using System;
using ReactiveUI;
using System.Linq;
using System.Reactive.Disposables;
using System.Reactive.Linq;
using System.Windows.Media.Imaging;
using Wabbajack.Lib;
using ReactiveUI.Fody.Helpers;
using System.Windows.Media;
using DynamicData;
using DynamicData.Binding;
using System.Reactive;
using Microsoft.Extensions.Logging;
using Microsoft.WindowsAPICodePack.Dialogs;
using Microsoft.WindowsAPICodePack.Shell;
using Wabbajack.Installer;
using Wabbajack.Lib.Extensions;
using Wabbajack.Lib.Interventions;
using Wabbajack.Paths;
using Wabbajack.RateLimiter;
using Wabbajack.View_Models;
using Consts = Wabbajack.Lib.Consts;

namespace Wabbajack;

enum ModManager
{
    Standard
}

public class InstallerVM : BackNavigatingVM, IBackNavigatingVM, ICpuStatusVM
{
    public SlideShow Slideshow { get; }

    public MainWindowVM MWVM { get; }

    private readonly ObservableAsPropertyHelper<ModListVM> _modList;
    public ModListVM ModList => _modList.Value;

    public FilePickerVM ModListLocation { get; }

    private readonly ObservableAsPropertyHelper<ISubInstallerVM> _installer;
    public ISubInstallerVM Installer => _installer.Value;

    private readonly ObservableAsPropertyHelper<bool> _installing;
    public bool Installing => _installing.Value;

    [Reactive]
    public bool StartedInstallation { get; set; }

    [Reactive]
    public ErrorResponse? Completed { get; set; }

    private readonly ObservableAsPropertyHelper<ImageSource> _image;
    public ImageSource Image => _image.Value;

    private readonly ObservableAsPropertyHelper<string> _titleText;
    public string TitleText => _titleText.Value;

    private readonly ObservableAsPropertyHelper<string> _authorText;
    public string AuthorText => _authorText.Value;

    private readonly ObservableAsPropertyHelper<string> _description;
    public string Description => _description.Value;

    private readonly ObservableAsPropertyHelper<string> _progressTitle;
    public string ProgressTitle => _progressTitle.Value;

    private readonly ObservableAsPropertyHelper<string> _modListName;
    public string ModListName => _modListName.Value;

    private readonly ObservableAsPropertyHelper<Percent> _percentCompleted;
    public Percent PercentCompleted => _percentCompleted.Value;

    public ObservableCollectionExtended<CPUDisplayVM> StatusList { get; } = new ObservableCollectionExtended<CPUDisplayVM>();
    public ObservableCollectionExtended<IStatusMessage> Log => MWVM.Log;

    private readonly ObservableAsPropertyHelper<ModManager?> _TargetManager;
    public ModManager? TargetManager => _TargetManager.Value;

    private readonly ObservableAsPropertyHelper<IUserIntervention> _ActiveGlobalUserIntervention;
    public IUserIntervention ActiveGlobalUserIntervention => _ActiveGlobalUserIntervention.Value;

    private readonly ObservableAsPropertyHelper<(int CurrentCPUs, int DesiredCPUs)> _CurrentCpuCount;
    public (int CurrentCPUs, int DesiredCPUs) CurrentCpuCount => _CurrentCpuCount.Value;

    private readonly ObservableAsPropertyHelper<bool> _LoadingModlist;
    private readonly ILogger<InstallerVM> _logger;
    public bool LoadingModlist => _LoadingModlist.Value;

    // Command properties
    public ReactiveCommand<Unit, Unit> ShowManifestCommand { get; }
    public ReactiveCommand<Unit, Unit> OpenReadmeCommand { get; }
    public ReactiveCommand<Unit, Unit> VisitModListWebsiteCommand { get; }
        
    public ReactiveCommand<Unit, Unit> CloseWhenCompleteCommand { get; }
    public ReactiveCommand<Unit, Unit> OpenLogsCommand { get; }
    public ReactiveCommand<Unit, Unit> GoToInstallCommand { get; }
    public ReactiveCommand<Unit, Unit> BeginCommand { get; }

    public InstallerVM(ILogger<InstallerVM> logger, MainWindowVM mainWindowVM) : base(logger, mainWindowVM)
    {
        _logger = logger;
        var downloadsPath = KnownFolders.Downloads.Path;
        /* TODO 
        var skyDrivePath = KnownFolders.SkyDrive.Path;

