WIP: Started rewriting the code to make it more null-safe.

src/main/kotlin/de/fabianonline/telegram_backup/Account.kt

@@ -0,0 +1,5 @@
+package de.fabianonline.telegram_backup
+
+class Account(val file_base: String, val phone_number: String) {
+
+}

src/main/kotlin/de/fabianonline/telegram_backup/CommandLineController.kt

@@ -31,7 +31,11 @@ import org.slf4j.Logger
 
 class CommandLineController {
 	private val storage: ApiStorage
-	var app: TelegramApp
+	val app: TelegramApp
+	val target_dir: String
+	val file_base: String
+	val phone_number: String
+	val account_file_base: String
 
 	private fun getLine(): String {
 		if (System.console() != null) {
@@ -53,25 +57,45 @@ class CommandLineController {
 	init {
 		logger.info("CommandLineController started. App version {}", Config.APP_APPVER)
 		
-		this.printHeader()
+		printHeader()
 		if (CommandLineOptions.cmd_version) {
 			System.exit(0)
 		} else if (CommandLineOptions.cmd_help) {
-			this.show_help()
+			show_help()
 			System.exit(0)
 		} else if (CommandLineOptions.cmd_license) {
-			CommandLineController.show_license()
+			show_license()
 			System.exit(0)
 		}
-		this.setupFileBase()
+
+		// Setup file_base
+		logger.debug("Target dir from Config: {}", Config.TARGET_DIR.anonymize())
+		target_dir = CommandLineOptions.val_target ?: Config.TARGET_DIR
+		logger.debug("Target dir after options: {}", target_dir)
+		println("Base directory for files: ${target_dir.anonymize()}")
+
 		if (CommandLineOptions.cmd_list_accounts) {
-			this.list_accounts()
+			Utils.print_accounts(target_dir)
 			System.exit(0)
 		}
+
+		logger.trace("Checking accounts")
+		try {
+			phone_number = selectAccount(target_dir, CommandLineOptions.val_account)
+		} catch(e: AccountNotFoundException) {
+			show_error("The specified account could not be found.")
+		} catch(e: NoAccountsException) {
+			println("No accounts found. Starting login process...")
+			CommandLineOptions.cmd_login = true
+		}
+
+		file_base = target_dir + File.separatorChar + account_to_use
+
+		account = Account(file_base, account_to_use)
+
 		logger.debug("Initializing TelegramApp")
 		app = TelegramApp(Config.APP_ID, Config.APP_HASH, Config.APP_MODEL, Config.APP_SYSVER, Config.APP_APPVER, Config.APP_LANG)
-		logger.trace("Checking accounts")
-		val account = this.selectAccount()
+
 		logger.debug("CommandLineOptions.cmd_login: {}", CommandLineOptions.cmd_login)
 		logger.info("Initializing ApiStorage")
 		storage = ApiStorage(account)
@@ -196,44 +220,22 @@ class CommandLineController {
 		println()
 	}
 
-	private fun setupFileBase() {
-		logger.debug("Target dir at startup: {}", Config.FILE_BASE.anonymize())
-		if (CommandLineOptions.val_target != null) {
-			Config.FILE_BASE = CommandLineOptions.val_target!!
-		}
-		logger.debug("Target dir after options: {}", Config.FILE_BASE.anonymize())
-		System.out.println("Base directory for files: " + Config.FILE_BASE.anonymize())
-	}
-
-	private fun selectAccount(): String? {
-		var account = "none"
-		val accounts = Utils.getAccounts()
-		if (CommandLineOptions.cmd_login) {
-			logger.debug("Login requested, doing nothing.")
-			// do nothing
-		} else if (CommandLineOptions.val_account != null) {
-			logger.debug("Account requested: {}", CommandLineOptions.val_account!!.anonymize())
+	private fun selectAccount(file_base: String, requested_account: String?): String {
+		val found_account: String?
+		val accounts = Utils.getAccounts(file_base)
+		if (requested_account != null) {
+			logger.debug("Account requested: {}", requested_account.anonymize())
 			logger.trace("Checking accounts for match.")
-			var found = false
-			for (acc in accounts) {
-				logger.trace("Checking {}", acc.anonymize())
-				if (acc == CommandLineOptions.val_account) {
-					found = true
-					logger.trace("Matches.")
-					break
-				}
+			found_account = accounts.find{it == requested_account}
+
+			if (found_account == null) {
+				throw AccountNotFoundException()
 			}
-			if (!found) {
-				show_error("Couldn't find account '" + CommandLineOptions.val_account!!.anonymize() + "'. Maybe you want to use '--login' first?")
-			}
-			account = CommandLineOptions.val_account!!
 		} else if (accounts.size == 0) {
-			println("No accounts found. Starting login process...")
-			CommandLineOptions.cmd_login = true
-			return null
+			throw NoAccountsException()
 		} else if (accounts.size == 1) {
-			account = accounts.firstElement()
-			System.out.println("Using only available account: " + account.anonymize())
+			found_account = accounts.firstElement()
+			println("Using only available account: " + account.anonymize())
 		} else {
 			show_error(("You didn't specify which account to use.\n" +
 				"Use '--account <x>' to use account <x>.\n" +
@@ -241,8 +243,8 @@ class CommandLineController {
 			System.exit(1)
 		}
 		logger.debug("accounts.size: {}", accounts.size)
-		logger.debug("account: {}", account.anonymize())
-		return account
+		logger.debug("account: {}", found_account.anonymize())
+		return found_account!!
 	}
 
