namespace Packt.Shared;

public class Person : object, IComparable<Person?>
{
  // properties
  public string? Name { get; set; }
  public DateTime DateOfBirth { get; set; }

  // methods
  public void WriteToConsole()
  {
    WriteLine($"{Name} was born on a {DateOfBirth:dddd}.");
  }

  // delegate field
  public event EventHandler? Shout;

  // data field
  public int AngerLevel;

  // method
  public void Poke()
  {
    AngerLevel++;
    if (AngerLevel >= 3)
    {
      /*
      // if something is listening...
      if (Shout != null)
      {
        // ...then call the delegate
        Shout(this, EventArgs.Empty);
      }
      */

      // simplified syntax available in C# 6 or later
      Shout?.Invoke(this, EventArgs.Empty);
    }
  }

  public int CompareTo(Person? other)
  {
    int position;
    if ((this is not null) && (other is not null))
    {
      if ((Name is not null) && (other.Name is not null))
      {
        // if both Name values are not null,
        // use the string implementation of CompareTo
        position = Name.CompareTo(other.Name);
      }
      else if ((Name is not null) && (other.Name is null))
      {
        position = -1; // else this Person precedes other Person
      }
      else if ((Name is null) && (other.Name is not null))
      {
        position = 1; // else this Person follows other Person
      }
      else
      {
        position = 0; // this Person and other Person are at same position
      }
    }
    else if ((this is not null) && (other is null))
    {
      position = -1; // this Person precedes other Person
    }
    else if ((this is null) && (other is not null))
    {
      position = 1; // this Person follows other Person
    }
    else
    {
      position = 0; // this Person and other Person are at same position
    }
    return position;
  }

  // overridden methods
  public override string ToString()
  {
    return $"{Name} is a {base.ToString()}";
  }

  public void TimeTravel(DateTime when)
  {
    if (when <= DateOfBirth)
    {
      throw new PersonException("If you travel back in time to a date earlier than your own birth, then the universe will explode!");
    }
    else
    {
      WriteLine($"Welcome to {when:yyyy}!");
    }
  }

}