using System;
using System.Collections.Generic;

namespace Python.Runtime.Codecs
{
 public class IterableDecoder : IPyObjectDecoder
 {
 internal static bool IsIterable(Type targetType)
 {
 //if it is a plain IEnumerable, we can decode it using sequence protocol.
 if (targetType == typeof(System.Collections.IEnumerable))
 return true;

 if (!targetType.IsGenericType)
 return false;

 return targetType.GetGenericTypeDefinition() == typeof(IEnumerable<>);
 }

 internal static bool IsIterable(PyType objectType)
 {
 return objectType.HasAttr("__iter__");
 }

 public bool CanDecode(PyType objectType, Type targetType)
 {
 return IsIterable(objectType) && IsIterable(targetType);
 }

 public bool TryDecode<T>(PyObject pyObj, out T value)
 {
 //first see if T is a plan IEnumerable
 if (typeof(T) == typeof(System.Collections.IEnumerable))
 {
 object enumerable = new CollectionWrappers.IterableWrapper<object>(pyObj);
 value = (T)enumerable;
 return true;
 }

 var elementType = typeof(T).GetGenericArguments()[0];
 var collectionType = typeof(CollectionWrappers.IterableWrapper<>).MakeGenericType(elementType);

 var instance = Activator.CreateInstance(collectionType, new[] { pyObj });
 value = (T)instance;
 return true;
 }

 public static IterableDecoder Instance { get; } = new IterableDecoder();

 public static void Register()
 {
 PyObjectConversions.RegisterDecoder(Instance);
 }
 }
}