This looks more or less usable...

src/main/java/de/fabianonline/telegram_backup/CommandLineController.java

@@ -59,7 +59,7 @@ public class CommandLineController {
 					String pw = new Scanner(System.in).nextLine();
 					user.verifyPassword(pw);
 				}
-				storage.setPrefix(user.getUser().getPhone());
+				storage.setPrefix("+" + user.getUser().getPhone());
 				
 				System.out.println("Next time, please run this tool with '--account " + user.getUser().getPhone() + " to use this account.");
 			}
@@ -67,7 +67,7 @@ public class CommandLineController {
 			System.out.println("You are logged in as " + user.getUserString());
 			
 			DownloadManager d = new DownloadManager(user, client);
-			d.downloadMessages();
+			d.downloadMessages(options.limit_messages);
 			d.downloadMedia();
 		} catch (RpcErrorException e) {
 			e.printStackTrace();
@@ -86,6 +86,7 @@ public class CommandLineController {
 		System.out.println("  --login                         Login to an existing telegram account.");
 		System.out.println("  --debug                         Show (lots of) debug information.");
 		System.out.println("  --list-accounts                 List all existing accounts ");
+		System.out.println("  --limit-messages <x>            Downloads at most the most recent <x> messages.");
 		
 		System.exit(0);
 	}
@@ -121,6 +122,7 @@ public class CommandLineController {
 		public boolean cmd_login = false;
 		public boolean cmd_debug = false;
 		public boolean cmd_list_accounts = false;
+		public Integer limit_messages = null;
 		
 		public CommandLineOptions(String[] args) {
 			String last_cmd = null;
@@ -129,6 +131,7 @@ public class CommandLineController {
 				if (last_cmd != null) {
 					switch(last_cmd) {
 						case "--account": this.account=arg; break;
+						case "--limit-messages": this.limit_messages=Integer.parseInt(arg); break;
 					}
 					last_cmd = null;
 					continue;
@@ -140,6 +143,7 @@ public class CommandLineController {
 					case "--login": this.cmd_login=true; break;
 					case "--debug": this.cmd_debug=true; break;
 					case "--list-accounts": this.cmd_list_accounts=true; break;
+					case "--limit-messages": last_cmd=arg; continue;
 					default: throw new RuntimeException("Unknown command " + arg);
 				}
 			}

src/main/java/de/fabianonline/telegram_backup/Config.java

@@ -15,7 +15,10 @@ class Config {
     public static final String FILE_NAME_DC = "dc.dat";
     public static final String FILE_NAME_DB = "database.sqlite";
     public static final String FILE_FILES_BASE = "files";
+    public static final String FILE_STICKER_BASE = "stickers";
     
     public static final int FILE_DOWNLOAD_BLOCK_SIZE = 1024*1024;
+    
+    public static final int DELAY_AFTER_GET_FILE = 750;
 }
 

src/main/java/de/fabianonline/telegram_backup/Database.java

@@ -1,16 +1,7 @@
 package de.fabianonline.telegram_backup;
 
-import com.github.badoualy.telegram.tl.api.TLMessage;
+import com.github.badoualy.telegram.tl.api.*;
-import com.github.badoualy.telegram.tl.api.TLMessageEmpty;
-import com.github.badoualy.telegram.tl.api.TLMessageService;
 import com.github.badoualy.telegram.tl.core.TLVector;
-import com.github.badoualy.telegram.tl.api.TLAbsMessage;
-import com.github.badoualy.telegram.tl.api.TLMessageMediaEmpty;
-import com.github.badoualy.telegram.tl.api.TLAbsPeer;
-import com.github.badoualy.telegram.tl.api.TLPeerUser;
-import com.github.badoualy.telegram.tl.api.TLPeerChat;
-import com.github.badoualy.telegram.tl.api.TLPeerChannel;
-import com.github.badoualy.telegram.tl.api.TLApiContext;
 
 import java.sql.Connection;
 import java.sql.DriverManager;
@@ -25,7 +16,7 @@ import java.io.ByteArrayOutputStream;
 import java.util.LinkedList;
 
 import de.fabianonline.telegram_backup.UserManager;
-
+import de.fabianonline.telegram_backup.StickerConverter;
 
 class Database {
 	private Connection conn;
@@ -41,10 +32,7 @@ class Database {
 		}
 		
