update liquidity mining

defi-development-mastery/1-defi-building-blocks/10-liquidity-mining/contracts/BonusToken.sol → defi-development-mastery/1-defi-building-blocks/10-liquidity-mining/contracts/GovernanceToken.sol

@@ -1,10 +1,10 @@
-pragma solidity ^0.7.2;
+pragma solidity ^0.7.3;
 
 import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
 import '@openzeppelin/contracts/access/Ownable.sol';
 
-contract BonusToken is ERC20, Ownable {
-  constructor() ERC20('Bonus Token', 'BTK') Ownable() {} 
+contract GovernanceToken is ERC20, Ownable {
+  constructor() ERC20('Governance Token', 'GTK') Ownable() {} 
 
   function mint(address to, uint amount) external onlyOwner() {
     _mint(to, amount);

defi-development-mastery/1-defi-building-blocks/10-liquidity-mining/contracts/LiquidityPool.sol

@@ -0,0 +1,42 @@
+pragma solidity ^0.7.3;
+
+import './UnderlyingToken.sol';
+import './LpToken.sol';
+import './GovernanceToken.sol';
+
+contract LiquidityPool is LpToken {
+  mapping(address => uint) public checkpoints;
+  UnderlyingToken public underlyingToken;
+  GovernanceToken public governanceToken;
+  uint constant public REWARD_PER_BLOCK = 1;
+
+  constructor(address _underlyingToken, address _governanceToken) {
+    underlyingToken = UnderlyingToken(_underlyingToken);
+    governanceToken = GovernanceToken(_governanceToken);
+  }
+
+  function deposit(uint amount) external {
+    if(checkpoints[msg.sender] == 0) {
+      checkpoints[msg.sender] = block.number;
+    }
+    _distributeRewards(msg.sender);
+    underlyingToken.transferFrom(msg.sender, address(this), amount);
+    _mint(msg.sender, amount);
+  }
+
+  function withdraw(uint amount) external {
+    require(balanceOf(msg.sender) >= amount, 'not enough lp token');
+    _distributeRewards(msg.sender);
+    underlyingToken.transfer(msg.sender, amount);
+    _burn(msg.sender, amount);
+  }
+
+  function _distributeRewards(address beneficiary) internal {
+    uint checkpoint = checkpoints[beneficiary];
+    if(block.number - checkpoint > 0) {
+      uint distributionAmount = (balanceOf(beneficiary) * (block.number - checkpoint) * REWARD_PER_BLOCK);
+      governanceToken.mint(beneficiary, distributionAmount);
+      checkpoints[beneficiary] = block.number; 
+    }
+  }
+}

defi-development-mastery/1-defi-building-blocks/10-liquidity-mining/contracts/LiquidityPool2.sol

@@ -0,0 +1,83 @@
+pragma solidity ^0.7.3;
+
+import './UnderlyingToken.sol';
+import './LpToken.sol';
+import './GovernanceToken.sol';
+
+//More advanced distribution mechanism with a fixed amount of reward per block
+//for the whole contract
+//WIP
+contract LiquidityPool2 is LpToken {
+  struct Checkpoint {
+    uint blockNumber;
+    uint avgTotalBalance;
+  }
+
+  mapping(address => Checkpoint) public checkpoints;
+  Checkpoint public globalCheckpoint;
+
+  uint constant public REWARD_PER_BLOCK = 1000 * 10 ** 18;
+
+  UnderlyingToken public underlyingToken;
+  GovernanceToken public governanceToken;
+  uint public genesisBlock;
+
+  constructor(address _underlyingToken, address _governanceToken) {
+    underlyingToken = UnderlyingToken(_underlyingToken);
+    governanceToken = GovernanceToken(_governanceToken);
+    globalCheckpoint.blockNumber = block.number;
+    genesisBlock = block.number;
+  }
+
+  function deposit(uint amount) external {
+    globalCheckpoint.avgTotalBalance = _getAvgTotalBalance();
+    globalCheckpoint.blockNumber = block.number;
+
+    _distributeRewards(msg.sender);
+
+    underlyingToken.transferFrom(msg.sender, address(this), amount);
+    _mint(msg.sender, amount);
+
+    globalCheckpoint.avgTotalBalance = _getAvgTotalBalance();
+    checkpoints[msg.sender].avgTotalBalance = globalCheckpoint.avgTotalBalance;
+    checkpoints[msg.sender].blockNumber = block.number;
+  }
+
+  function withdraw(uint amount) external {
+    require(balanceOf(msg.sender) >= amount, 'not enough lp token');
+
+    globalCheckpoint.avgTotalBalance = _getAvgTotalBalance();
+    globalCheckpoint.blockNumber = block.number;
+
+    _distributeRewards(msg.sender);
+
+    checkpoints[msg.sender].avgTotalBalance = globalCheckpoint.avgTotalBalance;
+    checkpoints[msg.sender].blockNumber = block.number;
+
+    underlyingToken.transfer(msg.sender, amount);
+    _burn(msg.sender, amount);
+
+    globalCheckpoint.avgTotalBalance = _getAvgTotalBalance();
+    checkpoints[msg.sender].avgTotalBalance = globalCheckpoint.avgTotalBalance;
+    checkpoints[msg.sender].blockNumber = block.number;
+  }
+
+  function _getAvgTotalBalance() public view returns(uint) {
+    if(block.number - genesisBlock == 0) {
+      return totalSupply();
+    }
+    return (globalCheckpoint.avgTotalBalance * (globalCheckpoint.blockNumber - genesisBlock) + totalSupply() * (block.number - globalCheckpoint.blockNumber)) / (block.number - genesisBlock);  
+  }
+
+  function _distributeRewards(address beneficiary) internal {
+    Checkpoint storage userCheckpoint = checkpoints[beneficiary];
+    if(block.number - userCheckpoint.blockNumber > 0) {
+      uint avgTotalBalanceRewardPeriod = (globalCheckpoint.avgTotalBalance * globalCheckpoint.blockNumber - userCheckpoint.avgTotalBalance * userCheckpoint.blockNumber) / (block.number - userCheckpoint.blockNumber);  
+      if(avgTotalBalanceRewardPeriod > 0) {
+        uint distributionAmount = (balanceOf(beneficiary) * (block.number - userCheckpoint.blockNumber) * REWARD_PER_BLOCK) / avgTotalBalanceRewardPeriod;
+        governanceToken.mint(beneficiary, distributionAmount);
+      }
+    }
+  }
+
+}

defi-development-mastery/1-defi-building-blocks/10-liquidity-mining/contracts/LpToken.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.7.2;
+pragma solidity ^0.7.3;
 
 import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
 

defi-development-mastery/1-defi-building-blocks/10-liquidity-mining/contracts/UnderlyingToken.sol

@@ -0,0 +1,11 @@
+pragma solidity ^0.7.3;
+
+import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
+
+contract UnderlyingToken is ERC20 {
+  constructor() ERC20('Underlying Token', 'UTK') {} 
+
+  function faucet(address to, uint amount) external {
+    _mint(to, amount);
+  }
+}