feat: implement ratio lender

src/enforcers/AstariaV1RatioLenderEnforcer.sol

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+//  SPDX-License-Identifier: Apache-2.0
+//   █████╗ ███████╗████████╗ █████╗ ██████╗ ██╗ █████╗     ██╗   ██╗ ██╗
+//  ██╔══██╗██╔════╝╚══██╔══╝██╔══██╗██╔══██╗██║██╔══██╗    ██║   ██║███║
+//  ███████║███████╗   ██║   ███████║██████╔╝██║███████║    ██║   ██║╚██║
+//  ██╔══██║╚════██║   ██║   ██╔══██║██╔══██╗██║██╔══██║    ╚██╗ ██╔╝ ██║
+//  ██║  ██║███████║   ██║   ██║  ██║██║  ██║██║██║  ██║     ╚████╔╝  ██║
+//  ╚═╝  ╚═╝╚══════╝   ╚═╝   ╚═╝  ╚═╝╚═╝  ╚═╝╚═╝╚═╝  ╚═╝      ╚═══╝   ╚═╝
+//
+//  Astaria v1 Lending
+//  Built on Starport https://github.com/astariaXYZ/starport
+//  Designed with love by Astaria Labs, Inc
+
+pragma solidity ^0.8.17;
+
+import {Starport} from "starport-core/Starport.sol";
+import {CaveatEnforcer} from "starport-core/enforcers/CaveatEnforcer.sol";
+import {BasePricing} from "v1-core/pricing/BasePricing.sol";
+import {AdditionalTransfer} from "starport-core/lib/StarportLib.sol";
+
+import {AstariaV1Lib} from "v1-core/lib/AstariaV1Lib.sol";
+
+import {ItemType} from "seaport-types/src/lib/ConsiderationEnums.sol";
+import {SpentItem} from "seaport-types/src/lib/ConsiderationStructs.sol";
+import {FixedPointMathLib} from "solady/src/utils/FixedPointMathLib.sol";
+
+contract AstariaV1RatioLenderEnforcer is CaveatEnforcer {
+    using FixedPointMathLib for uint256;
+    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
+    /*                       CUSTOM ERRORS                        */
+    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/
+
+    error InvalidLoanTerms();
+    error InvalidAdditionalTransfer();
+    error LoanRateLessThanCaveatRate();
+    error DebtBundlesNotSupported();
+    error CollateralBundlesNotSupported();
+    error DebtAmountExceedsDebtMax(uint256 maxDebt, uint256 loanAmount);
+    error BelowMinCollateralAmount();
+    error MaxDebtOrCollateralToDebtRatioZero();
+
+    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
+    /*                  CONSTANTS AND IMMUTABLES                  */
+    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/
+
+    uint256 constant MAX_DURATION = uint256(3 * 365 days); // 3 years
+
+    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
+    /*                          STRUCTS                           */
+    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/
+
+    struct Details {
+        bool matchIdentifier;
+        uint256 minCollateralAmount;
+        uint256 collateralToDebtRatio; // WAD
+        Starport.Loan loan;
+    }
+
+    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
+    /*                     PUBLIC FUNCTIONS                       */
+    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/
+
+    /// @notice Validates a loan against a caveat, w/ a minimum rate and a maximum amount
+    /// @dev Bundle support is not implemented, and will revert
+    /// @dev matchIdentifier = false will allow the loan to have a different identifier than the caveat
+    /// @dev Only viable for use w/ AstariaV1Pricing and AstariaV1Status modules
+    function validate(
+        AdditionalTransfer[] calldata additionalTransfers,
+        Starport.Loan calldata loan,
+        bytes calldata caveatData
+    ) public view virtual override returns (bytes4 selector) {
+        if (loan.debt.length > 1) {
+            revert DebtBundlesNotSupported();
+        }
+
+        if (loan.collateral.length > 1) {
+            revert CollateralBundlesNotSupported();
+        }
+
+        Starport.Terms calldata loanTerms = loan.terms;
+        uint256 loanRate = abi.decode(loanTerms.pricingData, (BasePricing.Details)).rate;
+        uint256 loanAmount = loan.debt[0].amount;
+        AstariaV1Lib.validateCompoundInterest(
+            loanAmount,
+            loanRate,
+            AstariaV1Lib.getBaseRecallMax(loanTerms.statusData),
+            AstariaV1Lib.getBasePricingDecimals(loanTerms.pricingData)
+        );
+
+        Details memory details = abi.decode(caveatData, (Details));
+
+        uint256 collateralAmount = loan.collateral[0].amount;
+        if (details.minCollateralAmount > collateralAmount) {
+            revert BelowMinCollateralAmount();
+        }
+
+        uint256 maxDebt = (collateralAmount * details.collateralToDebtRatio) / AstariaV1Lib.WAD;
+        if (loanAmount > maxDebt) {
+            revert DebtAmountExceedsDebtMax(maxDebt, loanAmount);
+        }
+
+        if (maxDebt == 0) {
+            revert MaxDebtOrCollateralToDebtRatioZero();
+        }
+
+        bytes memory caveatPricingData = details.loan.terms.pricingData;
+        if (loanRate < AstariaV1Lib.getBasePricingRate(caveatPricingData)) {
+            // Loan rate is less than the caveatDebt rate
+            revert LoanRateLessThanCaveatRate();
+        }
+
+        // Update the caveat loan rate
+        AstariaV1Lib.setBasePricingRate(caveatPricingData, loanRate);
+        Starport.Loan memory caveatLoan = details.loan;
+
+        // Update the caveat loan amount
+        caveatLoan.debt[0].amount = loanAmount;
+
+        if (!details.matchIdentifier) {
+            // Update the caveat loan identifier
+            uint256 i = 0;
+            for (; i < caveatLoan.collateral.length;) {
+                caveatLoan.collateral[i].identifier = loan.collateral[i].identifier;
+                unchecked {
+                    ++i;
+                }
+            }
+        }
+
+        // Hash and match w/ expected borrower
+        _validate(additionalTransfers, loan, caveatLoan);
+        selector = CaveatEnforcer.validate.selector;
+    }
+
+    function _validate(
+        AdditionalTransfer[] calldata additionalTransfers,
+        Starport.Loan calldata loan,
+        Starport.Loan memory caveatLoan
+    ) internal pure {
+        caveatLoan.borrower = loan.borrower;
+        caveatLoan.originator = loan.originator;
+
+        if (keccak256(abi.encode(loan)) != keccak256(abi.encode(caveatLoan))) {
+            revert InvalidLoanTerms();
+        }
+
+        if (additionalTransfers.length > 0) {
+            uint256 i = 0;
+            for (; i < additionalTransfers.length;) {
+                if (additionalTransfers[i].from == loan.issuer) revert InvalidAdditionalTransfer();
+                unchecked {
+                    ++i;
+                }
+            }
+        }
+    }
+}