From b66b93947d6a6ee492a9db75c5e931d5144ce8cc Mon Sep 17 00:00:00 2001
From: Timerix22 <timerix11@gmail.com>
Date: Tue, 6 Dec 2022 01:09:36 +0600
Subject: [PATCH] SpanHelper AfterLast and BeforeLast

---
 DTLib/Extensions/SpanHelper.cs | 61 +++++++++++++++++++++++++++++-----
 1 file changed, 53 insertions(+), 8 deletions(-)

diff --git a/DTLib/Extensions/SpanHelper.cs b/DTLib/Extensions/SpanHelper.cs
index 33971fb..6a3fbeb 100644
--- a/DTLib/Extensions/SpanHelper.cs
+++ b/DTLib/Extensions/SpanHelper.cs
@@ -3,37 +3,82 @@ namespace DTLib.Extensions;
 #if NETSTANDARD2_1 || NET6_0 || NET7_0 || NET8_0
 public static class SpanHelper
 {
-    public static ReadOnlySpan<char> After(this ReadOnlySpan<char> span, char c)
+    public static ReadOnlySpan<T> After<T>(this ReadOnlySpan<T> span, T c) where T : IEquatable<T>
     {
         var index = span.IndexOf(c);
         if (index == -1)
-            throw new Exception($"char <{c}> not found in span <{span}>");
+            throw new SpanHelperException<T>(c, span);
         return span.Slice(index+1);
     }
     
-    public static ReadOnlySpan<char> After(this ReadOnlySpan<char> span, ReadOnlySpan<char> s)
+    public static ReadOnlySpan<T> After<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> s) where T : IEquatable<T>
     {
         var index = span.IndexOf(s);
         if (index == -1)
-            throw new Exception($"span <{s}> not found in span <{span}>");
+            throw new SpanHelperException<T>(s, span);
         return span.Slice(index+s.Length);
     }
     
     
-    public static ReadOnlySpan<char> Before(this ReadOnlySpan<char> span, char c)
+    public static ReadOnlySpan<T> AfterLast<T>(this ReadOnlySpan<T> span, T c) where T : IEquatable<T>
+    {
+        var index = span.LastIndexOf(c);
+        if (index == -1)
+            throw new SpanHelperException<T>(c, span);
+        return span.Slice(index+1);
+    }
+    
+    public static ReadOnlySpan<T> AfterLast<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> s) where T : IEquatable<T>
+    {
+        var index = span.LastIndexOf(s);
+        if (index == -1)
+            throw new SpanHelperException<T>(s, span);
+        return span.Slice(index+s.Length);
+    }
+    
+    
+    public static ReadOnlySpan<T> Before<T>(this ReadOnlySpan<T> span, T c) where T : IEquatable<T>
     {
         var index = span.IndexOf(c);
         if (index == -1)
-            throw new Exception($"char <{c}> not found in span <{span}>");
+            throw new SpanHelperException<T>(c, span);
         return span.Slice(0,index);
     }
     
-    public static ReadOnlySpan<char> Before(this ReadOnlySpan<char> span, ReadOnlySpan<char> s)
+    public static ReadOnlySpan<T> Before<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> s) where T : IEquatable<T>
     {
         var index = span.IndexOf(s);
         if (index == -1)
-            throw new Exception($"span <{s}> not found in span <{span}>");
+            throw new SpanHelperException<T>(s, span);
         return span.Slice(0,index);
     }
+    
+    
+    public static ReadOnlySpan<T> BeforeLast<T>(this ReadOnlySpan<T> span, T c) where T : IEquatable<T>
+    {
+        var index = span.LastIndexOf(c);
+        if (index == -1)
+            throw new SpanHelperException<T>(c, span);
+        return span.Slice(0,index);
+    }
+    
+    public static ReadOnlySpan<T> BeforeLast<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> s) where T : IEquatable<T>
+    {
+        var index = span.LastIndexOf(s);
+        if (index == -1)
+            throw new SpanHelperException<T>(s, span);
+        return span.Slice(0,index);
+    }
+    
+    
+    public class SpanHelperException<T> : Exception
+    {
+        public SpanHelperException(T el, ReadOnlySpan<T> span)
+            : base($"{nameof(T)} {el} not found in span {span.ToString()}")
+        {}
+        public SpanHelperException(ReadOnlySpan<T> el, ReadOnlySpan<T> span)
+            : base($"ReadOnlySpan<{nameof(T)}> {el.ToString()} not found in span {span.ToString()}")
+        {}
+    }
 }
 #endif
\ No newline at end of file