// 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 System.ComponentModel.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Classification;
using Microsoft.CodeAnalysis.Editor.Shared.Extensions;
using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Shared.TestHooks;
using Microsoft.VisualStudio.Text;
using Microsoft.VisualStudio.Text.Adornments;
using Microsoft.VisualStudio.Text.Editor;
 
namespace Microsoft.CodeAnalysis.Editor.CSharp.EventHookup;
 
[Export]
[method: ImportingConstructor]
[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
internal sealed partial class EventHookupSessionManager(
    IThreadingContext threadingContext,
    IToolTipService toolTipService)
{
    public readonly IThreadingContext ThreadingContext = threadingContext;
    private readonly IToolTipService _toolTipService = toolTipService;
 
    private IToolTipPresenter _toolTipPresenter;
 
    private EventHookupSession _currentSessionDoNotAccessDirectly;
 
    internal EventHookupSession CurrentSession
    {
        get
        {
            ThreadingContext.ThrowIfNotOnUIThread();
            return _currentSessionDoNotAccessDirectly;
        }
 
        set
        {
            ThreadingContext.ThrowIfNotOnUIThread();
            _currentSessionDoNotAccessDirectly?.CancelBackgroundTasks();
            _currentSessionDoNotAccessDirectly = value;
        }
    }
 
    // For test purposes only!
    internal ClassifiedTextElement[] TEST_MostRecentToolTipContent { get; set; }
 
    public async Task EventHookupFoundInSessionAsync(
        EventHookupSession analyzedSession, string eventName, CancellationToken cancellationToken)
    {
        await this.ThreadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(alwaysYield: true, cancellationToken);
        if (cancellationToken.IsCancellationRequested)
            return;
 
        var caretPoint = analyzedSession.TextView.GetCaretPoint(analyzedSession.SubjectBuffer);
 
        // only generate tooltip if it is not already shown (_toolTipPresenter == null)
        // Ensure the analyzed session matches the current session and that the caret is still
        // in the session's tracking span.
        if (_toolTipPresenter == null &&
            CurrentSession == analyzedSession &&
            caretPoint.HasValue &&
            IsCaretWithinSpanOrAtEnd(analyzedSession.TrackingSpan, analyzedSession.SubjectBuffer.CurrentSnapshot, caretPoint.Value))
        {
            // Create a tooltip presenter that stays alive, even when the user types, without tracking the mouse.
            _toolTipPresenter = _toolTipService.CreatePresenter(analyzedSession.TextView,
                new ToolTipParameters(trackMouse: false, ignoreBufferChange: true));
 
            // tooltips text is: Program_MyEvents;      (Press TAB to insert)
            // GetEventNameTask() gets back the event name, only needs to add a semicolon after it.
            var textRuns = new[]
            {
                new ClassifiedTextRun(ClassificationTypeNames.MethodName, eventName, ClassifiedTextRunStyle.UseClassificationFont),
                new ClassifiedTextRun(ClassificationTypeNames.Punctuation, ";", ClassifiedTextRunStyle.UseClassificationFont),
                new ClassifiedTextRun(ClassificationTypeNames.Text, CSharpEditorResources.Press_TAB_to_insert),
            };
            var content = new[] { new ClassifiedTextElement(textRuns) };
 
            _toolTipPresenter.StartOrUpdate(analyzedSession.TrackingSpan, content);
 
            // For test purposes only!
            TEST_MostRecentToolTipContent = content;
 
            // Watch all text buffer changes & caret moves while this event hookup session is active
            analyzedSession.TextView.TextSnapshot.TextBuffer.Changed += TextBuffer_Changed;
            CurrentSession.Dismissed += () => { analyzedSession.TextView.TextSnapshot.TextBuffer.Changed -= TextBuffer_Changed; };
 
            analyzedSession.TextView.Caret.PositionChanged += Caret_PositionChanged;
            CurrentSession.Dismissed += () => { analyzedSession.TextView.Caret.PositionChanged -= Caret_PositionChanged; };
        }
    }
 
    private static bool IsCaretWithinSpanOrAtEnd(ITrackingSpan trackingSpan, ITextSnapshot textSnapshot, SnapshotPoint caretPoint)
    {
        var snapshotSpan = trackingSpan.GetSpan(textSnapshot);
 
        // If the caret is within the span, then we want to show the tooltip
        if (snapshotSpan.Contains(caretPoint))
        {
            return true;
        }
 
        // Otherwise if the span is empty, and at the end of the file, and the caret
        // is also at the end of the file, then show the tooltip.
        if (snapshotSpan.IsEmpty &&
            snapshotSpan.Start.Position == caretPoint.Position &&
            caretPoint.Position == textSnapshot.Length)
        {
            return true;
        }
 
        return false;
    }
 
    internal void BeginSession(
        EventHookupCommandHandler eventHookupCommandHandler,
        ITextView textView,
        ITextBuffer subjectBuffer,
        int position,
        Document document,
        IAsynchronousOperationListener asyncListener,
        Mutex testSessionHookupMutex)
    {
        CurrentSession = new EventHookupSession(
            this, eventHookupCommandHandler, textView, subjectBuffer, position, document, asyncListener, testSessionHookupMutex);
    }
 
    public void DismissExistingSessions()
    {
        ThreadingContext.ThrowIfNotOnUIThread();
 
        _toolTipPresenter?.Dismiss();
        _toolTipPresenter = null;
 
        CurrentSession = null;
 
        // For test purposes only!
        TEST_MostRecentToolTipContent = null;
    }
 
    /// <summary>
    /// If any text is deleted or any non-space text is entered, cancel the session.
    /// </summary>
    private void TextBuffer_Changed(object sender, TextContentChangedEventArgs e)
    {
        ThreadingContext.ThrowIfNotOnUIThread();
 
        foreach (var change in e.Changes)
        {
            if (change.OldText.Length > 0 || change.NewText.Any(c => c != ' '))
            {
                DismissExistingSessions();
                return;
            }
        }
    }
 
    /// <summary>
    /// If the caret moves outside the session's tracking span, cancel the session.
    /// </summary>
    private void Caret_PositionChanged(object sender, EventArgs e)
    {
        ThreadingContext.ThrowIfNotOnUIThread();
 
        if (CurrentSession == null)
        {
            DismissExistingSessions();
            return;
        }
 
        var caretPoint = CurrentSession.TextView.GetCaretPoint(CurrentSession.SubjectBuffer);
 
        if (!caretPoint.HasValue)
        {
            DismissExistingSessions();
        }
 
        var snapshotSpan = CurrentSession.TrackingSpan.GetSpan(CurrentSession.SubjectBuffer.CurrentSnapshot);
        if (snapshotSpan.Snapshot != caretPoint.Value.Snapshot || !snapshotSpan.Contains(caretPoint.Value))
        {
            DismissExistingSessions();
        }
    }
}