// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";


contract IsotopicAsset is ERC721Enumerable, Ownable {
  using Strings for uint256;

  string public baseURI;  
  string public baseExtension = ".json";

  bool public paused;

  mapping(address => uint256) public whitelisted;
  mapping(address => uint256) public balance;


  event BaseURIChanged(string indexed _oldBaseURI, string indexed _newBaseURI);
  event BaseExtensionChanged(string indexed _oldBaseExtension, string indexed _newBaseExtension);
  event PausedChanged(bool indexed _oldPaused, bool indexed _newPaused);

  constructor(  
    string memory _name,
    string memory _symbol,
    string memory _initBaseURI,
    bool _paused
  ) ERC721(_name, _symbol) {
    setBaseURI(_initBaseURI);
    paused = _paused;
  }

  function _baseURI() internal view virtual override returns (string memory) {
    return baseURI;
  }


  function mint(address _to, uint256 _mintAmount) public {   
    uint256 supply = totalSupply();
    require(!paused);
    require(_mintAmount > 0);

    if (msg.sender != owner()) {
        require(whitelisted[msg.sender] >= _mintAmount, "only whitelist addresses can mint");
    }

    for (uint256 i = 1; i <= _mintAmount; i++) {
      _safeMint(_to, supply + i);
    }

    if (msg.sender != owner()){
        whitelisted[msg.sender] -= _mintAmount;
    }

    balance[_to] += _mintAmount;
  }


  function walletOfOwner(address _owner) public view returns (uint256[] memory)
  {
    uint256 ownerTokenCount = balanceOf(_owner);
    uint256[] memory tokenIds = new uint256[](ownerTokenCount);
    for (uint256 i; i < ownerTokenCount; i++) {
      tokenIds[i] = tokenOfOwnerByIndex(_owner, i);
    }
    return tokenIds;
  }

  function tokenURI(uint256 tokenId) public view virtual override returns (string memory)
  {
    require(
      _exists(tokenId),
      "ERC721Metadata: URI query for nonexistent token"
    );

    string memory currentBaseURI = _baseURI();
    return bytes(currentBaseURI).length > 0 ? string(abi.encodePacked(currentBaseURI, baseExtension)) : "";
  }

  function setBaseURI(string memory _newBaseURI) public onlyOwner { 
    string memory oldBaseURI = baseURI;
    baseURI = _newBaseURI;
    emit BaseURIChanged(oldBaseURI, _newBaseURI);
  }

  function setBaseExtension(string memory _newBaseExtension) public onlyOwner {
    string memory oldBaseExtension = baseExtension; 
    baseExtension = _newBaseExtension;
    emit BaseExtensionChanged(oldBaseExtension, _newBaseExtension);
  }

  function pause(bool _state) public onlyOwner {  
    bool oldPaused = paused;
    paused = _state;
    emit PausedChanged(oldPaused, _state);
  }

 function setUserWhitelistAmount(address _user, uint256 _amount) public onlyOwner { 
    whitelisted[_user] = _amount;
  }

  function increaseUserWhitelistAmount(address _user, uint256 _amount) public onlyOwner { 
    whitelisted[_user] += _amount;
  }
  
  function getUserWhitelistAmount(address _user) public view returns (uint256){
    return whitelisted[_user];
  }

  function transferWhitelists(address _to, uint256 _amount) public {
    require(whitelisted[msg.sender] >= _amount, "Cannot transfer more whitelists than available.");
    whitelisted[_to] += _amount;
    whitelisted[msg.sender] -= _amount;
  }
}