using System;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Avalonia.Controls.Notifications;
using System.Threading.Tasks.Dataflow;
using Avalonia.Threading;
using AvaloniaEdit.Document;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using FluentAvalonia.UI.Controls;
using Microsoft.Extensions.Logging;
using StabilityMatrix.Avalonia.Services;
using StabilityMatrix.Avalonia.Views;
using StabilityMatrix.Core.Attributes;
using StabilityMatrix.Core.Helper;
using StabilityMatrix.Core.Helper.Factory;
using StabilityMatrix.Core.Models;
using StabilityMatrix.Core.Models.Packages;
using StabilityMatrix.Core.Processes;
using StabilityMatrix.Core.Python;
using StabilityMatrix.Core.Services;

namespace StabilityMatrix.Avalonia.ViewModels;

[View(typeof(LaunchPageView))]
public partial class LaunchPageViewModel : PageViewModelBase, IDisposable
{
    private readonly ILogger<LaunchPageViewModel> logger;
    private readonly ISettingsManager settingsManager;
    private readonly IPackageFactory packageFactory;
    private readonly IPyRunner pyRunner;
    private readonly INotificationService notificationService;
    public override string Title => "Launch";
    public override Symbol Icon => Symbol.PlayFilled;

    [ObservableProperty]
    private TextDocument consoleDocument = new();
    
    // Queue for console updates
    private readonly BufferBlock<ProcessOutput> consoleUpdateBuffer = new();
    // Task that updates the console (runs on UI thread)
    private Task? consoleUpdateTask;
    private CancellationTokenSource? consoleUpdateCts;
    
    [ObservableProperty] private bool launchButtonVisibility;
    [ObservableProperty] private bool stopButtonVisibility;
    [ObservableProperty] private bool isLaunchTeachingTipsOpen;
    [ObservableProperty] private bool showWebUiButton;
    
    [ObservableProperty] private InstalledPackage? selectedPackage;
    [ObservableProperty] private ObservableCollection<InstalledPackage> installedPackages = new();

    [ObservableProperty] private BasePackage? runningPackage;
    
    // private bool clearingPackages;
    private string webUiUrl = string.Empty;

    public LaunchPageViewModel(ILogger<LaunchPageViewModel> logger, ISettingsManager settingsManager, IPackageFactory packageFactory,
        IPyRunner pyRunner, INotificationService notificationService)
    {
        this.logger = logger;
        this.settingsManager = settingsManager;
        this.packageFactory = packageFactory;
        this.pyRunner = pyRunner;
        this.notificationService = notificationService;

        EventManager.Instance.PackageLaunchRequested +=
            async (s, e) => await OnPackageLaunchRequested(s, e);
        EventManager.Instance.OneClickInstallFinished += OnOneClickInstallFinished;
    }

    private async Task OnPackageLaunchRequested(object? sender, Guid e)
    {
        SelectedPackage = InstalledPackages.FirstOrDefault(x => x.Id == e);
        if (SelectedPackage is null) return;
        
        await LaunchAsync();
    }

    public override void OnLoaded()
    {
        LoadPackages();
        lock (InstalledPackages)
        {
            // Skip if no packages
            if (!InstalledPackages.Any())
            {
                //logger.LogTrace($"No packages for {nameof(LaunchViewModel)}");
                return;
            }

            var activePackageId = settingsManager.Settings.ActiveInstalledPackage;
            if (activePackageId != null)
            {
                SelectedPackage = InstalledPackages.FirstOrDefault(
                    x => x.Id == activePackageId) ?? InstalledPackages[0];
            }
        }
    }

    [RelayCommand]
    private async Task LaunchAsync()
    {
        var activeInstall = SelectedPackage;

        if (activeInstall == null)
        {
            // No selected package: error notification
            notificationService.Show(new Notification(
                message: "You must install and select a package before launching",
                title: "No package selected",
                type: NotificationType.Error));
            return;
        }

        var activeInstallName = activeInstall.PackageName;
        var basePackage = string.IsNullOrWhiteSpace(activeInstallName)
            ? null
            : packageFactory.FindPackageByName(activeInstallName);

        if (basePackage == null)
        {
            logger.LogWarning(
                "During launch, package name '{PackageName}' did not match a definition",
                activeInstallName);
            
            notificationService.Show(new Notification("Package name invalid",
                "Install package name did not match a definition. Please reinstall and let us know about this issue.",
                NotificationType.Error));
            return;
        }

        // If this is the first launch (LaunchArgs is null),
        // load and save a launch options dialog in background
        // so that dynamic initial values are saved.
        // if (activeInstall.LaunchArgs == null)
        // {
        //     var definitions = basePackage.LaunchOptions;
        //     // Open a config page and save it
        //     var dialog = dialogFactory.CreateLaunchOptionsDialog(definitions, activeInstall);
        //     var args = dialog.AsLaunchArgs();
        //     settingsManager.SaveLaunchArgs(activeInstall.Id, args);
        // }

        // Clear console
        ConsoleDocument.Text = string.Empty;

        await pyRunner.Initialize();

