pragma solidity ^0.4.24;


/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, throws on overflow.
  */
  function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
    if (a == 0) {
      return 0;
    }
    c = a * b;
    assert(c / a == b);
    return c;
  }

  /**
  * @dev Integer division of two numbers, truncating the quotient.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    // uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return a / b;
  }

  /**
  * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  /**
  * @dev Adds two numbers, throws on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }
}


/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
  address public owner;


  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  function Ownable() public {
    owner = msg.sender;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(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 {
    require(newOwner != address(0));
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}


/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  function totalSupply() public view returns (uint256);
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}


/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender) public view returns (uint256);
  function transferFrom(address from, address to, uint256 value) public returns (bool);
  function approve(address spender, uint256 value) public returns (bool);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}


/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure.
 * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
  function safeTransfer(ERC20Basic token, address to, uint256 value) internal {
    assert(token.transfer(to, value));
  }

  function safeTransferFrom(
    ERC20 token,
    address from,
    address to,
    uint256 value
  )
    internal
  {
    assert(token.transferFrom(from, to, value));
  }

  function safeApprove(ERC20 token, address spender, uint256 value) internal {
    assert(token.approve(spender, value));
  }
}


/**
 * @title Locker
 * @notice Locker holds tokens and releases them at a certain time.
 */
contract Locker is Ownable {
  using SafeMath for uint;
  using SafeERC20 for ERC20Basic;

  /**
   * It is init state only when adding release info is possible.
   * beneficiary only can release tokens when Locker is active.
   * After all tokens are released, locker is drawn.
   */
  enum State { Init, Ready, Active, Drawn }

  struct Beneficiary {
    uint ratio;             // ratio based on Locker's initial balance.
    uint withdrawAmount;    // accumulated tokens beneficiary released
    bool releaseAllTokens;
  }

  /**
   * @notice Release has info to release tokens.
   * If lock type is straight, only two release infos is required.
   *
   *     |
   * 100 |                _______________
   *     |              _/
   *  50 |            _/
   *     |         . |
   *     |       .   |
   *     |     .     |
   *     +===+=======+----*----------> time
   *     Locker  First    Last
   *  Activated  Release  Release
   *
   *
   * If lock type is variable, the release graph will be
   *
   *     |
   * 100 |                                 _________
   *     |                                |
   *  70 |                      __________|
   *     |                     |
   *  30 |            _________|
   *     |           |
   *     +===+=======+---------+----------*------> time
   *     Locker   First        Second     Last
   *  Activated   Release      Release    Release
   *
   *
   *
   * For the first straight release graph, parameters would be
   *   coeff: 100
   *   releaseTimes: [
   *     first release time,
   *     second release time
   *   ]
   *   releaseRatios: [
   *     50,
   *     100,
   *   ]
   *
   * For the second variable release graph, parameters would be
   *   coeff: 100
   *   releaseTimes: [
   *     first release time,
   *     second release time,
   *     last release time
   *   ]
   *   releaseRatios: [
   *     30,
   *     70,
   *     100,
   *   ]
   *
   */
  struct Release {
    bool isStraight;        // lock type : straight or variable
    uint[] releaseTimes;    //
    uint[] releaseRatios;   //
  }

  uint public activeTime;

  // ERC20 basic token contract being held
  ERC20Basic public token;

  uint public coeff;
  uint public initialBalance;
  uint public withdrawAmount; // total amount of tokens released

  mapping (address => Beneficiary) public beneficiaries;
  mapping (address => Release) public releases;  // beneficiary's lock
  mapping (address => bool) public locked; // whether beneficiary's lock is instantiated

  uint public numBeneficiaries;
  uint public numLocks;

  State public state;

  modifier onlyState(State v) {
    require(state == v);
    _;
  }

  modifier onlyBeneficiary(address _addr) {
    require(beneficiaries[_addr].ratio > 0);
    _;
  }

  event StateChanged(State _state);
  event Locked(address indexed _beneficiary, bool _isStraight);
  event Released(address indexed _beneficiary, uint256 _amount);

  function Locker(address _token, uint _coeff, address[] _beneficiaries, uint[] _ratios) public {
    require(_token != address(0));
    require(_beneficiaries.length == _ratios.length);

    token = ERC20Basic(_token);
    coeff = _coeff;
    numBeneficiaries = _beneficiaries.length;

    uint accRatio;

    for(uint i = 0; i < numBeneficiaries; i++) {
      require(_ratios[i] > 0);
      beneficiaries[_beneficiaries[i]].ratio = _ratios[i];

      accRatio = accRatio.add(_ratios[i]);
    }

    require(coeff == accRatio);
  }

  /**
   * @notice beneficiary can release their tokens after activated
   */
  function activate() external onlyOwner onlyState(State.Ready) {
    require(numLocks == numBeneficiaries); // double check : assert all releases are recorded

    initialBalance = token.balanceOf(this);
    require(initialBalance > 0);

    activeTime = now; // solium-disable-line security/no-block-members

    // set locker as active state
    state = State.Active;
    emit StateChanged(state);
  }

  function getReleaseType(address _beneficiary)
    public
    view
    onlyBeneficiary(_beneficiary)
    returns (bool)
  {
    return releases[_beneficiary].isStraight;
  }

  function getTotalLockedAmounts(address _beneficiary)
    public
    view
    onlyBeneficiary(_beneficiary)
    returns (uint)
  {
    return getPartialAmount(beneficiaries[_beneficiary].ratio, coeff, initialBalance);
  }

  function getReleaseTimes(address _beneficiary)
    public
    view
    onlyBeneficiary(_beneficiary)
    returns (uint[])
  {
    return releases[_beneficiary].releaseTimes;
  }

  function getReleaseRatios(address _beneficiary)
    public
    view
    onlyBeneficiary(_beneficiary)
    returns (uint[])
  {
    return releases[_beneficiary].releaseRatios;
  }

