// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Collections.Immutable;
using Microsoft.CodeAnalysis;

namespace Microsoft.Interop
{
    public static class IncrementalValuesProviderExtensions
    {
        /// <summary>
        /// Format the syntax nodes in the given provider such that we will not re-normalize if the input nodes have not changed.
        /// </summary>
        /// <typeparam name="TNode">A syntax node kind.</typeparam>
        /// <param name="provider">The input nodes</param>
        /// <returns>A provider of the formatted syntax nodes.</returns>
        /// <remarks>
        /// Normalizing whitespace is very expensive, so if a generator will have cases where the input information into the step
        /// that creates <paramref name="provider"/> may change but the results of <paramref name="provider"/> will say the same,
        /// using this method to format the code in a separate step will reduce the amount of work the generator repeats when the
        /// output code will not change.
        /// </remarks>
        public static IncrementalValuesProvider<TNode> SelectNormalized<TNode>(this IncrementalValuesProvider<TNode> provider)
            where TNode : SyntaxNode
        {
            return provider.Select(static (node, ct) => node.NormalizeWhitespace());
        }

        public static (IncrementalValuesProvider<T>, IncrementalValuesProvider<T2>) Split<T, T2>(this IncrementalValuesProvider<(T, T2)> provider)
        {
            return (provider.Select(static (data, ct) => data.Item1), provider.Select(static (data, ct) => data.Item2));
        }

        public static IncrementalValuesProvider<T> Concat<T>(this IncrementalValuesProvider<T> first, IncrementalValuesProvider<T> second)
        {
            return first.Collect().Combine(second.Collect()).SelectMany(static (data, ct) => data.Left.AddRange(data.Right));
        }
    }
}