using System;
using System.IO;
using System.Text;
using System.Threading.Tasks;
using Hncore.Infrastructure.Extension;
using Microsoft.AspNetCore.Http;

namespace Hncore.Infrastructure.CSV
{
    public class CsvTemporaryFile : IDisposable
    {
        private string filePath = "";
        private FileStream _fileStream;
        private StreamWriter _streamWriter;

        public CsvTemporaryFile()
        {
            var execDir = Path.GetDirectoryName(typeof(CsvTemporaryFile).Assembly.Location);

            string tempDir = Path.Combine(execDir, "temp", DateTime.Now.ToString("yyyyMMdd"));

            if (!Directory.Exists(tempDir))
            {
                Directory.CreateDirectory(tempDir);
            }

            filePath = Path.Combine(tempDir, Guid.NewGuid().ToString());

            _fileStream = new FileStream(filePath, FileMode.Create, FileAccess.Write);
            _streamWriter = new StreamWriter(_fileStream, Encoding.GetEncoding("GB2312"));
            _streamWriter.AutoFlush = true;
        }

        public void WriteLine(CsvRow row)
        {
            _streamWriter.WriteLine(row.ToString());
        }

        public async Task ResponseAsync(HttpResponse httpResponse, string fileName)
        {
            httpResponse.ContentType = "application/octet-stream";
            httpResponse.Headers.Add("Content-Disposition", $"attachment; filename={fileName.UrlEncode()}");
            httpResponse.Headers.Add("X-Suggested-Filename", fileName.UrlEncode());

            using (FileStream fs = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            {
                using (BufferedStream bs = new BufferedStream(fs))
                {
                    byte[] buffer = new byte[4096];
                    int bytesRead;

                    long total_read = 0;
                    DateTime begin = DateTime.Now;
                    TimeSpan ts = new TimeSpan();

                    while ((bytesRead = bs.Read(buffer, 0, buffer.Length)) > 0)
                    {
                        await httpResponse.Body.WriteAsync(buffer, 0, bytesRead);
                        await httpResponse.Body.FlushAsync();

                        total_read += bytesRead;
                        ts = DateTime.Now - begin;
                        if (total_read / ts.TotalSeconds > 1024 * 1000)
                        {
                            await Task.Delay(1);
                        }
                    }
                }
            }
        }

        public void Dispose()
        {
            _streamWriter?.Dispose();
            _fileStream?.Dispose();


            if (File.Exists(filePath))
            {
                File.Delete(filePath);
            }
        }
    }
}