Meta & Ecosystem Rewards (#90)

* Implemented MTA token
* Implemented Rewards mechanisms
* Tested suite

.gitignore

@@ -54,6 +54,7 @@ package-lock.json
 .coverage_artifacts/
 .coverage_contracts/
 coverage.json
+cache
 
 # sol-merger
 flat/

.solcover.js

@@ -14,6 +14,7 @@ module.exports = {
   skipFiles: [
     'Migrations.sol',
     'interfaces',
+    'integrations',
     'z_mocks',
     'shared/InitializableReentrancyGuard.sol',
     'integrations'

README.md

@@ -2,7 +2,7 @@
 <img src="https://mstable.org/assets/img/email/mstable_logo_horizontal_black.png" width="420" >
 
 [![CircleCI](https://circleci.com/gh/mstable/mStable-contracts.svg?style=svg&circle-token=a8bb29a97a0a0949a15cc28bd9b2245960287bc2)](https://circleci.com/gh/mstable/mStable-contracts)
-[![Coverage Status](https://coveralls.io/repos/github/mstable/mStable-contracts/badge.svg?t=7A5XxE)](https://coveralls.io/github/mstable/mStable-contracts)
+[![Coverage Status](https://coveralls.io/repos/github/mstable/mStable-contracts/badge.svg?branch=master)](https://coveralls.io/github/mstable/mStable-contracts?branch=master)
 [![Discord](https://img.shields.io/discord/525087739801239552?color=7289DA&label=discord%20)](https://discordapp.com/channels/525087739801239552/)
 
 

contracts/governance/ClaimableGovernor.sol

@@ -6,6 +6,8 @@ import { Governable } from "./Governable.sol";
  * @title   ClaimableGovernor
  * @author  Stability Labs Pty. Ltd.
  * @notice  2 way handshake for Governance transfer
+ * @dev     Overrides the public functions in Governable to provide
+ * a second step of validation.
  */
 contract ClaimableGovernor is Governable {
 

contracts/governance/Governable.sol

@@ -4,8 +4,10 @@ pragma solidity 0.5.16;
  * @title   Governable
  * @author  Stability Labs Pty. Ltd.
  * @notice  Simple contract implementing an Ownable pattern.
- * @dev     Derives from OpenZeppelin 2.3.0 Ownable.sol
+ * @dev     Derives from V2.3.0 @openzeppelin/contracts/ownership/Ownable.sol
  *          Modified to have custom name and features
+ *              - Removed `renounceOwnership`
+ *              - Changes `_owner` to `_governor`
  */
 contract Governable {
 

contracts/governance/InitializableGovernableWhitelist.sol

@@ -7,6 +7,8 @@ import { InitializableModule } from "../shared/InitializableModule.sol";
  * @author  Stability Labs Pty. Ltd.
  * @notice  Contract to store whitelisted address. The onlyWhitelisted() modifier should be used
  *          to allow the function calls only from the whitelisted addresses.
+ * @dev     Implementing contracts are responsible for adding their own add and remove methods
+ *          as the original purpose of this whitelist is for read optimisation.
  */
 contract InitializableGovernableWhitelist is InitializableModule {
 

contracts/interfaces/IMetaToken.sol

@@ -0,0 +1,25 @@
+pragma solidity 0.5.16;
+
+/**
+ * @title IMetaToken
+ * @dev Interface for MetaToken
+ */
+interface IMetaToken {
+    /** @dev Basic ERC20 funcs */
+    function name() external view returns (string memory);
+    function symbol() external view returns (string memory);
+    function decimals() external view returns (uint8);
+    function totalSupply() external view returns (uint256);
+    function balanceOf(address account) external view returns (uint256);
+    function transfer(address recipient, uint256 amount) external returns (bool);
+    function allowance(address owner, address spender) external view returns (uint256);
+    function approve(address spender, uint256 amount) external returns (bool);
+    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
+
+    /** @dev Burnable */
+    function burn(uint256 amount) external;
+    function burnFrom(address account, uint256 amount) external;
+
+    /** @dev Mintable */
+    function mint(address account, uint256 amount) external returns (bool);
+}

contracts/interfaces/IRewardsDistributionRecipient.sol

@@ -0,0 +1,8 @@
+pragma solidity 0.5.16;
+
+import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+
+interface IRewardsDistributionRecipient {
+    function notifyRewardAmount(uint256 reward) external;
+    function getRewardToken() external view returns (IERC20);
+}

