using iFileProxy.Models;
using System.Net.Http.Headers;
using System.Text.Json;

namespace iFileProxy.Helpers
{
    public class FileDownloadHelper
    {

        public static DownloadFileInfo GetDownloadFileInfo(string url)
        {
            var fileInfo = new DownloadFileInfo();
            var _httpClient = new HttpClient();
            using (var request = new HttpRequestMessage(HttpMethod.Head, url))
            {
                using (var response = _httpClient.Send(request))
                {
                    response.EnsureSuccessStatusCode();

                    // 获取文件大小
                    if (response.Content.Headers.TryGetValues("Content-Length", out var values))
                    {
                        if (long.TryParse(values.First(), out long fileSize))
                        {
                            fileInfo.Size = fileSize;
                        }
                        else
                            fileInfo.Size = -1;
                    }
                    else
                        fileInfo.Size = -1;

                    // 获取文件名，优先从 Content-Disposition 中提取，如果没有再从 URL 提取
                    fileInfo.FileName = ExtractFileNameFromContentDisposition(response.Content.Headers.ContentDisposition)
                                        ?? ExtractFileNameFromUrl(url);
                }
            }

            return fileInfo;
        }

        private static string ExtractFileNameFromContentDisposition(ContentDispositionHeaderValue contentDisposition)
        {
            if (contentDisposition != null)
            {
                // 检查是否有文件名
                var fileName = contentDisposition.FileName ?? contentDisposition.FileNameStar;
                return fileName;
            }
            return null;
        }

        private static string ExtractFileNameFromUrl(string url)
        {
            // 从 URL 中提取文件名，通常是 URL 路径的最后一部分
            Uri uri = new Uri(url);
            string fileName = Path.GetFileName(uri.LocalPath);
            return fileName;
        }

    }
}