  /**
   * @notice add new release record for beneficiary
   */
  function lock(address _beneficiary, bool _isStraight, uint[] _releaseTimes, uint[] _releaseRatios)
    external
    onlyOwner
    onlyState(State.Init)
    onlyBeneficiary(_beneficiary)
  {
    require(!locked[_beneficiary]);
    require(_releaseRatios.length != 0);
    require(_releaseRatios.length == _releaseTimes.length);

    uint i;
    uint len = _releaseRatios.length;

    // finally should release all tokens
    require(_releaseRatios[len - 1] == coeff);

    // check two array are ascending sorted
    for(i = 0; i < len - 1; i++) {
      require(_releaseTimes[i] < _releaseTimes[i + 1]);
      require(_releaseRatios[i] < _releaseRatios[i + 1]);
    }

    // 2 release times for straight locking type
    if (_isStraight) {
      require(len == 2);
    }

    numLocks = numLocks.add(1);

    // create Release for the beneficiary
    releases[_beneficiary].isStraight = _isStraight;

    // copy array of uint
    releases[_beneficiary].releaseTimes = _releaseTimes;
    releases[_beneficiary].releaseRatios = _releaseRatios;

    // lock beneficiary
    locked[_beneficiary] = true;
    emit Locked(_beneficiary, _isStraight);

    //  if all beneficiaries locked, change Locker state to change
    if (numLocks == numBeneficiaries) {
      state = State.Ready;
      emit StateChanged(state);
    }
  }

  /**
   * @notice transfer releasable tokens for beneficiary wrt the release graph
   */
  function release() external onlyState(State.Active) onlyBeneficiary(msg.sender) {
    require(!beneficiaries[msg.sender].releaseAllTokens);

    uint releasableAmount = getReleasableAmount(msg.sender);
    beneficiaries[msg.sender].withdrawAmount = beneficiaries[msg.sender].withdrawAmount.add(releasableAmount);

    beneficiaries[msg.sender].releaseAllTokens = beneficiaries[msg.sender].withdrawAmount == getPartialAmount(
      beneficiaries[msg.sender].ratio,
      coeff,
      initialBalance);

    withdrawAmount = withdrawAmount.add(releasableAmount);

    if (withdrawAmount == initialBalance) {
      state = State.Drawn;
      emit StateChanged(state);
    }

    token.transfer(msg.sender, releasableAmount);
    emit Released(msg.sender, releasableAmount);
  }

  function getReleasableAmount(address _beneficiary) internal view returns (uint) {
    if (releases[_beneficiary].isStraight) {
      return getStraightReleasableAmount(_beneficiary);
    } else {
      return getVariableReleasableAmount(_beneficiary);
    }
  }

  /**
   * @notice return releaseable amount for beneficiary in case of straight type of release
   */
  function getStraightReleasableAmount(address _beneficiary) internal view returns (uint releasableAmount) {
    Beneficiary memory _b = beneficiaries[_beneficiary];
    Release memory _r = releases[_beneficiary];

    // total amount of tokens beneficiary can release
    uint totalReleasableAmount = getTotalLockedAmounts(_beneficiary);

    uint firstTime = _r.releaseTimes[0];
    uint lastTime = _r.releaseTimes[1];

    // solium-disable security/no-block-members
    require(now >= firstTime); // pass if can release
    // solium-enable security/no-block-members

    if(now >= lastTime) { // inclusive to reduce calculation
      releasableAmount = totalReleasableAmount;
    } else {
      // releasable amount at first time
      uint firstAmount = getPartialAmount(
        _r.releaseRatios[0],
        coeff,
        totalReleasableAmount);

      // partial amount without first amount
      releasableAmount = getPartialAmount(
        now.sub(firstTime),
        lastTime.sub(firstTime),
        totalReleasableAmount.sub(firstAmount));
      releasableAmount = releasableAmount.add(firstAmount);
    }

    // subtract already withdrawn amounts
    releasableAmount = releasableAmount.sub(_b.withdrawAmount);
  }

  /**
   * @notice return releaseable amount for beneficiary in case of variable type of release
   */
  function getVariableReleasableAmount(address _beneficiary) internal view returns (uint releasableAmount) {
    Beneficiary memory _b = beneficiaries[_beneficiary];
    Release memory _r = releases[_beneficiary];

    // total amount of tokens beneficiary will receive
    uint totalReleasableAmount = getTotalLockedAmounts(_beneficiary);

    uint releaseRatio;

    // reverse order for short curcit
    for(uint i = _r.releaseTimes.length - 1; i >= 0; i--) {
      if (now >= _r.releaseTimes[i]) {
        releaseRatio = _r.releaseRatios[i];
        break;
      }
    }

    require(releaseRatio > 0);

    releasableAmount = getPartialAmount(
      releaseRatio,
      coeff,
      totalReleasableAmount);
    releasableAmount = releasableAmount.sub(_b.withdrawAmount);
  }

  /// https://github.com/0xProject/0x.js/blob/05aae368132a81ddb9fd6a04ac5b0ff1cbb24691/packages/contracts/src/current/protocol/Exchange/Exchange.sol#L497
  /// @notice Calculates partial value given a numerator and denominator.
  /// @param numerator Numerator.
  /// @param denominator Denominator.
  /// @param target Value to calculate partial of.
  /// @return Partial value of target.
  function getPartialAmount(uint numerator, uint denominator, uint target) public pure returns (uint) {
    return numerator.mul(target).div(denominator);
  }
}