 		String path = "jdbc:sqlite:" +
-			Config.FILE_BASE +
+			user_manager.getFileBase() +
-			File.separatorChar +
-			user_manager.getUser().getPhone() +
-			File.separatorChar +
 			Config.FILE_NAME_DB;
 		
 		try {
@@ -74,6 +62,7 @@ class Database {
 			System.out.println("Database version: " + version);
 			
 			if (version==0) {
+				System.out.println("  Updating to version 1...");
 				stmt.executeUpdate("CREATE TABLE messages ("
 						+ "id INTEGER PRIMARY KEY ASC, "
 						+ "dialog_id INTEGER, "
@@ -83,6 +72,7 @@ class Database {
 						+ "text TEXT, "
 						+ "time TEXT, "
 						+ "has_media BOOLEAN, "
+						+ "sticker TEXT, "
 						+ "data BLOB)");
 				stmt.executeUpdate("CREATE TABLE dialogs ("
 						+ "id INTEGER PRIMARY KEY ASC, "
@@ -98,6 +88,8 @@ class Database {
 				stmt.executeUpdate("INSERT INTO database_versions (version) VALUES (1)");
 				version = 1;
 			}
+			
+			System.out.println("Database is ready.");
 		} catch (SQLException e) {
 			System.out.println(e.getSQLState());
 			e.printStackTrace();
@@ -118,9 +110,9 @@ class Database {
 		try {
 			PreparedStatement ps = conn.prepareStatement(
 				"INSERT INTO messages " +
-				"(id, dialog_id, from_id, type, text, time, has_media, data) " + 
+				"(id, dialog_id, from_id, type, text, time, has_media, data, sticker) " + 
 				"VALUES " +
-				"(?,  ?,         ?,       ?,    ?,    ?,    ?,         ?)");
+				"(?,  ?,         ?,       ?,    ?,    ?,    ?,         ?,    ?)");
 			for (TLAbsMessage abs : all) {
 				if (abs instanceof TLMessage) {
 					TLMessage msg = (TLMessage) abs;
@@ -150,6 +142,7 @@ class Database {
 						} else if (msg.getMedia() instanceof TLMessageMediaPhoto) {
 							text = ((TLMessageMediaPhoto)msg.getMedia()).getCaption();
 						}
+						System.out.println("" + msg.getId() + ": >" + text + "<");
 					}
 					ps.setString(5, text);
 					ps.setString(6, ""+msg.getDate());
@@ -157,6 +150,24 @@ class Database {
 					ByteArrayOutputStream stream = new ByteArrayOutputStream();
 					msg.serializeBody(stream);
 					ps.setBytes(8, stream.toByteArray());
+					String sticker = null;
+					if (msg.getMedia()!=null && msg.getMedia() instanceof TLMessageMediaDocument) {
+						TLMessageMediaDocument md = (TLMessageMediaDocument)msg.getMedia();
+						if (md.getDocument() instanceof TLDocument) {
+							for (TLAbsDocumentAttribute attr : ((TLDocument)md.getDocument()).getAttributes()) {
+								if (attr instanceof TLDocumentAttributeSticker) {
+									sticker = StickerConverter.makeFilename((TLDocumentAttributeSticker)attr);
+									break;
+								}
+							}
+						}
+					}
+					if (sticker != null) {
+						System.out.println("" + msg.getId() + ": >" + msg.getMessage() + "< " + sticker);
+						ps.setString(9, sticker);
+					} else {
+						ps.setNull(9, Types.VARCHAR);
+					}
 					ps.addBatch();
 				} else if (abs instanceof TLMessageService) {
 					// Ignore service messages.

src/main/java/de/fabianonline/telegram_backup/DownloadManager.java

@@ -2,6 +2,7 @@ package de.fabianonline.telegram_backup;
 
 import de.fabianonline.telegram_backup.UserManager;
 import de.fabianonline.telegram_backup.Database;
+import de.fabianonline.telegram_backup.StickerConverter;
 
 import com.github.badoualy.telegram.api.TelegramClient;
 import com.github.badoualy.telegram.tl.core.TLIntVector;
@@ -10,6 +11,7 @@ import com.github.badoualy.telegram.tl.api.messages.TLAbsDialogs;
 import com.github.badoualy.telegram.tl.api.*;
 import com.github.badoualy.telegram.tl.api.upload.TLFile;
 import com.github.badoualy.telegram.tl.exception.RpcErrorException;
+import com.github.badoualy.telegram.tl.api.request.TLRequestUploadGetFile;
 
 import java.io.IOException;
 import java.io.File;
@@ -28,7 +30,7 @@ class DownloadManager {
 		this.db = new Database(u);
 	}
 	
-	public void downloadMessages() throws RpcErrorException, IOException {
+	public void downloadMessages(Integer limit) throws RpcErrorException, IOException {
 		System.out.print("Downloading dialogs... ");
 		TLAbsDialogs dialogs = client.messagesGetDialogs(
 			0,
@@ -44,6 +46,12 @@ class DownloadManager {
 		int max_database_id = db.getTopMessageID();
 		System.out.println("Top message ID in database is " + max_database_id);
 		
