Very simple deposit/withdraw logic and share accounting

.solhint.json

@@ -3,6 +3,7 @@
   "rules": {
     "func-name-mixedcase": "off",
     "var-name-mixedcase": "off",
+    "immutable-vars-naming": "off",
     "no-unused-vars": "error"
   }
 }

CONTRIBUTING.md

@@ -0,0 +1,12 @@
+# Contributing to Everlong
+
+## Bugfixes & issues
+
+If you find a bug, we recommend that you post an [issue](https://github.com/delvtech/everlong/issues) to allow for discussion before creating a pull request.
+
+## Release steps
+
+1. [ ] Double-check that the version in `contracts/libraries/Constants.sol` matches the version to be tagged. If it doesn't, open a PR to update the version before tagging.
+2. [ ] Tag the release with `git tag vX.Y.Z`.
+3. [ ] Push the release to Github with `git push --tags`
+4. [ ] Go to the `releases` tab in Github and add the new tag as a release. Click the "Generate Release Notes" button to generate release notes.

contracts/Everlong.sol

@@ -1,9 +1,13 @@
 // SPDX-License-Identifier: Apache-2.0
-pragma solidity 0.8.20;
+pragma solidity 0.8.22;
 
+import { IHyperdrive } from "hyperdrive/contracts/src/interfaces/IHyperdrive.sol";
+import { IEverlong } from "./interfaces/IEverlong.sol";
 import { EverlongAdmin } from "./internal/EverlongAdmin.sol";
 import { EverlongBase } from "./internal/EverlongBase.sol";
+import { EverlongERC4626 } from "./internal/EverlongERC4626.sol";
 import { EverlongPositions } from "./internal/EverlongPositions.sol";
+import { EVERLONG_KIND, EVERLONG_VERSION } from "./libraries/Constants.sol";
 
 ///           ,---..-.   .-.,---.  ,---.   ,-.    .---.  .-. .-.  ,--,
 ///           | .-' \ \ / / | .-'  | .-.\  | |   / .-. ) |  \| |.' .'
@@ -62,16 +66,64 @@ import { EverlongPositions } from "./internal/EverlongPositions.sol";
 /// @custom:disclaimer The language used in this code is for coding convenience
 ///                    only, and is not intended to, and does not, have any
 ///                    particular legal or regulatory significance.
-contract Everlong is EverlongAdmin, EverlongPositions {
-    /// @notice Initial configuration paramters for Everlong.
-    /// @param _name Name of the ERC20 token managed by Everlong.
-    /// @param _symbol Symbol of the ERC20 token managed by Everlong.
-    /// @param __hyperdrive Address of the Hyperdrive instance wrapped by Everlong.
-    /// @param __asBase Whether to use Hyperdrive's base token for bond purchases.
+contract Everlong is EverlongAdmin, EverlongPositions, EverlongERC4626 {
+    // ╭─────────────────────────────────────────────────────────╮
+    // │ Constructor                                             │
+    // ╰─────────────────────────────────────────────────────────╯
+
+    /// @notice Initial configuration paramters for EverlongERC4626.
+    /// @param __name Name of the ERC20 token managed by Everlong.
+    /// @param __symbol Symbol of the ERC20 token managed by Everlong.
+    /// @param __hyperdrive Address of the Hyperdrive instance.
+    /// @param __asBase Whether to use the base or shares token from Hyperdrive.
     constructor(
-        string memory _name,
-        string memory _symbol,
+        string memory __name,
+        string memory __symbol,
         address __hyperdrive,
         bool __asBase
-    ) EverlongBase(_name, _symbol, __hyperdrive, __asBase) {}
+    ) {
+        // Store constructor parameters.
+        _name = __name;
+        _symbol = __symbol;
+        _hyperdrive = __hyperdrive;
+        _asBase = __asBase;
+        _asset = __asBase
+            ? IHyperdrive(__hyperdrive).baseToken()
+            : IHyperdrive(__hyperdrive).vaultSharesToken();
+
+        // Set the admin to the contract deployer.
+        _admin = msg.sender;
+
+        // Attempt to retrieve the decimals from the {_asset} contract.
+        // If it does not implement `decimals() (uint256)`, use the default.
+        (bool success, uint8 result) = _tryGetAssetDecimals(_asset);
+        _decimals = success ? result : _DEFAULT_UNDERLYING_DECIMALS;
+    }
+
+    // ╭─────────────────────────────────────────────────────────╮
+    // │ Getters                                                 │
+    // ╰─────────────────────────────────────────────────────────╯
+
+    /// @notice Gets the Everlong instance's kind.
+    /// @return The Everlong instance's kind.
+    function kind() external view returns (string memory) {
+        return EVERLONG_KIND;
+    }
+
+    /// @notice Gets the Everlong instance's version.
+    /// @return The Everlong instance's version.
+    function version() external view returns (string memory) {
+        return EVERLONG_VERSION;
+    }
+
+    /// @notice Gets the address of the underlying Hyperdrive Instance.
+    function hyperdrive() external view returns (address) {
+        return _hyperdrive;
+    }
+
+    /// @notice Gets whether Everlong uses Hyperdrive's base token to
+    ///         transact.
+    function asBase() external view returns (bool) {
+        return _asBase;
+    }
 }

