using Microsoft.WindowsAzure.Storage.Blob;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Tango.Core.IO;

namespace Tango.Transport.Web
{
    public class StorageBlobDownloader : IWebFileDownloader
    {
        private bool _disposed;
        private FileStreamWrapper _stream;
        private long _fileSize;
        private String _fileName;

        public CloudBlockBlob Blob { get; private set; }

        public String Address { get; private set; }

        public event EventHandler<WebFileDownloaderProgressEventArgs> Progress;

        public StorageBlobDownloader(CloudBlockBlob blob, String fileName)
        {
            Blob = blob;
            _fileName = fileName;
        }

        public StorageBlobDownloader(String blobAddress, String fileName) : this(new CloudBlockBlob(new Uri(blobAddress)), fileName)
        {
            Address = blobAddress;
        }

        private void OnProgress(long current)
        {
            Progress?.Invoke(this, new WebFileDownloaderProgressEventArgs()
            {
                Current = current,
                Total = _fileSize,
            });
        }

        public async Task Download()
        {
            if (_disposed)
            {
                throw new ObjectDisposedException("The storage blob downloader can only be used once.");
            }

            await Blob.FetchAttributesAsync();
            _fileSize = Blob.Properties.Length;

            _stream = new FileStreamWrapper(_fileName, FileMode.Create, OnProgress);

            await Blob.DownloadToStreamAsync(_stream);
            Dispose();
        }

        public void Dispose()
        {
            if (!_disposed)
            {
                _disposed = true;

                if (_stream != null)
                {
                    _stream.Dispose();
                }
            }
        }

        public async Task<long> GetFileSize()
        {
            await Blob.FetchAttributesAsync();
            return Blob.Properties.Length;
        }
    }
}