OPDS Support (#526)

* Added some basic OPDS implementation

* Fixed an issue with feed href

* More changes

* Added library routes and moved user code to a method so we can hack in fixed code without authentication

* Images now load on the OPDS reusing our existing Image infrastructure.

* Added the ability to download and moved some download code to a dedicated service

* Download is working, pagination is implemented.

* Refactored libraries to use pagination

* Laid foundation for OpenSearch implementation

* Fixed up some serialization issues and some old code that wasn't referencing helper methods

* Ensure chapters are sorted when we send them over OPDS

* OpenSearch implemented

* Removed any support for OPDS-PS due to lack of apps supporting it.

* Don't distribute development.json nor stats directory on build.

* Implemented In Progress feed as well.

* Ability to enable OPDS for server. OPDS now accepts initial call as POST in case app uses username/password.

* UI now properly renders state for OPDS enablement. Added Collections routes.

* Fixed pagination startIndex on OPDS feeds when there is less than 1 page.

* Chunky Reader now works. It only accepts UTF-8 encodings

* More Chunky fixes

* More chunky changes, such a fussy client.

* Implemented the ability to have a custom api key assigned to a user and use that api key as your authentication token against OPDS routing.

* Implemented the ability to reset your API Key

* Fixed favicon not being sent back correctly

* Fixed an issue where images wouldn't send on OPDS feed.

* Implemented Page streaming and fixed a pagination bug

* Hooked in the ability to save progress in Kavita when Page Streaming

API/Services/Clients/StatsApiClient.cs

@@ -19,6 +19,7 @@ namespace API.Services.Clients
         {
             _client = client;
             _logger = logger;
+            _client.Timeout = TimeSpan.FromSeconds(30);
         }
 
         public async Task SendDataToStatsServer(UsageStatisticsDto data)

API/Services/DirectoryService.cs

@@ -432,5 +432,60 @@ namespace API.Services
                }
            }
        }
+
+        /// <summary>
+        /// Returns the human-readable file size for an arbitrary, 64-bit file size
+        /// <remarks>The default format is "0.## XB", e.g. "4.2 KB" or "1.43 GB"</remarks>
+        /// </summary>
+        /// https://www.somacon.com/p576.php
+        /// <param name="bytes"></param>
+        /// <returns></returns>
+       public static string GetHumanReadableBytes(long bytes)
+       {
+           // Get absolute value
+           var absoluteBytes = (bytes < 0 ? -bytes : bytes);
+           // Determine the suffix and readable value
+           string suffix;
+           double readable;
+           switch (absoluteBytes)
+           {
+               // Exabyte
+               case >= 0x1000000000000000:
+                   suffix = "EB";
+                   readable = (bytes >> 50);
+                   break;
+               // Petabyte
+               case >= 0x4000000000000:
+                   suffix = "PB";
+                   readable = (bytes >> 40);
+                   break;
+               // Terabyte
+               case >= 0x10000000000:
+                   suffix = "TB";
+                   readable = (bytes >> 30);
+                   break;
+               // Gigabyte
+               case >= 0x40000000:
+                   suffix = "GB";
+                   readable = (bytes >> 20);
+                   break;
+               // Megabyte
+               case >= 0x100000:
+                   suffix = "MB";
+                   readable = (bytes >> 10);
+                   break;
+               // Kilobyte
+               case >= 0x400:
+                   suffix = "KB";
+                   readable = bytes;
+                   break;
+               default:
+                   return bytes.ToString("0 B"); // Byte
+           }
+           // Divide by 1024 to get fractional value
+           readable = (readable / 1024);
+           // Return formatted number with suffix
+           return readable.ToString("0.## ") + suffix;
+       }
     }
 }

API/Services/DownloadService.cs

@@ -0,0 +1,59 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using API.Entities;
+using API.Interfaces.Services;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.StaticFiles;
+
+namespace API.Services
+{
+    public interface IDownloadService
+    {
+        Task<(byte[], string, string)> GetFirstFileDownload(IEnumerable<MangaFile> files);
+        string GetContentTypeFromFile(string filepath);
+    }
+    public class DownloadService : IDownloadService
+    {
+        private readonly IDirectoryService _directoryService;
+        private readonly FileExtensionContentTypeProvider _fileTypeProvider = new FileExtensionContentTypeProvider();
+
+        public DownloadService(IDirectoryService directoryService)
+        {
+            _directoryService = directoryService;
+        }
+
+        /// <summary>
+        /// Downloads the first file in the file enumerable for download
+        /// </summary>
+        /// <param name="files"></param>
+        /// <returns></returns>
+        public async Task<(byte[], string, string)> GetFirstFileDownload(IEnumerable<MangaFile> files)
+        {
+            var firstFile = files.Select(c => c.FilePath).First();
+            return (await _directoryService.ReadFileAsync(firstFile), GetContentTypeFromFile(firstFile), Path.GetFileName(firstFile));
+        }
+
+        public string GetContentTypeFromFile(string filepath)
+        {
+            // Figures out what the content type should be based on the file name.
+            if (!_fileTypeProvider.TryGetContentType(filepath, out var contentType))
+            {
+                contentType = Path.GetExtension(filepath).ToLowerInvariant() switch
+                {
+                    ".cbz" => "application/zip",
+                    ".cbr" => "application/vnd.rar",
+                    ".cb7" => "application/x-compressed",
+                    ".epub" => "application/epub+zip",
+                    ".7z" => "application/x-7z-compressed",
+                    ".7zip" => "application/x-7z-compressed",
+                    ".pdf" => "application/pdf",
+                    _ => contentType
+                };
+            }
+
+            return contentType;
+        }
+    }
+}