function startVesting(address receiver, VestingTerms calldata terms) public override onlyWallet {
        require(receiver != address(0), "Receiver cannot be 0.");
        require(terms.amount > 0, "Amount must be > 0.");
        require(terms.startTime != 0, "Start time must be set.");
        require(terms.period > 0, "Period must be set.");
        require(terms.claimed == 0, "Can not start vesting with already claimed tokens.");
        assert(isScheduleValid(terms));
        require(!isScheduleValid(vestingTerms[receiver]), "Vesting already started for account.");

        vestingTerms[receiver] = terms;
        token.safeTransferFrom(wallet, address(this), terms.amount);

        emit VestingAdded(receiver, terms);
    }

    function startVestingBatch(address[] calldata receivers, VestingTerms[] calldata terms)
        external
        override
        onlyWallet
    {
        require(receivers.length > 0, "Zero receivers.");
        require(receivers.length == terms.length, "Terms and receivers must have same length.");

        for (uint256 i = 0; i < receivers.length; i++) {
            startVesting(receivers[i], terms[i]);
        }
    }

    function claim() external override {
        claim(type(uint256).max);
    }

    function claim(uint256 value) public override {
        require(value > 0, "Claiming 0 tokens.");
        VestingTerms memory terms = vestingTerms[msg.sender];
        require(isScheduleValid(terms), "No vesting data for sender.");

        uint256 claimableTokens = _claimable(terms);
        if (value == type(uint256).max) {
            value = claimableTokens;
        } else {
            require(value <= claimableTokens, "Claiming amount exceeds allowed tokens.");
        }

        vestingTerms[msg.sender].claimed += value;
        token.safeTransfer(msg.sender, value);

        emit VestingClaimed(msg.sender, value);
    }

    function transferVesting(address oldAddress, address newAddress) external override onlyWallet {
        require(newAddress != address(0), "Receiver cannot be 0.");
        require(!isScheduleValid(vestingTerms[newAddress]), "Vesting already started for receiver.");
        vestingTerms[newAddress] = vestingTerms[oldAddress];
        delete vestingTerms[oldAddress];

        emit VestingTransferred(oldAddress, newAddress);
    }

    function stopVesting(address receiver) external override onlyWallet {
        require(receiver != address(0), "Receiver cannot be 0.");

        VestingTerms storage terms = vestingTerms[receiver];
        require(isScheduleValid(terms), "No vesting data for receiver.");

        uint256 claimableTokens = _claimable(terms);
        uint256 revokedTokens = terms.amount - terms.claimed - claimableTokens;
        assert(terms.amount == (terms.claimed + claimableTokens + revokedTokens));

        // Update schedule to allow claiming the reminder.
        terms.period = 0;
        terms.amount = terms.claimed + claimableTokens;

        // Transfer the unclaimable (revoked) part.
        if (revokedTokens > 0) {
            token.safeTransfer(wallet, revokedTokens);
        }

        emit VestingRemoved(receiver);
    }

    function claimable(address receiver) external view override returns (uint256) {
        VestingTerms memory terms = vestingTerms[receiver];
        require(isScheduleValid(terms), "No vesting data for receiver.");
        return _claimable(terms);
    }

    function _claimable(VestingTerms memory terms) private view returns (uint256 claimableTokens) {
        if (terms.startTime < block.timestamp) {
            uint256 maxTokens = (block.timestamp >= terms.startTime + terms.period)
                ? (terms.amount)
                : (terms.amount * (block.timestamp - terms.startTime)) / terms.period;

            if (terms.claimed < maxTokens) {
                claimableTokens = maxTokens - terms.claimed;
            }
        }
    }

    function isScheduleValid(VestingTerms memory terms) private pure returns (bool) {
        return terms.startTime != 0;
    }
}

// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/Address.sol";

/**
 * @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));
        }
    }

    /**
     * @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");
        }
    }
}

// File: contracts/token/vesting/IERC20Vesting.sol



// SPDX-License-Identifier: MIT
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

pragma solidity 0.8.6;

interface IERC20Vesting {
    /// @dev Vesting Terms for ERC tokens
    struct VestingTerms {
        /// @dev startTime for vesting
        uint256 startTime;
        /// @dev vesting Period
        uint256 period;
        /// @dev total amount of tokens to vest over period
        uint256 amount;
        /// @dev how much was claimed so far
        uint256 claimed;
    }

    /// A new vesting receiver was added.
    event VestingAdded(address indexed receiver, VestingTerms terms);

    /// An existing vesting receiver was removed.
    event VestingRemoved(address indexed receiver);

    /// An existing vesting receiver's address has changed.
    event VestingTransferred(address indexed oldReceiver, address newReceiver);

    /// Some portion of the available amount was claimed by the vesting receiver.
    event VestingClaimed(address indexed receiver, uint256 value);

    /// @return Address of account that starts and stops vesting for different parties
    function wallet() external view returns (address);

    /// @return Address of token that is being vested
    function token() external view returns (IERC20);

    /// @dev Returns terms on which particular reciever is getting vested tokens
    /// @param receiver Address of beneficiary
    /// @return Vesting terms of particular receiver
    function getVestingTerms(address receiver) external view returns (VestingTerms memory);

    /// @dev Adds new account for vesting
    /// @param receiver Beneficiary for vesting tokens
    /// @param terms Vesting terms for particular receiver
    function startVesting(address receiver, VestingTerms calldata terms) external;

    /// @dev Adds multiple accounts for vesting
    /// Arrays need to be of same length
    /// @param receivers Beneficiaries for vesting tokens
    /// @param terms Vesting terms for all accounts
    function startVestingBatch(address[] calldata receivers, VestingTerms[] calldata terms) external;

    /// @dev Transfers all vested tokens to the sender
    function claim() external;

    /// @dev Transfers a part of vested tokens to the sender
    /// @param value Number of tokens to claim
    ///              The special value type(uint256).max will try to claim all available tokens
    function claim(uint256 value) external;

    /// @dev Transfers vesting schedule from `msg.sender` to new address
    /// A receiver cannot have an existing vesting schedule.
    /// @param oldAddress Address for current token receiver
    /// @param newAddress Address for new token receiver
    function transferVesting(address oldAddress, address newAddress) external;

    /// @dev Stops vesting for receiver and sends unvested tokens back to wallet
    /// Any earned claimable amount is still claimable through `claim()`.
    /// Note that the account cannot be used again as the vesting receiver.
    /// @param receiver Address of account for which we are stopping vesting
    function stopVesting(address receiver) external;

    /// @dev Calculates the maximum amount of vested tokens that can be claimed for particular address
    /// @param receiver Address of token receiver
    /// @return Number of vested tokens one can claim
    function claimable(address receiver) external view returns (uint);
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @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
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        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} 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);
    }

    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

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}