// SPDX-License-Identifier: AGPL-3.0-or-later

pragma solidity 0.7.5;

library SafeERC20 {
    using SafeMath for uint256;
    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));
    }

    function safeApprove(IERC20 token, address spender, uint256 value) internal {

        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).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender)
            .sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function _callOptionalReturn(IERC20 token, bytes memory data) private {

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

library SafeMath {

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function add32(uint32 a, uint32 b) internal pure returns (uint32) {
        uint32 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {

        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }

    // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
    function sqrrt(uint256 a) internal pure returns (uint c) {
        if (a > 3) {
            c = a;
            uint b = add( div( a, 2), 1 );
            while (b < c) {
                c = b;
                b = div( add( div( a, b ), b), 2 );
            }
        } else if (a != 0) {
            c = 1;
        }
    }

    function percentageAmount( uint256 total_, uint8 percentage_ ) internal pure returns ( uint256 percentAmount_ ) {
        return div( mul( total_, percentage_ ), 1000 );
    }

    function substractPercentage( uint256 total_, uint8 percentageToSub_ ) internal pure returns ( uint256 result_ ) {
        return sub( total_, div( mul( total_, percentageToSub_ ), 1000 ) );
    }

    function percentageOfTotal( uint256 part_, uint256 total_ ) internal pure returns ( uint256 percent_ ) {
        return div( mul(part_, 100) , total_ );
    }

    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + ((a % 2 + b % 2) / 2);
    }

    function quadraticPricing( uint256 payment_, uint256 multiplier_ ) internal pure returns (uint256) {
        return sqrrt( mul( multiplier_, payment_ ) );
    }

  function bondingCurve( uint256 supply_, uint256 multiplier_ ) internal pure returns (uint256) {
      return mul( multiplier_, supply_ );
  }
}

interface IERC20 {

    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount) external returns (bool);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);
}

library Address {

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

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    function functionCall(
        address target, 
        bytes memory data, 
        string memory errorMessage
    ) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    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");
    }

    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");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _functionCallWithValue(
        address target, 
        bytes memory data, 
        uint256 weiValue, 
        string memory errorMessage
    ) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        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

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }

    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    function functionStaticCall(
        address target, 
        bytes memory data, 
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    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 {
            if (returndata.length > 0) {
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }

    function addressToString(address _address) internal pure returns(string memory) {
        bytes32 _bytes = bytes32(uint256(_address));
        bytes memory HEX = "0123456789abcdef";
        bytes memory _addr = new bytes(42);

        _addr[0] = '0';
        _addr[1] = 'x';

        for(uint256 i = 0; i < 20; i++) {
            _addr[2+i*2] = HEX[uint8(_bytes[i + 12] >> 4)];
            _addr[3+i*2] = HEX[uint8(_bytes[i + 12] & 0x0f)];
        }

        return string(_addr);

    }
}


interface IPolicy {

    function policy() external view returns (address);

    function renouncePolicy() external;
  
    function pushPolicy( address newPolicy_ ) external;

    function pullPolicy() external;
}

contract Policy is IPolicy {
    
    address internal _policy;
    address internal _newPolicy;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor () {
        _policy = msg.sender;
        emit OwnershipTransferred( address(0), _policy );
    }

    function policy() public view override returns (address) {
        return _policy;
    }

    modifier onlyPolicy() {
        require( _policy == msg.sender, "Ownable: caller is not the owner" );
        _;
    }

    function renouncePolicy() public virtual override onlyPolicy() {
        emit OwnershipTransferred( _policy, address(0) );
        _policy = address(0);
    }

    function pushPolicy( address newPolicy_ ) public virtual override onlyPolicy() {
        require( newPolicy_ != address(0), "Ownable: new owner is the zero address");
        _newPolicy = newPolicy_;
    }

    function pullPolicy() public virtual override {
        require( msg.sender == _newPolicy );
        emit OwnershipTransferred( _policy, _newPolicy );
        _policy = _newPolicy;
    }
}

interface ITreasury {
    function mintRewards( address _recipient, uint _amount ) external;
}

contract Distributor is Policy {
    using SafeMath for uint;
    using SafeMath for uint32;
    using SafeERC20 for IERC20;
    
    
    
