Implemented Model

MeetTheTeacher/Model/Comparison/ByHourComparer.cs

@@ -16,7 +16,20 @@ public sealed class ByHourComparer : ComparerBase, IComparer<Teacher>
 
     public int Compare(Teacher? x, Teacher? y)
     {
-        // TODO
+        int nullCheck = CheckNull(x, y);
-        return -1;
+        if (nullCheck != 2)
+        {
+            return nullCheck;
+        }
+        
+        // Ignore possibility of null, bc we already checked it above
+        int dayComparison = CompareEnum(x!.ConsultingHourWeekDay, y!.ConsultingHourWeekDay);
+        if (dayComparison != 0)
+        {
+            return ApplyCorrectDirection(dayComparison);
+        }
+
+        int unitComparison = CompareEnum(x.ConsultingHourUnit, y.ConsultingHourUnit);
+        return ApplyCorrectDirection(unitComparison);
     }
 }

MeetTheTeacher/Model/Comparison/ByNameComparer.cs

@@ -16,7 +16,12 @@ public sealed class ByNameComparer : ComparerBase, IComparer<Teacher>
 
     public int Compare(Teacher? x, Teacher? y)
     {
-        // TODO
+        int nullCheck = CheckNull(x, y);
-        return -1;
+        if (nullCheck != 2)
+        {
+            return nullCheck;
+        }
+        
+        return ApplyCorrectDirection(string.Compare(x!.Name, y!.Name, StringComparison.Ordinal));
     }
 }

MeetTheTeacher/Model/Comparison/ByRoomComparer.cs

@@ -8,7 +8,19 @@ public sealed class ByRoomComparer : IComparer<Teacher>
 {
     public int Compare(Teacher? x, Teacher? y)
     {
-        // TODO
+        if (x == null && y == null)
+        {
+            return 0;
+        }
+        if (x == null)
+        {
+            return 1;
+        }
+        if (y == null)
+        {
             return -1;
         }
+
+        return string.Compare(x!.Room, y!.Room, StringComparison.Ordinal);
+    }
 }

MeetTheTeacher/Model/Comparison/ComparerBase.cs

@@ -19,6 +19,58 @@ public abstract class ComparerBase
     /// </summary>
     protected bool Ascending { get; }
 
-	// TODO: consider moving the basic RefEquals code of CompareTo from the subclasses here
+    /// <summary>
-	// maybe also rename this to SortOrderComparerBase or something and introduce another, common base class for all three?
+    /// Checks if a <see cref="Teacher"/> is null
+    /// </summary>
+    /// <param name="x">Teacher x</param>
+    /// <param name="y">Teacher y</param>
+    /// <returns>0 if both are null, the comparison if only one is null and 2 if both are NOT null</returns>
+    protected int CheckNull(Teacher? x, Teacher? y)
+    {
+        if (x == null && y == null)
+        {
+            return 0;
+        }
+        if (x == null)
+        {
+            return Ascending ? 1 : -1;
+        }
+        if (y == null)
+        {
+            return Ascending ? -1 : 1;
+        }
+
+        return 2;
+    }
+
+    /// <summary>
+    /// Compares the two enums
+    /// </summary>
+    /// <param name="x">First enum</param>
+    /// <param name="y">Second enum</param>
+    /// <typeparam name="TEnum">Enum Type</typeparam>
+    /// <returns>The comparison</returns>
+    protected int CompareEnum<TEnum>(TEnum? x, TEnum? y) where TEnum : struct, Enum
+    {
+        if (!x.HasValue && !y.HasValue)
+        {
+            return 0;
+        }
+        if (!x.HasValue)
+        {
+            return -1;
+        }
+        if (!y.HasValue)
+        {
+            return 1;
+        }
+        return x.Value.CompareTo(y.Value);
+    }
+
+    /// <summary>
+    /// Applies the correct direction
+    /// </summary>
+    /// <param name="comparison">The comparison</param>
+    /// <returns><param name="comparison"> if <see cref="Ascending"/> is true, else returns negated value</param></returns>
+    protected int ApplyCorrectDirection(int comparison) => Ascending ? comparison : -comparison;
 }

