Add code comments to contracts

packages/contracts/contracts/Semaphore.sol

@@ -100,18 +100,24 @@ contract Semaphore is ISemaphore, SemaphoreGroups {
         groups[groupId].merkleRootCreationDates[merkleTreeRoot] = block.timestamp;
     }
 
+    /// @dev See {ISemaphore-validateProof}.
     function validateProof(
         uint256 groupId,
         SemaphoreProof calldata proof
     ) external override onlyExistingGroup(groupId) {
+        // The function will revert if the nullifier that is part of the proof,
+        // was already used inside the group with id groupId.
         if (groups[groupId].nullifiers[proof.nullifier]) {
             revert Semaphore__YouAreUsingTheSameNullifierTwice();
         }
 
+        // The function will revert if the proof is not verified successfully.
         if (!verifyProof(groupId, proof)) {
             revert Semaphore__InvalidProof();
         }
 
+        // Saves the nullifier so that it cannot be used again to successfully verify a proof
+        // that is part of the group with id groupId.
         groups[groupId].nullifiers[proof.nullifier] = true;
 
         emit ProofValidated(
@@ -125,20 +131,26 @@ contract Semaphore is ISemaphore, SemaphoreGroups {
         );
     }
 
+    /// @dev See {ISemaphore-verifyProof}.
     function verifyProof(
         uint256 groupId,
         SemaphoreProof calldata proof
     ) public view override onlyExistingGroup(groupId) returns (bool) {
+        // The function will revert if the Merkle tree depth is not supported.
         if (proof.merkleTreeDepth < 1 || proof.merkleTreeDepth > 12) {
             revert Semaphore__MerkleTreeDepthIsNotSupported();
         }
 
+        // Gets the number of leaves in the Incremental Merkle Tree that represents the group
+        // with id groupId which is the same as the number of members in the group groupId.
         uint256 merkleTreeSize = getMerkleTreeSize(groupId);
 
+        // The function will revert if there are no members in the group.
         if (merkleTreeSize == 0) {
             revert Semaphore__GroupHasNoMembers();
         }
 
+        // Gets the Merkle root of the Incremental Merkle Tree that represents the group with id groupId.
         uint256 currentMerkleTreeRoot = getMerkleTreeRoot(groupId);
 
         // A proof could have used an old Merkle tree root.

packages/contracts/contracts/base/SemaphoreGroups.sol

@@ -11,9 +11,12 @@ abstract contract SemaphoreGroups is ISemaphoreGroups {
     using InternalLeanIMT for LeanIMTData;
 
     /// @dev Gets a group id and returns its tree data.
+    /// The tree is an Incremental Merkle Tree
+    /// which is called Lean Incremental Merkle Tree.
     mapping(uint256 => LeanIMTData) internal merkleTrees;
 
     /// @dev Gets a group id and returns its admin.
+    /// The admin can be an Ethereum account or a smart contract.
     mapping(uint256 => address) internal admins;
 
     /// @dev Checks if the group admin is the transaction sender.

packages/contracts/contracts/base/SemaphoreVerifier.sol

@@ -21,6 +21,12 @@ contract SemaphoreVerifier {
     uint256 constant gammay1 = 4082367875863433681332203403145435568316851327593401208105741076214120093531;
     uint256 constant gammay2 = 8495653923123431417604973247489272438418190587263600148770280649306958101930;
 
+    // TODO: Add more variables when Semaphore supports tree depth > 12.
+    // Right now Semaphore supports tree depth 1-12.
+
+    // Verification Key points.
+    // These values are taken from the verification key json file generated with snarkjs.
+    // It allows to use the same verifier to verify proofs for all the tree depths supported by Semaphore.
     uint256[14][12] VK_POINTS = [
         [
             563562783592406106461234396505774794044312891062077216951605541624542949349,

packages/contracts/contracts/interfaces/ISemaphore.sol

@@ -17,7 +17,7 @@ interface ISemaphore {
         mapping(uint256 => bool) nullifiers;
     }
 
-    /// It defines all the group parameters used by Semaphore.sol.
+    /// It defines all the Semaphore proof parameters used by Semaphore.sol.
     struct SemaphoreProof {
         uint256 merkleTreeDepth;
         uint256 merkleTreeRoot;
@@ -27,7 +27,7 @@ interface ISemaphore {
         uint256[8] points;
     }
 
-    /// @dev Emitted when the Merkle tree duration of a group is updated.
+    /// @dev Event emitted when the Merkle tree duration of a group is updated.
     /// @param groupId: Id of the group.
     /// @param oldMerkleTreeDuration: Old Merkle tree duration of the group.
     /// @param newMerkleTreeDuration: New Merkle tree duration of the group.
@@ -37,7 +37,7 @@ interface ISemaphore {
         uint256 newMerkleTreeDuration
     );
 
-    /// @dev Emitted when a Semaphore proof is validated.
+    /// @dev Event emitted when a Semaphore proof is validated.
     /// @param groupId: Id of the group.
     /// @param merkleTreeDepth: Depth of the Merkle tree.
     /// @param merkleTreeRoot: Root of the Merkle tree.
@@ -60,7 +60,7 @@ interface ISemaphore {
 
