## Summary
`where`, `sort by`, `distinct` and the Advanced Search property test now compile through expression trees instead of the hand-rolled IL in `Emitter.cs`. The emitter and its three `Reflection.Emit` compilers were RunUO-era code from before expression trees existed; they were the only way to avoid per-object reflection at the time, and they are not any more.
Net: ~1,900 lines of IL bookkeeping deleted, one comparison engine instead of two, faster per object, cheaper to compile, collectible, and `Nullable<T>` properties work.
## Why
- **Bugs hid in the IL.** Equality on a type with value semantics but no `IComparable` (`TextDefinition`) was a raw `ceq`, so `where Message = 1060847` never matched. A chained binding (`Message.Number`) dereferenced every link unguarded, so the first swept object with a null intermediate killed the sweep with an NRE. A constant narrower or unsigned than `int` threw before compiling. A struct with no `CompareTo` reached `ceq` on two unboxed values, which is invalid IL. Every dynamic assembly was `Run`, so each `[global where` grew the process for good.
- **Advanced Search had its own engine.** Per entity and per leaf it re-split the expression, scanned the runtime type's properties by name, read the value by reflection, re-parsed the right-hand side and dispatched on type through ~300 lines of `CompareValues`. Same job, second implementation, second set of bugs.
## What changed
- `ICondition.Compile(MethodEmitter)` becomes `ICondition.Build(ParameterExpression)` returning an `Expression`. `ConditionalCompiler` assembles a `Func<object, bool>`, `SortCompiler` a `Comparison<T>`, `DistinctCompiler` both comparer interfaces over one lambda. The parsed constant is an `Expression.Constant`, so the generated type, its constructor and the per-condition field for non-primitive constants disappear with `PropertyValue`.
- `PropertyExpressions` holds the shared pieces: the chain walk with its null-intermediate guard, `CompareTo` resolution with the old null ordering, the integral/enum operator path, and constant parsing.
- `BaseExtension.Optimize` loses its `ref AssemblyEmitter` parameter. An out-of-tree extension that overrides `Optimize` needs to drop it.
- Advanced Search keeps its grammar (`~` negates, `@` is AND, `|` is OR and binds looser, string `>` is "starts with") and translates each leaf into the same conditions, compiled once per declaring type per search and memoized across the workers. Float and double keep their typed-precision tolerance through a small `EpsilonCondition` in the Advanced Search folder.
## Semantics preserved
- Equality on a non-comparable reference type is `object.Equals`, never reference identity. A non-comparable struct boxes into the same call.
- A null intermediate in a chained binding is no match, and stays no match under negation. Sort and distinct read it as `default(T)`.
- Unsigned relational compares stay unsigned; integral primitives and enums use the operator directly, nothing widens to a signed type. `float`, `double`, `decimal`, `string` and structs still go through the type's own `CompareTo`, so `string` equality stays culture-sensitive exactly as before.
- Only `==` and `!=` are valid for non-comparable types; a relational operator still throws at build time.
- `TypeCondition` is still first and still null-checks the cast target.
## Behavior changes
- **`Nullable<T>` works**, with C# lifted semantics in `where`: two nulls are equal, a null and a value are unequal, a null satisfies no relation. Sort keeps a total order with unset values at one end. A null *reference* keeps the ordering it had.
- **Advanced Search**: a leaf that cannot be parsed or resolved is no match even under `~` (it used to negate the failure and match every entity); `null` is the null value for equality on strings, nullables and reference types, as in `where`; dotted names walk into a property; static properties are no longer searchable.
## Measurements
`where`, from the handoff (Debug test host, single condition, ratios not absolutes):
| Approach | ns/object | Compile | Collectible | LOC |
|---|---:|---:|---|---:|
| `AssemblyBuilder` + IL (before) | 20.5 | 0.311 ms | no (`Run`) | ~1,916 |
| Expression trees (after) | ~12 | 0.187 ms warm | yes | ~600 |
Advanced Search, Release, one `SkillTeleporter`, 2M evaluations per leaf:
| Leaf | Before | After |
|---|---:|---:|
| `Hue=5` | 137 ns | 20 ns |
| `Name~~gate` | 121 ns | 39 ns |
| `Skill=Magery` | 116 ns | 21 ns |
| `Weight>0.5` | 122 ns | 28 ns |
Plus 0.5 to 2 ms to compile each declaring type a search meets (12 ms for the first compile in the process). All of it runs on the search workers; nothing new touches the loop.
