Game server admin API (#26880)

* Reapply "Game server api" (#26871)

This reverts commit 3aee197923.

* Rewrite 75% of the code it's good now

Content.Server/Administration/ServerApi.Utility.cs

@@ -0,0 +1,147 @@
+using System.Net;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Robust.Server.ServerStatus;
+
+namespace Content.Server.Administration;
+
+public sealed partial class ServerApi
+{
+    private void RegisterHandler(HttpMethod method, string exactPath, Func<IStatusHandlerContext, Task> handler)
+    {
+        _statusHost.AddHandler(async context =>
+        {
+            if (context.RequestMethod != method || context.Url.AbsolutePath != exactPath)
+                return false;
+
+            if (!await CheckAccess(context))
+                return true;
+
+            await handler(context);
+            return true;
+        });
+    }
+
+    private void RegisterActorHandler(HttpMethod method, string exactPath, Func<IStatusHandlerContext, Actor, Task> handler)
+    {
+        RegisterHandler(method, exactPath, async context =>
+        {
+            if (await CheckActor(context) is not { } actor)
+                return;
+
+            await handler(context, actor);
+        });
+    }
+
+    /// <summary>
+    /// Async helper function which runs a task on the main thread and returns the result.
+    /// </summary>
+    private async Task<T> RunOnMainThread<T>(Func<T> func)
+    {
+        var taskCompletionSource = new TaskCompletionSource<T>();
+        _taskManager.RunOnMainThread(() =>
+        {
+            try
+            {
+                taskCompletionSource.TrySetResult(func());
+            }
+            catch (Exception e)
+            {
+                taskCompletionSource.TrySetException(e);
+            }
+        });
+
+        var result = await taskCompletionSource.Task;
+        return result;
+    }
+
+    /// <summary>
+    /// Runs an action on the main thread. This does not return any value and is meant to be used for void functions. Use <see cref="RunOnMainThread{T}"/> for functions that return a value.
+    /// </summary>
+    private async Task RunOnMainThread(Action action)
+    {
+        var taskCompletionSource = new TaskCompletionSource();
+        _taskManager.RunOnMainThread(() =>
+        {
+            try
+            {
+                action();
+                taskCompletionSource.TrySetResult();
+            }
+            catch (Exception e)
+            {
+                taskCompletionSource.TrySetException(e);
+            }
+        });
+
+        await taskCompletionSource.Task;
+    }
+
+    private async Task RunOnMainThread(Func<Task> action)
+    {
+        var taskCompletionSource = new TaskCompletionSource();
+        // ReSharper disable once AsyncVoidLambda
+        _taskManager.RunOnMainThread(async () =>
+        {
+            try
+            {
+                await action();
+                taskCompletionSource.TrySetResult();
+            }
+            catch (Exception e)
+            {
+                taskCompletionSource.TrySetException(e);
+            }
+        });
+
+        await taskCompletionSource.Task;
+    }
+
+    /// <summary>
+    /// Helper function to read JSON encoded data from the request body.
+    /// </summary>
+    private static async Task<T?> ReadJson<T>(IStatusHandlerContext context) where T : notnull
+    {
+        try
+        {
+            var json = await context.RequestBodyJsonAsync<T>();
+            if (json == null)
+                await RespondBadRequest(context, "Request body is null");
+
+            return json;
+        }
+        catch (Exception e)
+        {
+            await RespondBadRequest(context, "Unable to parse request body", ExceptionData.FromException(e));
+            return default;
+        }
+    }
+
+    private static async Task RespondError(
+        IStatusHandlerContext context,
+        ErrorCode errorCode,
+        HttpStatusCode statusCode,
+        string message,
+        ExceptionData? exception = null)
+    {
+        await context.RespondJsonAsync(new BaseResponse(message, errorCode, exception), statusCode)
+            .ConfigureAwait(false);
+    }
+
+    private static async Task RespondBadRequest(
+        IStatusHandlerContext context,
+        string message,
+        ExceptionData? exception = null)
+    {
+        await RespondError(context, ErrorCode.BadRequest, HttpStatusCode.BadRequest, message, exception)
+            .ConfigureAwait(false);
+    }
+
+    private static async Task RespondOk(IStatusHandlerContext context)
+    {
+        await context.RespondJsonAsync(new BaseResponse("OK"))
+            .ConfigureAwait(false);
+    }
+
+    private static string FormatLogActor(Actor actor) => $"{actor.Name} ({actor.Guid})";
+}