use crate::command::{Action, Command};
use crate::constants::*;
use crate::geometry::*;
use crate::json;

mod player;
use player::*;

mod powerup;
use powerup::*;

pub mod map;
use map::*;

use arrayvec::ArrayVec;
use fnv::FnvHashSet;

#[derive(Debug, PartialEq, Eq, Clone)]
pub struct GameBoard {
    pub round: u16,
    pub max_rounds: u16,
    pub players: [Player; 2],
    pub powerups: ArrayVec<[Powerup; 2]>,
    pub map: Map,
    pub occupied_cells: FnvHashSet<Point2d<i8>>,
    pub outcome: SimulationOutcome,
}

#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum SimulationOutcome {
    PlayerWon(usize),
    Draw,
    Continue,
}

impl GameBoard {
    pub fn new(json: json::State) -> GameBoard {
        let commando_damage = json.my_player.worms[0].weapon.damage;
        let commando_range = json.my_player.worms[0].weapon.range;

        let player = Player {
            active_worm: json.active_worm_index().unwrap(),
            moves_score: json.my_player.score - json.my_player.health_score(),
            select_moves: json.my_player.remaining_worm_selections,
            worms: json
                .my_player
                .worms
                .iter()
                .map(|w| Worm {
                    id: w.id,
                    health: w.health,
                    position: Point2d::new(w.position.x, w.position.y),
                    weapon_damage: commando_damage,
                    weapon_range: commando_range,
                    rounds_until_unfrozen: w.rounds_until_unfrozen,
                    bombs: w.banana_bombs.as_ref().map(|b| b.count).unwrap_or(0),
                    snowballs: w.snowballs.as_ref().map(|b| b.count).unwrap_or(0),
                })
                .collect(),
        };

        let opponent = Player {
            active_worm: 0,
            moves_score: json.opponents[0].score - json.opponents[0].health_score(),
            select_moves: json.opponents[0].remaining_worm_selections,
            worms: json
                .opponents
                .iter()
                .flat_map(|o| &o.worms)
                .map(|w| Worm {
                    id: w.id,
                    health: w.health,
                    position: Point2d::new(w.position.x, w.position.y),
                    weapon_damage: commando_damage,
                    weapon_range: commando_range,
                    rounds_until_unfrozen: w.rounds_until_unfrozen,
                    bombs: if w.profession == json::WormType::Agent {
                        STARTING_BOMBS
                    } else {
                        0
                    },
                    snowballs: if w.profession == json::WormType::Technologist {
                        STARTING_SNOWBALLS
                    } else {
                        0
                    },
                })
                .collect(),
        };

        let mut map = Map::default();
        for cell in json.map.iter().flatten() {
            if cell.cell_type == json::CellType::Dirt {
                map.set(Point2d::new(cell.x, cell.y))
            }
        }

        let players = [player, opponent];
        let occupied_cells = players
            .iter()
            .flat_map(|p| p.worms.iter())
            .map(|w| w.position)
            .collect();

        GameBoard {
            round: json.current_round,
            max_rounds: json.max_rounds,
            players,
            powerups: json
                .map
                .iter()
                .flatten()
                .filter_map(|c| {
                    c.powerup.as_ref().map(|p| Powerup {
                        position: Point2d::new(c.x, c.y),
                        value: p.value,
                    })
                })
                .collect(),
            map,
            occupied_cells,
            outcome: SimulationOutcome::Continue,
        }
    }

    pub fn update(&mut self, json: json::State) {
        for w in &json.my_player.worms {
            if let Some(worm) = self.players[0].find_worm_mut(w.id) {
                worm.health = w.health;
                worm.position = Point2d::new(w.position.x, w.position.y);
                worm.bombs = w.banana_bombs.as_ref().map(|b| b.count).unwrap_or(0);
            }
        }
        for w in json.opponents.iter().flat_map(|o| &o.worms) {
            if let Some(worm) = self.players[1].find_worm_mut(w.id) {
                worm.health = w.health;
                worm.position = Point2d::new(w.position.x, w.position.y);
                // TODO: Update number of bombs / snowballs based on previous move
            }
        }
        self.players[0].moves_score = json.my_player.score - json.my_player.health_score();
        self.players[1].moves_score = json.opponents[0].score - json.opponents[0].health_score();