 	private fun cmd_stats() {
@@ -315,20 +317,6 @@ class CommandLineController {
 		println(" --list-channels       Lists all channels together with their ID")
 	}
 
-	private fun list_accounts() {
-		println("List of available accounts:")
-		val accounts = Utils.getAccounts()
-		if (accounts.size > 0) {
-			for (str in accounts) {
-				System.out.println(" " + str.anonymize())
-			}
-			println("Use '--account <x>' to use one of those accounts.")
-		} else {
-			println("NO ACCOUNTS FOUND")
-			println("Use '--login' to login to a telegram account.")
-		}
-	}
-
 	companion object {
 		private val logger = LoggerFactory.getLogger(CommandLineController::class.java)
 
@@ -342,4 +330,7 @@ class CommandLineController {
 			println("TODO: Print the GPL.")
 		}
 	}
+
+	class AccountNotFoundException() : Exception("Account not found") {}
+	class NoAccountsException() : Exception("No accounts found") {}
 }

src/main/kotlin/de/fabianonline/telegram_backup/Config.kt

@@ -29,7 +29,7 @@ object Config {
 	val APP_APPVER: String
 	val APP_LANG = "en"
 
-	var FILE_BASE = System.getProperty("user.home") + File.separatorChar + ".telegram_backup"
+	var TARGET_DIR = System.getProperty("user.home") + File.separatorChar + ".telegram_backup"
 	val FILE_NAME_AUTH_KEY = "auth.dat"
 	val FILE_NAME_DC = "dc.dat"
 	val FILE_NAME_DB = "database.sqlite"

src/main/kotlin/de/fabianonline/telegram_backup/Database.kt

@@ -51,6 +51,33 @@ class Database private constructor(var client: TelegramClient) {
 	private var conn: Connection? = null
 	private var stmt: Statement? = null
 	var user_manager: UserManager
+	
+	init {
+		private val logger = LoggerFactory.getLogger(Database::class.java)
+		
+		this.user_manager = UserManager.getInstance()
+		System.out.println("Opening database...")
+		try {
+			Class.forName("org.sqlite.JDBC")
+		} catch (e: ClassNotFoundException) {
+			CommandLineController.show_error("Could not load jdbc-sqlite class.")
+		}
+
+		val path = "jdbc:sqlite:${user_manager.fileBase}${Config.FILE_NAME_DB}"
+
+		try {
+			conn = DriverManager.getConnection(path)
+			stmt = conn!!.createStatement()
+		} catch (e: SQLException) {
+			CommandLineController.show_error("Could not connect to SQLITE database.")
+		}
+
+		// Run updates
+		val updates = DatabaseUpdates(conn!!, this)
+		updates.doUpdates()
+
+		System.out.println("Database is ready.")
+	}
 
 	fun getTopMessageID(): Int {
 		try {
@@ -69,34 +96,32 @@ class Database private constructor(var client: TelegramClient) {
 	fun getChatCount(): Int = queryInt("SELECT COUNT(*) FROM chats")
 	fun getUserCount(): Int = queryInt("SELECT COUNT(*) FROM users")
 
