// 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 System.Threading;
using Microsoft.CodeAnalysis.Diagnostics;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Formatting
{
    internal abstract partial class AbstractTriviaDataFactory
    {
        protected class ModifiedWhitespace : Whitespace
        {
            private readonly Whitespace? _original;
 
            public ModifiedWhitespace(SyntaxFormattingOptions options, int lineBreaks, int indentation, bool elastic, string language)
                : base(options, lineBreaks, indentation, elastic, language)
            {
                _original = null;
            }
 
            public ModifiedWhitespace(SyntaxFormattingOptions options, Whitespace original, int lineBreaks, int indentation, bool elastic, string language)
                : base(options, lineBreaks, indentation, elastic, language)
            {
                Contract.ThrowIfNull(original);
                _original = original;
            }
 
            public override bool ContainsChanges => false;
 
            public override TriviaData WithSpace(int space, FormattingContext context, ChainedFormattingRules formattingRules)
            {
                if (_original == null)
                {
                    return base.WithSpace(space, context, formattingRules);
                }
 
                if (this.LineBreaks == _original.LineBreaks && _original.Spaces == space)
                {
                    return _original;
                }
 
                return base.WithSpace(space, context, formattingRules);
            }
 
            public override TriviaData WithLine(int line, int indentation, FormattingContext context, ChainedFormattingRules formattingRules, CancellationToken cancellationToken)
            {
                if (_original == null)
                {
                    return base.WithLine(line, indentation, context, formattingRules, cancellationToken);
                }
 
                if (_original.LineBreaks == line && _original.Spaces == indentation)
                {
                    return _original;
                }
 
                return base.WithLine(line, indentation, context, formattingRules, cancellationToken);
            }
 
            public override TriviaData WithIndentation(
                int indentation, FormattingContext context, ChainedFormattingRules formattingRules, CancellationToken cancellationToken)
            {
                if (_original == null)
                {
                    return base.WithIndentation(indentation, context, formattingRules, cancellationToken);
                }
 
                if (this.LineBreaks == _original.LineBreaks && _original.Spaces == indentation)
                {
                    return _original;
                }
 
                return base.WithIndentation(indentation, context, formattingRules, cancellationToken);
            }
 
            public override void Format(
                FormattingContext context,
                ChainedFormattingRules formattingRules,
                Action<int, TokenStream, TriviaData> formattingResultApplier,
                CancellationToken cancellationToken,
                int tokenPairIndex = TokenPairIndexNotNeeded)
            {
                formattingResultApplier(tokenPairIndex, context.TokenStream, new FormattedWhitespace(this.Options, this.LineBreaks, this.Spaces, this.Language));
            }
        }
    }
}