namespace Python.Runtime.Codecs
{
 using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;

 /// <summary>
 /// Represents a group of <see cref="IPyObjectDecoder"/>s. Useful to group them by priority.
 /// </summary>
 public sealed class EncoderGroup: IPyObjectEncoder, IEnumerable<IPyObjectEncoder>, IDisposable
 {
 readonly List<IPyObjectEncoder> encoders = new();

 /// <summary>
 /// Add specified encoder to the group
 /// </summary>
 public void Add(IPyObjectEncoder item)
 {
 if (item is null) throw new ArgumentNullException(nameof(item));
 this.encoders.Add(item);
 }
 /// <summary>
 /// Remove all encoders from the group
 /// </summary>
 public void Clear() => this.encoders.Clear();

 /// <inheritdoc />
 public bool CanEncode(Type type) => this.encoders.Any(encoder => encoder.CanEncode(type));
 /// <inheritdoc />
 public PyObject? TryEncode(object value)
 {
 if (value is null) throw new ArgumentNullException(nameof(value));

 foreach (var encoder in this.GetEncoders(value.GetType()))
 {
 var result = encoder.TryEncode(value);
 if (result != null)
 {
 return result;
 }
 }

 return null;
 }

 /// <inheritdoc />
 public IEnumerator<IPyObjectEncoder> GetEnumerator() => this.encoders.GetEnumerator();
 IEnumerator IEnumerable.GetEnumerator() => this.encoders.GetEnumerator();

 public void Dispose()
 {
 foreach (var encoder in this.encoders.OfType<IDisposable>())
 {
 encoder.Dispose();
 }
 this.encoders.Clear();
 }
 }

 public static class EncoderGroupExtensions
 {
 /// <summary>
 /// Gets specific instances of <see cref="IPyObjectEncoder"/>
 /// (potentially selecting one from a collection),
 /// that can encode the specified <paramref name="type"/>.
 /// </summary>
 public static IEnumerable<IPyObjectEncoder> GetEncoders(this IPyObjectEncoder decoder, Type type)
 {
 if (decoder is null) throw new ArgumentNullException(nameof(decoder));

 if (decoder is IEnumerable<IPyObjectEncoder> composite)
 {
 foreach (var nestedEncoder in composite)
 foreach (var match in nestedEncoder.GetEncoders(type))
 {
 yield return match;
 }
 } else if (decoder.CanEncode(type))
 {
 yield return decoder;
 }
 }
 }
}