        self.players[0].select_moves = json.my_player.remaining_worm_selections;
        self.players[1].select_moves = json.opponents[0].remaining_worm_selections;

        self.powerups = json
            .map
            .iter()
            .flatten()
            .filter_map(|c| {
                c.powerup.as_ref().map(|p| Powerup {
                    position: Point2d::new(c.x, c.y),
                    value: p.value,
                })
            })
            .collect();

        for cell in json.map.iter().flatten() {
            if cell.cell_type == json::CellType::Air {
                self.map.clear(Point2d::new(cell.x, cell.y))
            }
        }

        for player in &mut self.players {
            player.clear_dead_worms();
        }
        self.players[0].active_worm = json.active_worm_index().unwrap_or(0);
        self.players[1].active_worm = json.opponent_active_worm_index().unwrap_or(0);

        self.round += 1;
        debug_assert_eq!(json.current_round, self.round);

        self.occupied_cells = self
            .players
            .iter()
            .flat_map(|p| p.worms.iter())
            .map(|w| w.position)
            .collect();

        // TODO: Do some asssertions about the state of lava
    }

    pub fn simulate(&mut self, moves: [Command; 2]) {
        self.simulate_worms_on_lava();
        self.simulate_tick_frozen_timers();
        self.simulate_select(moves);

        let actions = self.identify_actions(moves);

        self.simulate_moves(actions);
        self.simulate_digs(actions);
        self.simulate_bombs(actions);
        // TODO: Question order of actions on the forums
        self.simulate_snowballs(actions);
        self.simulate_shoots(actions);

        for player in &mut self.players {
            player.clear_dead_worms();
            player.next_active_worm();
        }

        self.round += 1;

        self.outcome = match (
            self.players[0].worms.len(),
            self.players[1].worms.len(),
            self.round > self.max_rounds,
        ) {
            (0, 0, _) => SimulationOutcome::Draw,
            (_, 0, _) => SimulationOutcome::PlayerWon(0),
            (0, _, _) => SimulationOutcome::PlayerWon(1),
            (_, _, true) => SimulationOutcome::Draw,
            _ => SimulationOutcome::Continue,
        };
    }

    fn simulate_worms_on_lava(&mut self) {
        let lava_map = LAVA_MAP[self.round as usize];
        self.players
            .iter_mut()
            .flat_map(|p| p.worms.iter_mut())
            .filter(|w| lava_map.at(w.position) == Some(true))
            .for_each(|ref mut w| w.health -= LAVA_DAMAGE);
    }

    fn simulate_tick_frozen_timers(&mut self) {
        self.players
            .iter_mut()
            .flat_map(|p| p.worms.iter_mut())
            .for_each(|ref mut w| {
                w.rounds_until_unfrozen = w.rounds_until_unfrozen.saturating_sub(1)
            });
    }

    fn identify_actions(&self, moves: [Command; 2]) -> [Action; 2] {
        let mut it = self.players.iter().zip(moves.iter()).map(|(p, m)| {
            if p.active_worm_is_frozen() {
                Action::DoNothing
            } else {
                m.action
            }
        });
        [it.next().unwrap(), it.next().unwrap()]
    }

    fn simulate_select(&mut self, moves: [Command; 2]) {
        moves
            .iter()
            .zip(self.players.iter_mut())
            .for_each(|(m, player)| {
                if let Some(worm) = m.worm {
                    debug_assert!(
                        player.select_moves > 0,
                        "Could not make select move, out of select tokens"
                    );
                    player.select_moves = player.select_moves.saturating_sub(1);
                    player.active_worm = player.find_worm_position(worm).unwrap_or(0);
                }
            });
    }

