[AdvPaste][JSON]Improve delimiter handling for CSV and add plain text parser (#33199)

* code changes

* rework code

* improvement

* regex: ignore case

* spell fixes

* update regex

* fixes

* more fixes

src/modules/AdvancedPaste/AdvancedPaste/Helpers/JsonHelper.cs

@@ -4,6 +4,8 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using System.Xml;
 using ManagedCommon;
@@ -14,6 +16,10 @@ namespace AdvancedPaste.Helpers
 {
     internal static class JsonHelper
     {
+        // List of supported CSV delimiters and Regex to detect separator property
+        private static readonly char[] CsvDelimArry = [',', ';', '\t'];
+        private static readonly Regex CsvSepIdentifierRegex = new Regex(@"^sep=(.)$", RegexOptions.IgnoreCase);
+
         internal static string ToJsonFromXmlOrCsv(DataPackageView clipboardData)
         {
             Logger.LogTrace();
@@ -53,11 +59,31 @@ namespace AdvancedPaste.Helpers
                 {
                     var csv = new List<string[]>();
 
-                    foreach (var line in text.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries))
+                    string[] lines = text.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
+
+                    // Detect the csv delimiter and the count of occurrence based on the first two csv lines.
+                    GetCsvDelimiter(lines, out char delim, out int delimCount);
+
+                    foreach (var line in lines)
                     {
-                        csv.Add(line.Split(","));
+                        // If line is separator property line, then skip it
+                        if (CsvSepIdentifierRegex.IsMatch(line))
+                        {
+                            continue;
+                        }
+
+                        // A CSV line is valid, if the delimiter occurs more or equal times in every line compared to the first data line. (More because sometimes the delimiter occurs in a data string.)
+                        if (line.Count(x => x == delim) >= delimCount)
+                        {
+                            csv.Add(line.Split(delim));
+                        }
+                        else
+                        {
+                            throw new FormatException("Invalid CSV format: Number of delimiters wrong in the current line.");
+                        }
                     }
 
+                    Logger.LogDebug("Convert from csv.");
                     jsonText = JsonConvert.SerializeObject(csv, Newtonsoft.Json.Formatting.Indented);
                 }
             }
@@ -66,7 +92,79 @@ namespace AdvancedPaste.Helpers
                 Logger.LogError("Failed parsing input as csv", ex);
             }
 
+            // Try convert Plain Text
+            try
+            {
+                if (string.IsNullOrEmpty(jsonText))
+                {
+                    var plainText = new List<string>();
+
+                    foreach (var line in text.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries))
+                    {
+                        plainText.Add(line);
+                    }
+
+                    Logger.LogDebug("Convert from plain text.");
+                    jsonText = JsonConvert.SerializeObject(plainText, Newtonsoft.Json.Formatting.Indented);
+                }
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError("Failed parsing input as plain text", ex);
+            }
+
             return string.IsNullOrEmpty(jsonText) ? text : jsonText;
         }
+
+        private static void GetCsvDelimiter(in string[] csvLines, out char delimiter, out int delimiterCount)
+        {
+            delimiter = '\0'; // Unicode "null" character.
+            delimiterCount = 0;
+
+            if (csvLines.Length > 1)
+            {
+                // Try to select the delimiter based on the separator property.
+                Match matchChar = CsvSepIdentifierRegex.Match(csvLines[0]);
+                if (matchChar.Success)
+                {
+                    // We can do matchChar[0] as the match only returns one character.
+                    // We get the count from the second line, as the first one only contains the character definition and not a CSV data line.
+                    char delimChar = matchChar.Groups[1].Value.Trim()[0];
+                    delimiter = delimChar;
+                    delimiterCount = csvLines[1].Count(x => x == delimChar);
+                }
+            }
+
+            if (csvLines.Length > 0 && delimiterCount == 0)
+            {
+                // Try to select the correct delimiter based on the first two CSV lines from a list of predefined delimiters.
+                foreach (char c in CsvDelimArry)
+                {
+                    int cntFirstLine = csvLines[0].Count(x => x == c);
+                    int cntNextLine = 0; // Default to 0 that the 'second line' check is always true.
+
+                    // Additional count if we have more than one line
+                    if (csvLines.Length >= 2)
+                    {
+                        cntNextLine = csvLines[1].Count(x => x == c);
+                    }
+
+                    // The delimiter is found if the count is bigger as from the last selected delimiter
+                    // and if the next csv line does not exist or has the same number or more occurrences of the delimiter.
+                    // (We check the next line to prevent false positives.)
+                    if (cntFirstLine > delimiterCount && (cntNextLine == 0 || cntNextLine >= cntFirstLine))
+                    {
+                        delimiter = c;
+                        delimiterCount = cntFirstLine;
+                    }
+                }
+            }
+
+            // If the delimiter count is 0, we can't detect it and it is no valid CSV.
+            if (delimiterCount == 0)
+            {
+                throw new FormatException("Invalid CSV format: Failed to detect the delimiter.");
+            }
+        }
     }
 }