updated confusing comments, set ownerOf to a variable in listable to …

…prevent calling it twice, added a checker on max quantity, added logic to remove from the recipient array in TransferFee

contracts/token/ERC721/extensions/ERC721ContractURI.sol

@@ -2,7 +2,7 @@
 
 pragma solidity ^0.8.0;
 
-//abstract implementation of ERC721
+//implementation of ERC721
 import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 
 

contracts/token/ERC721/extensions/ERC721Exchangable.sol

@@ -5,7 +5,6 @@ pragma solidity ^0.8.0;
 //custom abstract implementation of ERC721
 import "./ERC721Listable.sol";
 
-
 abstract contract ERC721Exchangable is ERC721Listable {
   /**
    * @dev Allows for a sender to avail of the offer price

contracts/token/ERC721/extensions/ERC721Listable.sol

@@ -2,10 +2,7 @@
 
 pragma solidity ^0.8.0;
 
-//abstract implementation of ERC721
-//used to store an item's metadata (ex. https://game.example/item-id-8u5h2m.json)
-//it already has IERC721Metadata and IERC721Enumerable, so no need to add it
-//usage: _setTokenURI(tokenId, tokenURI)
+//implementation of ERC721
 import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 
 abstract contract ERC721Listable is ERC721 {
@@ -29,31 +26,30 @@ abstract contract ERC721Listable is ERC721 {
    * @dev Allows token owners to list their tokens for sale
    */
   function list(uint256 tokenId, uint256 amount) public {
-    //get the owner
-    address owner = ownerOf(tokenId);
     //error if the sender is not the owner
     // even the contract owner cannot list a token
-    require(owner == msg.sender, "Only the token owner can list a token");
+    require(ownerOf(tokenId) == msg.sender, "Only the token owner can list a token");
     //add the listing
     listings[tokenId] = amount;
     //emit that something was listed
-    emit Listed(owner, tokenId, amount);
+    emit Listed(msg.sender, tokenId, amount);
   }
 
   /**
    * @dev Allows token owners to remove their token sale listing
    */
   function delist(uint256 tokenId) public {
+    address owner = ownerOf(tokenId);
     //error if the sender is not the owner
     // even the contract owner cannot delist a token
     require(
-      ownerOf(tokenId) == msg.sender,
+      owner == msg.sender,
       "Only the token owner can delist a token"
     );
     //remove the listing
     delete listings[tokenId];
     //emit that something was delisted
-    emit Delisted(ownerOf(tokenId), tokenId);
+    emit Delisted(owner, tokenId);
   }
 
   /**

contracts/token/ERC721/extensions/ERC721MaxQuantity.sol

@@ -2,10 +2,7 @@
 
 pragma solidity ^0.8.0;
 
-//abstract implementation of ERC721
-//used to store an item's metadata (ex. https://game.example/item-id-8u5h2m.json)
-//it already has IERC721Metadata and IERC721Enumerable, so no need to add it
-//usage: _setTokenURI(tokenId, tokenURI)
+//implementation of ERC721
 import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 
 //A simple way to get a counter that can only be incremented or decremented.
@@ -21,12 +18,13 @@ abstract contract ERC721MaxQuantity is ERC721 {
 
   Counters.Counter private _tokenIds;
 
-  uint256 public maxQuantity = 1;
+  uint256 public maxQuantity;
 
   /**
    * @dev Constructor function
    */
   constructor (uint256 _maxQuantity) {
+    require(_maxQuantity > 0, "Max quantity should be greater than 0");
     maxQuantity = _maxQuantity;
   }
 

contracts/token/ERC721/extensions/ERC721TransferFees.sol

@@ -2,10 +2,7 @@
 
 pragma solidity ^0.8.0;
 
-//abstract implementation of ERC721
-//used to store an item's metadata (ex. https://game.example/item-id-8u5h2m.json)
-//it already has IERC721Metadata and IERC721Enumerable, so no need to add it
-//usage: _setTokenURI(tokenId, tokenURI)
+//implementation of ERC721
 import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 
 abstract contract ERC721TransferFees is ERC721 {
@@ -29,7 +26,7 @@ abstract contract ERC721TransferFees is ERC721 {
     );
     require(
       (totalFees + fee) <= TOTAL_ALLOWABLE_FEES,
-      'Total fee should be more than 0'
+      'Exceeds total fees'
     );
 
