// 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.
 
#nullable disable
 
using System;
using System.Collections.Immutable;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.Interop;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel.Collections;
 
internal sealed class CodeElementSnapshot : Snapshot
{
    private readonly ImmutableArray<EnvDTE.CodeElement> _elements;
 
    public CodeElementSnapshot(ICodeElements codeElements)
    {
        var count = codeElements.Count;
        var elementsBuilder = ArrayBuilder<EnvDTE.CodeElement>.GetInstance(count);
 
        for (var i = 0; i < count; i++)
        {
            // We use "i + 1" since CodeModel indices are 1-based
            if (ErrorHandler.Succeeded(codeElements.Item(i + 1, out var element)))
            {
                elementsBuilder.Add(element);
            }
        }
 
        _elements = elementsBuilder.ToImmutableAndFree();
    }
 
    public CodeElementSnapshot(ImmutableArray<EnvDTE.CodeElement> elements)
        => _elements = elements;
 
    public override int Count
    {
        get { return _elements.Length; }
    }
 
    public override EnvDTE.CodeElement this[int index]
    {
        get
        {
            if (index < 0 || index >= _elements.Length)
            {
                throw new ArgumentOutOfRangeException(nameof(index));
            }
 
            return _elements[index];
        }
    }
}