// 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.Collections.Generic;
using System.Collections.Immutable;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Host
{
    internal abstract class AbstractSpanMappingService : ISpanMappingService
    {
        public abstract bool SupportsMappingImportDirectives { get; }
 
        public abstract Task<ImmutableArray<(string mappedFilePath, TextChange mappedTextChange)>> GetMappedTextChangesAsync(
            Document oldDocument,
            Document newDocument,
            CancellationToken cancellationToken);
 
        public abstract Task<ImmutableArray<MappedSpanResult>> MapSpansAsync(
            Document document,
            IEnumerable<TextSpan> spans,
            CancellationToken cancellationToken);
 
        protected static ImmutableArray<(string mappedFilePath, TextChange mappedTextChange)> MatchMappedSpansToTextChanges(
            ImmutableArray<TextChange> textChanges,
            ImmutableArray<MappedSpanResult> mappedSpanResults)
        {
            Contract.ThrowIfFalse(mappedSpanResults.Length == textChanges.Length);
 
            using var _ = ArrayBuilder<(string, TextChange)>.GetInstance(out var mappedFilePathAndTextChange);
            for (var i = 0; i < mappedSpanResults.Length; i++)
            {
                // Only include changes that could be mapped.
                var newText = textChanges[i].NewText;
                if (!mappedSpanResults[i].IsDefault && newText != null)
                {
                    var newTextChange = new TextChange(mappedSpanResults[i].Span, newText);
                    mappedFilePathAndTextChange.Add((mappedSpanResults[i].FilePath, newTextChange));
                }
            }
 
            return mappedFilePathAndTextChange.ToImmutable();
        }
    }
}