using System;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using CRAWLER.Infrastructure;
using CRAWLER.Models;
using CRAWLER.Services;

namespace CRAWLER.ViewModels;

internal sealed class MainWindowViewModel : ObservableObject
{
    private readonly InstrumentCatalogService _catalogService;
    private readonly IPdfOpener _pdfOpener;
    private InstrumentSummary _selectedSummary;
    private InstrumentRecord _selectedInstrument;
    private string _searchText;
    private int _pagesToScan;
    private string _statusText;
    private bool _isBusy;
    private CancellationTokenSource _selectionCancellationTokenSource;

    public MainWindowViewModel(InstrumentCatalogService catalogService, IPdfOpener pdfOpener)
    {
        _catalogService = catalogService;
        _pdfOpener = pdfOpener;
        _pagesToScan = _catalogService.DefaultPagesToScan;
        _statusText = "Готово.";
        Instruments = new ObservableCollection<InstrumentSummary>();
    }

    public ObservableCollection<InstrumentSummary> Instruments { get; }

    public InstrumentSummary SelectedSummary
    {
        get { return _selectedSummary; }
        set
        {
            if (SetProperty(ref _selectedSummary, value))
            {
                _ = LoadSelectedInstrumentAsync(value?.Id);
            }
        }
    }

    public InstrumentRecord SelectedInstrument
    {
        get { return _selectedInstrument; }
        private set { SetProperty(ref _selectedInstrument, value); }
    }

    public string SearchText
    {
        get { return _searchText; }
        set { SetProperty(ref _searchText, value); }
    }

    public int PagesToScan
    {
        get { return _pagesToScan; }
        set { SetProperty(ref _pagesToScan, value < 1 ? 1 : value); }
    }

    public string StatusText
    {
        get { return _statusText; }
        private set { SetProperty(ref _statusText, value); }
    }

    public bool IsBusy
    {
        get { return _isBusy; }
        private set { SetProperty(ref _isBusy, value); }
    }

    public async Task InitializeAsync()
    {
        await RunBusyAsync(async () =>
        {
            StatusText = "Подготовка базы данных...";
            await _catalogService.InitializeAsync(CancellationToken.None);
            await RefreshAsync();
        });
    }

    public async Task RefreshAsync(long? selectId = null)
    {
        await RunBusyAsync(async () =>
        {
            StatusText = "Загрузка списка записей...";

            var items = await _catalogService.SearchAsync(SearchText, CancellationToken.None);
            Instruments.Clear();
            foreach (var item in items)
            {
                Instruments.Add(item);
            }

            if (Instruments.Count == 0)
            {
                SelectedInstrument = null;
                SelectedSummary = null;
                StatusText = "Записи не найдены.";
                return;
            }

            var summary = selectId.HasValue
                ? Instruments.FirstOrDefault(item => item.Id == selectId.Value)
                : SelectedSummary == null
                    ? Instruments.FirstOrDefault()
                    : Instruments.FirstOrDefault(item => item.Id == SelectedSummary.Id) ?? Instruments.FirstOrDefault();

            SelectedSummary = summary;
            StatusText = $"Загружено записей: {Instruments.Count}.";
        });
    }

    public async Task<SyncResult> SyncAsync()
    {
        SyncResult result = null;

        await RunBusyAsync(async () =>
        {
            var progress = new Progress<string>(message => StatusText = message);
            result = await _catalogService.SyncFromSiteAsync(PagesToScan, progress, CancellationToken.None);
            await RefreshAsync(SelectedSummary?.Id);
        });

        return result;
    }

    public InstrumentRecord CreateNewDraft()
    {
        return new InstrumentRecord
        {
            SourceSystem = "Manual"
        };
    }

    public InstrumentRecord CreateDraftFromSelected()
    {
        return SelectedInstrument?.Clone();
    }

    public async Task<long> SaveAsync(InstrumentRecord draft, System.Collections.Generic.IEnumerable<string> pendingPdfPaths)
    {
        long id = 0;

        await RunBusyAsync(async () =>
        {
            StatusText = "Сохранение записи...";
            id = await _catalogService.SaveInstrumentAsync(draft, pendingPdfPaths, CancellationToken.None);
            await RefreshAsync(id);
            StatusText = "Изменения сохранены.";
        });

        return id;
    }

    public async Task DeleteSelectedAsync()
    {
        if (SelectedInstrument == null)
        {
            return;
        }

        var deletedId = SelectedInstrument.Id;

        await RunBusyAsync(async () =>
        {
            StatusText = "Удаление записи...";
            await _catalogService.DeleteInstrumentAsync(SelectedInstrument, CancellationToken.None);
            await RefreshAsync();
            StatusText = $"Запись {deletedId} удалена.";
        });
    }

    public async Task AddAttachmentsToSelectedAsync(System.Collections.Generic.IEnumerable<string> paths)
    {
        if (SelectedInstrument == null)
        {
            return;
        }

        await RunBusyAsync(async () =>
        {
            StatusText = "Копирование PDF-файлов...";
            await _catalogService.AddManualAttachmentsAsync(SelectedInstrument.Id, SelectedInstrument.RegistryNumber, paths, CancellationToken.None);
            await LoadSelectedInstrumentAsync(SelectedInstrument.Id);
            StatusText = "PDF-файлы добавлены.";
        });
    }

    public async Task RemoveAttachmentAsync(PdfAttachment attachment)
    {
        if (attachment == null || SelectedInstrument == null)
        {
            return;
        }

        await RunBusyAsync(async () =>
        {
            StatusText = "Удаление PDF-файла...";
            await _catalogService.RemoveAttachmentAsync(attachment, CancellationToken.None);
            await LoadSelectedInstrumentAsync(SelectedInstrument.Id);
            StatusText = "PDF-файл удалён.";
        });
    }

    public void OpenAttachment(PdfAttachment attachment)
    {
        _pdfOpener.OpenAttachment(attachment);
    }

    public void OpenSourceUrl()
    {
        if (SelectedInstrument != null && !string.IsNullOrWhiteSpace(SelectedInstrument.DetailUrl))
        {
            _pdfOpener.OpenUri(SelectedInstrument.DetailUrl);
        }
    }

    private async Task LoadSelectedInstrumentAsync(long? id)
    {
        _selectionCancellationTokenSource?.Cancel();
        _selectionCancellationTokenSource = new CancellationTokenSource();
        var token = _selectionCancellationTokenSource.Token;

        if (!id.HasValue)
        {
            SelectedInstrument = null;
            return;
        }

        try
        {
            var instrument = await _catalogService.GetByIdAsync(id.Value, token);
            if (!token.IsCancellationRequested)
            {
                SelectedInstrument = instrument;
            }
        }
        catch (OperationCanceledException)
        {
        }
    }

    private async Task RunBusyAsync(Func<Task> action)
    {
        if (IsBusy)
        {
            return;
        }

        try
        {
            IsBusy = true;
            await action();
        }
        finally
        {
            IsBusy = false;
        }
    }
}