#25: adapt XmlDataWriter to one file per entry strategy

GBase/DataHandling/Exceptions/InvalidXmlFileException.cs

@@ -0,0 +1,17 @@
+// Author: Gockner, Simon
+// Created: 2020-11-09
+// Copyright(c) 2020 SimonG. All Rights Reserved.
+
+using System;
+
+namespace GBase.DataHandling.Exceptions
+{
+    public class InvalidXmlFileException : Exception
+    {
+        public InvalidXmlFileException(string message)
+            : base(message)
+        {
+            
+        }
+    }
+}

GBase/DataHandling/XmlDataHandler.cs

@@ -144,7 +144,7 @@ namespace GBase.DataHandling
                 valueString = value.ToString();
 
             await _cache.TryRemoveValue<T, TProperty>(propertyName, value);
-            await _xmlDataWriter.Remove<T, TProperty>(propertyName, valueString);
+            await _xmlDataWriter.Remove<T, TProperty>(TODO, propertyName, valueString, TODO);
         }
 
         /// <summary>

GBase/DataHandling/XmlDataWriter.cs

@@ -8,6 +8,7 @@ using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Xml.Linq;
+using GBase.DataHandling.Exceptions;
 using GBase.Interfaces.DataHandling;
 using GBase.Interfaces.DataHandling.Xml;
 
@@ -52,6 +53,7 @@ namespace GBase.DataHandling
         /// <param name="cancellationToken"></param>
         /// <returns>A <see cref="Task"/> to await</returns>
         /// <exception cref="ArgumentNullException"><paramref name="propertyName"/></exception>
+        /// <exception cref="InvalidXmlFileException">No root element is set</exception>
         public async Task Write<T, TProperty>(FileStream file, string propertyName, string value, bool overwrite, CancellationToken cancellationToken)
         {
             string typeName = typeof(T).FullName;
@@ -59,43 +61,35 @@ namespace GBase.DataHandling
                 throw new ArgumentNullException(nameof(typeName));
             
             XDocument xmlDocument = await XDocument.LoadAsync(file, LoadOptions.None, cancellationToken);
-
             file.Seek(0, SeekOrigin.Begin); //reset stream to it's beginning to be able to save it
 
-            XElement typeElement = _rootElement.Element(typeName);
+            XElement rootElement = xmlDocument.Root;
-            if (typeElement != null) //type element already exists
+            if (rootElement == null)
+                throw new InvalidXmlFileException("No root element is set.");
+            
+            XElement propertyElement = rootElement.Element(propertyName);
+            if (propertyElement != null) //property element already exists
             {
-                XElement propertyElement = typeElement.Element(propertyName);
+                XElement valueElement = propertyElement.Element(XmlDataHandler.VALUE_ELEMENT_NAME);
-                if (propertyElement != null) //property element already exists
+                if (valueElement != null && overwrite) //value element exists and overwrite is true
                 {
-                    XElement valueElement = propertyElement.Element(XmlDataHandler.VALUE_ELEMENT_NAME);
+                    valueElement.Value = value; //overwrite existing value
-                    if (valueElement != null && overwrite) //value element exists and overwrite is true
-                    {
-                        valueElement.Value = value; //overwrite existing value
-                    }
-                    else if (!overwrite && propertyElement.Elements(XmlDataHandler.VALUE_ELEMENT_NAME).Any(v => v.Value.Equals(value))) //no overwrite and same value exists already
-                    {
-                        XElement sameValueElement = propertyElement.Elements(XmlDataHandler.VALUE_ELEMENT_NAME).First(v => v.Value.Equals(value));
-                        sameValueElement.Remove(); //remove the already existing value from its current position
-                        propertyElement.AddFirst(sameValueElement); //add it as the first element again
-                    }
-                    else //no value element exists or overwrite is false
-                        propertyElement.AddFirst(new XElement(XmlDataHandler.VALUE_ELEMENT_NAME) { Value = value }); //add a new value element
                 }
-                else //property element doesn't exist
+                else if (!overwrite && propertyElement.Elements(XmlDataHandler.VALUE_ELEMENT_NAME).Any(v => v.Value.Equals(value))) //no overwrite and same value exists already
                 {
-                    propertyElement = new XElement(propertyName, new XElement(XmlDataHandler.VALUE_ELEMENT_NAME) { Value = value }); //create the new property element with the value element
+                    XElement sameValueElement = propertyElement.Elements(XmlDataHandler.VALUE_ELEMENT_NAME).First(v => v.Value.Equals(value));
-                    propertyElement.SetAttributeValue(XmlDataHandler.VALUE_TYPE_ATTRIBUTE_NAME, typeof(TProperty).FullName); //add the property type attribute
+                    sameValueElement.Remove(); //remove the already existing value from its current position
-
+                    propertyElement.AddFirst(sameValueElement); //add it as the first element again
-                    typeElement.Add(propertyElement); //create new property element with the value element
                 }
+                else //no value element exists or overwrite is false
+                    propertyElement.AddFirst(new XElement(XmlDataHandler.VALUE_ELEMENT_NAME) { Value = value }); //add a new value element
             }
-            else //type element doesn't exist
+            else //property element doesn't exist
             {
-                XElement propertyElement = new XElement(propertyName, new XElement(XmlDataHandler.VALUE_ELEMENT_NAME) { Value = value }); //create the new property element with the value element
+                propertyElement = new XElement(propertyName, new XElement(XmlDataHandler.VALUE_ELEMENT_NAME) { Value = value }); //create the new property element with the value element
                 propertyElement.SetAttributeValue(XmlDataHandler.VALUE_TYPE_ATTRIBUTE_NAME, typeof(TProperty).FullName); //add the property type attribute
 
