// perft.rs
use crate::position::Position;
use crate::movegen::generate_moves;
use std::time::Instant;

pub fn perft(pos: &mut Position, depth: i32) -> u64 {
    if depth == 0 {
        return 1;
    }

    let mut nodes = 0;
    let mut moves = Vec::new();
    generate_moves(pos, &mut moves);

    for m in moves {
        if pos.do_move(m) {
            nodes += perft(pos, depth - 1);
            pos.undo_move(m);
        }
    }
    nodes
}

pub fn divide(pos: &mut Position, depth: i32) {
    println!("--- Perft Divide Depth {} ---", depth);
    let start = Instant::now();
    
    let mut total_nodes = 0;
    let mut moves = Vec::new();
    generate_moves(pos, &mut moves);

    for m in moves {
        if pos.do_move(m) {
            let nodes = perft(pos, depth - 1);
            pos.undo_move(m);
            
            let from = crate::uci::sq_to_str(m.from());
            let to = crate::uci::sq_to_str(m.to());
            let promo = match m.promotion() {
                crate::types::PieceType::Queen => "q",
                crate::types::PieceType::Rook => "r",
                crate::types::PieceType::Bishop => "b",
                crate::types::PieceType::Knight => "n",
                _ => ""
            };
            
            println!("{}{}{}: {}", from, to, promo, nodes);
            total_nodes += nodes;
        }
    }
    
    let elapsed = start.elapsed();
    println!("Total nodes: {}", total_nodes);
    println!("Time elapsed: {:?}", elapsed);
    if elapsed.as_secs_f64() > 0.0 {
        println!("NPS: {}", (total_nodes as f64 / elapsed.as_secs_f64()) as u64);
    }
}