     //if no recipient
@@ -56,7 +53,24 @@ abstract contract ERC721TransferFees is ERC721 {
    */
   function _removeFee(address recipient) internal {
     require(fees[recipient] != 0, 'Recipient has no fees');
+    //deduct total fees
     totalFees -= fees[recipient];
+    //remove fees from the map
     delete fees[recipient];
+    //Tricky logic to remove an element from an array...
+    //if there are at least 2 elements in the array,
+    if (_recipients.length > 1) {
+      //find the recipient
+      for (uint i = 0; i < _recipients.length; i++) {
+        if(_recipients[i] == recipient) {
+          //move the last element to the deleted element
+          _recipients[i] = _recipients[_recipients.length - 1];
+          break;
+        }
+      }
+    }
+
+    //either way remove the last element
+    _recipients.pop();
   }
 }

contracts/token/ERC721/presets/ERC721PresetAirDrop.sol

@@ -18,4 +18,7 @@ contract ERC721PresetAirDrop is ERC721AirDroppable {
   ERC721(_name, _symbol)
   ERC721AirDroppable(merkleroot)
   {}
+
+  //no methods or configuration needs to be added for this preset
+  //minting is disabled for this preset
 }

contracts/token/ERC721/presets/ERC721PresetContractURI.sol

@@ -36,6 +36,8 @@ contract ERC721PresetContractURI is ERC721, ERC721ContractURI {
   ERC721ContractURI(_uri)
   {}
 
+  //no methods or configuration needs to be added for this preset
+
   /**
    * @dev Basic mint and transfer
    */

contracts/token/ERC721/presets/ERC721PresetExchangable.sol

@@ -29,7 +29,7 @@ contract ERC721PresetExchangable is ERC721, ERC721Exchangable {
     string memory _symbol
   ) ERC721(_name, _symbol) {}
 
-  //no methods or configuration needs to be added for this mock
+  //no methods or configuration needs to be added for this preset
 
   /**
    * @dev Basic mint and transfer

contracts/token/ERC721/presets/ERC721PresetListable.sol

@@ -14,7 +14,7 @@ import "@openzeppelin/contracts/utils/Counters.sol";
 import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 
 //custom abstract implementation of ERC721
-//used to set secondary transfer fees
+//used to allow token owners to list their tokens for sale
 import "./../extensions/ERC721Listable.sol";
 
 contract ERC721PresetListable is ERC721, ERC721Listable {
@@ -30,7 +30,7 @@ contract ERC721PresetListable is ERC721, ERC721Listable {
     string memory _symbol
   ) ERC721(_name, _symbol) {}
 
-  //no methods or configuration needs to be added for this mock
+  //no methods or configuration needs to be added for this preset
 
   /**
    * @dev Basic mint and transfer

contracts/token/ERC721/presets/ERC721PresetMaxQuantity.sol

@@ -19,6 +19,8 @@ contract ERC721PresetMaxQuantity is ERC721MaxQuantity {
   ERC721MaxQuantity(_maxQuantity)
   {}
 
+  //no methods or configuration needs to be added for this preset
+
   /**
    * @dev Mint and transfer considering max quantity
    */

contracts/token/ERC721/presets/ERC721PresetPreMint.sol

@@ -18,4 +18,7 @@ contract ERC721PresetPreMint is ERC721PreMintable {
   ERC721(_name, _symbol)
   ERC721PreMintable(_recipients)
   {}
+
+  //no methods or configuration needs to be added for this preset
+  //minting is disabled for this preset
 }

contracts/token/ERC721/presets/ERC721PresetTransferFees.sol

@@ -22,11 +22,14 @@ contract ERC721PresetTransferFees is ERC721, ERC721TransferFees {
 
   Counters.Counter private _tokenIds;
 
-  //in this mock only the contract owner can add a fee
+  //in this preset only the contract owner can add a fee
   address owner;
 
   modifier onlyContractOwner {
-    require(msg.sender == owner, 'Restricted method access to only the contract owner');
+    require(
+      msg.sender == owner,
+      'Restricted method access to only the contract owner'
+    );
     _;
   }
 

contracts/token/ERC721/presets/ERC721PresetVanilla.sol

@@ -13,7 +13,6 @@ import "@openzeppelin/contracts/utils/Counters.sol";
 //implementation of ERC721
 import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
 
-
 contract ERC721PresetVanilla is ERC721 {
   using Counters for Counters.Counter;
 

contracts/token/ERC721/presets/ERC721PresetZeppelin.sol

@@ -22,7 +22,6 @@ import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
 //see: https://docs.openzeppelin.com/contracts/4.x/api/token/erc721#ERC721Burnable
 import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Burnable.sol";
 
-
 contract ERC721PresetZeppelin is ERC721URIStorage, ERC721Burnable {
   using Counters for Counters.Counter;