        if (downloadsPath != null && AbsolutePath.EntryPoint.IsChildOf(new AbsolutePath(downloadsPath)))
        {
            logger.LogError(Error(new CriticalFailureIntervention(
                "Wabbajack is running inside your Downloads folder. This folder is often highly monitored by antivirus software and these can often " +
                "conflict with the operations Wabbajack needs to perform. Please move Wabbajack outside of your Downloads folder and then restart the app.",
                "Cannot run inside Downloads", true));
        }

        if (skyDrivePath != null && AbsolutePath.EntryPoint.IsChildOf(new AbsolutePath(skyDrivePath)))
        {
            Utils.Error(new CriticalFailureIntervention(
                $"Wabbajack is running inside a OneDrive folder \"{skyDrivePath}\". This folder is known to cause issues with Wabbajack. " +
                "Please move Wabbajack outside of your OneDrive folder and then restart the app.",
                "Cannot run inside OneDrive", true));
        }*/

        MWVM = mainWindowVM;

        ModListLocation = new FilePickerVM
        {
            ExistCheckOption = FilePickerVM.CheckOptions.On,
            PathType = FilePickerVM.PathTypeOptions.File,
            PromptTitle = "Select a ModList to install"
        };
        ModListLocation.Filters.Add(new CommonFileDialogFilter("Wabbajack Modlist", "*.wabbajack"));

        // Swap to proper sub VM based on selected type
        _installer = this.WhenAny(x => x.TargetManager)
            // Delay so the initial VM swap comes in immediately, subVM comes right after
            .DelayInitial(TimeSpan.FromMilliseconds(50), RxApp.MainThreadScheduler)
            .Select<ModManager?, ISubInstallerVM>(type =>
            {
                switch (type)
                {
                    case ModManager.Standard:
                        return new MO2InstallerVM(this);
                    default:
                        return null;
                }
            })
            // Unload old VM
            .Pairwise()
            .Do(pair =>
            {
                pair.Previous?.Unload();
            })
            .Select(p => p.Current)
            .ToGuiProperty(this, nameof(Installer));

        // Load settings
        MWVM.Settings.SaveSignal
            .Subscribe(_ =>
            {
                MWVM.Settings.Installer.LastInstalledListLocation = ModListLocation.TargetPath;
            })
            .DisposeWith(CompositeDisposable);

        _IsActive = this.ConstructIsActive(MWVM)
            .ToGuiProperty(this, nameof(IsActive));

        // Active path represents the path to currently have loaded
        // If we're not actively showing, then "unload" the active path
        var activePath = Observable.CombineLatest(
                this.WhenAny(x => x.ModListLocation.TargetPath),
                this.WhenAny(x => x.IsActive),
                resultSelector: (path, active) => (path, active))
            .Select(x =>
            {
                if (!x.active) return default;
                return x.path;
            })
            // Throttle slightly so changes happen more atomically
            .Throttle(TimeSpan.FromMilliseconds(50), RxApp.MainThreadScheduler)
            .Replay(1)
            .RefCount();

        _modList = activePath
            .ObserveOn(RxApp.TaskpoolScheduler)
            // Convert from active path to modlist VM
            .Select(modListPath =>
            {
                if (modListPath == default) return default;
                if (!modListPath.FileExists()) return default;
                return new ModListVM(modListPath);
            })
            .DisposeOld()
            .ObserveOnGuiThread()
            .StartWith(default(ModListVM))
            .ToGuiProperty(this, nameof(ModList));

        // Force GC collect when modlist changes, just to make sure we clean up any loose large items immediately
        this.WhenAny(x => x.ModList)
            .Delay(TimeSpan.FromMilliseconds(50), RxApp.MainThreadScheduler)
            .Subscribe(x =>
            {
                GC.Collect();
            });

        _LoadingModlist = Observable.Merge(
                // When active path changes, mark as loading
                activePath
                    .Select(_ => true),
                // When the resulting modlist comes in, mark it as done
                this.WhenAny(x => x.ModList)
                    .Select(_ => false))
            .ToGuiProperty(this, nameof(LoadingModlist));
        _installing = this.WhenAny(x => x.Installer.ActiveInstallation)
            .Select(i => i != null)
            .ToGuiProperty(this, nameof(Installing));
        _TargetManager = this.WhenAny(x => x.ModList)
            .Select(modList => ModManager.Standard)
            .ToGuiProperty(this, nameof(TargetManager));

        // Add additional error check on ModList
        ModListLocation.AdditionalError = this.WhenAny(x => x.ModList)
            .Select<ModListVM, IErrorResponse>(modList =>
            {
                if (modList == null) return ErrorResponse.Fail("Modlist path resulted in a null object.");
                if (modList.Error != null) return ErrorResponse.Fail("Modlist is corrupt", modList.Error);
                if (modList.WabbajackVersion != null && modList.WabbajackVersion > Consts.CurrentMinimumWabbajackVersion)
                    return ErrorResponse.Fail("The Modlist you are trying to install was made using a newer Version of Wabbajack. Please update Wabbajack before installing!");
                return ErrorResponse.Success;
            });