+		if (limit != null) {
+			System.out.println("Limit is set to " + limit);
+			max_database_id = Math.max(max_database_id, max_message_id-limit);
+			System.out.println("New top message id 'in database' is " + max_database_id);
+		}
+		
 		int start_id = max_database_id + 1;
 		int current_start_id = start_id;
 		int end_id = max_message_id;
@@ -75,7 +83,30 @@ class DownloadManager {
 			TLAbsMessageMedia media = msg.getMedia();
 			
 			if (media instanceof TLMessageMediaPhoto) {
-				TLMessageMediaPhoto p = (TLMessageMediaPhoto) media;
+				this.downloadMessageMediaPhoto(msg, (TLMessageMediaPhoto)media);
+			} else if (media instanceof TLMessageMediaDocument) {
+				this.downloadMessageMediaDocument(msg, (TLMessageMediaDocument)media);
+			} else if (media instanceof TLMessageMediaVideo) {
+				this.downloadMessageMediaVideo(msg, (TLMessageMediaVideo)media);
+			} else if (media instanceof TLMessageMediaEmpty) {
+				// do nothing
+			} else if (media instanceof TLMessageMediaUnsupported) {
+				// do nothing
+			} else if (media instanceof TLMessageMediaGeo) {
+				// do nothing
+			} else if (media instanceof TLMessageMediaWebPage) {
+				// do nothing
+			} else if (media instanceof TLMessageMediaContact) {
+				// do nothing
+			} else if (media instanceof TLMessageMediaVenue) {
+				// do nothing
+			} else {
+				throw new RuntimeException("Unexpected " + media.getClass().getName());
+			}
+		}
+	}
+	
+	private void downloadMessageMediaPhoto(TLMessage msg, TLMessageMediaPhoto p) throws RpcErrorException, IOException {
 		if (p.getPhoto() instanceof TLPhoto) {
 			TLPhoto photo = (TLPhoto) p.getPhoto();
 			TLPhotoSize size = null;
@@ -92,12 +123,59 @@ class DownloadManager {
 			}
 			if (size.getLocation() instanceof TLFileLocation) {
 				this.downloadPhoto(msg.getId(), (TLFileLocation)size.getLocation());
-						return;
 			}
 		} else {
 			throw new RuntimeException("Got an unexpected " + p.getPhoto().getClass().getName());
 		}
 	}
+	
+	private void downloadMessageMediaDocument(TLMessage msg, TLMessageMediaDocument d) throws RpcErrorException, IOException {
+		if (d.getDocument() instanceof TLDocument) {
+			TLDocument doc = (TLDocument)d.getDocument();
+			//Determine files extension
+			String original_filename = null;
+			TLDocumentAttributeSticker sticker = null;
+			
+			String ext = null;
+			for(TLAbsDocumentAttribute attr : doc.getAttributes()) {
+				if (attr instanceof TLDocumentAttributeFilename) {
+					original_filename = ((TLDocumentAttributeFilename)attr).getFileName();
+				} else if (attr instanceof TLDocumentAttributeSticker) {
+					sticker = (TLDocumentAttributeSticker)attr;
+				}
+			}
+			if (original_filename != null) {
+				int i = original_filename.lastIndexOf('.');
+				if (i>0) ext = original_filename.substring(i+1);
+			}
+			if (ext==null) {
+				int i = doc.getMimeType().lastIndexOf('/');
+				String type = doc.getMimeType().substring(i+1).toLowerCase();
+				if (type.equals("unknown")) {
+					ext = "dat";
+				} else {
+					ext = type;
+				}
+			}
+			String filename;
+			if (sticker != null) {
+				filename = StickerConverter.makeFilenameWithPath(sticker);
+			} else {
+				filename = this.makeFilename(msg.getId(), ext);
+			}
+			
+			this.downloadDocument(filename, doc);
+		} else {
+			throw new RuntimeException("Got an unexpected " + d.getDocument().getClass().getName());
+		}
+	}
+	
+	private void downloadMessageMediaVideo(TLMessage msg, TLMessageMediaVideo v) throws RpcErrorException, IOException {
+		if (v.getVideo() instanceof TLVideo) {
+			TLVideo vid = (TLVideo)v.getVideo();
+			int i = vid.getMimeType().lastIndexOf('/');
+			String ext = vid.getMimeType().substring(i+1).toLowerCase();
+			this.downloadVideo(this.makeFilename(msg.getId(), ext), vid);
 		}
 	}
 	
@@ -117,9 +195,22 @@ class DownloadManager {
 		this.downloadFile(this.makeFilename(msgId, "jpg"), loc);
 	}
 	
