Add BankHub contract

src/BankHub.sol

@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity 0.8.28;
+
+import {IDRCoin} from "./IDRCoin.sol";
+import {UUPSUpgradeable} from "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
+
+contract BankHub is UUPSUpgradeable {
+    // constants
+    uint32 public constant MIN_INTEREST_RATE = 5;
+
+    // state variables
+    address public owner;
+    IDRCoin public idrcoin;
+
+    // mappings
+    mapping(address => bool) public whiteListed;
+    mapping(address => bool) public approved;
+    mapping(address => uint32) public interestRate;
+    mapping(address => uint256) public depositTimestamp;
+    mapping(address => uint256) public savingAmount;
+
+    constructor() {
+        // initialize
+        _disableInitializers();
+    }
+
+    function initialize() public initializer {
+        owner = msg.sender;
+    }
+
+    // user function
+    function deposit(uint256 _amount, address _toBank) public {
+        require(whiteListed[_toBank], "bank not whitelisted");
+        require(approved[_toBank], "bank not approved");
+        require(idrcoin.balanceOf(msg.sender) >= _amount, "insufficient balance");
+
+        // transfer user IDRCoin to bank
+        idrcoin.transferFrom(msg.sender, _toBank, _amount);
+        
+        // update user deposit timestamp and saving amount
+        depositTimestamp[msg.sender] = block.timestamp;
+        savingAmount[msg.sender] += _amount;
+    }
+
+    function withdraw(uint256 _amount, address _fromBank) public {
+        require(whiteListed[_fromBank], "bank not whitelisted");
+        require(savingAmount[msg.sender] >= _amount, "insufficient balance");
+
+        // calculate interest
+        uint256 timePassed = block.timestamp - depositTimestamp[msg.sender];
+        uint256 interest = (_amount * timePassed * interestRate[msg.sender]) /
+            100;
+
+        // transfer amount + interest to user
+        idrcoin.transferFrom(
+            address(_fromBank),
+            msg.sender,
+            _amount + interest
+        );
+    }
+
+    // bank function 
+
+    // this function is MANDATORY for bank to call before any deposit can be made
+    function approve() public {
+        require(whiteListed[msg.sender], "bank not whitelisted");
+        idrcoin.approve(address(this), idrcoin.balanceOf(msg.sender));
+        approved[msg.sender] = true;
+
+        // send IDRCoin to bank as reserve for operation
+        idrcoin.transferFrom(owner, msg.sender, 10 ether);
+    }
+
+    // admin function
+    function changeOwner(address _newOwner) public {
+        require(msg.sender == owner, "only owner can change owner");
+        owner = _newOwner;
+    }
+
+    // whitelist partner bank
+    function whiteList(address _bank) public {
+        require(msg.sender == owner, "only owner can whitelist");
+        whiteListed[_bank] = true;
+        interestRate[_bank] = MIN_INTEREST_RATE;
+    }
+
+    // revoke whitelist from partner bank
+    function revokeWhiteList(address _bank) public {
+        require(msg.sender == owner, "only owner can revoke whitelist");
+        if (idrcoin.balanceOf(_bank) > 0) {
+            idrcoin.transferFrom(_bank, owner, idrcoin.balanceOf(_bank));
+        }
+    }
+
+    // Implementation of the required UUPSUpgradeable function
+    function _authorizeUpgrade(address newImplementation) internal override {
+        require(msg.sender == owner, "only owner can authorize upgrades");
+    }
+}