contracts/meta-token/GovernedMinterRole.sol

@@ -0,0 +1,56 @@
+pragma solidity 0.5.16;
+
+import { Module } from "../shared/Module.sol";
+import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import { Roles } from "@openzeppelin/contracts/access/Roles.sol";
+
+/**
+ * @title  GovernedMinterRole
+ * @author OpenZeppelin (forked from @openzeppelin/contracts/access/roles/MinterRole.sol)
+ * @dev    Forked from OpenZeppelin 'MinterRole' with changes:
+ *          - `addMinter` modified from `onlyMinter` to `onlyGovernor`
+ *          - `removeMinter` function added, callable by `onlyGovernor`
+ */
+contract GovernedMinterRole is Module {
+
+    using Roles for Roles.Role;
+
+    event MinterAdded(address indexed account);
+    event MinterRemoved(address indexed account);
+
+    Roles.Role private _minters;
+
+    constructor(address _nexus) internal Module(_nexus) {
+    }
+
+    modifier onlyMinter() {
+        require(isMinter(msg.sender), "MinterRole: caller does not have the Minter role");
+        _;
+    }
+
+    function isMinter(address account) public view returns (bool) {
+        return _minters.has(account);
+    }
+
+    function addMinter(address account) public onlyGovernor {
+        _addMinter(account);
+    }
+
+    function removeMinter(address account) public onlyGovernor {
+        _removeMinter(account);
+    }
+
+    function renounceMinter() public {
+        _removeMinter(msg.sender);
+    }
+
+    function _addMinter(address account) internal {
+        _minters.add(account);
+        emit MinterAdded(account);
+    }
+
+    function _removeMinter(address account) internal {
+        _minters.remove(account);
+        emit MinterRemoved(account);
+    }
+}

contracts/meta-token/MetaToken.sol

@@ -0,0 +1,53 @@
+pragma solidity 0.5.16;
+
+import { GovernedMinterRole } from "./GovernedMinterRole.sol";
+import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import { ERC20Detailed } from "@openzeppelin/contracts/token/ERC20/ERC20Detailed.sol";
+import { ERC20Burnable } from "@openzeppelin/contracts/token/ERC20/ERC20Burnable.sol";
+
+/**
+ * @title  MetaToken
+ * @author Stability Labs Pty. Ltd.
+ * @dev    MetaToken is an ERC20 token, with mint privileges governed by mStable
+ * governors
+ */
+contract MetaToken is
+    ERC20,
+    GovernedMinterRole,
+    ERC20Detailed,
+    ERC20Burnable
+{
+
+    /**
+     * @dev MetaToken simply implements a detailed ERC20 token,
+     * and a governed list of minters
+     */
+    constructor(
+        address _nexus,
+        address _initialRecipient
+    )
+        public
+        GovernedMinterRole(_nexus)
+        ERC20Detailed(
+            "Meta",
+            "MTA",
+            18
+        )
+    {
+        // 100m initial supply
+        _mint(_initialRecipient, 100000000 * (10 ** 18));
+    }
+
+    // Forked from @openzeppelin
+    /**
+     * @dev See {ERC20-_mint}.
+     *
+     * Requirements:
+     *
+     * - the caller must have the {MinterRole}.
+     */
+    function mint(address account, uint256 amount) public onlyMinter returns (bool) {
+        _mint(account, amount);
+        return true;
+    }
+}

contracts/rewards/README.md

@@ -0,0 +1,28 @@
+
+
+## Files
+
+Why so many?
+
+Actually only 3 are base contracts
+
+### RewardsDistributor
+
+Allows reward allocators ("FundManagers") to distribute rewards.
+
+### StakingRewards
+
+`StakingRewards` is `RewardsDistributionRecipient`
+-------------->  is `StakingTokenWrapper`
+
+This preserves the code written, tested, audited and deployed by `Synthetix` (StakingRewards & StakingTokenWrapper).
+
+Originally: Synthetix (forked from /Synthetixio/synthetix/contracts/StakingRewards.sol)
+Audit: https://github.com/sigp/public-audits/blob/master/synthetix/unipool/review.pdf`
+
+### StakingRewardsWithPlatformToken
+
+`StakingRewardsWithPlatformToken` is `RewardsDistributionRecipient`
+------------------------------->  is `StakingTokenWrapper`
+
+`StakingRewardsWithPlatformToken` deploys `PlatformTokenVendor` during its constructor