    fn simulate_moves(&mut self, actions: [Action; 2]) {
        match actions {
            [Action::Move(p1), Action::Move(p2)] if p1.x == p2.x && p1.y == p2.y => {
                let damage = COLLISION_DAMAGE;

                debug_assert_eq!(
                    Some(false),
                    self.map.at(Point2d::new(p1.x, p1.y)),
                    "Movement target wasn't empty, ({}, {})",
                    p1.x,
                    p1.y
                );
                // Worms have a 50% chance of swapping places
                // here. I'm treating that as an edge case that I
                // don't need to handle for now.
                for player in &mut self.players {
                    if let Some(worm) = player.active_worm_mut() {
                        worm.health -= damage;
                    }
                    // You might expect damage score too here, but nope
                    player.moves_score += MOVE_SCORE;
                }
            }
            _ => {
                for player_index in 0..actions.len() {
                    if let Action::Move(p) = actions[player_index] {
                        debug_assert_eq!(
                            Some(false),
                            self.map.at(p),
                            "Movement target wasn't empty, ({}, {})",
                            p.x,
                            p.y
                        );

                        self.players[player_index].moves_score += MOVE_SCORE;

                        if let Some(worm) = self.players[player_index].active_worm_mut() {
                            debug_assert!(
                                (worm.position.x - p.x).abs() <= 1
                                    && (worm.position.y - p.y).abs() <= 1,
                                "Tried to move too far away, ({}, {})",
                                p.x,
                                p.y
                            );

                            self.occupied_cells.remove(&worm.position);
                            self.occupied_cells.insert(p);

                            worm.position = p;

                            self.powerups.retain(|power| {
                                if power.position == worm.position {
                                    worm.health += power.value;
                                    false
                                } else {
                                    true
                                }
                            });
                        }
                    }
                }
            }
        }
    }

    fn simulate_digs(&mut self, actions: [Action; 2]) {
        for player_index in 0..actions.len() {
            if let Action::Dig(p) = actions[player_index] {
                debug_assert!(
                    Some(true) == self.map.at(p)
                        || (player_index == 1 && actions[0] == Action::Dig(p)),
                    "Tried to dig through air, ({}, {})",
                    p.x,
                    p.y
                );
                debug_assert! {
                    (self.players[player_index].active_worm().unwrap().position.x - p.x).abs() <= 1 &&
                        (self.players[player_index].active_worm().unwrap().position.y - p.y).abs() <= 1,
                    "Tried to dig too far away, ({}, {})", p.x, p.y
                };

                self.players[player_index].moves_score += DIG_SCORE;

                self.map.clear(p);
            }
        }
    }

    fn simulate_bombs(&mut self, actions: [Action; 2]) {
        // NB: Damage radius has the cell distance rounded UP, throwing range has the cell distance rounded DOWN

        let map_clone = self.map.clone();

        for player_index in 0..actions.len() {
            if let Action::Bomb(p) = actions[player_index] {
                if self.map.at(p).is_some() {
                    if let Some(worm) = self.players[player_index].active_worm_mut() {
                        debug_assert!(worm.bombs > 0, "Worm is throwing a bomb it doesn't have");
                        debug_assert!((worm.position - p).magnitude_squared() < 6 * 6); // max range is 5, but it's 5 after rounding down

                        worm.bombs = worm.bombs.saturating_sub(1);

                        for &(damage_offset, weapon_damage) in BOMB_DAMAGES.iter() {
                            let target = p + damage_offset;

                            if map_clone.at(target) == Some(true) {
                                self.map.clear(target);
                                self.players[player_index].moves_score += DIG_SCORE;
                            }
                            self.powerups.retain(|powerup| powerup.position != target);

                            let target_own_worm: Option<&mut Worm> = self.players[player_index]
                                .worms
                                .iter_mut()
                                .find(|w| w.position == target);

