PrevaylerJr in Scala

PrevaylerJr.scala

import java.io._

class PrevaylerJr[T <: Serializable](initialState: T, pStorageFile: File) {

	private val storageFile = new File(pStorageFile.getAbsolutePath + ".tmp")

	private val system = {
		val fileToRead = if (pStorageFile.exists) pStorageFile else storageFile
		if (fileToRead.exists) {
			val input = new ObjectInputStream(new FileInputStream(fileToRead))
			/* Restore image */
			val sys = input.readObject.asInstanceOf[T]
			/* Restore commands */
			try while (true)
				input.readObject.asInstanceOf[(T) => _](sys)
			catch { case endOfStreamReached: EOFException => }
			sys
		} else
			initialState
	}

	private val journal = new ObjectOutputStream(new FileOutputStream(storageFile))
	writeToJournal(system)

	if (!pStorageFile.delete || !storageFile.renameTo(pStorageFile))
		throw new IOException("Unable to rename " + storageFile + " to "
			+ pStorageFile)

	private def writeToJournal(any: Any) = {
		journal.writeObject(any)
		journal.flush
	}

	def executeTransaction[R](transaction: (T) => R) = synchronized {
		writeToJournal(transaction)
		transaction(system)
	}

	def executeQuery[R](query: (T) => R) = synchronized {
		query(system)
	}

}