namespace ActivityPub;

///// <summary>
///// A class representing a link (either as a Uri or Link object)
///// </summary>
//public class LinkOrUri : OneOfBase<Uri, Link> {

//  protected LinkOrUri(OneOf<Uri, Link> _) : base(_) { }

//  public static implicit operator LinkOrUri(Uri _) => new LinkOrUri(_);
//  public static implicit operator LinkOrUri(Link _) => new LinkOrUri(_);
//  public static implicit operator LinkOrUri(string _) => new LinkOrUri(new Uri(_));

//  public static explicit operator Uri?(LinkOrUri _) => _.Match(uri => uri, link => link.Href);
//  public static explicit operator Link(LinkOrUri _) => _.Match(
//    uri => new Link { Href = uri },
//    link => link
//  );
//  public static explicit operator string?(LinkOrUri _) => ((Uri?)_)?.ToString();

//  public T? FetchObject<T>() where T : Object, new() {
//    Uri? uri = (Uri?)this;
//    if (uri == null) return default(T);

//    // TODO: Fetch the object from the uri instead of the below:
//    return this.Match(
//      uri => new T { Id = uri }, // TODO: Fetch the object
//      link => new T { Id = link.Href, Name = link.Name } // TODO: Fetch the object
//    );
//  }
//}

///// <summary>
///// A class representing either an object or link
///// </summary>
//public class GenericObjectOrLink<T> : OneOfBase<Uri, Link, T> where T : Object, new() {

//  protected GenericObjectOrLink(OneOf<Uri, Link, T> _) : base(_) { }

//  public static implicit operator GenericObjectOrLink<T>(Uri _) => new GenericObjectOrLink<T>(_);
//  public static implicit operator GenericObjectOrLink<T>(Link _) => new GenericObjectOrLink<T>(_);
//  public static implicit operator GenericObjectOrLink<T>(T _) => new GenericObjectOrLink<T>(_);
//  public static implicit operator GenericObjectOrLink<T>(string _) => new GenericObjectOrLink<T>(new Uri(_));

//  public static explicit operator Uri(GenericObjectOrLink<T> _) => _.Match(uri => uri, link => link.Href, obj => obj.Id);
//  public static explicit operator Link(GenericObjectOrLink<T> _) => _.Match(
//    uri => new Link { Href = uri },
//    link => link,
//    obj => new Link { Href = obj.Id, Name = obj.Name }
//  );
//  public static explicit operator T?(GenericObjectOrLink<T> _) => _.FetchObject();
//  public static explicit operator string?(GenericObjectOrLink<T> _) => ((Uri?)_)?.ToString();

//  public T? FetchObject(bool force = false) {
//    if (this.IsT2 && !force) return this.AsT2;
//    Uri? uri = (Uri?)this;
//    if (uri == null) return null;

//    // TODO: Fetch the object from the uri instead of the below:
//    return this.Match(
//      uri => new T { Id = uri }, // TODO: Fetch the object
//      link => new T { Id = link.Href, Name = link.Name }, // TODO: Fetch the object
//      obj => obj
//    );
//  }
//}

//public class ObjectOrLink : GenericObjectOrLink<Object> {
//  protected ObjectOrLink(OneOf<Uri, Link, Object> _) : base(_) { }
//  public bool IsUri => this.IsT0;
//  public bool IsLink => this.IsT1;
//  public bool IsObject => this.IsT2;
//}

///// <summary>
///// A class representing either a collection or link
///// </summary>
//public class CollectionOrLink : GenericObjectOrLink<Collection> {
//  protected CollectionOrLink(OneOf<Uri, Link, Collection> _) : base(_) { }
//}

///// <summary>
///// A class representing either a collection page or link
///// </summary>
//public class CollectionPageOrLink : GenericObjectOrLink<CollectionPage> {
//  protected CollectionPageOrLink(OneOf<Uri, Link, CollectionPage> _) : base(_) { }
//}

///// <summary>
///// A class representing a list of ObjectOrLinks
///// </summary>
//public class ListOrLink<T> : List<GenericObjectOrLink<T>> where T : Object, new() {
//  protected ListOrLink(List<GenericObjectOrLink<T>> _) : base(_) { }

