using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Input;
using MmdPdf.Services;

namespace MmdPdf.Features.Scan
{
    /// <summary>
    /// Asks the copier for pages. The person picks the machine, the feed, how much ink and how
    /// much detail; everything else is the copier's own default. The pages come back as image
    /// files which MainWindow turns into one document.
    ///
    /// A run cannot be interrupted mid-sheet - that is the copier's hardware, not a decision made
    /// here - so Cancel stops after the sheet in progress and keeps the pages already read.
    /// </summary>
    public partial class ScanDialog : Window
    {
        private readonly List<ScannerInfo> _scanners;
        private CancellationTokenSource? _cancel;
        private bool _running;

        /// <summary>Image files, one per page, in the order the copier read them.</summary>
        internal string[] Pages { get; private set; } = Array.Empty<string>();

        /// <summary>The person asked for the words to be made searchable afterwards.</summary>
        internal bool MakeSearchable { get; private set; }

        /// <summary>The person asked for crooked pages to be straightened afterwards.</summary>
        internal bool Straighten { get; private set; }

        public ScanDialog()
        {
            InitializeComponent();

            _scanners = ScanService.IsAvailable ? ScanService.ListScanners() : new List<ScannerInfo>();

            foreach (var s in _scanners) CopierBox.Items.Add(s.Name);
            if (_scanners.Count > 0)
            {
                CopierBox.SelectedIndex = 0;
            }
            else
            {
                CopierBox.Items.Add(ScanService.IsAvailable
                    ? "No copier found on this machine"
                    : "This machine has no imaging service");
                CopierBox.SelectedIndex = 0;
                CopierBox.IsEnabled = false;
                ScanBtn.IsEnabled = false;
                FootNote.Text = "Switch the copier on, or connect it, then open this again";
            }

            FeedBox.Items.Add("Feeder, one side");
            FeedBox.Items.Add("Feeder, both sides");
            FeedBox.Items.Add("Glass, one sheet");
            FeedBox.SelectedIndex = 0;

            ColourBox.Items.Add("Black and white");
            ColourBox.Items.Add("Shades of grey");
            ColourBox.Items.Add("Colour");
            ColourBox.SelectedIndex = 0;

            DetailBox.Items.Add("200 dpi, quick");
            DetailBox.Items.Add("300 dpi, good for text");
            DetailBox.Items.Add("600 dpi, fine detail");
            DetailBox.SelectedIndex = 1;

            foreach (var p in ScanService.PaperSizes) PaperBox.Items.Add(p);
            PaperBox.SelectedIndex = 0;
        }

        private void TitleBar_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            if (e.ButtonState == MouseButtonState.Pressed) DragMove();
        }

        private void Cancel_Click(object sender, RoutedEventArgs e)
        {
            if (_running)
            {
                _cancel?.Cancel();
                FootNote.Text = "Stopping after this sheet…";
                return;
            }
            DialogResult = false;
            Close();
        }

        private async void Scan_Click(object sender, RoutedEventArgs e)
        {
            if (_running || _scanners.Count == 0) return;

            var device = _scanners[Math.Max(0, CopierBox.SelectedIndex)];
            var feed = FeedBox.SelectedIndex switch
            {
                1 => ScanFeed.FeederBothSides,
                2 => ScanFeed.Flatbed,
                _ => ScanFeed.FeederOneSide,
            };
            var colour = ColourBox.SelectedIndex switch
            {
                1 => ScanColour.Greyscale,
                2 => ScanColour.Colour,
                _ => ScanColour.BlackAndWhite,
            };
            int dpi = DetailBox.SelectedIndex switch
            {
                0 => 200,
                2 => 600,
                _ => 300,
            };
            string paper = PaperBox.SelectedItem as string ?? "A4 portrait";

            MakeSearchable = SearchableBox.IsChecked == true;
            Straighten = StraightenBox.IsChecked == true;

            _running = true;
            _cancel = new CancellationTokenSource();
            ScanBtn.IsEnabled = false;
            CancelBtn.Content = "Stop";
            SetInputsEnabled(false);
            FootNote.Text = feed == ScanFeed.Flatbed ? "Reading the sheet on the glass…" : "Reading…";

            var progress = new Progress<int>(n =>
                FootNote.Text = n == 1 ? "1 page read" : n.ToString(CultureInfo.InvariantCulture) + " pages read");

            try
            {
                var token = _cancel.Token;
                var reporter = (IProgress<int>)progress;
                string[] pages = await Task.Run(() =>
                    ScanService.Acquire(device.DeviceId, feed, colour, dpi, paper,
                                        maxPages: feed == ScanFeed.Flatbed ? 1 : 200,
                                        cancel: token,
                                        onPage: reporter.Report).ToArray(), token);

                Pages = pages;
                if (pages.Length == 0)
                {
                    FootNote.Text = "The copier returned no pages";
                    ResetAfterRun();
                    return;
                }

                DialogResult = true;
                Close();
            }
            catch (OperationCanceledException)
            {
                FootNote.Text = "Stopped";
                ResetAfterRun();
            }
            catch (Exception ex)
            {
                FootNote.Text = "The copier could not be used: " + ex.Message;
                ResetAfterRun();
            }
        }

        private void ResetAfterRun()
        {
            _running = false;
            _cancel?.Dispose();
            _cancel = null;
            ScanBtn.IsEnabled = _scanners.Count > 0;
            CancelBtn.Content = "Cancel";
            SetInputsEnabled(true);
        }

        private void SetInputsEnabled(bool on)
        {
            CopierBox.IsEnabled = on && _scanners.Count > 0;
            FeedBox.IsEnabled = on;
            ColourBox.IsEnabled = on;
            DetailBox.IsEnabled = on;
            PaperBox.IsEnabled = on;
            SearchableBox.IsEnabled = on;
            StraightenBox.IsEnabled = on;
        }
    }
}