feat(cli): add command-line entry point

Main.scala

@@ -0,0 +1,60 @@
+package gambit
+
+@main def gambit(args: String*): Unit =
+  args.toList match
+    case Nil                => runDemo()
+    case "uci" :: _         => new Uci().run(scala.io.Source.stdin.getLines(), println)
+    case "selfplay" :: opts => runSelfPlay(opts)
+    case "epd" :: opts      => runEpd(opts)
+    case other              => runPerft(other)
+
+private def runEpd(opts: List[String]): Unit =
+  val timeMs = opts.headOption.map(_.toLong).getOrElse(500L)
+  println(s"EPD test-suite runner: ${WinAtChess.positions.length} positions, ${timeMs}ms each")
+  val t0 = System.nanoTime()
+  val results = Epd.runSuite(WinAtChess.positions, timeMs)
+  val ms = (System.nanoTime() - t0) / 1000000
+  print(Epd.report(results))
+  println(s"total wall time ${ms} ms")
+
+private def runDemo(): Unit =
+  println("gambit chess engine")
+  println("usage:")
+  println("  scala-cli run gambit -- uci")
+  println("  scala-cli run gambit -- selfplay [maxPlies] [depth]")
+  println("  scala-cli run gambit -- <fen|startpos> <depth>")
+  println()
+  runPerft(List("startpos", "4"))
+
+private def runPerft(args: List[String]): Unit =
+  val depth = args.last.toInt
+  val fenArg = args.dropRight(1).mkString(" ")
+  val fen = if fenArg.isEmpty || fenArg == "startpos" then Fen.startPosition else fenArg
+  val pos = Fen.parse(fen)
+  println(s"fen:  ${Fen.toFen(pos)}")
+  println(s"side: ${if pos.sideToMove == Color.White then "white" else "black"}")
+
+  val t0 = System.nanoTime()
+  val nodes = Perft.perft(pos, depth)
+  val ms = (System.nanoTime() - t0) / 1000000
+  val nps = if ms > 0 then nodes * 1000 / ms else 0
+  println(s"perft($depth) = $nodes  (${ms} ms, ${nps} nps)")
+
+  val searchDepth = math.min(math.max(depth, 4), 6)
+  val searcher = new Searcher
+  val searchPos = Fen.parse(fen)
+  val r = searcher.search(searchPos, searchDepth, 0)
+  println(s"bestmove ${Move.uci(r.bestMove)}  score ${r.score}  (depth ${r.depth}, ${searcher.nodes} nodes)")
+
+private def runSelfPlay(opts: List[String]): Unit =
+  val maxPlies = opts.headOption.map(_.toInt).getOrElse(200)
+  val depth = opts.drop(1).headOption.map(_.toInt).getOrElse(5)
+  val fenArg = opts.drop(2).mkString(" ")
+  val fen = if fenArg.isEmpty then Fen.startPosition else fenArg
+  println(s"self-play: maxPlies=$maxPlies depth=$depth")
+  println(s"start: $fen")
+  val outcome = Game.selfPlay(fen, maxPlies, depth, 0)
+  println(s"moves (${outcome.plies}): ${outcome.moves.mkString(" ")}")
+  println(s"result: ${outcome.result}")
+  println()
+  println(Game.pgn(outcome))