    /* ====== VARIABLES ====== */

    address public immutable OHM;
    address public immutable treasury;
    
    uint32 public immutable epochLength;
    uint32 public nextEpochTime;
    
    mapping( uint => Adjust ) public adjustments;
    
    
    /* ====== STRUCTS ====== */
        
    struct Info {
        uint rate; // in ten-thousandths ( 5000 = 0.5% )
        address recipient;
    }
    Info[] public info;
    
    struct Adjust {
        bool add;
        uint rate;
        uint target;
    }
    
    
    
    /* ====== CONSTRUCTOR ====== */

    constructor( address _treasury, address _ohm, uint32 _epochLength, uint32 _nextEpochTime ) {        
        require( _treasury != address(0) );
        treasury = _treasury;
        require( _ohm != address(0) );
        OHM = _ohm;
        epochLength = _epochLength;
        nextEpochTime = _nextEpochTime;
    }
    
    
    
    /* ====== PUBLIC FUNCTIONS ====== */
    
    /**
        @notice send epoch reward to staking contract
     */
    function distribute() external returns ( bool ) {
        if ( nextEpochTime <= uint32(block.timestamp) ) {
            nextEpochTime = nextEpochTime.add32( epochLength ); // set next epoch time
            
            // distribute rewards to each recipient
            for ( uint i = 0; i < info.length; i++ ) {
                if ( info[ i ].rate > 0 ) {
                    ITreasury( treasury ).mintRewards( // mint and send from treasury
                        info[ i ].recipient, 
                        nextRewardAt( info[ i ].rate ) 
                    );
                    adjust( i ); // check for adjustment
                }
            }
            return true;
        } else { 
            return false; 
        }
    }
    
    
    
    /* ====== INTERNAL FUNCTIONS ====== */

    /**
        @notice increment reward rate for collector
     */
    function adjust( uint _index ) internal {
        Adjust memory adjustment = adjustments[ _index ];
        if ( adjustment.rate != 0 ) {
            if ( adjustment.add ) { // if rate should increase
                info[ _index ].rate = info[ _index ].rate.add( adjustment.rate ); // raise rate
                if ( info[ _index ].rate >= adjustment.target ) { // if target met
                    adjustments[ _index ].rate = 0; // turn off adjustment
                }
            } else { // if rate should decrease
                info[ _index ].rate = info[ _index ].rate.sub( adjustment.rate ); // lower rate
                if ( info[ _index ].rate <= adjustment.target ) { // if target met
                    adjustments[ _index ].rate = 0; // turn off adjustment
                }
            }
        }
    }
    
    
    
    /* ====== VIEW FUNCTIONS ====== */

    /**
        @notice view function for next reward at given rate
        @param _rate uint
        @return uint
     */
    function nextRewardAt( uint _rate ) public view returns ( uint ) {
        return IERC20( OHM ).totalSupply().mul( _rate ).div( 1000000 );
    }

    /**
        @notice view function for next reward for specified address
        @param _recipient address
        @return uint
     */
    function nextRewardFor( address _recipient ) public view returns ( uint ) {
        uint reward;
        for ( uint i = 0; i < info.length; i++ ) {
            if ( info[ i ].recipient == _recipient ) {
                reward = nextRewardAt( info[ i ].rate );
            }
        }
        return reward;
    }
    
    
    
    /* ====== POLICY FUNCTIONS ====== */

    /**
        @notice adds recipient for distributions
        @param _recipient address
        @param _rewardRate uint
     */
    function addRecipient( address _recipient, uint _rewardRate ) external onlyPolicy() {
        require( _recipient != address(0) );
        info.push( Info({
            recipient: _recipient,
            rate: _rewardRate
        }));
    }

    /**
        @notice removes recipient for distributions
        @param _index uint
        @param _recipient address
     */
    function removeRecipient( uint _index, address _recipient ) external onlyPolicy() {
        require( _recipient == info[ _index ].recipient );
        info[ _index ].recipient = address(0);
        info[ _index ].rate = 0;
    }

    /**
        @notice set adjustment info for a collector's reward rate
        @param _index uint
        @param _add bool
        @param _rate uint
        @param _target uint
     */
    function setAdjustment( uint _index, bool _add, uint _rate, uint _target ) external onlyPolicy() {
        adjustments[ _index ] = Adjust({
            add: _add,
            rate: _rate,
            target: _target
        });
    }
}