using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.VisualStudio;
using Microsoft.VisualStudio.Shell;
using Microsoft.VisualStudio.Shell.Interop;
using Microsoft.VisualStudio.TextManager.Interop;
using Task = System.Threading.Tasks.Task;

namespace Prophet.CoopWithDsh
{
    [PackageRegistration(UseManagedResourcesOnly = true, AllowsBackgroundLoading = true)]
    [InstalledProductRegistration("DSH Open File Bridge", "Publishes open file metadata for DeepSeek Harness", "0.1.0")]
    [ProvideAutoLoad(UIContextGuids80.NoSolution, PackageAutoLoadFlags.BackgroundLoad)]
    [ProvideAutoLoad(UIContextGuids80.SolutionExists, PackageAutoLoadFlags.BackgroundLoad)]
    [Guid(PackageGuidString)]
    public sealed class CoopWithDshPackage : AsyncPackage, IVsRunningDocTableEvents
    {
        public const string PackageGuidString = "1e02d547-499b-41ed-a25e-b356a9687e31";
        private const int DebounceMilliseconds = 200;
        private const int HeartbeatMilliseconds = 15000;
        private IVsRunningDocumentTable? runningDocuments;
        private IVsSolution? solution;
        private SnapshotPublisher? publisher;
        private Timer? debounceTimer;
        private Timer? heartbeatTimer;
        private uint eventsCookie;
        private bool disposing;

        protected override async Task InitializeAsync(CancellationToken cancellationToken, IProgress<ServiceProgressData> progress)
        {
            await JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
            runningDocuments = await GetServiceAsync(typeof(SVsRunningDocumentTable)) as IVsRunningDocumentTable;
            solution = await GetServiceAsync(typeof(SVsSolution)) as IVsSolution;
            if (runningDocuments == null) throw new InvalidOperationException("Visual Studio Running Document Table is unavailable.");

            publisher = new SnapshotPublisher();
            ErrorHandler.ThrowOnFailure(runningDocuments.AdviseRunningDocTableEvents(this, out eventsCookie));
            debounceTimer = new Timer(_ => JoinableTaskFactory.RunAsync(PublishAsync), null, Timeout.Infinite, Timeout.Infinite);
            heartbeatTimer = new Timer(_ => JoinableTaskFactory.RunAsync(PublishAsync), null, HeartbeatMilliseconds, HeartbeatMilliseconds);
            AppDomain.CurrentDomain.ProcessExit += OnProcessExit;
            await PublishAsync();
        }

        private void SchedulePublish()
        {
            if (!disposing) debounceTimer?.Change(DebounceMilliseconds, Timeout.Infinite);
        }

        private async Task PublishAsync()
        {
            if (disposing || publisher == null || runningDocuments == null) return;
            await JoinableTaskFactory.SwitchToMainThreadAsync();
            var documents = EnumerateDocuments(runningDocuments);
            var workspace = ReadSolutionPath(solution);
            var snapshot = SnapshotModel.Create(publisher.InstanceId, Process.GetCurrentProcess().Id, workspace, documents, DateTimeOffset.UtcNow);
            try { publisher.Publish(snapshot); } catch (Exception error) { Trace.WriteLine($"DSH Open File Bridge publish failed: {error}"); }
        }

        private static IReadOnlyList<OpenDocument> EnumerateDocuments(IVsRunningDocumentTable table)
        {
            ThreadHelper.ThrowIfNotOnUIThread();
            ErrorHandler.ThrowOnFailure(table.GetRunningDocumentsEnum(out var iterator));
            var result = new List<OpenDocument>();
            var cookies = new uint[1];
            while (iterator.Next(1, cookies, out var fetched) == VSConstants.S_OK && fetched == 1)
            {
                IntPtr docData = IntPtr.Zero;
                try
                {
                    ErrorHandler.ThrowOnFailure(table.GetDocumentInfo(cookies[0], out _, out _, out _, out var moniker, out _, out _, out docData));
                    if (string.IsNullOrWhiteSpace(moniker) || !Path.IsPathRooted(moniker) || !File.Exists(moniker)) continue;
                    var dirty = false;
                    if (docData != IntPtr.Zero)
                    {
                        var value = Marshal.GetObjectForIUnknown(docData);
                        if (value is IVsPersistDocData persist && ErrorHandler.Succeeded(persist.IsDocDataDirty(out var isDirty))) dirty = isDirty != 0;
                    }
                    result.Add(new OpenDocument { Path = Path.GetFullPath(moniker), Label = Path.GetFileName(moniker), Dirty = dirty });
                }
                catch (Exception error) { Trace.WriteLine($"DSH Open File Bridge skipped one document: {error.Message}"); }
                finally { if (docData != IntPtr.Zero) Marshal.Release(docData); }
            }
            return result;
        }

        private static string? ReadSolutionPath(IVsSolution? solutionService)
        {
            ThreadHelper.ThrowIfNotOnUIThread();
            if (solutionService == null) return null;
            return ErrorHandler.Succeeded(solutionService.GetSolutionInfo(out _, out var solutionFile, out _)) && !string.IsNullOrWhiteSpace(solutionFile)
                ? solutionFile : null;
        }

        private void OnProcessExit(object sender, EventArgs e) => publisher?.Dispose();

        protected override void Dispose(bool disposing)
        {
            this.disposing = true;
            if (disposing)
            {
                AppDomain.CurrentDomain.ProcessExit -= OnProcessExit;
                debounceTimer?.Dispose();
                heartbeatTimer?.Dispose();
                if (runningDocuments != null && eventsCookie != 0)
                {
                    JoinableTaskFactory.Run(async () => {
                        await JoinableTaskFactory.SwitchToMainThreadAsync();
                        runningDocuments.UnadviseRunningDocTableEvents(eventsCookie);
                    });
                }
                publisher?.Dispose();
            }
            base.Dispose(disposing);
        }

        public int OnAfterFirstDocumentLock(uint docCookie, uint lockType, uint readLocks, uint editLocks) { SchedulePublish(); return VSConstants.S_OK; }
        public int OnBeforeLastDocumentUnlock(uint docCookie, uint lockType, uint readLocks, uint editLocks) { SchedulePublish(); return VSConstants.S_OK; }
        public int OnAfterSave(uint docCookie) { SchedulePublish(); return VSConstants.S_OK; }
        public int OnAfterAttributeChange(uint docCookie, uint attributes) { SchedulePublish(); return VSConstants.S_OK; }
        public int OnBeforeDocumentWindowShow(uint docCookie, int firstShow, IVsWindowFrame frame) { SchedulePublish(); return VSConstants.S_OK; }
        public int OnAfterDocumentWindowHide(uint docCookie, IVsWindowFrame frame) { SchedulePublish(); return VSConstants.S_OK; }
    }
}