Added upgradable token and pause logics

contracts/TokenDelegate.sol

@@ -1,54 +1,24 @@
 pragma solidity ^0.7.0;
 pragma experimental ABIEncoderV2;
 
+import {     
+    TokenDelegateStorageV1,
+    TokenEvents,
+    TimelockInterface,
+    TokenInterface
+} from "./TokenInterfaces.sol";
 import { SafeMath } from "./SafeMath.sol";
 
-// TODO - Rename it
-contract Token {
-    /// @notice EIP-20 token name for this token
-    string public constant name = "<Token Name>"; // TODO - Replace it
-
-    /// @notice EIP-20 token symbol for this token
-    string public constant symbol = "<TKN>"; // TODO - Replace it
-
+// TODO @thrilok209 @KaymasJain - Rename it
+contract TokenDelegate is TokenDelegateStorageV1, TokenEvents {
     /// @notice EIP-20 token decimals for this token
     uint8 public constant decimals = 18;
 
-    /// @notice Total number of tokens in circulation
-    uint public totalSupply = 10000000e18; // TODO - Replace it
-
-    /// @notice Token minter
-    address public minter;
-
-    /// @notice The timestamp after which minting may occur
-    uint public mintingAllowedAfter;
-
     /// @notice Minimum time between mints
-    uint32 public constant minimumTimeBetweenMints = 1 days * 7; // TODO - Replace it
+    uint32 public constant minimumTimeBetweenMints = 1 days * 7; // TODO @thrilok209 @KaymasJain - Replace it
 
     /// @notice Cap on the percentage of totalSupply that can be minted at each mint
-    uint8 public constant mintCap = 2; // TODO - Replace it
-
-    // Allowance amounts on behalf of others
-    mapping (address => mapping (address => uint96)) internal allowances;
-
-    // Official record of token balances for each account
-    mapping (address => uint96) internal balances;
-
-    /// @notice A record of each accounts delegate
-    mapping (address => address) public delegates;
-
-    /// @notice A checkpoint for marking number of votes from a given block
-    struct Checkpoint {
-        uint32 fromBlock;
-        uint96 votes;
-    }
-
-    /// @notice A record of votes checkpoints for each account, by index
-    mapping (address => mapping (uint32 => Checkpoint)) public checkpoints;
-
-    /// @notice The number of checkpoints for each account
-    mapping (address => uint32) public numCheckpoints;
+    uint8 public constant mintCap = 2; // TODO @thrilok209 @KaymasJain - Replace it
 
     /// @notice The EIP-712 typehash for the contract's domain
     bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)");
@@ -59,32 +29,27 @@ contract Token {
     /// @notice The EIP-712 typehash for the permit struct used by the contract
     bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
 
-    /// @notice A record of states for signing / validating signatures
-    mapping (address => uint) public nonces;
 
-    /// @notice An event thats emitted when an account changes its delegate
-    event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);
-
-    /// @notice An event thats emitted when a delegate account's vote balance changes
-    event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);
-
-    /// @notice An event thats emitted when the minter changes
-    event MinterChanged(address indexed oldMinter, address indexed newMinter);
-
-    /// @notice The standard EIP-20 transfer event
-    event Transfer(address indexed from, address indexed to, uint256 amount);
-
-    /// @notice The standard EIP-20 approval event
-    event Approval(address indexed owner, address indexed spender, uint256 amount);
-
-    constructor(address account, address minter_, uint mintingAllowedAfter_) {
-        require(mintingAllowedAfter_ >= block.timestamp, "Tkn::constructor: minting can only begin after deployment");
+    // TODO @mubaris - add comment of each parameter.
+    function initialize(address account, address minter_, uint mintingAllowedAfter_, bool transferPaused_) public {
+        require(mintingAllowedAfter == 0, "Token::initialize: can only initialize once");
+        require(address(minter) == address(0), "Token::initialize: can only initialize once");
+        require(mintingAllowedAfter_ >= block.timestamp, "Token::constructor: minting can only begin after deployment");
+        require(msg.sender == minter, "Token::initialize: admin only");
+        // TODO @mubaris - anything else to add in require statements?
 