     /// @dev It creates a group with a custom Merkle tree duration.
     /// @param groupId: Id of the group.
-    /// @param admin: Admin of the group.
+    /// @param admin: Admin of the group. It can be an Ethereum account or a smart contract.
     /// @param merkleTreeDuration: Merkle tree duration.
     function createGroup(uint256 groupId, address admin, uint256 merkleTreeDuration) external;
 
@@ -89,14 +89,14 @@ interface ISemaphore {
     /// @dev See {SemaphoreGroups-_removeMember}.
     function removeMember(uint256 groupId, uint256 identityCommitment, uint256[] calldata merkleProofSiblings) external;
 
-    /// @dev Saves the nullifier hash to avoid double signaling and emits an event
+    /// @dev Saves the nullifier hash to prevent double signaling and emits an event
     /// if the zero-knowledge proof is valid.
     /// @param groupId: Id of the group.
-    /// @param proof: Zero-knowledge proof.
+    /// @param proof: Semaphore zero-knowledge proof.
     function validateProof(uint256 groupId, SemaphoreProof calldata proof) external;
 
     /// @dev Verifies a zero-knowledge proof by returning true or false.
     /// @param groupId: Id of the group.
-    /// @param proof: Zero-knowledge proof.
+    /// @param proof: Semaphore zero-knowledge proof.
     function verifyProof(uint256 groupId, SemaphoreProof calldata proof) external view returns (bool);
 }

packages/contracts/contracts/interfaces/ISemaphoreGroups.sol

@@ -7,24 +7,24 @@ interface ISemaphoreGroups {
     error Semaphore__GroupAlreadyExists();
     error Semaphore__CallerIsNotTheGroupAdmin();
 
-    /// @dev Emitted when a new group is created.
+    /// @dev Event emitted when a new group is created.
     /// @param groupId: Id of the group.
     event GroupCreated(uint256 indexed groupId);
 
-    /// @dev Emitted when an admin is assigned to a group.
+    /// @dev Event emitted when an admin is assigned to a group.
     /// @param groupId: Id of the group.
     /// @param oldAdmin: Old admin of the group.
     /// @param newAdmin: New admin of the group.
     event GroupAdminUpdated(uint256 indexed groupId, address indexed oldAdmin, address indexed newAdmin);
 
-    /// @dev Emitted when a new identity commitment is added.
+    /// @dev Event emitted when a new identity commitment is added.
     /// @param groupId: Group id of the group.
     /// @param index: Merkle tree leaf index.
     /// @param identityCommitment: New identity commitment.
     /// @param merkleTreeRoot: New root hash of the tree.
     event MemberAdded(uint256 indexed groupId, uint256 index, uint256 identityCommitment, uint256 merkleTreeRoot);
 
-    /// @dev Emitted when many identity commitments are added at the same time.
+    /// @dev Event emitted when many identity commitments are added at the same time.
     /// @param groupId: Group id of the group.
     /// @param startIndex: Index of the first element of the new identity commitments in the merkle tree.
     /// @param identityCommitments: The new identity commitments.
@@ -36,7 +36,7 @@ interface ISemaphoreGroups {
         uint256 merkleTreeRoot
     );
 
-    /// @dev Emitted when an identity commitment is updated.
+    /// @dev Event emitted when an identity commitment is updated.
     /// @param groupId: Group id of the group.
     /// @param index: Identity commitment index.
     /// @param identityCommitment: Existing identity commitment to be updated.
@@ -50,14 +50,14 @@ interface ISemaphoreGroups {
         uint256 merkleTreeRoot
     );
 
-    /// @dev Emitted when a new identity commitment is removed.
+    /// @dev Event emitted when a new identity commitment is removed.
     /// @param groupId: Group id of the group.
     /// @param index: Identity commitment index.
     /// @param identityCommitment: Existing identity commitment to be removed.
     /// @param merkleTreeRoot: New root hash of the tree.
     event MemberRemoved(uint256 indexed groupId, uint256 index, uint256 identityCommitment, uint256 merkleTreeRoot);
 
-    /// @dev Returns the address of the group admin.
+    /// @dev Returns the address of the group admin. The group admin can be an Ethereum account or a smart contract.
     /// @param groupId: Id of the group.
     /// @return Address of the group admin.
     function getGroupAdmin(uint256 groupId) external view returns (address);

packages/contracts/contracts/interfaces/ISemaphoreVerifier.sol

@@ -3,6 +3,13 @@ pragma solidity 0.8.23;
 
 /// @title SemaphoreVerifier contract interface.
 interface ISemaphoreVerifier {
+    /// @dev Returns true if the proof was successfully verified.
+    /// @param _pA: Point A.
+    /// @param _pB: Point B.
+    /// @param _pC: Point C.
+    /// @param _pubSignals: Public signals.
+    /// @param merkleTreeDepth: Merkle tree depth.
+    /// @return True if the proof was successfully verified, false otherwise.
     function verifyProof(
         uint[2] calldata _pA,
         uint[2][2] calldata _pB,