fix "bug" in startpos handling (caused by my own hubris), also impl `quit` UCI command

src/main.rs

@@ -4,6 +4,7 @@ use chess::{Board, MoveGen, EMPTY};
 use config::INFO;
 use rand::seq::IteratorRandom;
 use std::io::{self, BufRead};
+use std::process;
 use std::str::FromStr;
 use vampirc_uci::parse_one;
 use vampirc_uci::{
@@ -35,11 +36,16 @@ fn main() {
             }
             UciMessage::UciNewGame => board = Some(Board::default()),
             UciMessage::Position {
-                startpos: _,
+                startpos,
                 fen,
                 moves,
             } => {
-                // NOTE: we can ignore startpos because UciNewGame already sets it to the default boardstate
+                if startpos {
+                    board = Some(
+                        Board::from_str("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1")
+                            .unwrap(),
+                    )
+                }
                 if let Some(fen) = fen {
                     board = Some(Board::from_str(fen.as_str()).expect("Invalid FEN board"))
                 }
@@ -84,9 +90,12 @@ fn main() {
                 if let Some(board) = board {
                     let iter = MoveGen::new_legal(&board).into_iter();
 
-                    println!("bestmove {}", iter.choose(&mut rng).unwrap())
+                    println!("bestmove {}", iter.choose(&mut rng).unwrap());
                 }
             }
+            UciMessage::Quit => {
+                process::exit(0);
+            }
             _ => {
                 todo!()
             }