using System.IO;
using System.Text;
using System.Windows;
using Microsoft.Web.WebView2.Core;
using Microsoft.Web.WebView2.Wpf;
using YY.Admin.Core.Util;

namespace YY.Admin.Infrastructure.Print;

/// <summary>
/// 使用隐藏 WebView2 窗口将 HTML 字符串渲染为 PDF base64。
/// 所有调用必须最终在 WPF UI 线程执行，由内部 Dispatcher 保证。
/// </summary>
public static class HtmlToPdfRenderer
{
    public static Task<string> RenderAsync(string html, double widthMm = 210, double heightMm = 297)
    {
        var tcs = new TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously);

        Application.Current.Dispatcher.InvokeAsync(async () =>
        {
            try
            {
                var result = await RenderOnUiThreadAsync(html, widthMm, heightMm);
                tcs.SetResult(result);
            }
            catch (Exception ex)
            {
                tcs.SetException(ex);
            }
        });

        return tcs.Task;
    }

    private static async Task<string> RenderOnUiThreadAsync(string html, double widthMm, double heightMm)
    {
        var tempHtml = Path.ChangeExtension(Path.GetTempFileName(), ".html");
        var tempPdf  = Path.ChangeExtension(Path.GetTempFileName(), ".pdf");
        Window? win  = null;

        try
        {
            File.WriteAllText(tempHtml, html, Encoding.UTF8);

            var userData = AppWritablePaths.EnsureDirectoryExists(
                Path.Combine(AppWritablePaths.LocalApplicationRoot, "WebView2", "HtmlToPdf"));
            var env = await CoreWebView2Environment.CreateAsync(browserExecutableFolder: null, userDataFolder: userData);
            var wv  = new WebView2();

            win = new Window
            {
                Width  = 1,
                Height = 1,
                Left   = -99999,
                Top    = -99999,
                ShowInTaskbar  = false,
                WindowStyle    = WindowStyle.None,
                Visibility     = Visibility.Visible
            };
            win.Content = wv;
            win.Show();

            await wv.EnsureCoreWebView2Async(env);

            var navTcs = new TaskCompletionSource();
            wv.CoreWebView2.NavigationCompleted += (_, _) => navTcs.TrySetResult();
            wv.CoreWebView2.Navigate(new Uri(tempHtml).AbsoluteUri);
            await navTcs.Task;

            // 短暂等待 JS/CSS 完成渲染
            await Task.Delay(200);

            var settings = env.CreatePrintSettings();
            settings.PageWidth          = widthMm / 25.4;
            settings.PageHeight         = heightMm / 25.4;
            settings.MarginTop          = 0;
            settings.MarginBottom       = 0;
            settings.MarginLeft         = 0;
            settings.MarginRight        = 0;
            settings.ShouldPrintHeaderAndFooter = false;
            settings.ShouldPrintBackgrounds     = true;

            await wv.CoreWebView2.PrintToPdfAsync(tempPdf, settings);

            var pdfBytes = File.ReadAllBytes(tempPdf);
            return Convert.ToBase64String(pdfBytes);
        }
        finally
        {
            win?.Close();
            try { File.Delete(tempHtml); } catch { }
            try { File.Delete(tempPdf);  } catch { }
        }
    }
}