//  public static implicit operator ListOrLink<T>(Uri _) => new ListOrLink<T>(new List<GenericObjectOrLink<T>> { _ });
//  public static implicit operator ListOrLink<T>(Link _) => new ListOrLink<T>(new List<GenericObjectOrLink<T>> { _ });
//  public static implicit operator ListOrLink<T>(T _) => new ListOrLink<T>(new List<GenericObjectOrLink<T>> { _ });
//  public static implicit operator ListOrLink<T>(string _) => new ListOrLink<T>(new List<GenericObjectOrLink<T>> { new Uri(_) });

//  public static explicit operator List<Uri>(ListOrLink<T> _) => _.Cast<Uri>().ToList();
//}

/// <summary>
/// Static functions for working with ActivityPub/ActivityStreams types
/// </summary>
public static class Types {

  /// <summary>
  /// Normalizes the type string to title case (all types in ActivityStreams start with a capital letter)
  /// </summary>
  /// <param name="type">The type string to normalize</param>
  /// <returns>The normalized type string (capital first letter)</returns>
  public static string Normalize(string type) {
    return Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(type.ToLower());
  }

  /// <summary>
  /// https://www.w3.org/TR/activitystreams-vocabulary/#activity-types
  /// </summary>
  public static readonly string[] Activity = [
    "Accept",
    "Add",
    "Announce",
    "Arrive",
    "Block",
    "Create",
    "Delete",
    "Dislike",
    "Flag",
    "Follow",
    "Ignore",
    "Invite",
    "Join",
    "Leave",
    "Like",
    "Listen",
    "Move",
    "Offer",
    "Question",
    "Reject",
    "Read",
    "Remove",
    "TentativeReject",
    "TentativeAccept",
    "Travel",
    "Undo",
    "Update",
    "View"
  ];

  /// <summary>
  /// https://www.w3.org/TR/activitystreams-vocabulary/#actor-types
  /// </summary>
  public static readonly string[] Actor = [
    "Application",
    "Group",
    "Organization",
    "Person",
    "Service"
  ];

  /// <summary>
  /// https://www.w3.org/TR/activitystreams-vocabulary/#object-types
  /// </summary>
  public static readonly string[] Object = [
    "Article",
    "Audio",
    "Document",
    "Event",
    "Image",
    "Note",
    "Page",
    "Place",
    "Profile",
    "Relationship",
    "Tombstone",
    "Video"
  ];

  /// <summary>
  /// https://www.w3.org/TR/activitystreams-vocabulary/#object-types
  /// </summary>
  public static readonly string[] Link = [
    "Mention"
  ];

  /// <summary>
  /// Checks if the object type is an activity type
  /// </summary>
  /// <param name="type">The type of the object</param>
  /// <returns>A boolean indicating whether the object is an activity type</returns>
  public static bool IsActivity(string type) => Activity.Contains(type);
  //public static bool IsActivity(this Object obj) => obj.Type == null ? false : IsActivity(obj.Type);

  /// <summary>
  /// Checks if the object type is an actor type
  /// </summary>
  /// <param name="type">The type of the object</param>
  /// <returns>A boolean indicating whether the object is an actor type</returns>
  public static bool IsActor(string type) => Actor.Contains(type);
  //public static bool IsActor(this Object obj) => obj.Type == null ? false : IsActor(obj.Type);

  /// <summary>
  /// Checks if the object type is an object type
  /// </summary>
  /// <param name="type">The type of the object</param>
  /// <returns>A boolean indicating whether the object is an object type</returns>
  public static bool IsObject(string type) => Object.Contains(type);
  //public static bool IsObject(this Object obj) => obj.Type == null ? false : IsObject(obj.Type);

  /// <summary>
  /// Checks if the object type is a link type
  /// </summary>
  /// <param name="type">The type of the object</param>
  /// <returns>A boolean indicating whether the object is a link type</returns>
  public static bool IsLink(string type) => Link.Contains(type);
  //public static bool IsLink(this Object obj) => obj.Type == null ? false : IsLink(obj.Type);

  /// <summary>
  /// Checks if the object type is an object or link type
  /// </summary>
  /// <param name="type">The type of the object</param>
  /// <returns>A boolean indicating whether the object is an object or link type</returns>
  public static bool IsObjectOrLink(string type) => Object.Concat(Link).Contains(type);
  //public static bool IsObjectOrLink(this Object obj) => obj.Type == null ? false : IsObjectOrLink(obj.Type);

}