using System;
using System.Collections;
using System.Collections.Generic;

namespace AspClassic.Scripting.Utils;

[Serializable]
internal sealed class ReadOnlyDictionary<TKey, TValue> : IDictionary<TKey, TValue>, ICollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable
{
	private sealed class ReadOnlyWrapper<T> : ICollection<T>, IEnumerable<T>, IEnumerable
	{
		private readonly ICollection<T> _collection;

		public int Count => _collection.Count;

		public bool IsReadOnly => true;

		internal ReadOnlyWrapper(ICollection<T> collection)
		{
			_collection = collection;
		}

		public void Add(T item)
		{
			throw new NotSupportedException("Collection is read-only.");
		}

		public void Clear()
		{
			throw new NotSupportedException("Collection is read-only.");
		}

		public bool Contains(T item)
		{
			return _collection.Contains(item);
		}

		public void CopyTo(T[] array, int arrayIndex)
		{
			_collection.CopyTo(array, arrayIndex);
		}

		public bool Remove(T item)
		{
			throw new NotSupportedException("Collection is read-only.");
		}

		public IEnumerator<T> GetEnumerator()
		{
			return _collection.GetEnumerator();
		}

		IEnumerator IEnumerable.GetEnumerator()
		{
			return _collection.GetEnumerator();
		}
	}

	private readonly IDictionary<TKey, TValue> _dict;

	public ICollection<TKey> Keys
	{
		get
		{
			ICollection<TKey> keys = _dict.Keys;
			if (!keys.IsReadOnly)
			{
				return new ReadOnlyWrapper<TKey>(keys);
			}
			return keys;
		}
	}

	public ICollection<TValue> Values
	{
		get
		{
			ICollection<TValue> values = _dict.Values;
			if (!values.IsReadOnly)
			{
				return new ReadOnlyWrapper<TValue>(values);
			}
			return values;
		}
	}

	public TValue this[TKey key] => _dict[key];

	TValue IDictionary<TKey, TValue>.this[TKey key]
	{
		get
		{
			return _dict[key];
		}
		set
		{
			throw new NotSupportedException("Collection is read-only.");
		}
	}

	public int Count => _dict.Count;

	public bool IsReadOnly => true;

	public ReadOnlyDictionary(IDictionary<TKey, TValue> dict)
	{
		ReadOnlyDictionary<TKey, TValue> readOnlyDictionary = dict as ReadOnlyDictionary<TKey, TValue>;
		_dict = ((readOnlyDictionary != null) ? readOnlyDictionary._dict : dict);
	}

	public bool ContainsKey(TKey key)
	{
		return _dict.ContainsKey(key);
	}

	public bool TryGetValue(TKey key, out TValue value)
	{
		return _dict.TryGetValue(key, out value);
	}

	void IDictionary<TKey, TValue>.Add(TKey key, TValue value)
	{
		throw new NotSupportedException("Collection is read-only.");
	}

	bool IDictionary<TKey, TValue>.Remove(TKey key)
	{
		throw new NotSupportedException("Collection is read-only.");
	}

	public bool Contains(KeyValuePair<TKey, TValue> item)
	{
		return _dict.Contains(item);
	}

	public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
	{
		_dict.CopyTo(array, arrayIndex);
	}

	void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> item)
	{
		throw new NotSupportedException("Collection is read-only.");
	}

	void ICollection<KeyValuePair<TKey, TValue>>.Clear()
	{
		throw new NotSupportedException("Collection is read-only.");
	}

	bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> item)
	{
		throw new NotSupportedException("Collection is read-only.");
	}

	public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
	{
		return _dict.GetEnumerator();
	}

	IEnumerator IEnumerable.GetEnumerator()
	{
		return _dict.GetEnumerator();
	}
}