Add some more logic and fix previous issues

src/AA.sol

@@ -9,7 +9,7 @@ contract AA is Ownable {
     string[] nfts; 
 
     mapping (address => bool) public airdropped;
-    address[] public allowed;
+    mapping (address => bool) public eligible;
 
     constructor(string memory name,
                 string memory symbol,
@@ -28,36 +28,47 @@ contract AA is Ownable {
 
     // Mint Function
     // Simplify
-    function _mint(address to, string memory uri) public onlyOwner {
-        dco2sc.safeMint(to, uri);
+    function mintNFT(address to, uint index) external onlyOwner {
+        require(!airdropped[to], "account already airdropped");
+        dco2sc.safeMint(to, nfts[index]);
+        removeNFTAt(index);
+        airdropped[to] = true;
     }
 
-    // @notice Random giveaway function
-    function airdrop() public {    
-        //require(eligible(msg.sender));
-        require(!airdropped[msg.sender], "address already airdropped");
-        // top 20 is for Auction
-        uint256 randomURI = getRandomNumber() % nfts.length - 20;
-        dco2sc.safeMint(msg.sender, nfts[randomURI]);
-        // Require remove the URI so that is not mintable again
-        airdropped[msg.sender] = true;
-
+    // @Notice Check if eligible
+    function checkIfEligible() public view returns (bool winner) {
+        if (airdropped[msg.sender] == true) {
+            winner = false;
+        } else if (eligible[msg.sender] == true) {
+            winner = true; 
+        } else {
+            winner = false;
         } 
-
-    // @eligible
-    function eligible(address to) public view returns (bool winner) {
         // require( callable until specific date)
         // Activity
         // Longest Holders
         // Top Holders
         // or Allowed Wallets()
+        return winner;
     }
 
-    // @notice allowed addresses that supports DECA
-    function allow(address supporter) public onlyOwner {
-        //require(eligible(supporter));
-        require(!airdropped[supporter], "address already airdropped");
-        allowed.push(supporter);
+    // @notice Random giveaway function
+    function airdrop() external {    
+        require(!airdropped[msg.sender], "account already airdropped");
+        require(checkIfEligible(), "account not eligible");
+        // top 20 is for Auction
+        uint256 randomURI = getRandomNumber() % nfts.length - 20;
+        dco2sc.safeMint(msg.sender, nfts[randomURI]);
+        removeNFTAt(randomURI);
+        // Require remove the URI so that is not mintable again
+        airdropped[msg.sender] = true;
+    }
+
+    // @notice adds addresses to the eligible list
+    // thanks for supporting DECA
+    function inviteEligible(address supporter) public onlyOwner {
+        require(!airdropped[msg.sender], "account already airdropped");
+        eligible[supporter] = true;
     }
     
 
@@ -67,6 +78,13 @@ contract AA is Ownable {
         randomNumber = block.prevrandao;
     }
 
+    // @notice removes NFT URI from index
+    function removeNFTAt(uint index) public {
+        require(index < nfts.length, "nft index out of bounds");
+        nfts[index] = nfts[nfts.length - 1];
+        nfts.pop();
+    }
+
 }