checkers/src/logic/board/board.rs

use crate::logic::{
    board::{
        field::Field,
        pawn::{CapturePath, MovePath, Pawn, PawnState},
    },
    math::{position::Position, vector::Vector2D},
    player::Player,
};

use std::ops::{Index, IndexMut};

use log::{debug, error, info, warn};

pub struct Board {
    board: Vec<Field>,
    pub size: usize,
}

impl Board {
    /// Board is always a square. Size parameter is a side of this square. Defaults to 8
    pub fn new(player1: &mut Player, player2: &mut Player, size: Option<usize>) -> Self {
        let size = size.unwrap_or(8);

        info!("Creating new board of size: {}", size);
        player1.end_row = Some(size - 1);
        player1.vertical_direction = Some(Vector2D { row: 1, column: 0 });

        player2.end_row = Some(0);
        player2.vertical_direction = Some(Vector2D { row: -1, column: 0 });

        let p1_ref: &Player = &*player1;
        let p2_ref: &Player = &*player2;

        let board: Vec<Field> = (0..size)
            .flat_map(|row| {
                (0..size).map(move |column| {
                    let is_row_even: bool = row % 2 == 0;
                    let is_column_even: bool = column % 2 == 0;
                    let is_valid_place_for_a_pawn: bool = is_row_even ^ is_column_even;
                    let position: Position = Position { row, column };

                    let current_player: Option<&Player> = if row < 3 {
                        Some(p1_ref)
                    } else if row >= size - 3 {
                        Some(p2_ref)
                    } else {
                        None
                    };

                    if let Some(player) = current_player
                        && is_valid_place_for_a_pawn
                    {
                        debug!("Placing new pawn at: {}, owned by: {}", position, player);
                        Field {
                            position,
                            pawn: Some(Pawn::new(player)),
                        }
                    } else {
                        debug!("Not placing any pawn at: {}", position);
                        Field {
                            position,
                            pawn: None,
                        }
                    }
                })
            })
            .collect();

        Board { board, size }
    }

    /// For testing
    fn new_empty(player1: &mut Player, player2: &mut Player, size: Option<usize>) -> Self {
        let size = size.unwrap_or(8);

        player1.end_row = Some(size - 1);
        player1.vertical_direction = Some(Vector2D { row: 1, column: 0 });

        player2.end_row = Some(0);
        player2.vertical_direction = Some(Vector2D { row: -1, column: 0 });

        let board: Vec<Field> = (0..size)
            .flat_map(|row| {
                (0..size).map(move |column| {
                    let position: Position = Position { row, column };
                    Field {
                        position,
                        pawn: None,
                    }
                })
            })
            .collect();

        Board { board, size }
    }

    fn place_pawn(&mut self, target: Position, owner: &Player) {
        self[target].pawn = Some(Pawn::new(owner));
    }

    /// Checks if move from position to position is valid.
    /// It returns true if you want to move pawn from position to position where there is no pawn
    ///
    /// Doesn't check turn
    ///
    /// Not meant for capturing
    fn is_move_valid(&self, from: &Position, to: &Position) -> bool {
        let Some(_) = &self[*from].pawn else {
            return false;
        };

        self[*to].pawn.is_none()
    }

    fn is_player_owner_of_the_pawn(&self, player: &Player, pawn: &Pawn) -> bool {
        player.id == pawn.owner
    }

    fn is_position_empty(&self, pos: Position) -> bool {
        pos.is_in_range(self.size) && self[pos].pawn.is_none()
    }

    fn is_pawn_movable(&self, pos: Position, player: &Player) -> bool {
        self.get_available_moves(pos, player)
            .is_some_and(|moves| !moves.is_empty())
    }

    pub fn get_available_moves(&self, pos: Position, player: &Player) -> Option<Vec<MovePath>> {
        let mut available_moves: Vec<MovePath> = vec![];
        let mut possible_directions: Vec<Vector2D> = vec![];

        if !pos.is_in_range(self.size) {
            warn!(
                "get_possible_moves got a value: {} that was out of range!",
                pos
            );
            return None;
        }

        let Some(pawn) = &self[pos].pawn else {
            return None;
        };

        let Some(direction) = player.vertical_direction else {
            error!("Player: {} doesn't have a direction set!", player.id);
            return None;
        };

