merge feature/nft

contracts/external/ERC20/InitializableERC20.sol

@@ -19,7 +19,7 @@ contract InitializableERC20 {
 
     bool public initialized;
 
-    mapping(address => uint256) balances;
+    mapping(address => uint256) internal balances;
     mapping(address => mapping(address => uint256)) internal allowed;
 
     event Transfer(address indexed from, address indexed to, uint256 amount);
@@ -43,12 +43,7 @@ contract InitializableERC20 {
     }
 
     function transfer(address to, uint256 amount) public returns (bool) {
-        require(to != address(0), "TO_ADDRESS_IS_EMPTY");
-        require(amount <= balances[msg.sender], "BALANCE_NOT_ENOUGH");
-
-        balances[msg.sender] = balances[msg.sender].sub(amount);
-        balances[to] = balances[to].add(amount);
-        emit Transfer(msg.sender, to, amount);
+        _transfer(msg.sender, to, amount);
         return true;
     }
 
@@ -81,4 +76,16 @@ contract InitializableERC20 {
     function allowance(address owner, address spender) public view returns (uint256) {
         return allowed[owner][spender];
     }
+
+    function _transfer(address sender, address recipient, uint256 amount) internal {
+        require(sender != address(0), "FROM_ADDRESS_IS_EMPTY");
+        require(recipient != address(0), "TO_ADDRESS_IS_EMPTY");
+        require(amount <= balances[sender], "BALANCE_NOT_ENOUGH");
+
+        balances[sender] = balances[sender].sub(amount);
+        balances[recipient] = balances[recipient].add(amount);
+
+        emit Transfer(sender, recipient, amount);
+    }
+
 }

contracts/external/ERC20/InitializableFragERC20.sol

@@ -0,0 +1,92 @@
+/*
+
+    Copyright 2020 DODO ZOO.
+    SPDX-License-Identifier: Apache-2.0
+
+*/
+
+pragma solidity 0.6.9;
+
+import {SafeMath} from "../../lib/SafeMath.sol";
+
+contract InitializableFragERC20 {
+    using SafeMath for uint256;
+
+    string public name;
+    string public symbol;
+    uint256 public totalSupply;
+
+    bool public initialized;
+
+    mapping(address => uint256) internal balances;
+    mapping(address => mapping(address => uint256)) internal allowed;
+
+    event Transfer(address indexed from, address indexed to, uint256 amount);
+    event Approval(address indexed owner, address indexed spender, uint256 amount);
+
+    function init(
+        address _creator,
+        uint256 _totalSupply,
+        string memory _name,
+        string memory _symbol
+    ) public {
+        require(!initialized, "TOKEN_INITIALIZED");
+        initialized = true;
+        totalSupply = _totalSupply;
+        balances[_creator] = _totalSupply;
+        name = _name;
+        symbol = _symbol;
+        emit Transfer(address(0), _creator, _totalSupply);
+    }
+
+    function decimals() public view returns (uint8) {
+        return 18;
+    }
+
+    function transfer(address to, uint256 amount) public returns (bool) {
+        _transfer(msg.sender, to, amount);
+        return true;
+    }
+
+    function balanceOf(address owner) public view returns (uint256 balance) {
+        return balances[owner];
+    }
+
+    function transferFrom(
+        address from,
+        address to,
+        uint256 amount
+    ) public returns (bool) {
+        require(to != address(0), "TO_ADDRESS_IS_EMPTY");
+        require(amount <= balances[from], "BALANCE_NOT_ENOUGH");
+        require(amount <= allowed[from][msg.sender], "ALLOWANCE_NOT_ENOUGH");
+
+        balances[from] = balances[from].sub(amount);
+        balances[to] = balances[to].add(amount);
+        allowed[from][msg.sender] = allowed[from][msg.sender].sub(amount);
+        emit Transfer(from, to, amount);
+        return true;
+    }
+
+    function approve(address spender, uint256 amount) public returns (bool) {
+        allowed[msg.sender][spender] = amount;
+        emit Approval(msg.sender, spender, amount);
+        return true;
+    }
+
+    function allowance(address owner, address spender) public view returns (uint256) {
+        return allowed[owner][spender];
+    }
+
+    function _transfer(address sender, address recipient, uint256 amount) internal {
+        require(sender != address(0), "FROM_ADDRESS_IS_EMPTY");
+        require(recipient != address(0), "TO_ADDRESS_IS_EMPTY");
+        require(amount <= balances[sender], "BALANCE_NOT_ENOUGH");
+
+        balances[sender] = balances[sender].sub(amount);
+        balances[recipient] = balances[recipient].add(amount);
+
+        emit Transfer(sender, recipient, amount);
+    }
+
+}

contracts/external/ERC20/InitializableMintableERC20.sol

@@ -18,7 +18,7 @@ contract InitializableMintableERC20 is InitializableOwnable {
     string public symbol;
     uint256 public totalSupply;
 
-    mapping(address => uint256) balances;
+    mapping(address => uint256) internal balances;
     mapping(address => mapping(address => uint256)) internal allowed;
 
     event Transfer(address indexed from, address indexed to, uint256 amount);
@@ -42,7 +42,7 @@ contract InitializableMintableERC20 is InitializableOwnable {
         emit Transfer(address(0), _creator, _initSupply);
     }
 
-    function transfer(address to, uint256 amount) public returns (bool) {
+    function transfer(address to, uint256 amount) public virtual returns (bool) {
         require(to != address(0), "TO_ADDRESS_IS_EMPTY");
         require(amount <= balances[msg.sender], "BALANCE_NOT_ENOUGH");
 
@@ -60,7 +60,7 @@ contract InitializableMintableERC20 is InitializableOwnable {
         address from,
         address to,
         uint256 amount
-    ) public returns (bool) {
+    ) public virtual returns (bool) {
         require(to != address(0), "TO_ADDRESS_IS_EMPTY");
         require(amount <= balances[from], "BALANCE_NOT_ENOUGH");
         require(amount <= allowed[from][msg.sender], "ALLOWANCE_NOT_ENOUGH");
@@ -72,7 +72,7 @@ contract InitializableMintableERC20 is InitializableOwnable {
         return true;
     }
 
-    function approve(address spender, uint256 amount) public returns (bool) {
+    function approve(address spender, uint256 amount) public virtual returns (bool) {
         allowed[msg.sender][spender] = amount;
         emit Approval(msg.sender, spender, amount);
         return true;
@@ -83,13 +83,21 @@ contract InitializableMintableERC20 is InitializableOwnable {
     }
 
     function mint(address user, uint256 value) external onlyOwner {
+        _mint(user, value);
+    }
+
+    function burn(address user, uint256 value) external onlyOwner {
+        _burn(user, value);
+    }
+
+    function _mint(address user, uint256 value) internal {
         balances[user] = balances[user].add(value);
         totalSupply = totalSupply.add(value);
         emit Mint(user, value);
         emit Transfer(address(0), user, value);
     }
 
-    function burn(address user, uint256 value) external onlyOwner {
+    function _burn(address user, uint256 value) internal {
         balances[user] = balances[user].sub(value);
         totalSupply = totalSupply.sub(value);
         emit Burn(user, value);