-                _rootElement.Add(new XElement(typeName, propertyElement)); //create a new type element with the new property element
+                rootElement.Add(propertyElement); //create new property element with the value element
             }
 
             //TODO: check if whole file is overwritten (probably) -> performance issues for large files?
@@ -107,19 +101,27 @@ namespace GBase.DataHandling
         /// </summary>
         /// <typeparam name="T">The <see cref="Type"/> of the property</typeparam>
         /// <typeparam name="TProperty">The <see cref="Type"/> of the property</typeparam>
+        /// <param name="file"></param>
         /// <param name="propertyName">The name of the property</param>
         /// <param name="value">The value to set</param>
+        /// <param name="cancellationToken"></param>
         /// <returns>A <see cref="Task"/> to await</returns>
         /// <exception cref="ArgumentNullException"><paramref name="propertyName"/></exception>
-        public async Task Remove<T, TProperty>(string propertyName, string value)
+        /// <exception cref="InvalidXmlFileException">No root element is set</exception>
+        public async Task Remove<T, TProperty>(FileStream file, string propertyName, string value, CancellationToken cancellationToken)
         {
             string typeName = typeof(T).FullName;
             if (typeName == null)
                 throw new ArgumentNullException(nameof(typeName));
 
-            _file.Seek(0, SeekOrigin.Begin); //reset stream to it's beginning to be able to save it
+            XDocument xmlDocument = await XDocument.LoadAsync(file, LoadOptions.None, cancellationToken);
+            file.Seek(0, SeekOrigin.Begin); //reset stream to it's beginning to be able to save it
 
-            XElement typeElement = _rootElement.Element(typeName);
+            XElement rootElement = xmlDocument.Root;
+            if (rootElement == null)
+                throw new InvalidXmlFileException("No root element is set.");
+            
+            XElement typeElement = rootElement.Element(typeName);
             XElement propertyElement = typeElement?.Element(propertyName);
             XElement valueElement = propertyElement?.Elements(XmlDataHandler.VALUE_ELEMENT_NAME).FirstOrDefault(e => e.Value.Equals(value));
             if (valueElement == null)
@@ -128,7 +130,7 @@ namespace GBase.DataHandling
             valueElement.Remove();
 
             //TODO: check if whole file is overwritten (probably) -> performance issues for large files?
-            await _xmlDocument.SaveAsync(_file, SaveOptions.OmitDuplicateNamespaces, _cancellationToken); //save the document with the added elements
+            await xmlDocument.SaveAsync(file, SaveOptions.OmitDuplicateNamespaces, cancellationToken); //save the document with the added elements
         }
     }
 }

GBase/Interfaces/DataHandling/IDataWriter.cs

@@ -41,9 +41,11 @@ namespace GBase.Interfaces.DataHandling
         /// </summary>
         /// <typeparam name="T">The <see cref="Type"/> of the property</typeparam>
         /// <typeparam name="TProperty">The <see cref="Type"/> of the property</typeparam>
+        /// <param name="file"></param>
         /// <param name="propertyName">The name of the property</param>
         /// <param name="value">The value to set</param>
+        /// <param name="cancellationToken"></param>
         /// <returns>A <see cref="Task"/> to await</returns>
-        Task Remove<T, TProperty>(string propertyName, string value);
+        Task Remove<T, TProperty>(FileStream file, string propertyName, string value, CancellationToken cancellationToken);
     }
 }

Test.GBase/DataHandling/XmlDataHandlerTest.cs

@@ -213,7 +213,7 @@ namespace Test.GBase.DataHandling
             await xmlDataHandler.RemoveValue<XmlDataHandlerTest, string>("property", "SomeString");
 
             xmlDataHandlerCacheMock.Verify(c => c.TryRemoveValue<XmlDataHandlerTest, string>("property", "SomeString"), Times.Once);
-            xmlDataWriterMock.Verify(w => w.Remove<XmlDataHandlerTest, string>("property", "SomeString"), Times.Once);
+            xmlDataWriterMock.Verify(w => w.Remove<XmlDataHandlerTest, string>(TODO, "property", "SomeString", TODO), Times.Once);
         }
 
         [Test]
@@ -238,7 +238,7 @@ namespace Test.GBase.DataHandling
             await xmlDataHandler.RemoveValue<XmlDataHandlerTest, List<string>>("property", stringList);
 
             xmlDataHandlerCacheMock.Verify(c => c.TryRemoveValue<XmlDataHandlerTest, List<string>>("property", stringList), Times.Once);
-            xmlDataWriterMock.Verify(w => w.Remove<XmlDataHandlerTest, List<string>>("property", $"{stringList[0]},{stringList[1]},{stringList[2]}"), Times.Once);
+            xmlDataWriterMock.Verify(w => w.Remove<XmlDataHandlerTest, List<string>>(TODO, "property", $"{stringList[0]},{stringList[1]},{stringList[2]}", TODO), Times.Once);
         }
 
         [Test]
@@ -262,7 +262,7 @@ namespace Test.GBase.DataHandling
             await xmlDataHandler.RemoveValue<XmlDataHandlerTest, string>("property", null);
 
             xmlDataHandlerCacheMock.Verify(c => c.TryRemoveValue<It.IsValueType, It.IsValueType>(It.IsAny<string>(), It.IsAny<It.IsValueType>()), Times.Never);
-            xmlDataWriterMock.Verify(w => w.Remove<It.IsValueType, It.IsValueType>(It.IsAny<string>(), It.IsAny<string>()), Times.Never);
+            xmlDataWriterMock.Verify(w => w.Remove<It.IsValueType, It.IsValueType>(TODO, It.IsAny<string>(), It.IsAny<string>(), TODO), Times.Never);
         }
 
         [Test]