        possible_directions.push(Vector2D { row: 0, column: -1 } + direction);
        possible_directions.push(Vector2D { row: 0, column: 1 } + direction);

        let max_multiplier: usize;

        if pawn.state == PawnState::Dame {
            possible_directions.push(Vector2D { row: 0, column: -1 } - direction);
            possible_directions.push(Vector2D { row: 0, column: 1 } - direction);
            max_multiplier = self.size - 1;
        } else {
            max_multiplier = 1;
        }

        for direction in &possible_directions {
            debug!("Checking direction {} for available moves", direction);

            let mut path: Vec<Position> = vec![];
            for multiplier in 1..=max_multiplier {
                if let Some(new_pos) = pos.checked_add(&(*direction * multiplier)) {
                    if self.is_position_empty(new_pos) {
                        debug!("Found available move at: {}", new_pos);
                        path.push(new_pos);
                    } else {
                        debug!("Position: {} wasn't empty!", new_pos);
                        break;
                    }
                } else {
                    debug!("Found position was out of bounds!");
                    break;
                }
            }

            if !path.is_empty() {
                available_moves.push(MovePath {
                    from: pos,
                    available_steps: path,
                })
            }
        }

        if available_moves.is_empty() {
            None
        } else {
            Some(available_moves)
        }
    }

    fn can_capture(
        &self,
        from: Position,
        to: Position,
        player: &Player,
        already_captured: &Vec<Position>,
        pawn: &Pawn,
    ) -> bool {
        debug!("=== Checkinf if pawn can capture from: {} to {}", from, to);

        if !self.is_player_owner_of_the_pawn(player, &pawn) {
            debug!("Player wasn't owner of the pawn...");
            return false;
        }

        if !to.is_in_range(self.size) {
            debug!("Position was out of range...");
            return false;
        }

        if already_captured.contains(&to) {
            debug!("Pawn was already captured...");
            return false;
        }

        let Some(captured_pawn) = &self[to].pawn else {
            debug!("There was no pawn there...");
            return false;
        };

        if self.is_player_owner_of_the_pawn(player, captured_pawn) {
            debug!("Player tried capturing his own pawn! Idiot");
            return false;
        }

        let delta_distance: Vector2D = to - from;
        let player_direction = player
            .vertical_direction
            .expect("Player vertical_direction not set!");

        let direction_condition: bool = if pawn.state == PawnState::Man {
            delta_distance.row == player_direction.row
        } else {
            delta_distance.row.abs() == 1
        };

        direction_condition
            && delta_distance.column.abs() == 1
            && to
                .checked_add(&delta_distance)
                .is_some_and(|pos| self.is_position_empty(pos))
    }

    fn find_captures(
        &self,
        start_pos: Position,
        current_pos: Position,
        current_path: &mut Vec<Position>,
        captured_enemies: &Vec<Position>,
        available_directions: &[Vector2D],
        player: &Player,
        all_paths: &mut Vec<CapturePath>,
        pawn: &Pawn,
    ) {
        let mut found_any_capture: bool = false;

        for direction in available_directions {
            let target_option: Option<Position> = current_pos.checked_add(direction);

            if let Some(target) = target_option
                && self.can_capture(current_pos, target, player, captured_enemies, &pawn)
            {
                if let Some(path_after_capture) = target.checked_add(direction) {
                    debug!(
                        "Found possible capture: {} -> {}",
                        current_pos, path_after_capture
                    );

                    found_any_capture = true;

                    let mut new_path = current_path.clone();
                    new_path.push(path_after_capture);

                    let mut new_enemies = captured_enemies.clone();
                    new_enemies.push(target);

                    self.find_captures(
                        start_pos,
                        path_after_capture,
                        &mut new_path,
                        &new_enemies,
                        available_directions,
                        player,
                        all_paths,
                        &pawn,
                    );
                }
            }
        }

        if !found_any_capture && !current_path.is_empty() && !captured_enemies.is_empty() {
            all_paths.push(CapturePath {
                from: start_pos,
                steps: current_path.to_vec(),
                captured_enemies: captured_enemies.to_vec(),
            });
        }
    }

