Add docs

Author: ernestognw

contracts/crosschain/axelar/AxelarGatewayBase.sol

@@ -5,38 +5,55 @@ pragma solidity ^0.8.0;
 import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
 import {IAxelarGateway} from "@axelar-network/axelar-gmp-sdk-solidity/contracts/interfaces/IAxelarGateway.sol";
 
+/**
+ * @dev Base implementation of a cross-chain gateway adapter for the Axelar Network.
+ *
+ * This contract allows developers to register equivalence between chains (i.e. CAIP-2 chain identifiers
+ * to Axelar chain identifiers) and remote gateways (i.e. gateways on other chains) to
+ * facilitate cross-chain communication.
+ */
 abstract contract AxelarGatewayBase is Ownable {
+    /// @dev A remote gateway has been registered for a chain.
     event RegisteredRemoteGateway(string caip2, string gatewayAddress);
+
+    /// @dev A chain equivalence has been registered.
     event RegisteredChainEquivalence(string caip2, string destinationChain);
 
+    /// @dev Error emitted when an unsupported chain is queried.
     error UnsupportedChain(string caip2);
 
+    /// @dev Axelar's official gateway for the current chain.
     IAxelarGateway public immutable localGateway;
 
     mapping(string caip2 => string remoteGateway) private _remoteGateways;
-    mapping(string caip2OrAxelar => string axelarOfCaip2) private _chainEquivalence;
+    mapping(string caip2OrAxelar => string axelarOrCaip2) private _chainEquivalence;
 
+    /// @dev Sets the local gateway address (i.e. Axelar's official gateway for the current chain).
     constructor(IAxelarGateway _gateway) {
         localGateway = _gateway;
     }
 
+    /// @dev Returns the equivalent chain given an id that can be either CAIP-2 or an Axelar network identifier.
     function getEquivalentChain(string memory input) public view virtual returns (string memory output) {
         output = _chainEquivalence[input];
         require(bytes(output).length > 0, UnsupportedChain(input));
     }
 
+    /// @dev Returns the remote gateway address for a given chain.
     function getRemoteGateway(string memory caip2) public view virtual returns (string memory remoteGateway) {
         remoteGateway = _remoteGateways[caip2];
         require(bytes(remoteGateway).length > 0, UnsupportedChain(caip2));
     }
 
+    /// @dev Registers a chain equivalence between a CAIP-2 chain identifier and an Axelar network identifier.
     function registerChainEquivalence(string calldata caip2, string calldata axelarSupported) public virtual onlyOwner {
         require(bytes(_chainEquivalence[caip2]).length == 0);
         _chainEquivalence[caip2] = axelarSupported;
         _chainEquivalence[axelarSupported] = caip2;
         emit RegisteredChainEquivalence(caip2, axelarSupported);
     }
 
+    /// @dev Registers a remote gateway address for a given CAIP-2 chain identifier.
     function registerRemoteGateway(string calldata caip2, string calldata remoteGateway) public virtual onlyOwner {
         require(bytes(_remoteGateways[caip2]).length == 0);
         _remoteGateways[caip2] = remoteGateway;

contracts/crosschain/axelar/AxelarGatewayDestination.sol

@@ -9,11 +9,18 @@ import {Strings} from "@openzeppelin/contracts@master/utils/Strings.sol";
 import {IERC7786GatewayDestinationPassive, IERC7786Receiver} from "../interfaces/draft-IERC7786.sol";
 import {AxelarGatewayBase} from "./AxelarGatewayBase.sol";
 
+/**
+ * @dev Implementation of an ERC7786 gateway destination adapter for the Axelar Network in dual mode.
+ *
+ * The contract provides an internal {_execute} function to be used by a child contract (active mode),
+ * Alternatively, it provides a way to set a message as executed by calling the {setExecutedMessage}
+ * function (passive mode).
+ */
 abstract contract AxelarGatewayDestination is IERC7786GatewayDestinationPassive, AxelarGatewayBase, AxelarExecutable {
     using Strings for address;
     using Strings for string;
 
-    /// @dev Passive mode
+    /// @dev Sets a message as executed so it can't be executed again. Should be called by the receiver contract.
     function setExecutedMessage(
         bytes calldata messageKey,
         string calldata source, // CAIP-2
@@ -44,14 +51,18 @@ abstract contract AxelarGatewayDestination is IERC7786GatewayDestinationPassive,
         );
     }
 
-    /// @dev Active mode
-    // In this function:
-    // - `remoteChain` is in the Axelar format. It should not be expected to be a proper CAIP-2 format
-    // - `remoteAccount` is the sender of the crosschain message. That should be the remote gateway on the chain which
-    //   the message originates from. It is NOT the sender of the crosschain message
-    //
-    // Proper CAIP-10 encoding of the message sender (including the CAIP-2 name of the origin chain can be found in
-    // the message)
+    /**
+     * @dev Active mode execution of a cross-chain message.
+     *
+     * In this function:
+     *
+     * - `remoteChain` is in the Axelar format. It should not be expected to be a proper CAIP-2 format
+     * - `remoteAccount` is the sender of the crosschain message. That should be the remote gateway on the chain which
+     *   the message originates from. It is NOT the sender of the crosschain message
+     *
+     * Proper CAIP-10 encoding of the message sender (including the CAIP-2 name of the origin chain can be found in
+     * the message)
+     */
     function _execute(
         string calldata remoteChain, // chain of the remote gateway - axelar format
         string calldata remoteAccount, // address of the remote gateway

contracts/crosschain/axelar/AxelarGatewaySource.sol

@@ -8,13 +8,21 @@ import {Strings} from "@openzeppelin/contracts@master/utils/Strings.sol";
 import {AxelarGatewayBase} from "./AxelarGatewayBase.sol";
 import {IERC7786GatewaySource} from "../interfaces/draft-IERC7786.sol";
 
+/**
+ * @dev Implementation of an ERC7786 gateway source adapter for the Axelar Network.
+ *
+ * The contract provides a way to send messages to a remote chain using the Axelar Network
+ * using the {sendMessage} function.
+ */
 abstract contract AxelarGatewaySource is IERC7786GatewaySource, AxelarGatewayBase {
     using Strings for address;
 
+    /// @inheritdoc IERC7786GatewaySource
     function supportsAttribute(bytes4 /*selector*/) public pure returns (bool) {
         return false;
     }
 
+    /// @inheritdoc IERC7786GatewaySource
     function sendMessage(
         string calldata destination, // CAIP-2 chain ID
         string calldata receiver, // i.e. address