contracts/interfaces/IEverlong.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: Apache-2.0
-pragma solidity 0.8.20;
+pragma solidity ^0.8.20;
 
 import { IERC4626 } from "openzeppelin/interfaces/IERC4626.sol";
 import { IEverlongAdmin } from "./IEverlongAdmin.sol";
@@ -31,12 +31,12 @@ interface IEverlong is
     // │ Errors                                                  │
     // ╰─────────────────────────────────────────────────────────╯
 
-    // Admin //
+    // ── Admin ──────────────────────────────────────────────────
 
     /// @notice Thrown when caller is not the admin.
     error Unauthorized();
 
-    // Positions //
+    // ── Positions ──────────────────────────────────────────────
 
     /// @notice Thrown when attempting to insert a position with
     ///         a `maturityTime` sooner than the most recent position's.
@@ -45,4 +45,8 @@ interface IEverlong is
     /// @notice Thrown when attempting to close a position with
     ///         a `bondAmount` greater than that contained by the position.
     error InconsistentPositionBondAmount();
+
+    /// @notice Thrown when a target idle amount is too high to be reached
+    ///         even after closing all positions.
+    error TargetIdleTooHigh();
 }

contracts/interfaces/IEverlongAdmin.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: Apache-2.0
-pragma solidity 0.8.20;
+pragma solidity ^0.8.20;
 
 interface IEverlongAdmin {
     // ╭─────────────────────────────────────────────────────────╮

contracts/interfaces/IEverlongEvents.sol

@@ -1,13 +1,13 @@
 // SPDX-License-Identifier: Apache-2.0
-pragma solidity 0.8.20;
+pragma solidity ^0.8.20;
 
 interface IEverlongEvents {
-    // Admin //
+    // ── Admin ──────────────────────────────────────────────────
 
     /// @notice Emitted when admin is transferred.
     event AdminUpdated(address indexed admin);
 
-    // Positions //
+    // ── Positions ──────────────────────────────────────────────
 
     /// @notice Emitted when a new position is added to the bond portfolio.
     /// @dev This event will only be emitted with new `maturityTime`s in the portfolio.

contracts/interfaces/IEverlongPositions.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: Apache-2.0
-pragma solidity 0.8.20;
+pragma solidity ^0.8.20;
 
 import { Position } from "../types/Position.sol";
 

contracts/internal/EverlongAdmin.sol

@@ -1,9 +1,9 @@
 // SPDX-License-Identifier: Apache-2.0
-pragma solidity 0.8.20;
+pragma solidity 0.8.22;
 
 import { IEverlong } from "../interfaces/IEverlong.sol";
 import { IEverlongAdmin } from "../interfaces/IEverlongAdmin.sol";
-import { EverlongBase } from "./EverlongBase.sol";
+import { EverlongBase } from "../internal/EverlongBase.sol";
 
 /// @author DELV
 /// @title EverlongAdmin

contracts/internal/EverlongBase.sol

@@ -1,12 +1,9 @@
 // SPDX-License-Identifier: Apache-2.0
-pragma solidity 0.8.20;
+pragma solidity 0.8.22;
 
