using System;
using System.IO;
using Prism.Commands;
using Prism.Mvvm;
using XP.Common.Localization;
using XP.Common.Logging.Interfaces;
using XP.Common.PdfViewer.Interfaces;

namespace XP.Common.PdfViewer.ViewModels
{
    /// <summary>
    /// PDF 阅读器窗口 ViewModel | PDF viewer window ViewModel
    /// 轻量级 ViewModel，核心功能由 RadPdfViewer 控件内置处理 | Lightweight ViewModel, core features handled by RadPdfViewer
    /// </summary>
    public class PdfViewerWindowViewModel : BindableBase
    {
        private readonly IPdfPrintService _printService;
        private readonly ILoggerService _logger;

        /// <summary>
        /// 窗口标题（含文件名）| Window title (with file name)
        /// </summary>
        public string Title { get; }

        /// <summary>
        /// PDF 文件路径（用于打印）| PDF file path (for printing)
        /// </summary>
        public string? FilePath { get; }

        /// <summary>
        /// PDF 文件流（用于流加载场景）| PDF file stream (for stream loading scenario)
        /// </summary>
        public Stream? PdfStream { get; }

        /// <summary>
        /// 打印命令（打开打印设置对话框）| Print command (open print settings dialog)
        /// </summary>
        public DelegateCommand PrintCommand { get; }

        /// <summary>
        /// 打印预览命令 | Print preview command
        /// </summary>
        public DelegateCommand PrintPreviewCommand { get; }

        /// <summary>
        /// 通过文件路径创建 ViewModel | Create ViewModel by file path
        /// </summary>
        /// <param name="filePath">PDF 文件路径 | PDF file path</param>
        /// <param name="printService">打印服务 | Print service</param>
        /// <param name="logger">日志服务 | Logger service</param>
        public PdfViewerWindowViewModel(
            string filePath,
            IPdfPrintService printService,
            ILoggerService logger)
        {
            _printService = printService ?? throw new ArgumentNullException(nameof(printService));
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));

            FilePath = filePath ?? throw new ArgumentNullException(nameof(filePath));
            PdfStream = null;

            // 使用多语言标题，包含文件名 | Use localized title with file name
            var fileName = Path.GetFileName(filePath);
            Title = LocalizationHelper.Get("PdfViewer_TitleWithFile", fileName);

            // 初始化命令 | Initialize commands
            PrintCommand = new DelegateCommand(ExecutePrint, CanExecutePrint);
            PrintPreviewCommand = new DelegateCommand(ExecutePrintPreview, CanExecutePrint);
        }

        /// <summary>
        /// 通过文件流创建 ViewModel | Create ViewModel by stream
        /// </summary>
        /// <param name="stream">PDF 文件流 | PDF file stream</param>
        /// <param name="title">窗口标题（可选）| Window title (optional)</param>
        /// <param name="printService">打印服务 | Print service</param>
        /// <param name="logger">日志服务 | Logger service</param>
        public PdfViewerWindowViewModel(
            Stream stream,
            string? title,
            IPdfPrintService printService,
            ILoggerService logger)
        {
            _printService = printService ?? throw new ArgumentNullException(nameof(printService));
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));

            PdfStream = stream ?? throw new ArgumentNullException(nameof(stream));
            FilePath = null;

            // 使用自定义标题或默认多语言标题 | Use custom title or default localized title
            Title = !string.IsNullOrWhiteSpace(title)
                ? title
                : LocalizationHelper.Get("PdfViewer_Title");

            // 初始化命令（流模式下无文件路径，命令不可用）| Initialize commands (no file path in stream mode, commands disabled)
            PrintCommand = new DelegateCommand(ExecutePrint, CanExecutePrint);
            PrintPreviewCommand = new DelegateCommand(ExecutePrintPreview, CanExecutePrint);
        }

        /// <summary>
        /// 执行打印（打开打印设置对话框）| Execute print (open print settings dialog)
        /// </summary>
        private void ExecutePrint()
        {
            try
            {
                _printService.PrintWithDialog(FilePath!);
            }
            catch (Exception ex)
            {
                _logger.Error(ex, "打印失败 | Print failed: {FilePath}", FilePath ?? string.Empty);
            }
        }

        /// <summary>
        /// 执行打印预览 | Execute print preview
        /// </summary>
        private void ExecutePrintPreview()
        {
            try
            {
                _printService.PrintPreview(FilePath!);
            }
            catch (Exception ex)
            {
                _logger.Error(ex, "打印预览失败 | Print preview failed: {FilePath}", FilePath ?? string.Empty);
            }
        }

        /// <summary>
        /// 判断打印命令是否可用（仅当 FilePath 有效时）| Check if print command is available (only when FilePath is valid)
        /// </summary>
        private bool CanExecutePrint()
        {
            return !string.IsNullOrEmpty(FilePath);
        }
    }
}