+	private void downloadDocument(String filename, TLDocument doc) throws RpcErrorException, IOException {
+		TLInputDocumentFileLocation loc = new TLInputDocumentFileLocation();
+		loc.setId(doc.getId());
+		loc.setAccessHash(doc.getAccessHash());
+		this.downloadFileFromDc(filename, loc, doc.getDcId());
+	}
+	
+	private void downloadVideo(String filename, TLVideo vid) throws RpcErrorException, IOException {
+		TLInputDocumentFileLocation loc = new TLInputDocumentFileLocation();
+		loc.setId(vid.getId());
+		loc.setAccessHash(vid.getAccessHash());
+		this.downloadFileFromDc(filename, loc, vid.getDcId());
+	}
+	
 	private String makeFilename(int id, String ext) {
-		String path = Config.FILE_BASE + 
+		String path = this.user.getFileBase() + 
-			File.separatorChar + 
 			Config.FILE_FILES_BASE +
 			File.separatorChar;
 		new File(path).mkdirs();
@@ -127,16 +218,41 @@ class DownloadManager {
 		return path + id + ".dat";
 	}
 	
+	private void downloadFile(String target, TLAbsInputFileLocation loc) throws RpcErrorException, IOException {
+		downloadFileFromDc(target, loc, null);
+	}
 	
-	private void downloadFile(String target, TLInputFileLocation loc) throws RpcErrorException, IOException {
+	private void downloadFileFromDc(String target, TLAbsInputFileLocation loc, Integer dcID) throws RpcErrorException, IOException {
-		FileOutputStream fos = new FileOutputStream(target);
+		// Don't download already existing files.
+		if (new File(target).isFile()) return;
+		
+		FileOutputStream fos = null;
+		try {
+			fos = new FileOutputStream(target);
 			int offset = 0;
 			TLFile response;
 			do {
-			response = this.client.uploadGetFile(loc, offset, Config.FILE_DOWNLOAD_BLOCK_SIZE);
+				TLRequestUploadGetFile req = new TLRequestUploadGetFile(loc, offset, Config.FILE_DOWNLOAD_BLOCK_SIZE);
+				if (dcID==null) {
+					response = (TLFile)this.client.executeRpcQuery(req);
+				} else {
+					response = (TLFile)this.client.executeRpcQuery(req, dcID);
+				}
 				offset += Config.FILE_DOWNLOAD_BLOCK_SIZE;
 				fos.write(response.getBytes().getData());
+				try { Thread.sleep(Config.DELAY_AFTER_GET_FILE); } catch(InterruptedException e) {}
 			} while(response.getBytes().getLength() == Config.FILE_DOWNLOAD_BLOCK_SIZE);
 			fos.close();
+		} catch (java.io.IOException ex) {
+			if (fos!=null) fos.close();
+			new File(target).delete();
+			System.out.println("IOException happened while downloading " + target);
+			throw ex;
+		} catch (RpcErrorException ex) {
+			if (fos!=null) fos.close();
+			new File(target).delete();
+			System.out.println("RpcErrorException happened while downloading " + target);
+			throw ex;
+		}
 	}
 }

src/main/java/de/fabianonline/telegram_backup/StickerConverter.java

@@ -0,0 +1,36 @@
+package de.fabianonline.telegram_backup;
+
+import com.github.badoualy.telegram.tl.api.*;
+import java.lang.StringBuilder;
+import java.io.File;
+
+class StickerConverter {
+	public static String makeFilenameWithPath(TLDocumentAttributeSticker attr) {
+		StringBuilder file = new StringBuilder();
+		file.append(makePath());
+		file.append(makeFilename(attr));
+		return file.toString();
+	}
+	
+	public static String makeFilename(TLDocumentAttributeSticker attr) {
+		StringBuilder file = new StringBuilder();
+		if (attr.getStickerset() instanceof TLInputStickerSetShortName) {
+			file.append(((TLInputStickerSetShortName)attr.getStickerset()).getShortName());
+		} else if (attr.getStickerset() instanceof TLInputStickerSetID) {
+			file.append(((TLInputStickerSetID)attr.getStickerset()).getId());
+		}
+		file.append("_");
+		file.append(attr.getAlt().hashCode());
+		file.append(".webp");
+		return file.toString();
+	}
+	
+	public static String makePath() {
+		String path = Config.FILE_BASE +
+			File.separatorChar +
+			Config.FILE_STICKER_BASE +
+			File.separatorChar;
+		new File(path).mkdirs();
+		return path;
+	}
+}

src/main/java/de/fabianonline/telegram_backup/UserManager.java

@@ -13,6 +13,7 @@ import com.github.badoualy.telegram.tl.core.TLBytes;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.io.IOException;
+import java.io.File;
 
 class UserManager {
 	public TLUser user = null;
@@ -91,4 +92,8 @@ class UserManager {
 	}
 	
 	public TLUser getUser() { return this.user; }
+	
+	public String getFileBase() {
+		return Config.FILE_BASE + File.separatorChar + "+" + this.user.getPhone() + File.separatorChar;
+	}
 }