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// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

contract RP {
    uint256 soldAmount = 0;
    uint256 decimals = 18;

uint256 checkPoint = 1000 * 10^decimals; // 1k
    uint256 nextCheckPoint = checkPoint * 10; // 10k

uint256 price = 0.2 ether;

function sellRp(uint256 _amount) public returns (uint256) {
        uint256 payout;
        uint256 left;
        // 0. balance check of RP amount
        // 0-0. check global limit on RP sellable
        // 0-1. check RP sellable limit on user

// 1. calculate maticAmount for _amount
        if(checkPoint >= soldAmount + _amount) {
            payout = _amount * price / 10^decimals;
            soldAmount += _amount;
        } else {
            left = _amount;
            // need bounds to prevent exceeding block gas limit
            while(left > 0) {
                uint256 discrepancy = checkPoint - soldAmount;

if(discrepancy > left) {
                    payout += left * price / 10^decimals;
                    soldAmount += left;
                    left = 0;
                    break;
                }

payout += discrepancy * price / 10^decimals;
                left -= discrepancy;

soldAmount += discrepancy;

checkPoint = nextCheckPoint;
                nextCheckPoint = nextCheckPoint * 2;

price = price / 2;
            }
        }
        // 3. withdraw RP from user to RP using safeTransferFrom()

// 4. burn RP tokens

// 5. transfer WMATIC to msg.sender

return payout;
    }

// onlyOwner modifier will be added
    function setPrice(uint256 _price) public {
        // checks if needed
        price = _price;
    }

}