// 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.
 
#nullable disable
 
using System;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis
{
    public partial class Workspace
    {
        /// <summary>
        /// A class that responds to text buffer changes
        /// </summary>
        private class TextTracker
        {
            private readonly Workspace _workspace;
            private readonly DocumentId _documentId;
            internal readonly SourceTextContainer TextContainer;
            private readonly EventHandler<TextChangeEventArgs> _weakOnTextChanged;
            private readonly Action<Workspace, DocumentId, SourceText, PreservationMode> _onChangedHandler;
 
            internal TextTracker(
                Workspace workspace,
                DocumentId documentId,
                SourceTextContainer textContainer,
                Action<Workspace, DocumentId, SourceText, PreservationMode> onChangedHandler)
            {
                _workspace = workspace;
                _documentId = documentId;
                this.TextContainer = textContainer;
                _onChangedHandler = onChangedHandler;
 
                // use weak event so TextContainer cannot accidentally keep workspace alive.
                _weakOnTextChanged = WeakEventHandler<TextChangeEventArgs>.Create(this, (target, sender, args) => target.OnTextChanged(sender, args));
            }
 
            public void Connect()
                => this.TextContainer.TextChanged += _weakOnTextChanged;
 
            public void Disconnect()
                => this.TextContainer.TextChanged -= _weakOnTextChanged;
 
            private void OnTextChanged(object sender, TextChangeEventArgs e)
            {
                // ok, the version changed.  Report that we've got an edit so that we can analyze
                // this source file and update anything accordingly.
                _onChangedHandler(_workspace, _documentId, e.NewText, PreservationMode.PreserveIdentity);
            }
        }
    }
}