1 files changed, 148 insertions, 0 deletions
diff --git a/src/Editor/Language/Def/Intellisense/Snippet/ExpansionTemplate.cs b/src/Editor/Language/Def/Intellisense/Snippet/ExpansionTemplate.cs
new file mode 100644
index 0000000..356d2bd
--- /dev/null
+++ b/src/Editor/Language/Def/Intellisense/Snippet/ExpansionTemplate.cs
@@ -0,0 +1,148 @@
+//
+//  Copyright (c) Microsoft Corporation. All rights reserved.
+//  Licensed under the MIT License. See License.txt in the project root for license information.
+//
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+
+namespace Microsoft.VisualStudio.Text.Editor.Expansion
+{
+    public class ExpansionTemplate
+    {
+        private string snippetFullText;
+        private readonly List<ExpansionField> tokens = new List<ExpansionField>();
+        private int selectedOffset;
+        private int editOffset;
+        private string snippetFirst;
+        private string snippetLast;
+
+        public CodeSnippet Snippet { get; set; }
+
+        public ExpansionTemplate(string filePath)
+            :this(CodeSnippet.ReadSnippetsFromFile(filePath).First())
+        {
+            
+        }
+
+        public ExpansionTemplate(CodeSnippet snippet)
+        {
+            Snippet = snippet;
+            Parse();
+        }
+
+        private void Parse()
+        {
+            foreach (var field in Snippet.Fields)
+            {
+                tokens.Add(field);
+            }
+
+            var matches = Regex.Matches(Snippet.Code, @"\$(\w+)\$");
+
+            var total = new StringBuilder();
+            int index = 0;
+            int indexCorrection = 0;
+            foreach (Match match in matches)
+            {
+                string fieldName = match.Groups[1].Value;
+                string substitution = GetDefaultValue(fieldName) ?? "";
+                if (match.Index > index)
+                {
+                    total.Append(Snippet.Code.Substring(index, match.Index - index));
+                }
+
+                AddToken(total.Length, fieldName);
+                total.Append(substitution);
+
+                index = match.Index + match.Length;
+                indexCorrection += substitution.Length;
+            }
+
+            if (index <= Snippet.Code.Length - 1)
+            {
+                total.Append(Snippet.Code.Substring(index, Snippet.Code.Length - index));
+            }
+
+            this.snippetFullText = total.ToString();
+            this.snippetFirst = snippetFullText.Substring(0, selectedOffset);
+            this.snippetLast = snippetFullText.Substring(selectedOffset, snippetFullText.Length - selectedOffset);
+        }
+
+        private string GetDefaultValue(string fieldName)
+        {
+            ExpansionField field = FindField(fieldName);
+            if (field == null)
+            {
+                return null;
+            }
+
+            return field.Default;
+        }
+
+        private void AddToken(int position, string fieldName)
+        {
+            ExpansionField field = FindField(fieldName);
+            if (field != null)
+            {
+                field.AddOffset(position);
+            }
+            else if (fieldName == "selected")
+            {
+                this.selectedOffset = position;
+            }
+            else if (fieldName == "end")
+            {
+                this.editOffset = position;
+            }
+        }
+
+        private ExpansionField FindField(string fieldName)
+        {
+            return tokens.FirstOrDefault(t => t.ID == fieldName);
+        }
+
+        public string GetCodeSnippet()
+        {
+            return snippetFullText;
+        }
+
+        public int GetSelectedOffset()
+        {
+            return selectedOffset;
+        }
+
+        public int GetEditOffset()
+        {
+            return editOffset;
+        }
+
+        public string GetCodeSnippet(bool all, bool first)
+        {
+            if (all)
+            {
+                return snippetFullText;
+            }
+            else if (first)
+            {
+                return snippetFirst;
+            }
+            else
+            {
+                return snippetLast;
+            }
+        }
+
+        public IEnumerable<ExpansionField> Fields
+        {
+            get
+            {
+                return tokens;
+            }
+        }
+    }
+}