## Also fixed: Advanced Search map filters
Found while testing the property test in game. The map boxes are independent checkboxes, but the worker applied each ticked map as "must be on this map", so ticking two or more (all maps and Internal, say) rejected every entity before any other filter ran. Present since #1649; the default of Felucca alone never showed it. An entity now passes when its map is any of the ticked ones, with none ticked meaning no map constraint. Pinned by a worker test.
## Test plan
- [x] `UOContent.Tests`: 862 passed, 0 failed
- [x] `Server.Tests`: 869 passed, 0 failed
- [x] Every commit builds and its tests pass on its own (bisectable)
- [ ] In game: `[global where`, `[area where`, `[condition`, `sort by`, `distinct`, Advanced Search property test
### Summary
Updates all calls to container.EnumerateItems() to properly dispose of the underlying PooledRefQueue so that we are properly recycling pooled arrays.
Fix [add command failing with ambiguous type names + refactor for performance
### Problem
[add blight would fail with "No type with that name was found" because multiple types contain "blight" (e.g., Server.Items.Blight, Server.Ethics.Evil.Blight, Server.Items.BlightGrippedLongbow, Server.Items.QuiverOfBlight). The old code only succeeded when exactly one type matched the search regardless of constructability and inheriting Mobi les/Items.
### Solution
Exact match takes priority: If a type's name exactly equals the search string (case-insensitive), use it directly. Otherwise, show the AddGump with all partial matches.
- [add blight → Creates Blight (exact name match)
- [add bligh → Shows gump with Blight, BlightGrippedLongbow, etc.
### Refactoring
- CommandEventArgs context: Added GetContext<T>/SetContext<T> to pass resolved type through the command chain without method signature changes
- Removed TrySetupTarget duplication: Validation now happens only in ValidateArgs, eliminating redundant code paths
- Split type matching:
- ExactMatch(string) → Returns Type for exact name match (used by [add)
- MatchEmptyCtor(string) → Returns ConstructorInfo[] for gump display (empty-callable constructors only)
### Memory & Performance Improvements
| Optimization | Benefit |
|-------------------------------|----------------------------------------------------------------------------------------------|
| _mobileItemTypes cache | Filters Mobile/Item types once per assembly, reused on all subsequent searches |
| ReadOnlySpan<string> for args | Avoids string[] heap allocations when slicing arguments |
| ValueStringBuilder | Stack-allocated string building, avoids StringBuilder heap allocation |
| Single type resolution | Type resolved once in ValidateArgs, passed via context to Execute (was resolved 2-3x before) |
### Summary
- Fixes `[AdvancedSearch` being accessible by players 😱
- Adds `[GenCommands` to generate the same commands html page on https://muo.gg/commands.
- Fixes `[helpinfo` so all commands properly show up!
> [!WARNING]
> ### Developer Warning:
> Commands must now be registered in the `Configure` bootup phase.
> If a command is not registered early enough, it may not be available to systems like [helpinfo
> that cache their information.
> [!NOTE]
> ### Developer Note:
> Various commands related to generating content have been changed to _Developer_ and above access level.
### Screenshots
<img width="673" alt="image" src="https://github.com/modernuo/ModernUO/assets/3953314/b105b5c9-5eb4-4ace-93ff-1bfb31e7132f">
<img width="547" alt="image" src="https://github.com/modernuo/ModernUO/assets/3953314/e97487e8-47a5-4aa7-89cc-9fe3deda584d">
## Breaking Changes
* The Firewall and IP Limiter have been rewritten. Please read the notes carefully!
* `TcpServer.Instances` moved back to `NetState.Instances` - sorry - it was stupid to move it to begin with.
> [!Note]
> Sockets that fail the IP Limiter or Firewall will be immediately and forcibly disconnected.
> This means they will be stuck at "Verifying account..." if it was a real client.
### Summary
- Removes firewall wildcard support.
- Removes `AccessRestrictions`.
- Moves Firewall/IPLimiter to the core.
- Moves `TcpServer` to its own thread.
- Removes the `SocketConnect` and `SocketDisconnect` event sinks.
- Moves `Instances` back to `NetState.Instances`.
- Fixes a long standing bug with bad handling of duplicate listener addresses.
