using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using System.Web;
using Avalonia.Controls;
using Avalonia.Platform.Storage;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using CommunityToolkit.Mvvm.Messaging;
using GazpromApp.Messages;
using GazpromApp.Models;
using GazpromApp.Utils;
using Microsoft.EntityFrameworkCore;

namespace GazpromApp.ViewModels;

public partial class MainWindowViewModel : ViewModelBase
{
    public ObservableCollection<PointViewModel> Points { get; set; }

    [ObservableProperty]
    private object? _selectedItem;
    
    [ObservableProperty]
    private ViewModelBase? _selectedItemViewModel;
    
    [RelayCommand]
    private async Task AddPoint()
    {
        IsLoading = true;
        
        var point = new PointViewModel(new Point {Name = "Новый объект", Description = "Описание объекта"});
        
        _context.Point.Add(point.GetPoint());
        await _context.SaveChangesAsync();
        
        Points.Add(point);
        
        IsLoading = false;
    }

    [RelayCommand]
    private async Task ImportPoint(Window w)
    {
        Directory.CreateDirectory(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "GazpromApp"));
        var files = await w.StorageProvider.OpenFilePickerAsync(new FilePickerOpenOptions
        {
            AllowMultiple = true,
            SuggestedStartLocation = 
                await w.StorageProvider.TryGetFolderFromPathAsync(
                    Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "GazpromApp"))
        });
        
        if (files.Count < 1) return;
        
        IsLoading = true;
        
        foreach (var file in files)
        {
            var url = file.Path.AbsolutePath;
            var decoded = HttpUtility.UrlDecode(url);
            var point = DataSerialization.LoadPoint(decoded);
            point?.SetPropertyParents();
            point?.SetEquipmentParents();

            if (point == null) continue;
            _context.Point.Add(point);
            await _context.SaveChangesAsync();
            _context.Update(point);
            await _context.SaveChangesAsync();

            Points.Add(new PointViewModel(point));
        }
        
        IsLoading = false;
    }

    [RelayCommand]
    private async Task ExportPoint(Window w)
    {
        Directory.CreateDirectory(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "GazpromApp"));
        var folder = await w.StorageProvider.OpenFolderPickerAsync(new FolderPickerOpenOptions
        {
            AllowMultiple = false,
            SuggestedStartLocation =
                await w.StorageProvider.TryGetFolderFromPathAsync(
                    Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "GazpromApp"))
        });
        if (folder.Count != 1) return;
        foreach (var point in Points)
            DataSerialization.SavePoint(point.GetPoint(), Path.Combine(HttpUtility.UrlDecode(folder[0].Path.AbsolutePath), point.Name + ".json") );
    }

    [ObservableProperty]
    [NotifyCanExecuteChangedFor(nameof(SyncDbCommand))]
    private bool _canSync = false;
    
    private bool CanSyncDb() => CanSync;
    
    [RelayCommand(CanExecute = nameof(CanSyncDb))]
    private async Task SyncDb()
    {
        IsLoading = true;
        
        foreach (var point in _pointsToUpdate)
        {
            _context.Update(point.GetPoint());
                
            var index = Points.IndexOf(point);
            if (index != -1)
                Points[index] = point;
        }
        await _context.SaveChangesAsync();
        
        foreach (var point in _pointsToDelete)
        {
            var pointInDb = await _context.Point.FindAsync(point.GetPoint().Id);
            if (pointInDb == null) continue;
                
            _context.Remove(pointInDb);

            Points.Remove(point);
        }
        await _context.SaveChangesAsync();
        
        _pointsToUpdate.Clear();
        _pointsToDelete.Clear();
        
        
        IsLoading = false;
        CanSync = false;
    }
    
    // Visual and other properties
    [ObservableProperty] private bool _isLoading = true;
    
    private readonly AppDbContext _context;
    
    private async Task LoadChildrenForProperties(List<Property> properties, HashSet<Guid> loadedIds)
    {
        if (properties.Count == 0)
            return;

        var parentIds = properties.Select(p => p.Id)
            .Where(id => !loadedIds.Contains(id))
            .ToList();
        
        if (parentIds.Count == 0)
            return;
        
        parentIds.ForEach(id => loadedIds.Add(id));

        var children = await _context.Property
            .Where(p => p.ParentPropertyId.HasValue && parentIds.Contains(p.ParentPropertyId.Value))
            .OrderBy(p => p.CreationDate)
            .ToListAsync();

        if (children.Count != 0)
        {
            var childrenLookup = children.ToLookup(child => child.ParentPropertyId);

