// 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.

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

namespace Roslyn.Utilities;

internal static partial class ImmutableArrayExtensions
{
    public static ImmutableArray<T> ToImmutableArray<T>(this HashSet<T> set)
    {
        // [.. set] currently allocates, even for the empty case.  Workaround that until that is solved by the compiler.
        if (set.Count == 0)
            return [];

        return [.. set];
    }

    public static bool Contains<T>(this ImmutableArray<T> items, T item, IEqualityComparer<T>? equalityComparer)
        => items.IndexOf(item, 0, equalityComparer) >= 0;

    public static ImmutableArray<T> ToImmutableArrayOrEmpty<T>(this T[]? items)
    {
        if (items == null)
        {
            return [];
        }

        return ImmutableArray.Create<T>(items);
    }

    public static ImmutableArray<T> ToImmutableAndClear<T>(this ImmutableArray<T>.Builder builder)
    {
        if (builder.Count == 0)
            return [];

        if (builder.Count == builder.Capacity)
            return builder.MoveToImmutable();

        var result = builder.ToImmutable();
        builder.Clear();
        return result;
    }
}