// Contract: Vesting
// Target function: function claim()
// SPDX-License-Identifier: (c) Otsea.fi, 2021

pragma solidity ^0.6.12;


/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 * 
 * @dev Completely default OpenZeppelin.
 */
contract Ownable {
    address private _owner;
    address private _pendingOwner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    function initializeOwnable() internal {
        require(_owner == address(0), "already initialized");
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), msg.sender);
    }


    /**
     * @return the address of the owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "msg.sender is not owner");
        _;
    }

    /**
     * @return true if `msg.sender` is the owner of the contract.
     */
    function isOwner() public view returns (bool) {
        return msg.sender == _owner;

    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _pendingOwner = newOwner;
    }

    function receiveOwnership() public {
        require(msg.sender == _pendingOwner, "only pending owner can call this function");
        _transferOwnership(_pendingOwner);
        _pendingOwner = address(0);
    }

    /**
     * @dev Transfers control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0));
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }

    uint256[50] private __gap;
}

/**
 * @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);
}

/**
 * @title SafeMath
 * @dev Unsigned math operations with safety checks that revert on error
 * 
 * @dev Default OpenZeppelin
 */
library SafeMath {
    /**
     * @dev Multiplies two unsigned integers, reverts on 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-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b);

        return c;
    }

    /**
     * @dev Integer division of two unsigned integers truncating the quotient, reverts on division by zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Adds two unsigned integers, reverts on overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);

        return c;
    }

    /**
     * @dev Divides two unsigned integers and returns the remainder (unsigned integer modulo),
     * reverts when dividing by zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }
}

contract Vesting {

    using SafeMath for uint256;

    IERC20 public token;

    uint256 public totalTokens;
    uint256 public releaseStart;
    uint256 public releaseEnd;

    mapping (address => uint256) public starts;
    mapping (address => uint256) public grantedToken;

    // this means, released but unclaimed amounts
    mapping (address => uint256) public released;

    event Claimed(address indexed _user, uint256 _amount, uint256 _timestamp);
    event Transfer(address indexed _from, address indexed _to, uint256 _amount, uint256 _timestamp);

    // do not input same recipient in the _recipients, it will lead to locked token in this contract
    function initialize(
        address _token,
        uint256 _totalTokens,
        uint256 _start,
        uint256 _period,
        address[] calldata _recipients,
        uint256[] calldata _grantedToken
    )
      public
    {
        require(releaseEnd == 0, "Contract is already initialized.");
        require(_recipients.length == _grantedToken.length, "Array lengths do not match.");

        releaseEnd = _start.add(_period);
        releaseStart = _start;

        token = IERC20(_token);
        token.transferFrom(msg.sender, address(this), _totalTokens);
        totalTokens = _totalTokens;
        uint256 sum = 0;

        for(uint256 i = 0; i<_recipients.length; i++) {
            starts[_recipients[i]] = releaseStart;
            grantedToken[_recipients[i]] = _grantedToken[i];
            sum = sum.add(_grantedToken[i]);
        }

        // We're gonna just set the weight as full tokens. Ensures grantedToken were entered correctly as well.
        require(sum == totalTokens, "Weight does not match tokens being distributed.");
    }