From 873b48e2f88c95b780cbea46fd5e36795ce80cf9 Mon Sep 17 00:00:00 2001
From: Laura Hausmann <laura@hausmann.dev>
Date: Wed, 8 Jan 2025 12:16:22 +0100
Subject: [PATCH] [backend/core] Add CollapseWhitespace rewrite policy
 (ISH-625)

---
 .../CollapseWhitespaceRewritePolicy.cs        | 51 +++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 Iceshrimp.Backend/Core/Policies/CollapseWhitespaceRewritePolicy.cs

diff --git a/Iceshrimp.Backend/Core/Policies/CollapseWhitespaceRewritePolicy.cs b/Iceshrimp.Backend/Core/Policies/CollapseWhitespaceRewritePolicy.cs
new file mode 100644
index 00000000..ddf36bbd
--- /dev/null
+++ b/Iceshrimp.Backend/Core/Policies/CollapseWhitespaceRewritePolicy.cs
@@ -0,0 +1,51 @@
+using System.Text.RegularExpressions;
+using Iceshrimp.Backend.Core.Database.Tables;
+using Iceshrimp.Backend.Core.Federation.ActivityStreams.Types;
+using Iceshrimp.Backend.Core.Services;
+using Iceshrimp.MfmSharp;
+
+namespace Iceshrimp.Backend.Core.Policies;
+
+public partial class CollapseWhitespaceRewritePolicy(
+	bool enabled,
+	int priority
+) : IRewritePolicy
+{
+	public string                          Name         => nameof(CollapseWhitespaceRewritePolicy);
+	public bool                            Enabled      => enabled;
+	public int                             Priority     => priority;
+	public IRewritePolicy.HookLocationEnum HookLocation => IRewritePolicy.HookLocationEnum.PostLogic;
+
+	[GeneratedRegex(" +")] private static partial Regex WhitespaceRegex { get; }
+
+	public void Apply(NoteService.NoteCreationData data)
+	{
+		if (data.Text == null || !IsApplicable(data)) return;
+		data.Text       = WhitespaceRegex.Replace(data.Text, " ");
+		data.ParsedText = MfmParser.Parse(data.Text);
+	}
+
+	public void Apply(NoteService.NoteUpdateData data)
+	{
+		if (data.Text == null || !IsApplicable(data)) return;
+		data.Text       = WhitespaceRegex.Replace(data.Text, " ");
+		data.ParsedText = MfmParser.Parse(data.Text);
+	}
+
+	public void Apply(ASNote note, User actor) { }
+
+	private static bool IsApplicable(NoteService.NoteCreationData data)
+		=> data.Text != null && data.Text.Contains("  ") && !data.Text.Contains("$[");
+
+	private static bool IsApplicable(NoteService.NoteUpdateData data)
+		=> data.Text != null && data.Text.Contains("  ") && !data.Text.Contains("$[");
+}
+
+public class CollapseWhitespaceRewritePolicyConfiguration : IPolicyConfiguration<CollapseWhitespaceRewritePolicy>
+{
+	public CollapseWhitespaceRewritePolicy Apply() => new(Enabled, Priority);
+	IPolicy IPolicyConfiguration.          Apply() => Apply();
+
+	public bool Enabled  { get; set; }
+	public int  Priority { get; set; }
+}