    pub fn get_available_captures(
        &self,
        from: Position,
        player: &Player,
    ) -> Option<Vec<CapturePath>> {
        let Some(capturing_pawn) = &self[from].pawn else {
            return None;
        };

        if !self.is_player_owner_of_the_pawn(player, capturing_pawn) {
            return None;
        }

        let mut available_captures: Vec<CapturePath> = vec![];
        let move_directions: Vec<Vector2D> = if capturing_pawn.state == PawnState::Man {
            let player_direction: Vector2D = player
                .vertical_direction
                .expect("Player direction is not set!");

            vec![
                Vector2D { row: 0, column: 1 } + player_direction,
                Vector2D { row: 0, column: -1 } + player_direction,
            ]
        } else {
            vec![
                Vector2D { row: 1, column: 1 },
                Vector2D { row: 1, column: -1 },
                Vector2D { row: -1, column: 1 },
                Vector2D {
                    row: -1,
                    column: -1,
                },
            ]
        };

        self.find_captures(
            from,
            from,
            &mut vec![],
            &vec![],
            &move_directions,
            player,
            &mut available_captures,
            capturing_pawn,
        );

        Some(available_captures)
    }

    pub fn capture(&mut self, path: &CapturePath, capturing_player: &Player) -> bool {
        /*
        debug!("Capturing: {}", path);
        */

        // TODO! Maybe return false ??

        let mut from = path.from;

        for (next_pos, enemy_path) in path.iter() {
            self[*enemy_path].pawn.take();
            self.move_pawn_anywhere(capturing_player, from, *next_pos);
            from = *next_pos;
        }

        true
    }

    pub fn get_player_pawns_positions(&self, player: &Player) -> Vec<Position> {
        self.board
            .iter()
            .filter_map(|field| {
                if let Some(pawn) = &field.pawn
                    && pawn.owner == player.id
                {
                    Some(field.position)
                } else {
                    None
                }
            })
            .collect()
    }

    /// Returns true if move was successful
    pub fn move_pawn(&mut self, player: &Player, from: Position, to: Position) -> bool {
        if !self.is_move_valid(&from, &to) {
            warn!("Tried invalid move: {} -> {}", from, to);
            return false;
        }

        if !self.is_player_owner_of_the_pawn(&player, self[from].pawn.as_ref().unwrap()) {
            warn!("Player {} tried moving a pawn which he doesn own!", player);
            debug!("Tried moving from {} to {}", from, to);
            return false;
        }

        let Some(end_row) = player.end_row else {
            warn!(
                "Tried moving pawn of player {}, who wasn't initialized by the board!",
                player.id
            );
            return false;
        };

        // we can safely unwrap, because if there's not pawn function returns false earlier
        let mut moving_pawn: Pawn = self[from].pawn.take().unwrap();

        if to.row == end_row {
            moving_pawn.state = super::pawn::PawnState::Dame;
        }

        self[to.row][to.column].pawn = Some(moving_pawn);

        true
    }

    fn move_pawn_anywhere(&mut self, player: &Player, from: Position, to: Position) -> bool {
        let Some(pawn) = &self[from].pawn else {
            warn!(
                "Tried moving pawn from: {}, but there is no pawn there!",
                from
            );
            return false;
        };

        if self[to].pawn.is_some() {
            warn!(
                "Tried moving pawn from {} to {}, but there was a pawn at the destination!",
                from, to
            );
            return false;
        }

        if !self.is_player_owner_of_the_pawn(player, &pawn) {
            warn!("Player {} tried moving a pawn which he doesn own!", player);
            return false;
        }

        let Some(end_row) = player.end_row else {
            warn!(
                "Tried moving pawn of player {}, who wasn't initialized by the board!",
                player.id
            );
            return false;
        };

        let mut moving_pawn: Pawn = self[from].pawn.take().unwrap();

        if to.row == end_row {
            moving_pawn.state = super::pawn::PawnState::Dame;
        }

        debug!("Placing pawn from {} to {}", from, to);
        self[to].pawn = Some(moving_pawn);

        true
    }
}

impl Index<usize> for Board {
    type Output = [Field];

    fn index<'a>(&'a self, i: usize) -> &'a [Field] {
        let start = i * &self.size;
        let end: usize = start + &self.size;
        &self.board[start..end]
    }
}

impl Index<Position> for Board {
    type Output = Field;

    fn index(&self, index: Position) -> &Self::Output {
        &self[index.row][index.column]
    }
}

impl IndexMut<usize> for Board {
    fn index_mut<'a>(&'a mut self, i: usize) -> &'a mut [Field] {
        let start = i * &self.size;
        let end: usize = start + &self.size;
        &mut self.board[start..end]
    }
}

impl IndexMut<Position> for Board {
    fn index_mut(&mut self, index: Position) -> &mut Self::Output {
        &mut self[index.row][index.column]
    }
}

