From 65d8141d1827b17b7cb82613b7bca81f24c384ea Mon Sep 17 00:00:00 2001
From: Laura Hausmann <laura@hausmann.dev>
Date: Mon, 23 Jan 2023 17:54:18 +0100
Subject: [PATCH] Simplify algorithm for message input paging

---
 ...{MessagePaging.cs => PagedMessageInput.cs} |  2 +-
 tgcli/Util.cs                                 | 22 +++++++++----------
 2 files changed, 11 insertions(+), 13 deletions(-)
 rename tgcli.Tests/{MessagePaging.cs => PagedMessageInput.cs} (97%)

diff --git a/tgcli.Tests/MessagePaging.cs b/tgcli.Tests/PagedMessageInput.cs
similarity index 97%
rename from tgcli.Tests/MessagePaging.cs
rename to tgcli.Tests/PagedMessageInput.cs
index 75dcdee..f420297 100644
--- a/tgcli.Tests/MessagePaging.cs
+++ b/tgcli.Tests/PagedMessageInput.cs
@@ -1,6 +1,6 @@
 namespace tgcli.Tests;
 
-public class MessagePaging {
+public class PagedMessageInput {
 	[Theory]
 	[InlineData(0)]
 	[InlineData(76)]
diff --git a/tgcli/Util.cs b/tgcli/Util.cs
index 511e23f..1fb1165 100644
--- a/tgcli/Util.cs
+++ b/tgcli/Util.cs
@@ -380,24 +380,22 @@ public static class Util {
 		const int wraparoundOffsetPostW = wraparoundOffsetPost + 1; // offset + 1 (character on the edge), for easier calculations
 
 		if (absoluteCursorPosition > message.Length)
-			throw new ArgumentOutOfRangeException();
+			throw new ArgumentOutOfRangeException(nameof(absoluteCursorPosition), "Cursor position exceeds message length");
 
-		if (message.Length < bufferWidth)
-			return (message, absoluteCursorPosition);
+		if (message.Length < bufferWidth)             // entire message fits in buffer
+			return (message, absoluteCursorPosition); // return input as-is
 
-		if (absoluteCursorPosition < bufferWidth - wraparoundOffsetPre - 1)
-			return (TruncateString(message, bufferWidth, $"{Ansi.Inverse}>{Ansi.InverseOff}"), absoluteCursorPosition);
+		if (absoluteCursorPosition < bufferWidth - wraparoundOffsetPre - 1)                                             // message is longer than buffer but we're on the first page
+			return (TruncateString(message, bufferWidth, $"{Ansi.Inverse}>{Ansi.InverseOff}"), absoluteCursorPosition); // return input as-is but truncated and with a > indicator
 
-		var finalCursorPos = absoluteCursorPosition - bufferWidth + wraparoundOffsetPreW + wraparoundOffsetPostW;
-		var wraparounds    = (finalCursorPos - wraparoundOffsetPostW) / (bufferWidth - wraparoundOffsetPreW - wraparoundOffsetPostW);
-		finalCursorPos += wraparoundOffsetPostW * wraparounds;
+		var wraparounds    = (absoluteCursorPosition - wraparoundOffsetPostW) / (bufferWidth - wraparoundOffsetPreW - wraparoundOffsetPostW);
+		var finalCursorPos = absoluteCursorPosition - bufferWidth + wraparoundOffsetPreW + wraparoundOffsetPostW * wraparounds;
 		finalCursorPos %= bufferWidth - wraparoundOffsetPreW;
 
-		var messageOffset = (bufferWidth - wraparoundOffsetPreW - wraparoundOffsetPostW) * wraparounds;
-		var finalMessage  = message[(bufferWidth - wraparoundOffsetPreW - wraparoundOffsetPost)..];
-		finalMessage = finalMessage[messageOffset..];
+		var messageOffset = (bufferWidth - wraparoundOffsetPreW - wraparoundOffsetPostW) * wraparounds + 1; // +1 to account for the first wrap not having a < indicator
+		var finalMessage  = message[messageOffset..];
 
-		finalMessage = TruncateString(finalMessage, bufferWidth - 1, $"{Ansi.Inverse}>{Ansi.InverseOff}");
+		finalMessage = TruncateString(finalMessage, bufferWidth - 1, $"{Ansi.Inverse}>{Ansi.InverseOff}"); // replace the last character with a > indicator if required
 
 		return ($"{Ansi.Inverse}<{Ansi.InverseOff}" + finalMessage, finalCursorPos);
 	}