Koreader Progress Sync (#3823)

Co-authored-by: Joseph Milazzo <josephmajora@gmail.com>

API/Helpers/Builders/KoreaderBookDtoBuilder.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Security.Cryptography;
+using System.Text;
+using API.DTOs.Koreader;
+
+namespace API.Helpers.Builders;
+
+public class KoreaderBookDtoBuilder : IEntityBuilder<KoreaderBookDto>
+{
+    private readonly KoreaderBookDto _dto;
+    public KoreaderBookDto Build() => _dto;
+
+    public KoreaderBookDtoBuilder(string documentHash)
+    {
+        _dto = new KoreaderBookDto()
+        {
+            Document = documentHash,
+            Device = "Kavita"
+        };
+    }
+
+    public KoreaderBookDtoBuilder WithDocument(string documentHash)
+    {
+        _dto.Document = documentHash;
+        return this;
+    }
+
+    public KoreaderBookDtoBuilder WithProgress(string progress)
+    {
+        _dto.Progress = progress;
+        return this;
+    }
+
+    public KoreaderBookDtoBuilder WithPercentage(int? pageNum, int pages)
+    {
+        _dto.Percentage = (pageNum ?? 0) / (float) pages;
+        return this;
+    }
+
+    public KoreaderBookDtoBuilder WithDeviceId(string installId, int userId)
+    {
+        var hash = SHA256.HashData(Encoding.UTF8.GetBytes(installId + userId));
+        _dto.Device_id = Convert.ToHexString(hash);
+        return this;
+    }
+}

API/Helpers/Builders/MangaFileBuilder.cs

@@ -60,4 +60,17 @@ public class MangaFileBuilder : IEntityBuilder<MangaFile>
         _mangaFile.Id = Math.Max(id, 0);
         return this;
     }
+
+    /// <summary>
+    /// Generate the Hash on the underlying file
+    /// </summary>
+    /// <remarks>Only applicable to Epubs</remarks>
+    public MangaFileBuilder WithHash()
+    {
+        if (_mangaFile.Format != MangaFormat.Epub) return this;
+
+        _mangaFile.KoreaderHash = KoreaderHelper.HashContents(_mangaFile.FilePath);
+
+        return this;
+    }
 }

API/Helpers/KoreaderHelper.cs

@@ -0,0 +1,113 @@
+using API.DTOs.Progress;
+using System;
+using System.IO;
+using System.Security.Cryptography;
+using System.Text;
+using API.Services.Tasks.Scanner.Parser;
+
+namespace API.Helpers;
+
+/// <summary>
+/// All things related to Koreader
+/// </summary>
+/// <remarks>Original developer: https://github.com/MFDeAngelo</remarks>
+public static class KoreaderHelper
+{
+    /// <summary>
+    /// Hashes the document according to a custom Koreader hashing algorithm.
+    /// Look at the util.partialMD5 method in the attached link.
+    /// Note: Only applies to epub files
+    /// </summary>
+    /// <remarks>The hashing algorithm is relatively quick as it only hashes ~10,000 bytes for the biggest of files.</remarks>
+    /// <see href="https://github.com/koreader/koreader/blob/master/frontend/util.lua#L1040"/>
+    /// <param name="filePath">The path to the file to hash</param>
+    public static string HashContents(string filePath)
+    {
+        if (string.IsNullOrEmpty(filePath) || !File.Exists(filePath) || !Parser.IsEpub(filePath))
+        {
+            return null;
+        }
+
+        using var file = File.OpenRead(filePath);
+
+        const int step = 1024;
+        const int size = 1024;
+        var md5 = MD5.Create();
+        var buffer = new byte[size];
+
+        for (var i = -1; i < 10; i++)
+        {
+            file.Position = step << 2 * i;
+            var bytesRead = file.Read(buffer, 0, size);
+            if (bytesRead > 0)
+            {
+                md5.TransformBlock(buffer, 0, bytesRead, buffer, 0);
+            }
+            else
+            {
+                break;
+            }
+        }
+
+        file.Close();
+        md5.TransformFinalBlock([], 0, 0);
+
+        return md5.Hash == null ? null : Convert.ToHexString(md5.Hash).ToUpper();
+    }
+
+    /// <summary>
+    /// Koreader can identify documents based on contents or title.
+    /// For now, we only support by contents.
+    /// </summary>
+    public static string HashTitle(string filePath)
+    {
+        var fileName = Path.GetFileName(filePath);
+        var fileNameBytes = Encoding.ASCII.GetBytes(fileName);
+        var bytes = MD5.HashData(fileNameBytes);
+
+        return Convert.ToHexString(bytes);
+    }
+
+    public static void UpdateProgressDto(ProgressDto progress, string koreaderPosition)
+    {
+        var path = koreaderPosition.Split('/');
+        if (path.Length < 6)
+        {
+            return;
+        }
+
+        var docNumber = path[2].Replace("DocFragment[", string.Empty).Replace("]", string.Empty);
+        progress.PageNum = int.Parse(docNumber) - 1;
+        var lastTag = path[5].ToUpper();
+
+        if (lastTag == "A")
+        {
+            progress.BookScrollId = null;
+        }
+        else
+        {
+            // The format that Kavita accepts as a progress string. It tells Kavita where Koreader last left off.
+            progress.BookScrollId = $"//html[1]/BODY/APP-ROOT[1]/DIV[1]/DIV[1]/DIV[1]/APP-BOOK-READER[1]/DIV[1]/DIV[2]/DIV[1]/DIV[1]/DIV[1]/{lastTag}";
+        }
+    }
+
+
+    public static string GetKoreaderPosition(ProgressDto progressDto)
+    {
+        string lastTag;
+        var koreaderPageNumber = progressDto.PageNum + 1;
+
+        if (string.IsNullOrEmpty(progressDto.BookScrollId))
+        {
+            lastTag = "a";
+        }
+        else
+        {
+            var tokens = progressDto.BookScrollId.Split('/');
+            lastTag = tokens[^1].ToLower();
+        }
+
+        // The format that Koreader accepts as a progress string. It tells Koreader where Kavita last left off.
+        return $"/body/DocFragment[{koreaderPageNumber}]/body/div/{lastTag}";
+    }
+}