Implemented the add text element function

I18N Commander/Processor/TextElementProcessor.cs

@@ -1,5 +1,4 @@
-using System.Collections;
-using DataModel.Database;
+using DataModel.Database;
 using DataModel.Database.Common;
 using Microsoft.EntityFrameworkCore;
 
@@ -11,4 +10,49 @@ public static class TextElementProcessor
     {
         return Task.FromResult(db.TextElements.Where(n => n.Section == section).AsAsyncEnumerable());
     }
+
+    public static async Task<ProcessorResult<TextElement>> AddTextElement(DataContext db, string? currentSectionKey, string elementName)
+    {
+        if(string.IsNullOrWhiteSpace(currentSectionKey))
+            throw new ArgumentOutOfRangeException(nameof(currentSectionKey));
+        
+        var currentSection = await db.Sections.FirstOrDefaultAsync(n => n.DataKey == currentSectionKey);
+        if (currentSection is null)
+            throw new ArgumentOutOfRangeException(nameof(currentSectionKey));
+
+        // Remove any whitespaces from the element name, regardless of how many e.g. spaces the user typed:
+        var code = string.Join('_', elementName.Split(' ', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)).ToUpperInvariant();
+        
+        // Check, if this key already exists:
+        if (await db.TextElements.AnyAsync(n => n.Section == currentSection && n.Code == code))
+        {
+            var rng = new Random();
+            while (await db.TextElements.AnyAsync(n => n.Section == currentSection && n.Code == code))
+            {
+                // Add a random number to the end of the key:
+                code += $"_{rng.Next(1, 10_000)}";
+            }
+        }
+        
+        var textElement = new TextElement
+        {
+            Name = elementName,
+            Code = code,
+            Section = currentSection,
+        };
+        
+        // Add the new element to the database:
+        await db.TextElements.AddAsync(textElement);
+
+        try
+        {
+            // Save the changes:
+            await db.SaveChangesAsync();
+            return new ProcessorResult<TextElement>(textElement);
+        }
+        catch (DbUpdateException updateException)
+        {
+            return updateException.ToProcessorResult<TextElement>();
+        }
+    }
 }