use crate::{bitboard::pop_count, board::*};

impl Board {
    pub fn perft(&mut self, depth: u8, print: bool) -> (u64, u64, u64, u64, u64) {
        if depth == 0 {
            return (1, 0, 0, 0, 0) // This a leaf, exactly one node
        }
        let color = self.color_to_move();

        let moves = self.generate_pseudolegal_moves(color);

        if print {
            println!("Running perft for depth {}. Color to move is {:?}\n{} moves available", depth, color, moves.len());
            println!("{} moves available", moves.len());
        }

        let mut total = 0;
        let mut captures = 0;
        let mut checks = 0;
        let mut castles = 0;
        let mut en_passants = 0;

        for mov in moves {
            let ep_target_before = self.ep_target.clone();
            let castling_rights_before = self.castling_rights.clone();
            let captured_piece = self.make_move(mov);
            // King can not be in check after our own move
            if !self.is_king_in_check(color) {
                if depth == 1 {
                    match mov.kind {
                        MoveKind::Capture => {
                            captures += 1;
                        }
                        MoveKind::EnPassant => {
                            en_passants += 1;
                            captures += 1;
                        }
                        MoveKind::Castle => {
                            castles += 1;
                        }
                        _ => {}
                    }
                    if self.is_king_in_check(color.flip()) {
                        checks += 1;
                    }
                }

                if print {
                    println!("{:?}", mov);
                    self.print();
                }
                let (children_total, children_tactical, children_checks, children_castles, children_ep) = self.perft(depth - 1, print);
                total += children_total;
                captures += children_tactical;
                checks += children_checks;
                castles += children_castles;
                en_passants += children_ep;

            }
            self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before);
        }

        if print {
            println!("Found {} nodes in this subtree (depth {})", total, depth);
        }

        (total, captures, checks, castles, en_passants)
    }
    pub fn evaluate(&self) -> f32 {
        let mut eval = 0f32;
        let pieces = self.pieces_by_color(self.color());
        eval += pop_count(pieces[PieceType::Pawn as usize]) as f32;
        eval += pop_count(pieces[PieceType::Bishop as usize]) as f32 * 3.;
        eval += pop_count(pieces[PieceType::Knight as usize]) as f32 * 3.;
        eval += pop_count(pieces[PieceType::Rook as usize]) as f32 * 4.5;
        eval += pop_count(pieces[PieceType::Queen as usize]) as f32 * 9.;
        eval
    }

    pub fn negamax_search(&mut self, mut alpha: f32, beta: f32, depth_left: u8) -> f32 {
        let color = Color::from(self.ply as u8 % 2);

        self.print();

        if depth_left == 0 {
            return self.evaluate();
        }
        let moves = self.generate_pseudolegal_moves(color);

        for mov in moves {
            let ep_target_before = self.ep_target.clone();
            let castling_rights_before = self.castling_rights.clone();
            let captured_piece = self.make_move(mov);

            if !self.is_king_in_check(color) {
                let evaluation = -self.negamax_search(-beta, -alpha, depth_left - 1);
                self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before);

                if evaluation >= beta {
                    return beta; // Fail-hard beta-cutoff
                }
                if evaluation > alpha {
                    alpha = evaluation
                }
            } else {
                self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before);
            }
        }
        alpha
    }

}


#[cfg(test)]
mod tests {
    use std::f32::INFINITY;

    use crate::board::Board;

    #[test]
    fn perft() {
        let mut board = Board::new();

        assert_eq!(board.perft(0, false), (1, 0, 0, 0, 0));
        assert_eq!(board.perft(1, false), (20, 0, 0, 0, 0));
        assert_eq!(board.perft(2, false), (400, 0, 0, 0, 0));
        assert_eq!(board.perft(3, false), (8902, 34, 12, 0, 0));
        assert_eq!(board.perft(4, false), (197281, 1576, 469, 0, 0));
        // assert_eq!(board.perft(5, false), (4865609, 82719, 27351, 0, 258));
        // assert_eq!(board.perft(6, false), (119060324, 2812008, 809099, 0, 5248));
    }

    #[test]
    fn position_perft() {
        let fen = String::from("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - ");
        let mut board = Board::from_FEN(fen);
        assert_eq!(board.perft(0, false), (1, 0, 0, 0, 0));
        assert_eq!(board.perft(1, false), (48, 8, 0, 2, 0));
        assert_eq!(board.perft(2, false), (2039, 351, 3, 91, 1));
        assert_eq!(board.perft(3, false), (97862, 17102, 993, 3162, 45));
    }

    #[test]
    fn negamax_search() {
        let fen = String::from("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - ");
        let mut board = Board::from_FEN(fen);

        let eval = board.negamax_search(-INFINITY, INFINITY, 4);
        println!("{}", eval);
    }
}