        BackCommand = ReactiveCommand.Create(
            execute: () =>
            {
                StartedInstallation = false;
                Completed = null;
                mainWindowVM.NavigateTo(mainWindowVM.ModeSelectionVM);
            },
            canExecute: Observable.CombineLatest(
                    this.WhenAny(x => x.Installing)
                        .Select(x => !x),
                    this.ConstructCanNavigateBack(),
                    resultSelector: (i, b) => i && b)
                .ObserveOnGuiThread());

        _percentCompleted = this.WhenAny(x => x.Installer.ActiveInstallation)
            .StartWith(default(IInstaller))
            .CombineLatest(
                this.WhenAny(x => x.Completed),
                (installer, completed) =>
                {
                    if (installer == null)
                    {
                        return Observable.Return<Percent>(completed != null ? Percent.One : Percent.Zero);
                    }
                    return installer.PercentCompleted.StartWith(Percent.Zero);
                })
            .Switch()
            .Debounce(TimeSpan.FromMilliseconds(25), RxApp.MainThreadScheduler)
            .ToGuiProperty(this, nameof(PercentCompleted));

        Slideshow = new SlideShow(this);

        // Set display items to ModList if configuring or complete,
        // or to the current slideshow data if installing
        _image = Observable.CombineLatest(
                this.WhenAny(x => x.ModList.Error),
                this.WhenAny(x => x.ModList)
                    .Select(x => x?.ImageObservable ?? Observable.Return(default(BitmapImage)))
                    .Switch()
                    .StartWith(default(BitmapImage)),
                this.WhenAny(x => x.Slideshow.Image)
                    .StartWith(default(BitmapImage)),
                this.WhenAny(x => x.Installing),
                this.WhenAny(x => x.LoadingModlist),
                resultSelector: (err, modList, slideshow, installing, loading) =>
                {
                    if (err != null)
                    {
                        return ResourceLinks.WabbajackErrLogo.Value;
                    }
                    if (loading) return default;
                    return installing ? slideshow : modList;
                })
            .Select<BitmapImage, ImageSource>(x => x)
            .ToGuiProperty(this, nameof(Image));
        _titleText = Observable.CombineLatest(
                this.WhenAny(x => x.ModList)
                    .Select(modList => modList?.Name ?? string.Empty),
                this.WhenAny(x => x.Slideshow.TargetMod.State.Name)
                    .StartWith(default(string)),
                this.WhenAny(x => x.Installing),
                resultSelector: (modList, mod, installing) => installing ? mod : modList)
            .ToGuiProperty(this, nameof(TitleText));
        _authorText = Observable.CombineLatest(
                this.WhenAny(x => x.ModList)
                    .Select(modList => modList?.Author ?? string.Empty),
                this.WhenAny(x => x.Slideshow.TargetMod.State.Author)
                    .StartWith(default(string)),
                this.WhenAny(x => x.Installing),
                resultSelector: (modList, mod, installing) => installing ? mod : modList)
            .ToGuiProperty(this, nameof(AuthorText));
        _description = Observable.CombineLatest(
                this.WhenAny(x => x.ModList)
                    .Select(modList => modList?.Description ?? string.Empty),
                this.WhenAny(x => x.Slideshow.TargetMod.State.Description)
                    .StartWith(default(string)),
                this.WhenAny(x => x.Installing),
                resultSelector: (modList, mod, installing) => installing ? mod : modList)
            .ToGuiProperty(this, nameof(Description));
        _modListName = Observable.CombineLatest(
                this.WhenAny(x => x.ModList.Error)
                    .Select(x => x != null),
                this.WhenAny(x => x.ModList)
                    .Select(x => x?.Name),
                resultSelector: (err, name) =>
                {
                    if (err) return "Corrupted Modlist";
                    return name;
                })
            .Merge(this.WhenAny(x => x.Installer.ActiveInstallation)
                .Where(c => c != null)
                .SelectMany(c => c.TextStatus))
            .ToGuiProperty(this, nameof(ModListName));

        ShowManifestCommand = ReactiveCommand.Create(() =>
        {
            UIUtils.OpenWebsite(new Uri("https://www.wabbajack.org/#/modlists/manifest"));
        }, this.WhenAny(x => x.ModList)
            .Select(x => x?.SourceModList != null)
            .ObserveOnGuiThread());
            
