// 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;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.PooledObjects;
 
namespace Microsoft.CodeAnalysis.CSharp.UseObjectInitializer;
 
using static CSharpSyntaxTokens;
using static SyntaxFactory;
 
internal static class UseInitializerHelpers
{
    public static BaseObjectCreationExpressionSyntax GetNewObjectCreation(
        BaseObjectCreationExpressionSyntax baseObjectCreation,
        SeparatedSyntaxList<ExpressionSyntax> expressions)
    {
        if (baseObjectCreation is ObjectCreationExpressionSyntax { ArgumentList.Arguments.Count: 0 } objectCreation)
        {
            baseObjectCreation = objectCreation
                .WithType(objectCreation.Type.WithTrailingTrivia(objectCreation.ArgumentList.GetTrailingTrivia()))
                .WithArgumentList(null);
        }
 
        var firstExpression = expressions.First();
        var initializerKind = firstExpression is AssignmentExpressionSyntax
            ? SyntaxKind.ObjectInitializerExpression
            : SyntaxKind.CollectionInitializerExpression;
 
        return baseObjectCreation.WithInitializer(InitializerExpression(initializerKind, expressions));
    }
 
    public static void AddExistingItems<TMatch, TElementSyntax>(
        BaseObjectCreationExpressionSyntax objectCreation,
        ArrayBuilder<SyntaxNodeOrToken> nodesAndTokens,
        bool addTrailingComma,
        Func<TMatch?, ExpressionSyntax, TElementSyntax> createElement)
        where TMatch : struct
        where TElementSyntax : SyntaxNode
    {
        if (objectCreation.Initializer != null)
        {
            foreach (var nodeOrToken in objectCreation.Initializer.Expressions.GetWithSeparators())
            {
                if (nodeOrToken.IsToken)
                    nodesAndTokens.Add(nodeOrToken.AsToken());
                else
                    nodesAndTokens.Add(createElement(null, (ExpressionSyntax)nodeOrToken.AsNode()!));
            }
        }
 
        // If we have an odd number of elements already, add a comma at the end so that we can add the rest of the
        // items afterwards without a syntax issue.
        if (addTrailingComma && nodesAndTokens.Count % 2 == 1)
        {
            var last = nodesAndTokens.Last();
            nodesAndTokens.RemoveLast();
            nodesAndTokens.Add(last.WithTrailingTrivia());
            nodesAndTokens.Add(CommaToken.WithTrailingTrivia(last.GetTrailingTrivia()));
        }
    }
}