-import { IHyperdrive } from "hyperdrive/contracts/src/interfaces/IHyperdrive.sol";
 import { DoubleEndedQueue } from "openzeppelin/utils/structs/DoubleEndedQueue.sol";
-import { IERC20 } from "openzeppelin/interfaces/IERC20.sol";
 import { IEverlongEvents } from "../interfaces/IEverlongEvents.sol";
-import { EVERLONG_KIND, EVERLONG_VERSION } from "../libraries/Constants.sol";
-import { EverlongERC4626 } from "./EverlongERC4626.sol";
+import { EverlongStorage } from "./EverlongStorage.sol";
 
 // TODO: Reassess whether centralized configuration management makes sense.
 //       https://github.com/delvtech/everlong/pull/2#discussion_r1703799747
@@ -16,79 +13,21 @@ import { EverlongERC4626 } from "./EverlongERC4626.sol";
 /// @custom:disclaimer The language used in this code is for coding convenience
 ///                    only, and is not intended to, and does not, have any
 ///                    particular legal or regulatory significance.
-abstract contract EverlongBase is EverlongERC4626, IEverlongEvents {
+abstract contract EverlongBase is EverlongStorage, IEverlongEvents {
     using DoubleEndedQueue for DoubleEndedQueue.Bytes32Deque;
 
     // ╭─────────────────────────────────────────────────────────╮
-    // │ Storage                                                 │
+    // │ Stateful                                                │
     // ╰─────────────────────────────────────────────────────────╯
 
-    // Admin //
+    /// @dev Rebalances the Everlong bond portfolio if needed.
+    function _rebalance() internal virtual;
 
-    /// @dev Address of the contract admin.
-    address internal _admin;
-
-    // Hyperdrive //
-
-    /// @dev Address of the Hyperdrive instance wrapped by Everlong.
-    address public immutable hyperdrive;
-
-    /// @dev Whether to use Hyperdrive's base token to purchase bonds.
-    //          If false, use the Hyperdrive's `vaultSharesToken`.
-    bool internal immutable _asBase;
-
-    // Positions //
-
-    // TODO: Reassess using a more tailored data structure.
-    /// @dev Utility data structure to manage the position queue.
-    ///      Supports pushing and popping from both the front and back.
-    DoubleEndedQueue.Bytes32Deque internal _positions;
-
-    // ╭─────────────────────────────────────────────────────────╮
-    // │ Constructor                                             │
-    // ╰─────────────────────────────────────────────────────────╯
-
-    /// @notice Initial configuration paramters for Everlong.
-    /// @param _name Name of the ERC20 token managed by Everlong.
-    /// @param _symbol Symbol of the ERC20 token managed by Everlong.
-    /// @param _hyperdrive Address of the Hyperdrive instance wrapped by Everlong.
-    /// @param __asBase Whether to use Hyperdrive's base token for bond purchases.
-    constructor(
-        string memory _name,
-        string memory _symbol,
-        address _hyperdrive,
-        bool __asBase
-    )
-        EverlongERC4626(
-            _name,
-            _symbol,
-            __asBase
-                ? IHyperdrive(_hyperdrive).baseToken()
-                : IHyperdrive(_hyperdrive).vaultSharesToken()
-        )
-    {
-        // Store constructor parameters.
-        hyperdrive = _hyperdrive;
-        _asBase = __asBase;
-        _admin = msg.sender;
-
-        // Give 1 wei approval to make the slot "dirty".
-        IERC20(_asset).approve(_hyperdrive, 1);
-    }
-
-    // ╭─────────────────────────────────────────────────────────╮
-    // │ Getters                                                 │
-    // ╰─────────────────────────────────────────────────────────╯
-
-    /// @notice Returns the kind of the Everlong instance.
-    /// @return Everlong contract kind.
-    function kind() public view virtual returns (string memory) {
-        return EVERLONG_KIND;
-    }
-
-    /// @notice Returns the version of the Everlong instance.
-    /// @return Everlong contract version.
-    function version() public view virtual returns (string memory) {
-        return EVERLONG_VERSION;
-    }
+    /// @dev Close positions until sufficient idle liquidity is held.
+    /// @dev Reverts if the target is unreachable.
+    /// @param _target Target amount of idle liquidity to reach.
+    /// @return idle Amount of idle after the increase.
+    function _increaseIdle(
+        uint256 _target
+    ) internal virtual returns (uint256 idle);
 }