#### Firewall
The firewall has been completely rewritten. There is now an "Admin Firewall" which saves to the config file. Secondarily, there is an internal firewall used exclusively by the TcpServer while processing sockets. The Admin firewall mirrors it's additions/deletions to the internal firewall by adding requests to a queue.
> [!IMPORTANT]
> **Wildcard firewall entries, such as `X`, `*`, `?` are not allowed.**
> **Ranges in between IP classes or sextets are not allowed.**
> **Please make sure to use one of the following:**
> * IP Address - `192.168.1.1`
> * CIDR - `192.168.1.0/24`
> * Range - `192.168.1.1-192.168.1.100`
#### IP Limiter
The IP Limiter has been completely rewritten. The available configurations are:
```json
"ipLimiter.enable": "True",
"ipLimiter.maxConnectionsPerIP": 10,
"ipLimiter.clearConnectionAttemptsDuration": "00:00:00:10",
"ipLimiter.clearThrottledDuration": "00:00:02:00",
```
The IP Limiter is set up to prevent spamming connections from the same IP. Every time an IP connects, it is added to a connection list. After 10 attempts, the IP is added to the throttle list. To keep the system fast, the connection list is entirely wiped every 10 seconds, and the throttle list is entirely wiped every 2 minutes.
## BREAKING CHANGE
- Deletes `map.GetObjectsInRange` and `map.GetObejctsInBounds`
### Notes
Developers are expected to enumerate mobiles and items separately now using `map.GetMobilesInRange` and `map.GetItemsInRange`. This helps keep the code streamlined so we don't have to maintain multiple copies of ref struct enumerators that do the same thing.
### Fixes
- [X] Fixes bug with planks closing
- [X] Fixes issue with iterating items/mobiles from a null map
### Summary
Container enumeration is in dire need of optimization. Thanks to @stefanomerotta for initiating this work with PR #1443. This PR handles a small part of what Stefan started. Also included are some bug fixes.
### Method Signatures
```cs
// Use with foreach without moving/deleting items
FindItemsByTypeEnumerator<T> FindItemsByType<T>(bool recurse = true, Predicate<T> predicate = null)
// Use with foreach when moving/deleting items
QueuedItemsEnumerator<T> EnumerateItemsByType<T>(bool recurse = true, Predicate<T> predicate = null)
// Use when iterating multiple times or queuing
PooledRefQueue<T> QueueItemsByType<T>(bool recurse = true, Predicate<T> predicate = null)
// Use when iterating multiples times or manipulating elements without traversing
PooledRefList<T> ListItemsByType<T>(bool recurse = true, Predicate<T> predicate = null)
```
* `FindItemsByType<T>` has changed from returning `List<T>` to `FindItemsByTypeEnumerator<T>` - This method is not safe to use in situations where an item may get consumed, deleted, or moved.
* `EnumerateItemsByType<T>` was added as a safe way to iterate and manipulate items.
* **Note**: EnumerateItemsByType will _completely traverse the container_ before iteration starts because it uses `QueueItemsByType` under the hood.
* `QueueItemsByType<T>` and `ListItemsByType<T>` was added to return a queue or list of items to iterate multiple times and manipulate the items. This isn't the most efficient since it uses a predicate and can result in 2 or 3 total iterations unnecessarily.
### Bug Fixes
- [X] Fishing had an error in the random check that may have caused slight bias.
- [X] Fixes some issues with the type caching
- [X] Changes type check default to ignore case
- [X] Splits out type caching of insensitive and sensitive lists. This means less stuff to iterate through when checking a type against the string.
- [X] Adds an ArrayEnumerator, mostly for reference purposes (copy/paste as needed)
- [X] Removes some string allocations (e.g. split)
- [X] Optimizes some collections
- [X] Converts insensitive to extension methods of built-ins.
- [X] Adds ordinal (case sensitive) string helpers
- [X] Fixes conditionals for in-game commands so they use Ordinal comparisons.
- [X] Replaces ToLower.Contains with InsensitiveContains
- [X] Adds ValueStringBuilder
- [X] Implements ValueStringBuilder in a few places where it makes sense
- [X] Removes the redundant Wrap function and replaces it with an optimized version
- [X] Fixes list conversions in Utility
Closes#351
Bumps release version
- [X] Fixes several bugs
- [X] Updates more ordinal issues
- [X] Cleans up the code a bit
- [X] Turns classes static that should have been
- [X] Changes TcpServer.Instances to a HashSet
Bumps release version
