using System;
using System.IO;
using System.Windows;
using System.Windows.Controls;
using Telerik.Windows.Documents.Fixed.FormatProviders.Pdf;
using XP.Common.PdfViewer.Exceptions;
using XP.Common.PdfViewer.ViewModels;

namespace XP.Common.PdfViewer.Views
{
    /// <summary>
    /// PDF 阅读器窗口 code-behind | PDF viewer window code-behind
    /// 负责在 Loaded 事件中加载 PDF 文档，在 Closed 事件中释放资源
    /// Responsible for loading PDF document on Loaded event and releasing resources on Closed event
    /// </summary>
    public partial class PdfViewerWindow : Window
    {
        // 防止缩略图选择和页面跳转之间的循环触发 | Prevent circular trigger between thumbnail selection and page navigation
        private bool _isSyncingSelection;

        public PdfViewerWindow()
        {
            InitializeComponent();
            Loaded += OnLoaded;
            Closed += OnClosed;
        }

        /// <summary>
        /// 窗口加载事件：通过 PdfFormatProvider 加载 PDF 文档到 RadPdfViewer
        /// Window loaded event: load PDF document into RadPdfViewer via PdfFormatProvider
        /// </summary>
        private void OnLoaded(object sender, RoutedEventArgs e)
        {
            var vm = DataContext as PdfViewerWindowViewModel;
            if (vm == null) return;

            try
            {
                var provider = new PdfFormatProvider();

                if (vm.PdfStream != null)
                {
                    // 从文件流加载 PDF | Load PDF from stream
                    pdfViewer.Document = provider.Import(vm.PdfStream);
                }
                else if (!string.IsNullOrEmpty(vm.FilePath))
                {
                    // 从文件路径加载 PDF | Load PDF from file path
                    using var stream = File.OpenRead(vm.FilePath);
                    pdfViewer.Document = provider.Import(stream);
                }

                // 文档加载后，监听页面变化以同步缩略图选中状态 | After document loaded, listen for page changes to sync thumbnail selection
                pdfViewer.CurrentPageChanged += PdfViewer_CurrentPageChanged;

                // 初始选中第一页缩略图 | Initially select first page thumbnail
                if (thumbnailListBox.Items.Count > 0)
                {
                    thumbnailListBox.SelectedIndex = 0;
                }
            }
            catch (Exception ex) when (ex is not PdfLoadException)
            {
                // 捕获加载异常并包装为 PdfLoadException | Catch loading exceptions and wrap as PdfLoadException
                throw new PdfLoadException(
                    "PDF 文件加载失败 | PDF file load failed",
                    vm.FilePath,
                    ex);
            }
        }

        /// <summary>
        /// 缩略图列表选择变化：跳转到对应页面 | Thumbnail selection changed: navigate to corresponding page
        /// ListBox.SelectedIndex 从 0 开始，RadPdfViewer.CurrentPageNumber 从 1 开始
        /// ListBox.SelectedIndex is 0-based, RadPdfViewer.CurrentPageNumber is 1-based
        /// </summary>
        private void ThumbnailListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (_isSyncingSelection) return;
            if (thumbnailListBox.SelectedIndex < 0) return;

            _isSyncingSelection = true;
            try
            {
                // SelectedIndex(0-based) + 1 = CurrentPageNumber(1-based)
                pdfViewer.CurrentPageNumber = thumbnailListBox.SelectedIndex + 1;
            }
            finally
            {
                _isSyncingSelection = false;
            }
        }

        /// <summary>
        /// PDF 阅读器页面变化：同步缩略图选中状态 | PDF viewer page changed: sync thumbnail selection
        /// </summary>
        private void PdfViewer_CurrentPageChanged(object? sender, EventArgs e)
        {
            if (_isSyncingSelection) return;

            _isSyncingSelection = true;
            try
            {
                // CurrentPageNumber(1-based) - 1 = SelectedIndex(0-based)
                var index = pdfViewer.CurrentPageNumber - 1;
                if (index >= 0 && index < thumbnailListBox.Items.Count)
                {
                    thumbnailListBox.SelectedIndex = index;
                    thumbnailListBox.ScrollIntoView(thumbnailListBox.SelectedItem);
                }
            }
            finally
            {
                _isSyncingSelection = false;
            }
        }

        /// <summary>
        /// 窗口关闭事件：释放 RadPdfViewer 文档资源
        /// Window closed event: release RadPdfViewer document resources
        /// </summary>
        private void OnClosed(object? sender, EventArgs e)
        {
            // 取消事件订阅 | Unsubscribe events
            pdfViewer.CurrentPageChanged -= PdfViewer_CurrentPageChanged;

            // RadPdfViewer 内部管理文档资源，设置 Document = null 触发释放
            // RadPdfViewer internally manages document resources, setting Document = null triggers release
            pdfViewer.Document = null;
        }
    }
}