Mirror 25908: Chat Censorship Systems (#444)

## Mirror of PR #25908: [SS14-17313 Chatfactor: Chat Censorship
Systems](space-wizards/space-station-14#25908)
from <img src="https://avatars.githubusercontent.com/u/10567778?v=4"
alt="space-wizards" width="22"/>
[space-wizards](https://github.com/space-wizards)/[space-station-14](https://github.com/space-wizards/space-station-14)

###### `bf98a6a8bb2a57fb149459d6b053eaaf6abc8cd7`

PR opened by <img
src="https://avatars.githubusercontent.com/u/732532?v=4" width="16"/><a
href="https://github.com/FairlySadPanda"> FairlySadPanda</a> at
2024-03-07 12:13:16 UTC - merged at 2024-03-25 23:50:20 UTC

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PR changed 4 files with 576 additions and 0 deletions.

The PR had the following labels:
- Status: Needs Review


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<details open="true"><summary><h1>Original Body</h1></summary>

> <!-- Please read these guidelines before opening your PR:
https://docs.spacestation14.io/en/getting-started/pr-guideline -->
> <!-- The text between the arrows are comments - they will not be
visible on your PR. -->
> 
> ## About the PR
> Adds some systems to manage chat censorship:
> 
> 1. No-op: does nothing
> 2. SimpleCensor: a regex-free censor with a variety of rules to use
> 3. RegexCensor: a censor that uses regex.
> 
> This exposes a singleton backed by a builder pattern (ChatCensor) that
is set up, probably during the code init phase, and then globally
available for your censorship needs.
> 
> ## Why / Balance
> Partial fulfilment of #17313 
> 
> ## Technical details
> CE wants regex, CE gets regex
> 
> Otherwise SimpleCensor is designed to be usable by people who don't
want to faff with regex.
> 
> This would be setup during server or client init, so would be driven
by Cvars.
> 
> ## Media
> <!-- 
> PRs which make ingame changes (adding clothing, items, new features,
etc) are required to have media attached that showcase the changes.
> Small fixes/refactors are exempt.
> Any media may be used in SS14 progress reports, with clear credit
given.
> 
> If you're unsure whether your PR will require media, ask a maintainer.
> 
> Check the box below to confirm that you have in fact seen this (put an
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> -->
> 
> - [x] I have added screenshots/videos to this PR showcasing its
changes ingame, **or** this PR does not require an ingame showcase
> 
> ## Breaking changes
> nope
> **Changelog**
> nope


</details>

Co-authored-by: SimpleStation14 <Unknown>

Content.Shared/Chat/V2/Moderation/ChatCensor.cs

@@ -0,0 +1,59 @@
+using System.Linq;
+
+namespace Content.Shared.Chat.V2.Moderation;
+
+public interface IChatCensor
+{
+    public bool Censor(string input, out string output, char replaceWith = '*');
+}
+
+public sealed class CompoundChatCensor(IEnumerable<IChatCensor> censors) : IChatCensor
+{
+    public bool Censor(string input, out string output, char replaceWith = '*')
+    {
+        var censored = false;
+
+        foreach (var censor in censors)
+        {
+            if (censor.Censor(input, out output, replaceWith))
+            {
+                censored = true;
+            }
+        }
+
+        output = input;
+
+        return censored;
+    }
+}
+
+public sealed class ChatCensorFactory
+{
+    private List<IChatCensor> _censors = new();
+
+    public void With(IChatCensor censor)
+    {
+        _censors.Add(censor);
+    }
+
+    /// <summary>
+    /// Builds a ChatCensor that combines all the censors that have been added to this.
+    /// </summary>
+    public IChatCensor Build()
+    {
+        return new CompoundChatCensor(_censors.ToArray());
+    }
+
+    /// <summary>
+    /// Resets the build state to zero, allowing for different rules to be provided to the next censor(s) built.
+    /// </summary>
+    /// <returns>True if the builder had any setup prior to the reset.</returns>
+    public bool Reset()
+    {
+        var notEmpty = _censors.Count > 0;
+
+        _censors = new List<IChatCensor>();
+
+        return notEmpty;
+    }
+}

Content.Shared/Chat/V2/Moderation/RegexCensor.cs

@@ -0,0 +1,15 @@
+using System.Text.RegularExpressions;
+
+namespace Content.Shared.Chat.V2.Moderation;
+
+public sealed class RegexCensor(Regex censorInstruction) : IChatCensor
+{
+    private readonly Regex _censorInstruction = censorInstruction;
+
+    public bool Censor(string input, out string output, char replaceWith = '*')
+    {
+        output = _censorInstruction.Replace(input, replaceWith.ToString());
+
+        return !string.Equals(input, output);
+    }
+}