-	val missingIDs: LinkedList<Int>
-		get() {
-			try {
-				val missing = LinkedList<Int>()
-				val max = getTopMessageID()
-				val rs = stmt!!.executeQuery("SELECT message_id FROM messages WHERE source_type IN ('group', 'dialog') ORDER BY id")
-				rs.next()
-				var id = rs.getInt(1)
-				for (i in 1..max) {
-					if (i == id) {
-						rs.next()
-						if (rs.isClosed()) {
-							id = Integer.MAX_VALUE
-						} else {
-							id = rs.getInt(1)
-						}
-					} else if (i < id) {
-						missing.add(i)
+	fun getMissingIDs: LinkedList<Int>()
+		try {
+			val missing = LinkedList<Int>()
+			val max = getTopMessageID()
+			val rs = stmt!!.executeQuery("SELECT message_id FROM messages WHERE source_type IN ('group', 'dialog') ORDER BY id")
+			rs.next()
+			var id = rs.getInt(1)
+			for (i in 1..max) {
+				if (i == id) {
+					rs.next()
+					if (rs.isClosed()) {
+						id = Integer.MAX_VALUE
+					} else {
+						id = rs.getInt(1)
 					}
+				} else if (i < id) {
+					missing.add(i)
 				}
-				rs.close()
-				return missing
-			} catch (e: SQLException) {
-				e.printStackTrace()
-				throw RuntimeException("Could not get list of ids.")
 			}
-
+			rs.close()
+			return missing
+		} catch (e: SQLException) {
+			e.printStackTrace()
+			throw RuntimeException("Could not get list of ids.")
 		}
+	}
 
 	fun getMessagesWithMedia(): LinkedList<TLMessage?> {
 		try {
@@ -207,30 +232,7 @@ class Database private constructor(var client: TelegramClient) {
 
 	}
 
-	init {
-		this.user_manager = UserManager.getInstance()
-		System.out.println("Opening database...")
-		try {
-			Class.forName("org.sqlite.JDBC")
-		} catch (e: ClassNotFoundException) {
-			CommandLineController.show_error("Could not load jdbc-sqlite class.")
-		}
-
-		val path = "jdbc:sqlite:${user_manager.fileBase}${Config.FILE_NAME_DB}"
-
-		try {
-			conn = DriverManager.getConnection(path)
-			stmt = conn!!.createStatement()
-		} catch (e: SQLException) {
-			CommandLineController.show_error("Could not connect to SQLITE database.")
-		}
-
-		// Run updates
-		val updates = DatabaseUpdates(conn!!, this)
-		updates.doUpdates()
-
-		System.out.println("Database is ready.")
-	}
+	
 
 	fun backupDatabase(currentVersion: Int) {
 		val filename = String.format(Config.FILE_NAME_DB_BACKUP, currentVersion)
@@ -550,7 +552,9 @@ class Database private constructor(var client: TelegramClient) {
 	fun fetchSetting(key: String): String? {
 		val rs = stmt!!.executeQuery("SELECT value FROM settings WHERE key='${key}'")
 		rs.next()
-		return rs.getString(1)
+		val result = rs.getString(1)
+		rs.close()
+		return result
 	}
 	
 	fun saveSetting(key: String, value: String?) {
@@ -562,6 +566,7 @@ class Database private constructor(var client: TelegramClient) {
 			ps.setString(2, value)
 		}
 		ps.execute()
+		ps.close()
 	}
 	
 	fun getIdsFromQuery(query: String): LinkedList<Int> {
@@ -787,18 +792,6 @@ class Database private constructor(var client: TelegramClient) {
 	}
 
 	companion object {
-		private val logger = LoggerFactory.getLogger(Database::class.java)
-		internal var instance: Database? = null
-
-		fun init(c: TelegramClient) {
-			instance = Database(c)
-		}
-
-		fun getInstance(): Database {
-			if (instance == null) throw RuntimeException("Database is not initialized but getInstance() was called.")
-			return instance!!
-		}
-
 		fun bytesToTLMessage(b: ByteArray?): TLMessage? {
 			try {
 				if (b == null) return null

src/main/kotlin/de/fabianonline/telegram_backup/Utils.kt

@@ -34,9 +34,23 @@ object Utils {
 
 	private val logger = LoggerFactory.getLogger(Utils::class.java) as Logger
 
-	fun getAccounts(): Vector<String> {
+	fun print_accounts(file_base: String) {
+		println("List of available accounts:")
+		val accounts = getAccounts(file_base)
+		if (accounts.size > 0) {
+			for (str in accounts) {
+				println(" " + str.anonymize())
+			}
+			println("Use '--account <x>' to use one of those accounts.")
+		} else {
+			println("NO ACCOUNTS FOUND")
+			println("Use '--login' to login to a telegram account.")
+		}
+	}
+
+	fun getAccounts(file_base: String): Vector<String> {
 		val accounts = Vector<String>()
-		val folder = File(Config.FILE_BASE)
+		val folder = File(file_base)
 		val files = folder.listFiles()
 		if (files != null)
 			for (f in files) {