Add query print loop

src/main/scala/pl/edu/agh/kis/eis/ndl/repl/REPL.scala

@@ -12,47 +12,62 @@ trait REPL extends App with LazyLogging {
   val parser: NDLParser = new NDLParser
   type Domain = parser.sExpParser.Domain
   type Result = Iterator[QueryExecutor[Domain]#Result]
+  type Evaluation = (KnowledgeBase[Domain], Result)
 
   def executeQuery: QueryExecutor[Domain] => Query[Domain] => Result
 
   def readInput(): String = StdIn.readLine()
+  def write: Any => Unit = Predef.print
+  def writeln: Any => Unit = println
 
   def read(): parser.sExpParser.ParseResult[NDL[Domain]] = {
     val input: String = readInput()
     val parsed = parser.parser(new CharSequenceReader(input))
-    logger.debug("parse result: {}", parsed)
+    logger.trace("parse result: {}", parsed)
     parsed
   }
 
-  def eval(kb: KnowledgeBase[Domain], in: NDL[Domain]): (KnowledgeBase[Domain], Result) = {
+  def eval(kb: KnowledgeBase[Domain], in: NDL[Domain]): Evaluation = {
     in match {
       case fact: Fact[Domain] =>
-        logger.debug("eval(): expanding kb")
+        logger.trace("eval(): expanding kb")
         (kb.addFact(fact), Iterator.empty)
       case q: Query[Domain] =>
-        logger.debug("eval(): query")
+        logger.trace("eval(): query")
         (kb, executeQuery(kb)(q))
     }
   }
 
+  def print: Evaluation => Unit = { case r@(_, bindingIterator) =>
+    if (bindingIterator.hasNext) {
+      write(queryPrompt)
+      readInput()
+      // FIXME implement binding .toString()
+      writeln(bindingIterator.next().toList.map(x => s"(${x.name} ${x.value})").mkString(", "))
+      print(r)
+    }
+  }
+
   val prompt: String = "> "
+  val queryPrompt: String = "? "
   def mode: String
 
   @tailrec
   final def loop(kb: KnowledgeBase[Domain]): Unit = {
-    print(prompt)
+    write(prompt)
 
     val str = read()
     if (str.successful) {
-      val (newKb, queryResult) = eval(kb, str.get)
-      logger.debug("kb after eval: {}", newKb.facts)
-      logger.debug("evaluated query: {}", queryResult.toList)
+      val e@(newKb, queryResult) = eval(kb, str.get)
+      logger.trace("kb after eval: {}", newKb.facts)
+      logger.trace("evaluated query: {}", queryResult.toList)
+      print(e)
       loop(newKb)
     } else {
       loop(kb)
     }
   }
 
-  println(s"NDL REPL: $mode")
+  writeln(s"NDL REPL: $mode")
   loop(new KnowledgeBase[Domain](Set.empty))
 }