            foreach (var parent in properties.Where(parent => childrenLookup.Contains(parent.Id)))
            {
                parent.Properties.Clear();
                parent.Properties.AddRange(childrenLookup[parent.Id]);   
            }

            await LoadChildrenForProperties(children, loadedIds);
        }
    }
    
    private async Task LoadChildrenForEquipments(List<Equipment> equipments, HashSet<Guid> loadedIds)
    {
        if (equipments.Count == 0)
            return;

        var parentIds = equipments.Select(e => e.Id)
            .Where(id => !loadedIds.Contains(id))
            .ToList();

        if (parentIds.Count == 0)
            return;

        parentIds.ForEach(id => loadedIds.Add(id));

        var children = await _context.Equipment
            .Where(e => e.ParentEquipmentId.HasValue && parentIds.Contains(e.ParentEquipmentId.Value))
            .OrderBy(e => e.CreationDate)
            .ToListAsync();

        if (children.Count != 0)
        {
            var childrenLookup = children.ToLookup(child => child.ParentEquipmentId);

            foreach (var parent in equipments.Where(parent => childrenLookup.Contains(parent.Id)))
            {
                parent.Equipments.Clear();
                parent.Equipments.AddRange(childrenLookup[parent.Id]);   
            }

            await LoadChildrenForEquipments(children, loadedIds);
        }
    }


    private async Task LoadDataAsync()
    {
        IsLoading = true;
        
        // ReSharper disable once EntityFramework.NPlusOne.IncompleteDataQuery
        var pointsFromDb = await _context.Point
            .OrderBy(p => p.CreationDate)
            .Include(p => p.Images
                .OrderBy(i => i.CreationDate))
            .Include(p => p.Equipment
                .OrderBy(e => e.CreationDate))
                .ThenInclude(e => e.Properties
                    .OrderBy(p => p.CreationDate))
            .Include(p => p.Equipment)
                .ThenInclude(e => e.Images
                    .OrderBy(i => i.CreationDate))
            .Include(p => p.Equipment)
                .ThenInclude(e => e.Inspections
                    .OrderBy(i => i.CreationDate))
            .Include(p => p.Properties
                .OrderBy(p => p.CreationDate))
            .ToListAsync();

        var topLevelProperties = pointsFromDb.SelectMany(p => p.Properties)
            .Concat(pointsFromDb.SelectMany(p => p.Equipment).SelectMany(e => e.Properties))
            .ToList();

        var topLevelEquipments = pointsFromDb.SelectMany(p => p.Equipment)
           .ToList();

        if (topLevelProperties.Count != 0)
            await LoadChildrenForProperties(topLevelProperties, []);

        if (topLevelEquipments.Count != 0)
            await LoadChildrenForEquipments(topLevelEquipments, []);
        
        Points.Clear();
        foreach (var point in pointsFromDb)
            Points.Add(new PointViewModel(point));

        IsLoading = false;
    }
    
    private readonly ObservableCollection<PointViewModel> _pointsToUpdate = [];
    private readonly ObservableCollection<PointViewModel> _pointsToDelete = [];
    
    private void EditPoint(object sender, EditPointMessage msg)
    {
        if (!_pointsToUpdate.Contains(msg.Point))
            _pointsToUpdate.Add(msg.Point);
        CanSync = true;
    }

    private void RemovePoint(object sender, RemovePointMessage msg)
    {
        if (!_pointsToDelete.Contains(msg.Point))
            _pointsToDelete.Add(msg.Point);
        Points.Remove(msg.Point);
        CanSync = true;
    }

    private void HandleSelectionChanged(object sender, SelectionChangedMessage msg)
    {
        SelectedItemViewModel = msg.ViewModel switch
        {
            PointViewModel pointViewModel => new EditPointViewModel(pointViewModel),
            EquipmentViewModel equipmentViewModel => new EditEquipmentViewModel(equipmentViewModel),
            _ => msg.ViewModel
        };
    }
    
    public MainWindowViewModel(AppDbContext context)
    {
        Points = [];
        _context = context;
        _ = LoadDataAsync();
        
        WeakReferenceMessenger.Default.Register<EditPointMessage>(this, EditPoint);
        WeakReferenceMessenger.Default.Register<RemovePointMessage>(this, RemovePoint);
        WeakReferenceMessenger.Default.Register<SelectionChangedMessage>(this, HandleSelectionChanged);
    }

    public MainWindowViewModel()
    {
        Points = [new PointViewModel(new Point()) { Name = "Новый объект", Description = "Описание объекта" }];
        _context = new AppDbContext();
        IsLoading = false;
    }
}