MeetTheTeacher/Model/CsvData.cs

@@ -35,13 +35,13 @@ public sealed class CsvData
     ///     Gets a CSV header based on <see cref="HeaderNames" />
     /// </summary>
     /// <returns>A CSV header line</returns>
-    public string GetHeader() => null!; // TODO
+    public string GetHeader() => string.Join(Separator.ToString(), HeaderNames);
 
     /// <summary>
     ///     Gets a CSV data line based on <see cref="Data" />
     /// </summary>
     /// <returns>A CSV data line</returns>
-    public string GetData() => null!; // TODO
+    public string GetData() => string.Join(Separator.ToString(), Data);
 
     /// <summary>
     ///     Allows to deconstruct the object into its header and data parts
@@ -50,8 +50,7 @@ public sealed class CsvData
     /// <param name="data">Set to <see cref="Data" /></param>
     public void Deconstruct(out IReadOnlyList<string> headerNames, out IReadOnlyList<string> data)
     {
-        // TODO
+        headerNames = HeaderNames;
-        headerNames = null!;
+        data = Data;
-        data = null!;
     }
 }

MeetTheTeacher/Model/Teacher.cs

@@ -45,10 +45,25 @@ public class Teacher : ICsvRepresentable
     {
         get
         {
-            // TODO
+            if (ConsultingHour == null)
-            return null!;
+            {
+                return null;
+            }
+            
+            return ConsultingHourUnit == null ? ConsultingHour.ToString() : $"{ConsultingHour} ({ConsultingHourUnit})";
         }
     }
 
-    public virtual CsvData ToCsvData() => null!; // TODO
+    public virtual CsvData ToCsvData()
+    {
+        List<string> headerNames = ["Name", "Day", "ConsultingHour", "Room"];
+        List<string> dataLine = [
+            Name, 
+            ConsultingHourWeekDay?.ToString() ?? string.Empty, 
+            ConsultingHourTime ?? string.Empty, 
+            Room ?? string.Empty
+        ];
+        var data = new CsvData(headerNames, dataLine);
+        return data;
+    }
 }

MeetTheTeacher/Model/TeacherWithBusinessCard.cs

@@ -26,7 +26,16 @@ public sealed class TeacherWithBusinessCard : Teacher
 
     public override CsvData ToCsvData()
     {
-        // TODO (remember to maybe use the base implementation...)
+        var data = base.ToCsvData();
-        return null!;
+        (IReadOnlyList<string> headerNamesBase, IReadOnlyList<string> dataLineBase) = data;
+        
+        var headerNames = (List<string>)headerNamesBase;
+        var dataLine = (List<string>)dataLineBase;
+        
+        headerNames.Add("Image");
+        dataLine.Add($"{BaseUrl}/{Id}");
+        
+        var csvData = new CsvData(headerNames, dataLine);
+        return csvData;
     }
 }

MeetTheTeacher/Model/TimeFrame.cs

@@ -21,18 +21,30 @@ public readonly record struct TimeFrame(TimeOnly Start, TimeOnly End)
     /// <returns>True if time frame could be parsed successfully; false otherwise</returns>
     public static bool TryParse(string timeFrame, out TimeFrame? result)
     {
-        // TODO
         result = null;
+        string[] timeFrames = timeFrame.Split("-");
+        if (timeFrames.Length != 2)
+        {
             return false;
         }
         
+        if (!TimeOnly.TryParse(timeFrames[0], out TimeOnly start) || !TimeOnly.TryParse(timeFrames[1], out TimeOnly end))
+        {
+            return false;
+        }
+
+        if (start > end)
+        {
+            (start, end) = (end, start);
+        }
+        
+        result = new TimeFrame(start, end);
+        return true;
+    }
+
     /// <summary>
     ///     Returns a string representation of the time frame in format HH:MM-HH:MM
     /// </summary>
     /// <returns></returns>
-    public override string ToString()
+    public override string ToString() => $"{Start}-{End}";
-    {
-        // TODO
-        return null!; 
-    }
 }