        OpenReadmeCommand = ReactiveCommand.Create(
            execute: () => this.ModList?.OpenReadme(),
            canExecute: this.WhenAny(x => x.ModList)
                .Select(modList => !string.IsNullOrEmpty(modList?.Readme))
                .ObserveOnGuiThread());
            
        OpenLogsCommand = ReactiveCommand.Create(
            execute: () => UIUtils.OpenFolder(Consts.LogsFolder));
        VisitModListWebsiteCommand = ReactiveCommand.Create(
            execute: () =>
            {
                UIUtils.OpenWebsite(ModList.Website);
                return Unit.Default;
            },
            canExecute: this.WhenAny(x => x.ModList.Website)
                .Select(x => x != null)
                .ObserveOnGuiThread());

        _progressTitle = this.WhenAnyValue(
                x => x.Installing,
                x => x.StartedInstallation,
                x => x.Completed,
                selector: (installing, started, completed) =>
                {
                    if (installing)
                    {
                        return "Installing";
                    }
                    else if (started)
                    {
                        if (completed == null) return "Installing";
                        return completed.Value.Succeeded ? "Installed" : "Failed";
                    }
                    else
                    {
                        return "Awaiting Input";
                    }
                })
            .ToGuiProperty(this, nameof(ProgressTitle));

        UIUtils.BindCpuStatus(
                this.WhenAny(x => x.Installer.ActiveInstallation)
                    .SelectMany(c => c?.QueueStatus ?? Observable.Empty<CPUStatus>()),
                StatusList)
            .DisposeWith(CompositeDisposable);

        BeginCommand = ReactiveCommand.CreateFromTask(
            canExecute: this.WhenAny(x => x.Installer.CanInstall)
                .Select(err => err.Succeeded),
            execute: async () =>
            {
                try
                {
                    UIUtils.Log($"Starting to install {ModList.Name}");
                    IsBackEnabledSubject.OnNext(false);
                    var success = await this.Installer.Install();
                    Completed = ErrorResponse.Create(success);
                    try
                    {
                        this.ModList?.OpenReadme();
                    }
                    catch (Exception ex)
                    {
                        UIUtils.Error(ex);
                    }
                }
                catch (Exception ex)
                {
                    Utils.Error(ex, $"Encountered error, can't continue");
                    while (ex.InnerException != null) ex = ex.InnerException;
                    Completed = ErrorResponse.Fail(ex);
                }
                finally
                {
                    IsBackEnabledSubject.OnNext(true);
                }
            });

        // When sub installer begins an install, mark state variable
        BeginCommand.StartingExecution()
            .Subscribe(_ =>
            {
                StartedInstallation = true;
            })
            .DisposeWith(CompositeDisposable);

        // Listen for user interventions, and compile a dynamic list of all unhandled ones
        var activeInterventions = this.WhenAny(x => x.Installer.ActiveInstallation)
            .WithLatestFrom(
                this.WhenAny(x => x.Installer),
                (activeInstall, installer) =>
                {
                    if (activeInstall == null) return Observable.Empty<IChangeSet<IUserIntervention>>();
                    return activeInstall.LogMessages
                        .WhereCastable<IStatusMessage, IUserIntervention>()
                        .ToObservableChangeSet()
                        .AutoRefresh(i => i.Handled)
                        .Filter(i => !i.Handled)
                        .Transform(x => installer.InterventionConverter(x));
                })
            .Switch()
            .AsObservableList();

        // Find the top intervention /w no CPU ID to be marked as "global"
        _ActiveGlobalUserIntervention = activeInterventions.Connect()
            .Filter(x => x.CpuID == WorkQueue.UnassignedCpuId)
            .QueryWhenChanged(query => query.FirstOrDefault())
            .ToGuiProperty(this, nameof(ActiveGlobalUserIntervention));

        CloseWhenCompleteCommand = ReactiveCommand.CreateFromTask(
            canExecute: this.WhenAny(x => x.Completed)
                .Select(x => x != null),
            execute: async () =>
            {
                await MWVM.ShutdownApplication();
            });

        GoToInstallCommand = ReactiveCommand.Create(
            canExecute: Observable.CombineLatest(
                this.WhenAny(x => x.Completed)
                    .Select(x => x != null),
                this.WhenAny(x => x.Installer.SupportsAfterInstallNavigation),
                resultSelector: (complete, supports) => complete && supports),
            execute: () =>
            {
                Installer.AfterInstallNavigation();
            });

        _CurrentCpuCount = this.WhenAny(x => x.Installer.ActiveInstallation.Queue.CurrentCpuCount)
            .Switch()
            .ToGuiProperty(this, nameof(CurrentCpuCount));
    }
}