                            if let Some(target_worm) = target_own_worm {
                                target_worm.health -= weapon_damage;
                                self.players[player_index].moves_score -=
                                    weapon_damage * ATTACK_SCORE_MULTIPLIER;
                                if target_worm.health <= 0 {
                                    self.players[player_index].moves_score -= KILL_SCORE;
                                    self.occupied_cells.remove(&target_worm.position);
                                }
                            }

                            let target_opponent_worm: Option<&mut Worm> = self.players
                                [GameBoard::opponent(player_index)]
                            .worms
                            .iter_mut()
                            .find(|w| w.position == target);
                            if let Some(target_worm) = target_opponent_worm {
                                target_worm.health -= weapon_damage;
                                self.players[player_index].moves_score +=
                                    weapon_damage * ATTACK_SCORE_MULTIPLIER;
                                if target_worm.health <= 0 {
                                    self.players[player_index].moves_score += KILL_SCORE;
                                    self.occupied_cells.remove(&target_worm.position);
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    pub fn simulate_snowballs(&mut self, actions: [Action; 2]) {
        // TODO: simulalte snowballs
    }

    fn simulate_shoots(&mut self, actions: [Action; 2]) {
        'players_loop: for player_index in 0..actions.len() {
            if let Action::Shoot(dir) = actions[player_index] {
                if let Some(worm) = self.players[player_index].active_worm() {
                    let (center, weapon_range, weapon_damage) =
                        { (worm.position, worm.weapon_range, worm.weapon_damage) };
                    let diff = dir.as_vec();

                    let range = if dir.is_diagonal() {
                        ((f32::from(weapon_range) + 1.) / 2f32.sqrt()).floor() as i8
                    } else {
                        weapon_range as i8
                    };

                    for distance in 1..=range {
                        let target = center + diff * distance;
                        match self.map.at(target) {
                            Some(false) => {
                                let target_own_worm: Option<&mut Worm> = self.players[player_index]
                                    .worms
                                    .iter_mut()
                                    .find(|w| w.position == target);

                                if let Some(target_worm) = target_own_worm {
                                    target_worm.health -= weapon_damage;
                                    self.players[player_index].moves_score -=
                                        weapon_damage * ATTACK_SCORE_MULTIPLIER;
                                    if target_worm.health <= 0 {
                                        self.players[player_index].moves_score -= KILL_SCORE;
                                        self.occupied_cells.remove(&target_worm.position);
                                    }
                                    continue 'players_loop;
                                }

                                let target_opponent_worm: Option<&mut Worm> = self.players
                                    [GameBoard::opponent(player_index)]
                                .worms
                                .iter_mut()
                                .find(|w| w.position == target);

                                if let Some(target_worm) = target_opponent_worm {
                                    target_worm.health -= weapon_damage;
                                    self.players[player_index].moves_score +=
                                        weapon_damage * ATTACK_SCORE_MULTIPLIER;
                                    if target_worm.health <= 0 {
                                        self.players[player_index].moves_score += KILL_SCORE;
                                        self.occupied_cells.remove(&target_worm.position);
                                    }

                                    continue 'players_loop;
                                }
                            }
                            _ => break,
                        }
                    }

                    // You get here if the shot missed. Hits are an early return.
                    self.players[player_index].moves_score += MISSED_ATTACK_SCORE;
                }
            }
        }
    }

    pub fn opponent(player_index: usize) -> usize {
        (player_index + 1) % 2
    }

    pub fn valid_selects(&self, player_index: usize) -> ArrayVec<[i32; 2]> {
        if self.players[player_index].select_moves > 0 {
            self.players[player_index]
                .worms
                .iter()
                .enumerate()
                .filter(|(p, _w)| self.players[player_index].active_worm != *p)
                .map(|(_p, w)| w.id)
                .collect()
        } else {
            ArrayVec::new()
        }
    }