#[cfg(test)]
mod tests {

    use super::*;

    fn init_logger() {
        let _ = env_logger::builder().is_test(true).try_init();
    }

    #[test]
    fn new_board_test() {
        init_logger();

        let mut player1: Player = Player::new("Morbius".to_string());
        let mut player2: Player = Player::new("Milo".to_string());

        let test_board: Board = Board::new(&mut player1, &mut player2, None);
        let size: usize = test_board.size;

        for row in 0..size {
            for column in 0..size {
                assert_eq!(test_board[row][column].position.row, row);
                assert_eq!(test_board[row][column].position.column, column);
            }
        }

        for row in 0..size {
            for column in 0..size {
                let is_row_even: bool = row % 2 == 0;
                let is_column_even: bool = column % 2 == 0;
                let is_valid_place_for_a_pawn: bool =
                    (is_row_even ^ is_column_even) && (row < 3 || row >= size - 3);

                if is_valid_place_for_a_pawn {
                    assert!(test_board[row][column].pawn.is_some());
                    // we unwrap, because some value has to be here, if it's not then something is wrong
                    // beside we check for that in the assert above
                    assert!(test_board[row][column].pawn.as_ref().unwrap().state == PawnState::Man);

                    if row < 3 {
                        assert_eq!(
                            test_board[row][column].pawn.as_ref().unwrap().owner,
                            player1.id
                        )
                    } else if row >= size - 3 {
                        assert_eq!(
                            test_board[row][column].pawn.as_ref().unwrap().owner,
                            player2.id
                        )
                    }
                } else {
                    assert!(test_board[row][column].pawn.is_none());
                }
            }
        }
    }

    #[test]
    fn test_overloaded_operators() {
        init_logger();

        let mut player1: Player = Player::new("Morbius".to_string());
        let mut player2: Player = Player::new("Milo".to_string());

        let test_board: Board = Board::new(&mut player1, &mut player2, None);

        let row1 = 0;
        let column1 = 0;

        let position1: Position = Position {
            row: row1,
            column: column1,
        };

        let row2 = row1;
        let column2 = 1;

        let position2: Position = Position {
            row: row2,
            column: column2,
        };

        assert_eq!(test_board[row1][column1], test_board[position1]);
        assert_eq!(test_board[row2][column2], test_board[position2]);

        assert!(test_board[position1].pawn.is_none());
        assert!(test_board[position2].pawn.is_some());
    }

    #[test]
    fn test_moving_pawn() {
        init_logger();

        let mut player1: Player = Player::new("Morbius".to_string());
        let mut player2: Player = Player::new("Milo".to_string());

        let mut test_board: Board = Board::new(&mut player1, &mut player2, None);

        // we cant move pawn into another pawn; this should fail
        assert!(!test_board.move_pawn(
            &player1,
            Position { row: 0, column: 1 },
            Position { row: 1, column: 0 },
        ));

        // player can't move pawn that he doesn't own; this should fail
        assert!(!test_board.move_pawn(
            &player2,
            Position { row: 2, column: 1 },
            Position { row: 3, column: 0 },
        ));

        // walid move
        assert!(test_board.move_pawn(
            &player1,
            Position { row: 2, column: 1 },
            Position { row: 3, column: 0 }
        ));

        assert!(test_board[3][0].pawn.is_some());
        assert_eq!(test_board[3][0].pawn.as_ref().unwrap().owner, player1.id);
        assert!(test_board[2][1].pawn.is_none());
    }

