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

namespace AspClassic.Scripting.Utils;

internal abstract class CheckedDictionaryEnumerator : IDictionaryEnumerator, IEnumerator<KeyValuePair<object, object>>, IDisposable, IEnumerator
{
	private enum EnumeratorState
	{
		NotStarted,
		Started,
		Ended
	}

	private EnumeratorState _enumeratorState;

	public DictionaryEntry Entry
	{
		get
		{
			CheckEnumeratorState();
			return new DictionaryEntry(Key, Value);
		}
	}

	public object Key
	{
		get
		{
			CheckEnumeratorState();
			return GetKey();
		}
	}

	public object Value
	{
		get
		{
			CheckEnumeratorState();
			return GetValue();
		}
	}

	public object Current => Entry;

	KeyValuePair<object, object> IEnumerator<KeyValuePair<object, object>>.Current => new KeyValuePair<object, object>(Key, Value);

	private void CheckEnumeratorState()
	{
		if (_enumeratorState == EnumeratorState.NotStarted)
		{
			throw Error.EnumerationNotStarted();
		}
		if (_enumeratorState == EnumeratorState.Ended)
		{
			throw Error.EnumerationFinished();
		}
	}

	public bool MoveNext()
	{
		if (_enumeratorState == EnumeratorState.Ended)
		{
			throw Error.EnumerationFinished();
		}
		bool flag = DoMoveNext();
		if (flag)
		{
			_enumeratorState = EnumeratorState.Started;
		}
		else
		{
			_enumeratorState = EnumeratorState.Ended;
		}
		return flag;
	}

	public void Reset()
	{
		DoReset();
		_enumeratorState = EnumeratorState.NotStarted;
	}

	public void Dispose()
	{
		GC.SuppressFinalize(this);
	}

	protected abstract object GetKey();

	protected abstract object GetValue();

	protected abstract bool DoMoveNext();

	protected abstract void DoReset();
}