Show rules on first connection (#5715)

* Implement showing rules on first connection

* Clean up RulesManager

* Change changelog and rules unread to use CVars

* Fix missing change

* Rename InfoWindow to RulesAndInfoWindow

* Change default server.id to unknown

* Fix invalid file contents and getting CVar

Content.Client/Info/RulesManager.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Globalization;
+using System.IO;
+using Content.Client.HUD;
+using Content.Shared.CCVar;
+using Robust.Shared.Configuration;
+using Robust.Shared.ContentPack;
+using Robust.Shared.IoC;
+using Robust.Shared.Network;
+using Robust.Shared.Utility;
+
+namespace Content.Client.Info;
+
+public sealed class RulesManager
+{
+    [Dependency] private readonly IClientNetManager _clientNetManager = default!;
+    [Dependency] private readonly IResourceManager _resource = default!;
+    [Dependency] private readonly IConfigurationManager _configManager = default!;
+
+    public event Action? OpenRulesAndInfoWindow;
+
+    private void OnConnectStateChanged(ClientConnectionState state)
+    {
+        if (state != ClientConnectionState.Connected)
+            return;
+
+        var path = new ResourcePath($"/rules_last_seen_{_configManager.GetCVar(CCVars.ServerId)}");
+        var showRules = true;
+        if (_resource.UserData.Exists(path)
+            && DateTime.TryParse(_resource.UserData.ReadAllText(path), null, DateTimeStyles.AssumeUniversal,
+                out var lastReadTime))
+            showRules = lastReadTime < DateTime.UtcNow - TimeSpan.FromDays(60);
+        else
+            SaveLastReadTime();
+
+        if (showRules)
+            OpenRulesAndInfoWindow?.Invoke();
+    }
+
+    /// <summary>
+    ///     Ran when the user opens ("read") the rules, stores the new ID to disk.
+    /// </summary>
+    public void SaveLastReadTime()
+    {
+        using var file = _resource.UserData.Create(new ResourcePath($"/rules_last_seen_{_configManager.GetCVar(CCVars.ServerId)}"));
+        using var sw = new StreamWriter(file);
+
+        sw.Write(DateTime.UtcNow.ToUniversalTime());
+    }
+
+    public void Initialize()
+    {
+        _clientNetManager.ClientConnectStateChanged += OnConnectStateChanged;
+    }
+}