feat(protocol): add uci protocol handler

Uci.scala

@@ -0,0 +1,110 @@
+package gambit
+
+final class Uci:
+  private val searcher = new Searcher
+  private var pos = Fen.parse(Fen.startPosition)
+  private val history = scala.collection.mutable.ArrayBuffer[Long](pos.hash)
+  private var worker: Thread = null
+
+  def handle(line: String): List[String] =
+    val tokens = line.trim.split("\\s+").filter(_.nonEmpty).toList
+    tokens match
+      case Nil => Nil
+      case cmd :: rest =>
+        cmd match
+          case "uci"        => idLines
+          case "isready"    => List("readyok")
+          case "ucinewgame" => resetGame(); Nil
+          case "position"   => setPosition(rest); Nil
+          case "go" =>
+            val collected = scala.collection.mutable.ListBuffer[String]()
+            runGo(rest, collected += _)
+            collected.toList
+          case "stop" => searcher.stop(); Nil
+          case "quit" => Nil
+          case _      => Nil
+
+  def run(input: Iterator[String], out: String => Unit): Unit =
+    var quit = false
+    while !quit && input.hasNext do
+      val line = input.next()
+      val tokens = line.trim.split("\\s+").filter(_.nonEmpty).toList
+      tokens match
+        case "quit" :: _ => searcher.stop(); joinWorker(); quit = true
+        case "stop" :: _ => searcher.stop(); joinWorker()
+        case "go" :: rest =>
+          joinWorker()
+          worker = new Thread(() => runGo(rest, out))
+          worker.setDaemon(true)
+          worker.start()
+        case ("position" | "ucinewgame") :: _ =>
+          joinWorker()
+          handle(line).foreach(out)
+        case _ => handle(line).foreach(out)
+
+  private def idLines: List[String] =
+    List("id name gambit", "id author gambit", "uciok")
+
+  private def joinWorker(): Unit =
+    if worker != null then
+      worker.join()
+      worker = null
+
+  private def resetGame(): Unit =
+    searcher.tt.clear()
+    pos = Fen.parse(Fen.startPosition)
+    history.clear()
+    history += pos.hash
+
+  private def setPosition(args: List[String]): Unit =
+    val rest =
+      args match
+        case "startpos" :: tail =>
+          pos = Fen.parse(Fen.startPosition)
+          tail
+        case "fen" :: tail =>
+          val movesIdx = tail.indexOf("moves")
+          val fenTokens = if movesIdx < 0 then tail else tail.take(movesIdx)
+          pos = Fen.parse(fenTokens.mkString(" "))
+          if movesIdx < 0 then Nil else tail.drop(movesIdx)
+        case other => other
+    history.clear()
+    history += pos.hash
+    rest match
+      case "moves" :: moveTokens => applyMoves(moveTokens)
+      case _                     => ()
+
+  private def applyMoves(moveTokens: List[String]): Unit =
+    for token <- moveTokens do
+      val legal = new MoveList()
+      MoveGen.generateLegal(pos, legal)
+      var i = 0
+      var found = -1
+      while i < legal.size && found < 0 do
+        if Move.uci(legal(i)) == token then found = legal(i)
+        i += 1
+      if found >= 0 then
+        pos.make(found)
+        history += pos.hash
+
+  private def runGo(args: List[String], emit: String => Unit): Unit =
+    val limits = TimeControl.parse(args)
+    val whiteToMove = pos.sideToMove == Color.White
+    val plan = TimeControl.plan(limits, whiteToMove)
+    searcher.onIteration = (d, score, nodes, ms, pv) => emit(infoLine(d, score, nodes, ms, pv))
+    searcher.setGameHistory(history.toArray, history.size - 1)
+    val result = searcher.search(pos, plan.depth, plan.timeMs)
+    searcher.onIteration = (_, _, _, _, _) => ()
+    val bestMove = if result.bestMove != 0 then Move.uci(result.bestMove) else "0000"
+    emit(s"bestmove $bestMove")
+
+  private def infoLine(depth: Int, score: Int, nodes: Long, ms: Long, pv: List[Int]): String =
+    val scoreStr =
+      if math.abs(score) >= TT.MateBound then
+        val plies = Searcher.MateValue - math.abs(score)
+        val movesToMate = (plies + 1) / 2
+        s"mate ${if score > 0 then movesToMate else -movesToMate}"
+      else s"cp $score"
+    val nps = if ms > 0 then nodes * 1000 / ms else nodes
+    val pvStr = pv.map(Move.uci).mkString(" ")
+    s"info depth $depth score $scoreStr nodes $nodes nps $nps time $ms pv $pvStr"