contracts/rewards/RewardsDistributionRecipient.sol

@@ -0,0 +1,49 @@
+pragma solidity 0.5.16;
+
+import { Module } from "../shared/Module.sol";
+import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import { IRewardsDistributionRecipient } from "../interfaces/IRewardsDistributionRecipient.sol";
+
+/**
+ * @title  RewardsDistributionRecipient
+ * @author Originally: Synthetix (forked from /Synthetixio/synthetix/contracts/RewardsDistributionRecipient.sol)
+ *         Changes by: Stability Labs Pty. Ltd.
+ * @notice RewardsDistributionRecipient gets notified of additional rewards by the rewardsDistributor
+ * @dev    Changes: Addition of Module and abstract `getRewardToken` func + cosmetic
+ */
+contract RewardsDistributionRecipient is IRewardsDistributionRecipient, Module {
+
+    // @abstract
+    function notifyRewardAmount(uint256 reward) external;
+    function getRewardToken() external view returns (IERC20);
+
+    // This address has the ability to distribute the rewards
+    address public rewardsDistributor;
+
+    /** @dev Recipient is a module, governed by mStable governance */
+    constructor(address _nexus, address _rewardsDistributor)
+        internal
+        Module(_nexus)
+    {
+        rewardsDistributor = _rewardsDistributor;
+    }
+
+    /**
+     * @dev Only the rewards distributor can notify about rewards
+     */
+    modifier onlyRewardsDistributor() {
+        require(msg.sender == rewardsDistributor, "Caller is not reward distributor");
+        _;
+    }
+
+    /**
+     * @dev Change the rewardsDistributor - only called by mStable governor
+     * @param _rewardsDistributor   Address of the new distributor
+     */
+    function setRewardsDistribution(address _rewardsDistributor)
+        external
+        onlyGovernor
+    {
+        rewardsDistributor = _rewardsDistributor;
+    }
+}

contracts/rewards/RewardsDistributor.sol

@@ -0,0 +1,87 @@
+pragma solidity 0.5.16;
+
+import { IRewardsDistributionRecipient } from "../interfaces/IRewardsDistributionRecipient.sol";
+
+import { InitializableGovernableWhitelist } from "../governance/InitializableGovernableWhitelist.sol";
+import { SafeERC20, IERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
+
+/**
+ * @title  RewardsDistributor
+ * @author Stability Labs Pty. Ltd.
+ * @notice RewardsDistributor allows Fund Managers to send rewards (usually in MTA)
+ * to specified Reward Recipients.
+ */
+contract RewardsDistributor is InitializableGovernableWhitelist {
+
+    using SafeERC20 for IERC20;
+
+    event RemovedFundManager(address indexed _address);
+    event DistributedReward(address funder, address recipient, address rewardToken, uint256 amount);
+
+    /** @dev Recipient is a module, governed by mStable governance */
+    constructor(
+        address _nexus,
+        address[] memory _fundManagers
+    )
+        public
+    {
+        InitializableGovernableWhitelist._initialize(_nexus, _fundManagers);
+    }
+
+    /**
+     * @dev Allows the mStable governance to add a new FundManager
+     * @param _address  FundManager to add
+     */
+    function addFundManager(address _address)
+        external
+        onlyGovernor
+    {
+        _addWhitelist(_address);
+    }
+
+    /**
+     * @dev Allows the mStable governance to remove inactive FundManagers
+     * @param _address  FundManager to remove
+     */
+    function removeFundManager(address _address)
+        external
+        onlyGovernor
+    {
+        require(_address != address(0), "Address is zero");
+        require(whitelist[_address], "Address is not whitelisted");
+
+        whitelist[_address] = false;
+
+        emit RemovedFundManager(_address);
+    }
+
+    /**
+     * @dev Distributes reward tokens to list of recipients and notifies them
+     * of the transfer. Only callable by FundManagers
+     * @param _recipients  Array of Reward recipients to credit
+     * @param _amounts     Amounts of reward tokens to distribute
+     */
+    function distributeRewards(
+        IRewardsDistributionRecipient[] calldata _recipients,
+        uint256[] calldata _amounts
+    )
+        external
+        onlyWhitelisted
+    {
+        uint256 len = _recipients.length;
+        require(len > 0, "Must choose recipients");
+        require(len == _amounts.length, "Mismatching inputs");
+
+        for(uint i = 0; i < len; i++){
+            uint256 amount = _amounts[i];
+            IRewardsDistributionRecipient recipient = _recipients[i];
+            // Send the RewardToken to recipient
+            IERC20 rewardToken = recipient.getRewardToken();
+            rewardToken.safeTransferFrom(msg.sender, address(recipient), amount);
+            // Only after successfull tx - notify the contract of the new funds
+            recipient.notifyRewardAmount(amount);
+
+            emit DistributedReward(msg.sender, address(recipient), address(rewardToken), amount);
+        }
+    }
+}