        // Get path from package
        var packagePath = $"{settingsManager.LibraryDir}\\{activeInstall.LibraryPath!}";

        basePackage.ConsoleOutput += OnProcessOutputReceived;
        basePackage.Exited += OnProcessExited;
        basePackage.StartupComplete += RunningPackageOnStartupComplete;
        
        // Start task to update console from queue
        consoleUpdateCts = new CancellationTokenSource();
        // Run in UI thread
        consoleUpdateTask = Dispatcher.UIThread.InvokeAsync(async () 
                => await BeginUpdateConsole(consoleUpdateCts.Token), DispatcherPriority.Render);

        // Update shared folder links (in case library paths changed)
        //sharedFolders.UpdateLinksForPackage(basePackage, packagePath);

        // Load user launch args from settings and convert to string
        var userArgs = settingsManager.GetLaunchArgs(activeInstall.Id);
        var userArgsString = string.Join(" ", userArgs.Select(opt => opt.ToArgString()));

        // Join with extras, if any
        userArgsString = string.Join(" ", userArgsString, basePackage.ExtraLaunchArguments);
        await basePackage.RunPackage(packagePath, userArgsString);
        RunningPackage = basePackage;
    }
    
    private async Task BeginUpdateConsole(CancellationToken ct)
    {
        try
        {
            while (true)
            {
                ct.ThrowIfCancellationRequested();
                var output = await consoleUpdateBuffer.ReceiveAsync(ct);
                using var update = ConsoleDocument.RunUpdate();
                // Handle remove
                if (output.ClearLines > 0)
                {
                    for (var i = 0; i < output.ClearLines; i++)
                    {
                        var lastLineIndex = ConsoleDocument.LineCount - 1;
                        var line = ConsoleDocument.Lines[lastLineIndex];
                        ConsoleDocument.Remove(line.Offset, line.Length);
                    }
                }
                // Add new line
                ConsoleDocument.Insert(ConsoleDocument.TextLength, output.Text);
            }
        }
        catch (OperationCanceledException)
        {
        }
    }
    
    public async Task Stop()
    {
        if (RunningPackage is null) return;
        await RunningPackage.Shutdown();
        
        RunningPackage = null;
        ShowWebUiButton = false;
        
        // Can't use buffer here since is null after shutdown
        Dispatcher.UIThread.Post(() =>
        {
            var msg = $"{Environment.NewLine}Stopped process at {DateTimeOffset.Now}{Environment.NewLine}";
            ConsoleDocument.Insert(ConsoleDocument.TextLength, msg );
        });
    }

    public void OpenWebUi()
    {
        if (!string.IsNullOrWhiteSpace(webUiUrl))
        {
            ProcessRunner.OpenUrl(webUiUrl);
        }
    }
    
    private void OnProcessExited(object? sender, int exitCode)
    {
        if (sender is BasePackage package)
        {
            package.ConsoleOutput -= OnProcessOutputReceived;
            package.Exited -= OnProcessExited;
            package.StartupComplete -= RunningPackageOnStartupComplete;
        }
        RunningPackage = null;
        ShowWebUiButton = false;
        var msg =
            $"{Environment.NewLine}Process finished with exit code {exitCode}{Environment.NewLine}";
        
        // Add to buffer
        consoleUpdateBuffer.Post(new ProcessOutput { RawText = msg, Text = msg });
        
        // Task that waits until buffer is empty, then stops the console update task
        Task.Run(async () =>
        {
            Debug.WriteLine($"Waiting for console update buffer to empty ({consoleUpdateBuffer.Count})");
            while (consoleUpdateBuffer.Count > 0)
            {
                await Task.Delay(100);
            }
            Debug.WriteLine("Console update buffer empty, stopping console update task");
            consoleUpdateCts?.Cancel();
            consoleUpdateCts = null;
            consoleUpdateTask = null;
        });
    }

    // Callback for processes
    private void OnProcessOutputReceived(object? sender, ProcessOutput output)
    {
        consoleUpdateBuffer.Post(output);
    }
    
    private void OnOneClickInstallFinished(object? sender, bool e)
    {
        OnLoaded();
    }
    
    private void RunningPackageOnStartupComplete(object? sender, string e)
    {
        webUiUrl = e;
        ShowWebUiButton = !string.IsNullOrWhiteSpace(webUiUrl);
    }
    
    private void LoadPackages()
    {
        var packages = settingsManager.Settings.InstalledPackages;
        if (!packages?.Any() ?? true)
        {
            InstalledPackages.Clear();
            return;
        }
        
        InstalledPackages.Clear();

        foreach (var package in packages)
        {
            InstalledPackages.Add(package);
        }
    }
    
    public void Dispose()
    {
        // Dispose updates
        consoleUpdateBuffer.Complete();
        consoleUpdateCts?.Cancel();
        consoleUpdateCts = null;
        consoleUpdateTask = null;
        
        RunningPackage?.Shutdown();
        GC.SuppressFinalize(this);
    }
}