Group implementation

src/JSCalendar.Net/Converters/DurationJsonConverter.cs

@@ -48,7 +48,7 @@ private static Duration ParseDuration(string durationString)
         };
     }
 
-    private static int? ParseIntGroup(Group group)
+    private static int? ParseIntGroup(System.Text.RegularExpressions.Group group)
     {
         if (group.Success && int.TryParse(group.Value, out var value)) return value;
 

src/JSCalendar.Net/Converters/JSCalendarObjectConverter.cs

@@ -0,0 +1,41 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace JSCalendar.Net.Converters;
+
+/// <summary>
+///     JSON converter for IJSCalendarObject interface to support polymorphic deserialization.
+///     This converter reads the @type property to determine whether to deserialize an Event or Task.
+/// </summary>
+public class JSCalendarObjectConverter : JsonConverter<IJSCalendarObject>
+{
+    public override IJSCalendarObject? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        // Read the JSON as a JsonDocument to inspect the @type property
+        using var jsonDoc = JsonDocument.ParseValue(ref reader);
+        var root = jsonDoc.RootElement;
+
+        // Check for @type property
+        if (!root.TryGetProperty("@type", out var typeProperty))
+        {
+            throw new JsonException("Missing @type property in JSCalendar object");
+        }
+
+        var typeName = typeProperty.GetString();
+
+        // Deserialize based on the @type value
+        var json = root.GetRawText();
+        return typeName switch
+        {
+            "Event" => JsonSerializer.Deserialize<Event>(json, options),
+            "Task" => JsonSerializer.Deserialize<Task>(json, options),
+            _ => throw new JsonException($"Unknown JSCalendar object type: {typeName}")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, IJSCalendarObject value, JsonSerializerOptions options)
+    {
+        // Serialize the concrete type
+        JsonSerializer.Serialize(writer, value, value.GetType(), options);
+    }
+}

src/JSCalendar.Net/Event.cs

@@ -7,7 +7,7 @@ namespace JSCalendar.Net;
 ///     Represents a calendar event in JSCalendar format (RFC 8984).
 ///     This is the main type for calendar events.
 /// </summary>
-public sealed class Event
+public sealed class Event : IJSCalendarObject
 {
     // Metadata Properties (Section 4.1)
 

src/JSCalendar.Net/Group.cs

@@ -0,0 +1,120 @@
+using System.Text.Json.Serialization;
+
+namespace JSCalendar.Net;
+
+/// <summary>
+///     Represents a collection of events and/or tasks in JSCalendar format (RFC 8984 Section 2.3).
+///     A Group is used to organize related calendar objects together.
+/// </summary>
+public sealed class Group
+{
+    // Metadata Properties (Section 4.1)
+
+    /// <summary>
+    ///     Type identifier. MUST be "Group".
+    /// </summary>
+    [JsonPropertyName("@type")]
+    public string Type { get; init; } = "Group";
+
+    /// <summary>
+    ///     Globally unique identifier for this group (Section 4.1.2).
+    ///     REQUIRED property.
+    /// </summary>
+    [JsonPropertyName("uid")]
+    public required string Uid { get; init; }
+
+    /// <summary>
+    ///     Producer identifier that created this group (Section 4.1.4).
+    /// </summary>
+    [JsonPropertyName("prodId")]
+    public string? ProdId { get; init; }
+
+    /// <summary>
+    ///     Date and time this group was created (Section 4.1.5).
+    /// </summary>
+    [JsonPropertyName("created")]
+    public DateTimeOffset? Created { get; init; }
+
+    /// <summary>
+    ///     Date and time this group was last updated (Section 4.1.6).
+    ///     REQUIRED property.
+    /// </summary>
+    [JsonPropertyName("updated")]
+    public required DateTimeOffset Updated { get; init; }
+
+    // What and Where Properties (Section 4.2)
+
+    /// <summary>
+    ///     Short summary or name of the group (Section 4.2.1).
+    ///     Default: empty String
+    /// </summary>
+    [JsonPropertyName("title")]
+    public string Title { get; init; } = "";
+
+    /// <summary>
+    ///     Detailed description of the group (Section 4.2.2).
+    ///     Default: empty String
+    /// </summary>
+    [JsonPropertyName("description")]
+    public string Description { get; init; } = "";
+
+    /// <summary>
+    ///     Content type of the description (Section 4.2.3).
+    ///     Default: "text/plain"
+    /// </summary>
+    [JsonPropertyName("descriptionContentType")]
+    public string DescriptionContentType { get; init; } = "text/plain";
+
+    /// <summary>
+    ///     Links to external resources associated with this group (Section 4.2.7).
+    /// </summary>
+    [JsonPropertyName("links")]
+    public Dictionary<string, Link>? Links { get; init; }
+
+    /// <summary>
+    ///     Language tag for this group (Section 4.2.8).
+    /// </summary>
+    [JsonPropertyName("locale")]
+    public string? Locale { get; init; }
+
+    /// <summary>
+    ///     Keywords or tags for this group (Section 4.2.9).
+    /// </summary>
+    [JsonPropertyName("keywords")]
+    public Dictionary<string, bool>? Keywords { get; init; }
+
+    /// <summary>
+    ///     Categories for this group (Section 4.2.10).
+    /// </summary>
+    [JsonPropertyName("categories")]
+    public Dictionary<string, bool>? Categories { get; init; }
+
+    /// <summary>
+    ///     Color to use when displaying this group (Section 4.2.11).
+    /// </summary>
+    [JsonPropertyName("color")]
+    public string? Color { get; init; }
+
+    // Time Zone Properties (Section 4.7)
+
+    /// <summary>
+    ///     Time zone definitions referenced by entries in this group (Section 4.7.2).
+    /// </summary>
+    [JsonPropertyName("timeZones")]
+    public Dictionary<string, TimeZone>? TimeZones { get; init; }
+
+    // Group-specific Properties (Section 5.3)
+
+    /// <summary>
+    ///     Collection of Event and/or Task objects in this group (Section 5.3.1).
+    ///     REQUIRED property.
+    /// </summary>
+    [JsonPropertyName("entries")]
+    public required List<IJSCalendarObject> Entries { get; init; }
+
+    /// <summary>
+    ///     Source URI from which updated versions of this group may be retrieved (Section 5.3.2).
+    /// </summary>
+    [JsonPropertyName("source")]
+    public string? Source { get; init; }
+}

src/JSCalendar.Net/IJSCalendarObject.cs

@@ -0,0 +1,27 @@
+using System.Text.Json.Serialization;
+using JSCalendar.Net.Converters;
+
+namespace JSCalendar.Net;
+
+/// <summary>
+///     Marker interface for JSCalendar objects that can be entries in a Group.
+///     This interface is implemented by Event and Task objects.
+/// </summary>
+[JsonConverter(typeof(JSCalendarObjectConverter))]
+public interface IJSCalendarObject
+{
+    /// <summary>
+    ///     Type identifier for this JSCalendar object.
+    /// </summary>
+    string Type { get; }
+
+    /// <summary>
+    ///     Globally unique identifier for this object.
+    /// </summary>
+    string Uid { get; }
+
+    /// <summary>
+    ///     Date and time this object was last updated.
+    /// </summary>
+    DateTimeOffset Updated { get; }
+}

src/JSCalendar.Net/Task.cs

@@ -6,7 +6,7 @@ namespace JSCalendar.Net;
 /// <summary>
 ///     Represents a task/todo item in JSCalendar format (RFC 8984 Section 2.2).
 /// </summary>
-public sealed class Task
+public sealed class Task : IJSCalendarObject
 {
     // Metadata Properties (Section 4.1)