using FATrace.WPLApp.Core;
using FATrace.WPLApp.Services;
using Prism.Commands;
using System;
using System.Collections.ObjectModel;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;

namespace FATrace.WPLApp.ViewModels
{
    /// <summary>
    /// 使用手册（PDF）查看页 VM
    /// </summary>
    public class HelpManualViewModel : NavigationViewModel
    {
        private readonly ILogService _log;

        public HelpManualViewModel(ILogService log)
        {
            _log = log;

            PdfFiles = new ObservableCollection<PdfFileItem>();
            RefreshCommand = new DelegateCommand(async () => await LoadReportPdfsAsync(), () => !IsBusy)
                .ObservesProperty(() => IsBusy);
        }

        private bool _isBusy;
        /// <summary>
        /// 是否忙碌（用于提示与禁用按钮）
        /// </summary>
        public bool IsBusy
        {
            get => _isBusy;
            set { _isBusy = value; RaisePropertyChanged(); }
        }

        private string? _statusText;
        /// <summary>
        /// 页面状态文本（例如：未找到PDF）
        /// </summary>
        public string? StatusText
        {
            get => _statusText;
            set { _statusText = value; RaisePropertyChanged(); }
        }

        /// <summary>
        /// Report 目录下的 PDF 文件列表
        /// </summary>
        public ObservableCollection<PdfFileItem> PdfFiles { get; }

        private PdfFileItem? _selectedPdf;
        /// <summary>
        /// 当前选择的 PDF
        /// </summary>
        public PdfFileItem? SelectedPdf
        {
            get => _selectedPdf;
            set
            {
                _selectedPdf = value;
                RaisePropertyChanged();
                PdfFilePath = _selectedPdf?.FullPath;
            }
        }

        private string? _pdfFilePath;
        /// <summary>
        /// 当前打开的 PDF 文件路径（绑定到 Syncfusion PdfViewerControl.ItemSource）
        /// </summary>
        public string? PdfFilePath
        {
            get => _pdfFilePath;
            set { _pdfFilePath = value; RaisePropertyChanged(); }
        }

        /// <summary>
        /// 刷新/重新扫描 PDF 文件
        /// </summary>
        public DelegateCommand RefreshCommand { get; }

        /// <summary>
        /// 获取运行目录下 Report 文件夹绝对路径
        /// </summary>
        /// <returns>Report 文件夹绝对路径</returns>
        private string GetReportFolder()
        {
            var baseDir = AppDomain.CurrentDomain.BaseDirectory;
            var folder = Path.Combine(baseDir, "Report");
            try
            {
                if (!Directory.Exists(folder))
                {
                    Directory.CreateDirectory(folder);
                }
            }
            catch (Exception ex)
            {
                _log.Error($"HelpManual: 创建Report目录失败: {ex}");
            }
            return folder;
        }

        /// <summary>
        /// 扫描 Report 目录并加载 PDF 列表（默认打开第一个）
        /// </summary>
        /// <returns>Task</returns>
        private async Task LoadReportPdfsAsync()
        {
            if (IsBusy) return;
            try
            {
                IsBusy = true;
                StatusText = string.Empty;

                var folder = GetReportFolder();
                _log.Info($"HelpManual: 扫描PDF目录: {folder}");

                var list = await Task.Run(() =>
                {
                    if (!Directory.Exists(folder))
                        return Array.Empty<PdfFileItem>();

                    var files = Directory.GetFiles(folder, "*.pdf", SearchOption.TopDirectoryOnly)
                        .Select(p => new PdfFileItem(Path.GetFileName(p), p))
                        .OrderByDescending(a => a.FileName)
                        .ToArray();

                    return files;
                });

                Application.Current.Dispatcher.Invoke(() =>
                {
                    PdfFiles.Clear();
                    foreach (var f in list) PdfFiles.Add(f);

                    if (PdfFiles.Count == 0)
                    {
                        SelectedPdf = null;
                        PdfFilePath = null;
                        StatusText = "未在程序目录下的 Report 文件夹找到 PDF 文件，请将手册PDF放入该目录后点击【刷新】。";
                        return;
                    }

                    // 保持原选择（若仍存在），否则默认第一个
                    var keep = SelectedPdf != null
                        ? PdfFiles.FirstOrDefault(a => string.Equals(a.FullPath, SelectedPdf.FullPath, StringComparison.OrdinalIgnoreCase))
                        : null;

                    SelectedPdf = keep ?? PdfFiles[0];
                });
            }
            catch (Exception ex)
            {
                _log.Error($"HelpManual: 扫描/加载PDF失败: {ex}");
                StatusText = $"加载PDF失败: {ex.Message}";
                MessageBox.Show($"加载PDF失败: {ex.Message}", "错误", MessageBoxButton.OK, MessageBoxImage.Error);
            }
            finally
            {
                IsBusy = false;
            }
        }

        /// <summary>
        /// 页面导航进入时自动加载
        /// </summary>
        /// <param name="navigationContext">导航上下文</param>
        public override async void OnNavigatedTo(Prism.Regions.NavigationContext navigationContext)
        {
            await LoadReportPdfsAsync();
        }

        /// <summary>
        /// PDF 文件下拉项
        /// </summary>
        public class PdfFileItem
        {
            /// <summary>
            /// 构造
            /// </summary>
            /// <param name="fileName">文件名</param>
            /// <param name="fullPath">完整路径</param>
            public PdfFileItem(string fileName, string fullPath)
            {
                FileName = fileName;
                FullPath = fullPath;
            }

            /// <summary>
            /// 文件名
            /// </summary>
            public string FileName { get; }

            /// <summary>
            /// 完整路径
            /// </summary>
            public string FullPath { get; }

            /// <summary>
            /// 用于下拉显示
            /// </summary>
            /// <returns>文件名</returns>
            public override string ToString() => FileName;
        }
    }
}