From 10664b74fdf99f46380cc816718b7ac75b1c53a3 Mon Sep 17 00:00:00 2001
From: Leandro Fernandes Vieira <leandro.vieira@stone.com.br>
Date: Sat, 30 Dec 2023 21:45:31 -0300
Subject: [PATCH] draft

---
 .../Reader/FixedLengthReaderBuilder.cs        |  4 +-
 RecordParser/Parsers/FixedLengthReader.cs     | 10 ++-
 RecordParser/Visitors/MemoryVisitor.cs        | 78 +++++++++++++++++++
 3 files changed, 90 insertions(+), 2 deletions(-)
 create mode 100644 RecordParser/Visitors/MemoryVisitor.cs

diff --git a/RecordParser/Builders/Reader/FixedLengthReaderBuilder.cs b/RecordParser/Builders/Reader/FixedLengthReaderBuilder.cs
index 1a4514f..67bcf27 100644
--- a/RecordParser/Builders/Reader/FixedLengthReaderBuilder.cs
+++ b/RecordParser/Builders/Reader/FixedLengthReaderBuilder.cs
@@ -98,7 +98,9 @@ public IFixedLengthReader<T> Build(CultureInfo cultureInfo = null, Func<T> facto
 
             func = CultureInfoVisitor.ReplaceCulture(func, cultureInfo);
 
-            return new FixedLengthReader<T>(func.Compile());
+            var memory = new SpanReplacerVisitor().Modify(func);
+
+            return new FixedLengthReader<T>(func.Compile(true), memory.Compile(true));
         }
     }
 }
diff --git a/RecordParser/Parsers/FixedLengthReader.cs b/RecordParser/Parsers/FixedLengthReader.cs
index d67e549..d428c01 100644
--- a/RecordParser/Parsers/FixedLengthReader.cs
+++ b/RecordParser/Parsers/FixedLengthReader.cs
@@ -5,16 +5,24 @@ namespace RecordParser.Parsers
     public interface IFixedLengthReader<T>
     {
         T Parse(ReadOnlySpan<char> line);
+        T Parse(ReadOnlyMemory<char> line);
         bool TryParse(ReadOnlySpan<char> line, out T result);
     }
 
     internal class FixedLengthReader<T> : IFixedLengthReader<T>
     {
         private readonly FuncSpanT<T> parser;
+        private readonly Func<ReadOnlyMemory<char>, T> parser2;
 
-        internal FixedLengthReader(FuncSpanT<T> parser)
+        internal FixedLengthReader(FuncSpanT<T> parser, Func<ReadOnlyMemory<char>, T> parser2)
         {
             this.parser = parser;
+            this.parser2 = parser2;
+        }
+
+        public T Parse(ReadOnlyMemory<char> line)
+        {
+            return parser2(line);
         }
 
         public T Parse(ReadOnlySpan<char> line)
diff --git a/RecordParser/Visitors/MemoryVisitor.cs b/RecordParser/Visitors/MemoryVisitor.cs
new file mode 100644
index 0000000..2989fb0
--- /dev/null
+++ b/RecordParser/Visitors/MemoryVisitor.cs
@@ -0,0 +1,78 @@
+using System;
+using System.Linq;
+using System.Linq.Expressions;
+
+namespace RecordParser.Visitors
+{
+    internal class SpanReplacerVisitor : ExpressionVisitor
+    {
+        private readonly static ParameterExpression memory = Expression.Parameter(typeof(ReadOnlyMemory<char>), "memory");
+        private readonly static MemberExpression span = Expression.Property(memory, "Span");
+
+
+
+        public Expression<Func<ReadOnlyMemory<char>, T>> Modify<T>(Expression<FuncSpanT<T>> ex)
+        {
+            if (ex is null) return null;
+
+            var body = Visit(ex.Body);
+
+            body = new StaticMethodVisitor().Visit(body);
+
+            var lamb = Expression.Lambda<Func<ReadOnlyMemory<char>, T>>(body, memory);
+
+            return lamb;
+        }
+
+    
+
+        protected override Expression VisitParameter(ParameterExpression node)
+        {
+            if (node.Type == typeof(ReadOnlySpan<char>))
+                return span;
+
+            return base.VisitParameter(node);
+        }
+
+        class StaticMethodVisitor : ExpressionVisitor
+        {
+            public static string ToString(ReadOnlySpan<char> span) => span.ToString();
+            public static ReadOnlySpan<char> Trim(ReadOnlySpan<char> span) => span.Trim();
+            public static ReadOnlySpan<char> Slice1(ReadOnlySpan<char> span, int start) => span.Slice(start);
+            public static ReadOnlySpan<char> Slice2(ReadOnlySpan<char> span, int start, int count) => span.Slice(start, count);
+
+            protected override Expression VisitMethodCall(MethodCallExpression node)
+            {
+                if (node.Object?.Type == typeof(ReadOnlySpan<char>))
+                {
+                    var args = node.Arguments.Prepend(node.Object).ToArray();
+
+                    if (node.Method.Name == "Slice")
+                    {
+                        Delegate f = node.Arguments.Count == 1 
+                            ? StaticMethodVisitor.Slice1
+                            : StaticMethodVisitor.Slice2;
+
+                        return Expression.Call(f.Method, args);
+                    }
+
+                    if (node.Method.Name == "ToString")
+                    {
+                        var f = StaticMethodVisitor.ToString;
+
+                        return Expression.Call(f.Method, args);
+                    }
+
+                    if (node.Method.Name == "Trim")
+                    {
+                        var f = StaticMethodVisitor.Trim;
+
+                        return Expression.Call(f.Method, args);
+                    }
+                }
+
+                return base.VisitMethodCall(node);
+            }
+        }
+    }
+}