         balances[account] = uint96(totalSupply);
         emit Transfer(address(0), account, totalSupply);
         minter = minter_;
         emit MinterChanged(address(0), minter);
         mintingAllowedAfter = mintingAllowedAfter_;
+        transferPaused = transferPaused_;
+
+        if (transferPaused) {
+            emit TransferPaused(msg.sender);
+        } else {
+            emit TransferUnpaused(msg.sender);
+        }
     }
 
     /**
@@ -97,6 +62,24 @@ contract Token {
         minter = minter_;
     }
 
+    /**
+     * @notice Pause the token transfer
+     */
+    function pauseTransfer() external {
+        require(msg.sender == minter, "Tkn::pauseTransfer: only the minter can pause token transfer");
+        transferPaused = true;
+        emit TransferPaused(msg.sender);
+    }
+
+    /**
+     * @notice Unpause the token transfer
+     */
+    function unpauseTransfer() external {
+        require(msg.sender == minter, "Tkn::unpauseTransfer: only the minter can unpause token transfer");
+        transferPaused = false;
+        emit TransferUnpaused(msg.sender);
+    }
+
     /**
      * @notice Get the number of tokens `spender` is approved to spend on behalf of `account`
      * @param account The address of the account holding the funds
@@ -321,6 +304,7 @@ contract Token {
     }
 
     function _transferTokens(address src, address dst, uint96 amount) internal {
+        require(!transferPaused, "Tkn::_transferTokens: transfer paused");
         require(src != address(0), "Tkn::_transferTokens: cannot transfer from the zero address");
         require(dst != address(0), "Tkn::_transferTokens: cannot transfer to the zero address");
 

contracts/TokenDelegator.sol

@@ -0,0 +1,82 @@
+pragma solidity ^0.7.0;
+pragma experimental ABIEncoderV2;
+
+import { TokenDelegatorStorage, TokenEvents } from "./TokenInterfaces.sol";
+
+contract TokenDelegator is TokenDelegatorStorage, TokenEvents {
+    constructor(
+        address account,
+        address minter_,
+        address implementation_,
+        uint mintingAllowedAfter_,
+        uint changeImplementationAfter_
+    ) {
+        // Admin set to msg.sender for initialization
+        minter = msg.sender;
+
+        delegateTo(
+            implementation_,
+            abi.encodeWithSignature(
+                "initialize(address,address,uint256)",
+                account,
+                minter_,
+                mintingAllowedAfter_
+            )
+        );
+
+        changeImplementationAfter = changeImplementationAfter_;
+
+        _setImplementation(implementation_);
+
+        minter = minter_;
+    }
+
+    /**
+     * @notice Called by the admin to update the implementation of the delegator
+     * @param implementation_ The address of the new implementation for delegation
+     */
+    function _setImplementation(address implementation_) public {
+        require(msg.sender == minter, "TokenDelegator::_setImplementation: admin only");
+        require(implementation_ != address(0), "TokenDelegator::_setImplementation: invalid implementation address");
+        require(changeImplementationAfter >= block.timestamp, "TokenDelegator::_setImplementation: can change implementation changeImplementationAfter time only");
+
+        address oldImplementation = implementation;
+        implementation = implementation_;
+
+        emit NewImplementation(oldImplementation, implementation);
+    }
+
+    /**
+     * @notice Internal method to delegate execution to another contract
+     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
+     * @param callee The contract to delegatecall
+     * @param data The raw data to delegatecall
+     */
+    function delegateTo(address callee, bytes memory data) internal {
+        (bool success, bytes memory returnData) = callee.delegatecall(data);
+        assembly {
+            if eq(success, 0) {
+                revert(add(returnData, 0x20), returndatasize())
+            }
+        }
+    }
+
+    /**
+     * @dev Delegates execution to an implementation contract.
+     * It returns to the external caller whatever the implementation returns
+     * or forwards reverts.
+     */
+    fallback () external payable {
+        // delegate all other functions to current implementation
+        (bool success, ) = implementation.delegatecall(msg.data);
+
+        assembly {
+            let free_mem_ptr := mload(0x40)
+            returndatacopy(free_mem_ptr, 0, returndatasize())
+
+            switch success
+            case 0 { revert(free_mem_ptr, returndatasize()) }
+            default { return(free_mem_ptr, returndatasize()) }
+        }
+    }
+}

