using System.ComponentModel;
using System.Text;

namespace Qrakhen.Qamp.Memory;

public struct BufferSpan
{
   public static readonly BufferSpan None = new(0, 0);

   public int Start { get; set; } = 0;
   public int End { get; set; } = 0;

   public bool HasSelection => Start - End != 0;

   public BufferSpan(int start, int end)
   {
      Start = start;
      End = end;
   }

   public BufferSpan Synchronized<T>(TailBuffer<T> source)
   {
      return new BufferSpan(Start, Math.Min(End, source.Tail));
   }

   public T[] GetSelectedRegion<T>(TailBuffer<T> source)
   {
      return source.Data[Start..End];
   }
}

public class LineBuffer : TailBuffer<byte>, INotifyPropertyChanged
{
   public Encoding Encoding { get; }
   public string Cached { get; private set; } = "";
   public event PropertyChangedEventHandler? PropertyChanged;

   public LineBuffer(Encoding encoding, int size = 0x80) : base(size)
   {
      Encoding = encoding;
   }

   public LineBuffer(string data) : this(data, Encoding.ASCII) { }
   public LineBuffer(string data, Encoding encoding) : this(encoding.GetBytes(data), encoding) { }
   public LineBuffer(byte[] data, Encoding encoding) : base(data)
   {
      Encoding = encoding;
      Cached = ToString();
   }

   protected override void SetTail(int tail = -1)
   {
      base.SetTail(tail);
      Cached = ToString();
      PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Cached)));
   }

   public void Insert(int cursor, string data)
       => Insert(cursor, Encoding.GetBytes(data));

   public string ToString(BufferSpan span)
   {
      var synced = span.Synchronized(this);
      if (!synced.HasSelection)
         return string.Empty;
      return Encoding.GetString(Data[synced.Start..synced.End]);
   }

   public override string ToString()
   {
      if (Tail == 0 || Encoding == null)
         return string.Empty;
      return Encoding.GetString(Data, 0, Tail);
   }

   public override object Clone()
   {
      return new LineBuffer(_data.ToArray(), Encoding);
   }

   public static implicit operator LineBuffer(string s) => new LineBuffer(s);
}