// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

namespace Microsoft.CodeAnalysis;

internal readonly partial struct SymbolKeyResolution
{
    public readonly struct Enumerable<TSymbol> where TSymbol : ISymbol
    {
        private readonly SymbolKeyResolution _resolution;

        internal Enumerable(SymbolKeyResolution resolution)
            => _resolution = resolution;

        public Enumerator<TSymbol> GetEnumerator()
            => new(_resolution);
    }

    public struct Enumerator<TSymbol> where TSymbol : ISymbol
    {
        private readonly SymbolKeyResolution _symbolKeyResolution;
        private int _index;

        internal Enumerator(SymbolKeyResolution symbolKeyResolution)
        {
            _symbolKeyResolution = symbolKeyResolution;
            _index = -1;
        }

        public bool MoveNext()
        {
            if (_symbolKeyResolution.Symbol != null)
            {
                return ++_index == 0 && _symbolKeyResolution.Symbol is TSymbol;
            }

            while (++_index < _symbolKeyResolution.CandidateSymbols.Length)
            {
                if (_symbolKeyResolution.CandidateSymbols[_index] is TSymbol)
                {
                    return true;
                }
            }

            return false;
        }

        public readonly TSymbol Current
        {
            get
            {
                if (_symbolKeyResolution.Symbol != null)
                {
                    return (TSymbol)_symbolKeyResolution.Symbol;
                }

                return (TSymbol)_symbolKeyResolution.CandidateSymbols[_index];
            }
        }
    }
}