contracts/TokenInterfaces.sol

@@ -0,0 +1,102 @@
+pragma solidity ^0.7.0;
+pragma experimental ABIEncoderV2;
+
+interface TimelockInterface {
+    function delay() external view returns (uint);
+    function GRACE_PERIOD() external view returns (uint);
+    function acceptAdmin() external;
+    function queuedTransactions(bytes32 hash) external view returns (bool);
+    function queueTransaction(address target, uint value, string calldata signature, bytes calldata data, uint eta) external returns (bytes32);
+    function cancelTransaction(address target, uint value, string calldata signature, bytes calldata data, uint eta) external;
+    function executeTransaction(address target, uint value, string calldata signature, bytes calldata data, uint eta) external payable returns (bytes memory);
+}
+
+interface TokenInterface {
+    function getPriorVotes(address account, uint blockNumber) external view returns (uint96);
+}
+
+contract TokenEvents {
+    
+    /// @notice An event thats emitted when an account changes its delegate
+    event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);
+
+    /// @notice An event thats emitted when a delegate account's vote balance changes
+    event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);
+
+    /// @notice An event thats emitted when the minter changes
+    event MinterChanged(address indexed oldMinter, address indexed newMinter);
+
+    /// @notice The standard EIP-20 transfer event
+    event Transfer(address indexed from, address indexed to, uint256 amount);
+
+    /// @notice The standard EIP-20 approval event
+    event Approval(address indexed owner, address indexed spender, uint256 amount);
+
+    /// @notice Emitted when implementation is changed
+    event NewImplementation(address oldImplementation, address newImplementation);
+
+    /// @notice An event thats emitted when the token transfered is paused
+    event TransferPaused(address minter);
+
+    /// @notice An event thats emitted when the token transfered is unpaused
+    event TransferUnpaused(address minter);
+}
+
+contract TokenDelegatorStorage {
+    /// @notice Administrator Token minter
+    address public minter;
+
+    /// @notice Active brains of Token
+    address public implementation;
+
+    /// @notice The timestamp after which implementation maybe change
+    uint public changeImplementationAfter;
+
+}
+
+/**
+ * @title Storage for Token Delegate
+ * @notice For future upgrades, do not change TokenDelegateStorageV1. Create a new
+ * contract which implements TokenDelegateStorageV1 and following the naming convention
+ * TokenDelegateStorageVX.
+ */
+contract TokenDelegateStorageV1 is TokenDelegatorStorage {
+    /// @notice EIP-20 token name for this token
+    string public name = "<Token Name>"; // TODO - Replace it
+
+    /// @notice EIP-20 token symbol for this token
+    string public symbol = "<TKN>"; // TODO - Replace it
+
+    /// @notice Total number of tokens in circulation
+    uint public totalSupply = 10000000e18; // TODO - Replace it
+
+    /// @notice The timestamp after which minting may occur
+    uint public mintingAllowedAfter;
+
+    // Allowance amounts on behalf of others
+    mapping (address => mapping (address => uint96)) internal allowances;
+
+    // Official record of token balances for each account
+    mapping (address => uint96) internal balances;
+
+    /// @notice A record of each accounts delegate
+    mapping (address => address) public delegates;
+
+    /// @notice A checkpoint for marking number of votes from a given block
+    struct Checkpoint {
+        uint32 fromBlock;
+        uint96 votes;
+    }
+
+    /// @notice A record of votes checkpoints for each account, by index
+    mapping (address => mapping (uint32 => Checkpoint)) public checkpoints;
+
+    /// @notice The number of checkpoints for each account
+    mapping (address => uint32) public numCheckpoints;
+
+    /// @notice A record of states for signing / validating signatures
+    mapping (address => uint) public nonces;
+
+    /// @notice token transfer pause state
+    bool public transferPaused;
+}

package.json

@@ -15,6 +15,7 @@
     "chai": "^4.3.4",
     "ethereum-waffle": "^3.3.0",
     "ethers": "^5.0.32",
-    "hardhat": "^2.1.1"
+    "hardhat": "^2.1.1",
+    "solc": "^0.7.0"
   }
 }