add permissionless lending features

academy/lending-protocol/contracts/GlobalLedger.sol

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.28;
+
+import "@nilfoundation/smart-contracts/contracts/Nil.sol";
+
+// @title GlobalLedger
+// @dev Tracks deposits, loans, and repayments across LendingPool contracts
+contract GlobalLedger {
+    struct Deposit {
+        uint256 amount;
+        bool exists;
+    }
+
+    struct Loan {
+        uint256 amount;
+        bool exists;
+    }
+
+    mapping(address => mapping(TokenId => Deposit)) public deposits;
+    mapping(address => mapping(TokenId => Loan)) public loans;
+
+    event DepositRecorded(address indexed user, TokenId token, uint256 amount);
+    event LoanRecorded(address indexed user, TokenId token, uint256 amount);
+    event LoanRepaid(address indexed user, TokenId token, uint256 amount);
+
+    /// @notice Record a deposit from LendingPool
+    function recordDeposit(address user, TokenId token, uint256 amount) external payable {
+        require(amount > 0, "Invalid deposit amount");
+
+        if (!deposits[user][token].exists) {
+            deposits[user][token] = Deposit(amount, true);
+        } else {
+            deposits[user][token].amount += amount;
+        }
+
+        emit DepositRecorded(user, token, amount);
+    }
+
+    /// @notice Get user's deposit for a specific token
+    function getDeposit(address user, TokenId token) external view returns (uint256) {
+        return deposits[user][token].amount;
+    }
+
+    /// @notice Record a loan taken from a LendingPool
+    function recordLoan(address user, TokenId token, uint256 amount) external payable {
+        require(amount > 0, "Invalid loan amount");
+
+        if (!loans[user][token].exists) {
+            loans[user][token] = Loan(amount, true);
+        } else {
+            loans[user][token].amount += amount;
+        }
+
+        emit LoanRecorded(user, token, amount);
+    }
+
+    /// @notice Get user's outstanding loan for a specific token
+    function getLoan(address user, TokenId token) external view returns (uint256) {
+        return loans[user][token].amount;
+    }
+
+    /// @notice Record loan repayment and reduce outstanding balance
+    function repayLoan(address user, TokenId token, uint256 amount) external payable {
+        require(amount > 0, "Invalid repayment amount");
+        require(loans[user][token].exists, "No active loan");
+
+        if (loans[user][token].amount <= amount) {
+            delete loans[user][token];
+        } else {
+            loans[user][token].amount -= amount;
+        }
+
+        emit LoanRepaid(user, token, amount);
+    }
+}