attempt to compress game pgn as binary data

app/mongodb/PgnBinary.scala

@@ -0,0 +1,38 @@
+package lila
+package mongodb
+
+object PgnBinary {
+
+  def encode(pgn: String): Array[Byte] = {
+    val ints = pgnToInts(pgn)
+    val bytes = ints grouped 4 map { 
+      case Nil => 0
+      case a :: Nil => a
+      case a :: b :: Nil => a + 32 
+
+  def decode(bytes: Array[Byte]): String = ""
+
+  private def pgnToInts(str: String): List[Int] = 
+    stringToInt get (str take 1) map (i => (str drop 1, i)) orElse {
+      if (str startsWith "O-O-O") stringToInt("O-O-O") map (i => (str drop 5), i)
+      else if (str startsWith "O-O") stringToInt("O-O") map (i => (str drop 3), i)
+      else None
+    } fold ((int, rest) => int :: consumeString(rest), Nil)
+
+  private val symbols: List[String] = " " :: {
+    ('a' to 'h').map(_.toString) ++
+      (1 to 8).map(_.toString) ++
+      "RNBQKPx=+#".toList.map(_.toString) ++
+      Seq("O-O", "O-O-O")
+  }.toList
+
+  private val stringToInt: Map[String, Int] = symbols.zipWithIndex.toMap
+  private val intToString: Map[Int, String] = (stringToByte map {
+    case (a, b) ⇒ (b, a)
+  }).toMap
+
+  // utility methods for printing a byte array
+  def showArray(b: Array[Byte]) = b.map(showByte).mkString(" ")
+  def showByte(b: Byte) = pad(((b + 256) % 256).toHexString.toUpperCase)
+  private def pad(s: String) = if (s.length == 1) "0" + s else s
+}