    #[test]
    fn test_getting_pawn_moves() {
        init_logger();

        let mut p1: Player = Player::new("Morbius".to_string());
        let mut p2: Player = Player::new("Milo".to_string());

        let mut board: Board = Board::new_empty(&mut p1, &mut p2, None);

        board.place_pawn(Position { row: 0, column: 0 }, &p1);
        board[0][0].pawn.as_mut().unwrap().state = PawnState::Dame;

        let result: Vec<MovePath> = board
            .get_available_moves(Position { row: 0, column: 0 }, &p1)
            .unwrap();

        assert_eq!(result.len(), 1);
        assert_eq!(
            result[0],
            MovePath {
                from: Position { row: 0, column: 0 },
                available_steps: vec![
                    Position { row: 1, column: 1 },
                    Position { row: 2, column: 2 },
                    Position { row: 3, column: 3 },
                    Position { row: 4, column: 4 },
                    Position { row: 5, column: 5 },
                    Position { row: 6, column: 6 },
                    Position { row: 7, column: 7 },
                ]
            }
        );
    }

    #[test]
    fn test_getting_player_pawns_positions() {
        init_logger();

        let mut p1: Player = Player::new("Morbius".to_string());
        let mut p2: Player = Player::new("Milo".to_string());
        let test_board: Board = Board::new(&mut p1, &mut p2, None);

        let expected_positions: Vec<Position> = (0..test_board.size)
            .into_iter()
            .flat_map(|row| {
                (0..test_board.size).filter_map(move |column| {
                    let is_row_even: bool = row % 2 == 0;
                    let is_column_even: bool = column % 2 == 0;
                    let is_valid_place_for_a_pawn: bool = (is_row_even ^ is_column_even) && row < 3;

                    if is_valid_place_for_a_pawn {
                        Some(Position { row, column })
                    } else {
                        None
                    }
                })
            })
            .collect();

        assert_eq!(
            expected_positions,
            test_board.get_player_pawns_positions(&p1)
        );
    }

    #[test]
    fn test_is_movable() {
        init_logger();

        let mut p1: Player = Player::new("Morbius".to_string());
        let mut p2: Player = Player::new("Milo".to_string());
        let test_board: Board = Board::new(&mut p1, &mut p2, None);

        assert!(test_board.is_pawn_movable(Position { row: 2, column: 1 }, &p1));
        assert!(!test_board.is_pawn_movable(
            Position {
                row: 10,
                column: 12
            },
            &p1
        ));
        assert!(!test_board.is_pawn_movable(Position { row: 0, column: 0 }, &p1));
    }

    #[test]
    fn test_getting_captures_path() {
        init_logger();

        let mut p1 = Player::new("Morbius".to_string());
        let mut p2 = Player::new("Milo".to_string());

        let mut board = Board::new_empty(&mut p1, &mut p2, None);

        let start_pos = Position { row: 2, column: 2 };

        board.place_pawn(start_pos, &p1);

        board.place_pawn(Position { row: 3, column: 3 }, &p2);
        board.place_pawn(Position { row: 5, column: 3 }, &p2);

        let captures_result = board.get_available_captures(start_pos, &p1);

        assert!(captures_result.is_some(),);

        let paths = captures_result.unwrap();

        assert_eq!(paths.len(), 1,);

        let expected_path = vec![
            Position { row: 4, column: 4 },
            Position { row: 6, column: 2 },
        ];

        assert_eq!(paths[0].steps, expected_path,);
    }

    #[test]
    fn test_capturing() {
        init_logger();

        let mut p1 = Player::new("Morbius".to_string());
        let mut p2 = Player::new("Milo".to_string());

        let mut board = Board::new_empty(&mut p1, &mut p2, None);

        let start_pos = Position { row: 2, column: 2 };

        board.place_pawn(start_pos, &p1);

        board.place_pawn(Position { row: 3, column: 3 }, &p2);
        board.place_pawn(Position { row: 5, column: 3 }, &p2);

        let captures_result = board.get_available_captures(start_pos, &p1);
        let path = &captures_result.unwrap()[0];

        board.capture(path, &p1);

        assert!(
            board[6][2]
                .pawn
                .as_ref()
                .is_some_and(|pawn| pawn.owner == p1.id)
        );
        assert!(board[3][3].pawn.is_none());
        assert!(board[5][3].pawn.is_none());
    }
}