pragma solidity ^0.4.24;

import "./ICheckpoint.sol";
import "../../interfaces/ISecurityToken.sol";
import "openzeppelin-solidity/contracts/math/SafeMath.sol";
import "openzeppelin-solidity/contracts/math/Math.sol";
import "openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";

/////////////////////
// Module permissions
/////////////////////
//                                        Owner       DISTRIBUTE
// pushDividendPaymentToAddresses           X               X
// pushDividendPayment                      X               X
// createDividend                           X
// createDividendWithCheckpoint             X
// reclaimDividend                          X

/**
 * @title Checkpoint module for issuing ERC20 dividends
 */
contract ERC20DividendCheckpoint is ICheckpoint {
    using SafeMath for uint256;

    bytes32 public constant DISTRIBUTE = "DISTRIBUTE";

    struct Dividend {
      uint256 checkpointId;
      uint256 created; // Time at which the dividend was created
      uint256 maturity; // Time after which dividend can be claimed - set to 0 to bypass
      uint256 expiry;  // Time until which dividend can be claimed - after this time any remaining amount can be withdrawn by issuer - set to very high value to bypass
      address token; // Address of ERC20 token that dividend is denominated in
      uint256 amount; // Dividend amount in base token amounts
      uint256 claimedAmount; // Amount of dividend claimed so far
      uint256 totalSupply; // Total supply at the associated checkpoint (avoids recalculating this)
      bool reclaimed;
      mapping (address => bool) claimed; // List of addresses which have claimed dividend
    }

    // List of all dividends
    Dividend[] public dividends;

    event ERC20DividendDeposited(address indexed _depositor, uint256 _checkpointId, uint256 _created, uint256 _maturity, uint256 _expiry, address _token, uint256 _amount, uint256 _totalSupply, uint256 _dividendIndex);
    event ERC20DividendClaimed(address indexed _payee, uint256 _dividendIndex, address _token, uint256 _amount);
    event ERC20DividendReclaimed(address indexed _claimer, uint256 _dividendIndex, address _token, uint256 _claimedAmount);

    modifier validDividendIndex(uint256 _dividendIndex) {
        require(_dividendIndex < dividends.length, "Incorrect dividend index");
        require(now >= dividends[_dividendIndex].maturity, "Dividend maturity is in the future");
        require(now < dividends[_dividendIndex].expiry, "Dividend expiry is in the past");
        require(!dividends[_dividendIndex].reclaimed, "Dividend has been reclaimed by issuer");
        _;
    }

    /**
     * @notice Constructor
     * @param _securityToken Address of the security token
     * @param _polyAddress Address of the polytoken
     */
    constructor (address _securityToken, address _polyAddress) public
    IModule(_securityToken, _polyAddress)
    {
    }

    /**
    * @notice Init function i.e generalise function to maintain the structure of the module contract
    * @return bytes4
    */
    function getInitFunction() public pure returns (bytes4) {
        return bytes4(0);
    }

    /**
     * @notice Creates a dividend and checkpoint for the dividend
     * @param _maturity Time from which dividend can be paid
     * @param _expiry Time until dividend can no longer be paid, and can be reclaimed by issuer
     * @param _token Address of ERC20 token in which dividend is to be denominated
     * @param _amount Amount of specified token for dividend
     */
    function createDividend(uint256 _maturity, uint256 _expiry, address _token, uint256 _amount) public onlyOwner {
        require(_expiry > _maturity);
        require(_expiry > now);
        require(_token != address(0));
        require(_amount > 0);
        require(ERC20(_token).transferFrom(msg.sender, address(this), _amount), "Unable to transfer tokens for dividend");
        uint256 dividendIndex = dividends.length;
        uint256 checkpointId = ISecurityToken(securityToken).createCheckpoint();
        uint256 currentSupply = ISecurityToken(securityToken).totalSupply();
        dividends.push(
          Dividend(
            checkpointId,
            now,
            _maturity,
            _expiry,
            _token,
            _amount,
            0,
            currentSupply,
            false
          )
        );
        emit ERC20DividendDeposited(msg.sender, checkpointId, now, _maturity, _expiry, _token, _amount, currentSupply, dividendIndex);
    }

    /**
     * @notice Creates a dividend with a provided checkpoint
     * @param _maturity Time from which dividend can be paid
     * @param _expiry Time until dividend can no longer be paid, and can be reclaimed by issuer
     * @param _token Address of ERC20 token in which dividend is to be denominated
     * @param _amount Amount of specified token for dividend
     * @param _checkpointId Checkpoint id from which to create dividends
     */
    function createDividendWithCheckpoint(uint256 _maturity, uint256 _expiry, address _token, uint256 _amount, uint256 _checkpointId) payable public onlyOwner {
        require(_expiry > _maturity);
        require(_expiry > now);
        require(_checkpointId <= ISecurityToken(securityToken).currentCheckpointId());
        uint256 dividendIndex = dividends.length;
        uint256 currentSupply = ISecurityToken(securityToken).totalSupplyAt(_checkpointId);
        require(ERC20(_token).transferFrom(msg.sender, address(this), _amount), "Unable to transfer tokens for dividend");
        dividends.push(
          Dividend(
            _checkpointId,
            now,
            _maturity,
            _expiry,
            _token,
            _amount,
            0,
            currentSupply,
            false
          )
        );
        emit ERC20DividendDeposited(msg.sender, _checkpointId, now, _maturity, _expiry, _token, _amount, currentSupply, dividendIndex);
    }

