refactor(contracts): revisit functions visibility and inheritance

contracts/contracts/MACI.sol

@@ -218,7 +218,15 @@ contract MACI is IMACI, Params, Utilities, Ownable {
 
     address _owner = owner();
 
-    address p = pollFactory.deploy(_duration, maxValues, _treeDepths, _coordinatorPubKey, this, topupCredit, _owner);
+    address p = pollFactory.deploy(
+      _duration,
+      maxValues,
+      _treeDepths,
+      _coordinatorPubKey,
+      address(this),
+      topupCredit,
+      _owner
+    );
 
     address mp = messageProcessorFactory.deploy(_verifier, _vkRegistry, p, _owner);
     address tally = tallyFactory.deploy(_verifier, _vkRegistry, p, mp, _owner);

contracts/contracts/MessageProcessor.sol

@@ -29,7 +29,7 @@ contract MessageProcessor is Ownable, SnarkCommon, Hasher, CommonUtilities, IMes
   error BatchEndIndexTooLarge();
 
   // the number of children per node in the merkle trees
-  uint256 private constant TREE_ARITY = 5;
+  uint256 internal constant TREE_ARITY = 5;
 
   /// @inheritdoc IMessageProcessor
   bool public processingComplete;

contracts/contracts/PollFactory.sol

@@ -30,10 +30,10 @@
     MaxValues calldata _maxValues,
     TreeDepths calldata _treeDepths,
     PubKey calldata _coordinatorPubKey,
-    IMACI _maci,
+    address _maci,
     TopupCredit _topupCredit,
     address _pollOwner
-  ) public returns (address pollAddr) {
+  ) public virtual returns (address pollAddr) {
     /// @notice Validate _maxValues
     /// maxVoteOptions must be less than 2 ** 50 due to circuit limitations;
     /// it will be packed as a 50-bit value along with other values as one
@@ -46,7 +46,11 @@
     AccQueue messageAq = new AccQueueQuinaryMaci(_treeDepths.messageTreeSubDepth);
 
     /// @notice the smart contracts that a Poll would interact with
-    ExtContracts memory extContracts = ExtContracts({ maci: _maci, messageAq: messageAq, topupCredit: _topupCredit });
+    ExtContracts memory extContracts = ExtContracts({
+      maci: IMACI(_maci),
+      messageAq: messageAq,
+      topupCredit: _topupCredit
+    });
 
     // deploy the poll
     Poll poll = new Poll(_duration, _maxValues, _treeDepths, _coordinatorPubKey, extContracts);

contracts/contracts/Tally.sol

@@ -15,7 +15,7 @@ import { CommonUtilities } from "./utilities/CommonUtilities.sol";
 /// @notice The Tally contract is used during votes tallying
 /// and by users to verify the tally results.
 contract Tally is Ownable, SnarkCommon, CommonUtilities, Hasher {
-  uint256 private constant TREE_ARITY = 5;
+  uint256 internal constant TREE_ARITY = 5;
 
   /// @notice The commitment to the tally results. Its initial value is 0, but after
   /// the tally of each batch is proven on-chain via a zk-SNARK, it should be

contracts/contracts/TallyFactory.sol

@@ -14,7 +14,7 @@ contract TallyFactory is ITallySubsidyFactory {
     address _poll,
     address _messageProcessor,
     address _owner
-  ) public returns (address tallyAddr) {
+  ) public virtual returns (address tallyAddr) {
     // deploy Tally for this Poll
     Tally tally = new Tally(_verifier, _vkRegistry, _poll, _messageProcessor);
     tally.transferOwnership(_owner);

contracts/contracts/TallyNonQv.sol

@@ -15,7 +15,7 @@
 /// @notice The TallyNonQv contract is used during votes tallying
 /// and by users to verify the tally results.
 contract TallyNonQv is Ownable, SnarkCommon, CommonUtilities, Hasher {
-  uint256 private constant TREE_ARITY = 5;
+  uint256 internal constant TREE_ARITY = 5;
 
   /// @notice The commitment to the tally results. Its initial value is 0, but after
   /// the tally of each batch is proven on-chain via a zk-SNARK, it should be
@@ -79,13 +79,13 @@
 
   /// @notice Check if all ballots are tallied
   /// @return tallied whether all ballots are tallied
-  function isTallied() external view returns (bool tallied) {
+  function isTallied() public view returns (bool tallied) {
     (uint8 intStateTreeDepth, , , ) = poll.treeDepths();
     (uint256 numSignUps, ) = poll.numSignUpsAndMessages();
 
     // Require that there are untallied ballots left
     tallied = tallyBatchNum * (TREE_ARITY ** intStateTreeDepth) >= numSignUps;
   }
 
   /// @notice generate hash of public inputs for tally circuit
   /// @param _numSignUps: number of signups

contracts/contracts/TallyNonQvFactory.sol

@@ -14,7 +14,7 @@ contract TallyNonQvFactory is ITallySubsidyFactory {
     address _poll,
     address _messageProcessor,
     address _owner
-  ) public returns (address tallyAddr) {
+  ) public virtual returns (address tallyAddr) {
     // deploy Tally for this Poll
     TallyNonQv tally = new TallyNonQv(_verifier, _vkRegistry, _poll, _messageProcessor);
     tally.transferOwnership(_owner);

contracts/contracts/interfaces/IPollFactory.sol

@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: MIT
 pragma solidity ^0.8.10;
 
-import { IMACI } from "./IMACI.sol";
 import { TopupCredit } from "../TopupCredit.sol";
 import { Params } from "../utilities/Params.sol";
 import { DomainObjs } from "../utilities/DomainObjs.sol";
@@ -23,7 +22,7 @@ interface IPollFactory {
     Params.MaxValues memory _maxValues,
     Params.TreeDepths memory _treeDepths,
     DomainObjs.PubKey memory _coordinatorPubKey,
-    IMACI _maci,
+    address _maci,
     TopupCredit _topupCredit,
     address _pollOwner
   ) external returns (address);