1. // SPDX-License-Identifier: MIT
2. pragma solidity ^0.8.0;
3.  
4. // Import ERC20 interface and other necessary contracts
5. import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
6. import "@openzeppelin/contracts/access/Ownable.sol";
7.  
8. contract VPNIDGenerator is Ownable {
9.     IERC20 public sVPNToken;
10.     uint256 public nextID;
11.     uint256 constant public IDLength = 15;
12.     uint256 public paymentAmountMonthly = 200000; // Default monthly payment amount
13.     uint256 public paymentAmountYearly = 2200000; // Default yearly payment amount, assuming some discount or different rate
14.  
15.     event IDGenerated(address indexed payer, string indexed generatedID, string paymentType);
16.     event TokenContractUpdated(address indexed newTokenContract);
17.     event MonthlyPaymentAmountUpdated(uint256 newPaymentAmount);
18.     event YearlyPaymentAmountUpdated(uint256 newPaymentAmount);
19.  
20.     mapping(address => string[]) public userIDs; // Mapping to store user IDs against wallet address
21.     mapping(string => bool) public usedIDs; // Mapping to track used IDs
22.  
23.     constructor(address _sVPNTokenAddress, address initialOwner) Ownable(initialOwner) {
24.         sVPNToken = IERC20(_sVPNTokenAddress);
25.         nextID = 1;
26.     }
27.  
28.     modifier validPayment(uint256 paymentAmount) {
29.         require(sVPNToken.allowance(msg.sender, address(this)) >= paymentAmount, "Insufficient allowance");
30.         require(sVPNToken.balanceOf(msg.sender) >= paymentAmount, "Insufficient balance");
31.         _;
32.     }
33.  
34.     function payForUniqueIDMonthly() external validPayment(paymentAmountMonthly) {
35.         require(sVPNToken.transferFrom(msg.sender, address(this), paymentAmountMonthly), "Token transfer failed");
36.         string memory generatedID = generateUniqueID();
37.         userIDs[msg.sender].push(generatedID);
38.         emit IDGenerated(msg.sender, generatedID, "Monthly");
39.     }
40.  
41.     function payForUniqueIDYearly() external validPayment(paymentAmountYearly) {
42.         require(sVPNToken.transferFrom(msg.sender, address(this), paymentAmountYearly), "Token transfer failed");
43.         string memory generatedID = generateUniqueID();
44.         userIDs[msg.sender].push(generatedID);
45.         emit IDGenerated(msg.sender, generatedID, "Yearly");
46.     }
47.  
48.     function generateUniqueID() internal returns (string memory) {
49.         bytes memory characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
50.         bytes memory result = new bytes(IDLength);
51.  
52.         uint256 rand = uint256(keccak256(abi.encodePacked(block.timestamp, block.difficulty, nextID))) % characters.length;
53.  
54.         for (uint256 i = 0; i < IDLength; i++) {
55.             if (i == IDLength - 1) {
56.                 result[i] = bytes1(uint8(48 + (rand % 10))); // ASCII code for numbers 0-9
57.             } else {
58.                 result[i] = characters[rand % characters.length];
59.             }
60.             rand = rand / characters.length;
61.         }
62.  
63.         string memory newID = string(result);
64.  
65.         // Check if the ID already exists, regenerate if necessary
66.         while (usedIDs[newID]) {
67.             rand = uint256(keccak256(abi.encodePacked(rand))) % characters.length;
68.             for (uint256 i = 0; i < IDLength; i++) {
69.                 if (i == IDLength - 1) {
70.                     result[i] = bytes1(uint8(48 + (rand % 10))); // ASCII code for numbers 0-9
71.                 } else {
72.                     result[i] = characters[rand % characters.length];
73.                 }
74.                 rand = rand / characters.length;
75.             }
76.             newID = string(result);
77.         }
78.  
79.         usedIDs[newID] = true;
80.         nextID++;
81.         return newID;
82.     }
83.  
84.     function getUserIDs(address userAddress) external view returns (string[] memory) {
85.         return userIDs[userAddress];
86.     }
87.  
88.     function withdrawTokens(uint256 _amount) external onlyOwner {
89.         require(sVPNToken.transfer(owner(), _amount), "Token transfer failed");
90.     }
91.  
92.     function updateTokenContract(address _newTokenContract) external onlyOwner {
93.         require(_newTokenContract != address(0), "Invalid token contract address");
94.         sVPNToken = IERC20(_newTokenContract);
95.         emit TokenContractUpdated(_newTokenContract);
96.     }
97.  
98.     function updateMonthlyPaymentAmount(uint256 _newPaymentAmount) external onlyOwner {
99.         require(_newPaymentAmount > 0, "Invalid payment amount");
100.         paymentAmountMonthly = _newPaymentAmount;
101.         emit MonthlyPaymentAmountUpdated(_newPaymentAmount);
102.     }
103.  
104.     function updateYearlyPaymentAmount(uint256 _newPaymentAmount) external onlyOwner {
105.         require(_newPaymentAmount > 0, "Invalid payment amount");
106.         paymentAmountYearly = _newPaymentAmount;
107.         emit YearlyPaymentAmountUpdated(_newPaymentAmount);
108.     }
109. }