    /**
     * @notice Issuer can push dividends to provided addresses
     * @param _dividendIndex Dividend to push
     * @param _payees Addresses to which to push the dividend
     */
    function pushDividendPaymentToAddresses(uint256 _dividendIndex, address[] _payees) public withPerm(DISTRIBUTE) validDividendIndex(_dividendIndex) {
        Dividend storage dividend = dividends[_dividendIndex];
        for (uint256 i = 0; i < _payees.length; i++) {
            if (!dividend.claimed[_payees[i]]) {
                _payDividend(_payees[i], dividend, _dividendIndex);
            }
        }
    }

    /**
     * @notice Issuer can push dividends using the investor list from the security token
     * @param _dividendIndex Dividend to push
     * @param _start Index in investor list at which to start pushing dividends
     * @param _iterations Number of addresses to push dividends for
     */
    function pushDividendPayment(uint256 _dividendIndex, uint256 _start, uint256 _iterations) public withPerm(DISTRIBUTE) validDividendIndex(_dividendIndex) {
        Dividend storage dividend = dividends[_dividendIndex];
        uint256 numberInvestors = ISecurityToken(securityToken).getInvestorsLength();
        for (uint256 i = _start; i < Math.min256(numberInvestors, _start.add(_iterations)); i++) {
            address payee = ISecurityToken(securityToken).investors(i);
            if (!dividend.claimed[payee]) {
                _payDividend(payee, dividend, _dividendIndex);
            }
        }
    }

    /**
     * @notice Investors can pull their own dividends
     * @param _dividendIndex Dividend to pull
     */
    function pullDividendPayment(uint256 _dividendIndex) public validDividendIndex(_dividendIndex)
    {
        Dividend storage dividend = dividends[_dividendIndex];
        require(!dividend.claimed[msg.sender], "Dividend already reclaimed");
        _payDividend(msg.sender, dividend, _dividendIndex);
    }

    /**
     * @notice Internal function for paying dividends
     * @param _payee address of investor
     * @param _dividend storage with previously issued dividends
     * @param _dividendIndex Dividend to pay
     */
    function _payDividend(address _payee, Dividend storage _dividend, uint256 _dividendIndex) internal {
        uint256 claim = calculateDividend(_dividendIndex, _payee);
        _dividend.claimed[_payee] = true;
        _dividend.claimedAmount = claim.add(_dividend.claimedAmount);
        if (claim > 0) {
            require(ERC20(_dividend.token).transfer(_payee, claim), "Unable to transfer tokens");
            emit ERC20DividendClaimed(_payee, _dividendIndex, _dividend.token, claim);
        }
    }

    /**
     * @notice Issuer can reclaim remaining unclaimed dividend amounts, for expired dividends
     * @param _dividendIndex Dividend to reclaim
     */
    function reclaimDividend(uint256 _dividendIndex) public onlyOwner {
        require(_dividendIndex < dividends.length, "Incorrect dividend index");
        require(now >= dividends[_dividendIndex].expiry, "Dividend expiry is in the future");
        require(!dividends[_dividendIndex].reclaimed, "Dividend already claimed");
        dividends[_dividendIndex].reclaimed = true;
        Dividend storage dividend = dividends[_dividendIndex];
        uint256 remainingAmount = dividend.amount.sub(dividend.claimedAmount);
        require(ERC20(dividend.token).transfer(msg.sender, remainingAmount), "Unable to transfer tokens");
        emit ERC20DividendReclaimed(msg.sender, _dividendIndex, dividend.token, remainingAmount);
    }

    /**
     * @notice Calculate amount of dividends claimable
     * @param _dividendIndex Dividend to calculate
     * @param _payee Affected investor address
     * @return unit256
     */
    function calculateDividend(uint256 _dividendIndex, address _payee) public view returns(uint256) {
        Dividend storage dividend = dividends[_dividendIndex];
        if (dividend.claimed[_payee]) {
            return 0;
        }
        uint256 balance = ISecurityToken(securityToken).balanceOfAt(_payee, dividends[_dividendIndex].checkpointId);
        return balance.mul(dividends[_dividendIndex].amount).div(dividends[_dividendIndex].totalSupply);
    }

    /**
     * @notice Get the index according to the checkpoint id
     * @param _checkpointId Checkpoint id to query
     * @return uint256
     */
    function getDividendIndex(uint256 _checkpointId) public view returns(uint256[]) {
        uint256 counter = 0;
        for(uint256 i = 0; i < dividends.length; i++) {
            if (dividends[i].checkpointId == _checkpointId) {
                counter++;
            }
        }

       uint256[] memory index = new uint256[](counter);
       counter = 0;
       for(uint256 j = 0; j < dividends.length; j++) {
           if (dividends[j].checkpointId == _checkpointId) {
               index[counter] = j;
               counter++;
           }
       }
       return index;
    }

    /**
     * @notice Return the permissions flag that are associated with STO
     * @return bytes32 array
     */
    function getPermissions() public view returns(bytes32[]) {
        bytes32[] memory allPermissions = new bytes32[](1);
        allPermissions[0] = DISTRIBUTE;
        return allPermissions;
    }

}