add collateral manager storage structs and packing helpers for collateral positions

Author: ademolahh

src/CollateralManager.sol

@@ -1,4 +1,13 @@
 // SPDX-License-Identifier: MIT
 pragma solidity 0.8.30;
 
-contract CollateralManager { }
+import { ICollateralManager } from "./interfaces/ICollateralManager.sol";
+import { CollateralUtils } from "./libraries/CollateralUtils.sol";
+import { SafeCastLib } from "solady/utils/SafeCastLib.sol";
+
+contract CollateralManager is ICollateralManager {
+    using SafeCastLib for uint256;
+    using CollateralUtils for CollateralStore;
+
+    mapping(address => CollateralStore) private collateral;
+}

src/interfaces/ICollateralManager.sol

@@ -1,4 +1,14 @@
 // SPDX-License-Identifier: MIT
 pragma solidity 0.8.30;
 
-interface ICollateralManager { }
+interface ICollateralManager {
+    struct CollateralStore {
+        uint256[] slot; // first 160 token | 96 amount
+        mapping(address => uint256) index;
+    }
+
+    struct CollateralPosition {
+        address token;
+        uint256 amount;
+    }
+}

src/libraries/CollateralUtils.sol

@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: SEE LICENSE IN LICENSE
+pragma solidity 0.8.30;
+
+import { ICollateralManager } from "../interfaces/ICollateralManager.sol";
+import { SafeCastLib } from "solady/utils/SafeCastLib.sol";
+
+library CollateralUtils {
+    using SafeCastLib for *;
+    uint256 constant AMOUNT_BITS = 96;
+    uint256 constant AMOUNT_MASK = (uint256(1) << AMOUNT_BITS) - 1;
+
+    function pack(address _token, uint96 _amount) internal pure returns (uint256 packed) {
+        packed = uint256(uint160(_token)) << AMOUNT_BITS | _amount;
+    }
+
+    function unpack(uint256 _packed) internal pure returns (address token, uint96 amount) {
+        token = address((_packed >> AMOUNT_BITS).toUint160());
+        amount = _packed.toUint96();
+    }
+
+    function add(ICollateralManager.CollateralStore storage _store, address _token, uint96 _amount) internal {
+        if (_store.index[_token] != 0) revert();
+        _store.slot.push(pack(_token, _amount));
+        _store.index[_token] = _store.slot.length;
+    }
+
+    function update(ICollateralManager.CollateralStore storage _store, address _token, uint96 _amount) internal {
+        uint256 idx = _store.index[_token];
+        if (idx == 0) revert();
+
+        _store.slot[idx - 1] = pack(_token, _amount);
+    }
+
+    function remove(ICollateralManager.CollateralStore storage _store, address _token) internal {
+        uint256 idx = _store.index[_token];
+        uint256 slotLength = _store.slot.length;
+
+        if (idx != slotLength) {
+            uint256 lastPack = _store.slot[slotLength - 1];
+            (address lastToken,) = unpack(lastPack);
+
+            _store.slot[idx - 1] = lastPack;
+            _store.index[lastToken] = idx;
+        }
+
+        _store.slot.pop();
+        delete _store.index[_token];
+    }
+
+    function get(ICollateralManager.CollateralStore storage _store, address _token)
+        internal
+        view
+        returns (uint96 amount)
+    {
+        uint256 idx = _store.index[_token];
+        if (idx == 0) return 0;
+        (, amount) = unpack(_store.slot[idx - 1]);
+    }
+
+    function getAll(ICollateralManager.CollateralStore storage _store)
+        internal
+        view
+        returns (ICollateralManager.CollateralPosition[] memory position)
+    {
+        uint256 length = _store.slot.length;
+        position = new ICollateralManager.CollateralPosition[](length);
+        for (uint256 i = 0; i < length; i++) {
+            (address token, uint96 amount) = unpack(_store.slot[i]);
+            position[i] = ICollateralManager.CollateralPosition({ token: token, amount: amount });
+        }
+    }
+
+    function getAllCollateralValue(
+        ICollateralManager.CollateralStore storage _store,
+        function(address) internal view returns (uint256) getTokenValueInUsd
+    ) internal view returns (uint256 value) {
+        for (uint256 i = 0; i < _store.slot.length; i++) {
+            (address token, uint96 amount) = unpack(_store.slot[i]);
+
+            value += uint256(amount) * getTokenValueInUsd(token);
+        }
+    }
+}