    pub fn valid_moves_for_worm(&self, worm: &Worm) -> ArrayVec<[Action; 8]> {
        Direction::ALL
            .iter()
            .map(Direction::as_vec)
            .map(|d| worm.position + d)
            .filter(|p| !self.occupied_cells.contains(p))
            .filter_map(|p| match self.map.at(p) {
                Some(false) => Some(Action::Move(p)),
                Some(true) => Some(Action::Dig(p)),
                _ => None,
            })
            .collect()
    }

    pub fn valid_move_commands(&self, player_index: usize) -> ArrayVec<[Command; 24]> {
        let active = self.players[player_index].active_worm();
        let no_select = active
            .iter()
            .flat_map(|w| self.valid_moves_for_worm(w))
            .map(Command::new);

        self.valid_selects(player_index)
            .iter()
            .flat_map(|select_worm| self.players[player_index].find_worm(*select_worm))
            .flat_map(move |w| {
                self.valid_moves_for_worm(w)
                    .into_iter()
                    .map(move |a| Command::with_select(w.id, a))
            })
            .chain(no_select)
            .collect()
    }

    pub fn valid_shoot_commands(&self, player_index: usize) -> ArrayVec<[Command; 24]> {
        let all_dirs = Direction::ALL;
        let no_select = all_dirs.iter().map(|d| Command::new(Action::Shoot(*d)));

        self.valid_selects(player_index)
            .iter()
            .flat_map(|select_worm| {
                all_dirs
                    .iter()
                    .map(move |d| Command::with_select(*select_worm, Action::Shoot(*d)))
            })
            .chain(no_select)
            .collect()
    }

    pub fn valid_bomb_commands(&self, player_index: usize) -> Vec<Command> {
        let agent_worm = self.players[player_index]
            .worms
            .iter()
            .enumerate()
            .find(|(_p, w)| w.bombs > 0);
        match agent_worm {
            Some((worm_i, worm)) => {
                let select = if worm_i == self.players[player_index].active_worm {
                    None
                } else {
                    Some(worm.id)
                };

                if select.is_none() || self.players[player_index].select_moves > 0 {
                    let mut result = Vec::with_capacity(11 * 11 - 12);

                    for y in worm.position.y - 5..=worm.position.y + 5 {
                        for x in worm.position.x - 5..=worm.position.x + 5 {
                            let target = Point2d::new(x, y);
                            if (worm.position - target).magnitude_squared() < 36 {
                                result.push(Command {
                                    worm: select,
                                    action: Action::Bomb(target),
                                });
                            }
                        }
                    }

                    result
                } else {
                    Vec::new()
                }
            }
            None => Vec::new(),
        }
    }

    pub fn sensible_shoot_commands(
        &self,
        player_index: usize,
        center: Point2d<i8>,
        weapon_range: u8,
    ) -> ArrayVec<[Command; 8]> {
        let range = weapon_range as i8;
        let dir_range = ((f32::from(weapon_range) + 1.) / 2f32.sqrt()).floor() as i8;

        self.players[GameBoard::opponent(player_index)]
            .worms
            .iter()
            .filter_map(|w| {
                let diff = w.position - center;
                if diff.x == 0 && diff.y.abs() <= range {
                    if diff.y > 0 {
                        Some((Direction::South, diff.y))
                    } else {
                        Some((Direction::North, -diff.y))
                    }
                } else if diff.y == 0 && diff.x.abs() <= range {
                    if diff.x > 0 {
                        Some((Direction::East, diff.x))
                    } else {
                        Some((Direction::West, -diff.x))
                    }
                } else if diff.x.abs() == diff.y.abs() && diff.x.abs() <= dir_range {
                    match (diff.x > 0, diff.y > 0) {
                        (true, true) => Some((Direction::SouthEast, diff.x)),
                        (false, true) => Some((Direction::SouthWest, -diff.x)),
                        (true, false) => Some((Direction::NorthEast, diff.x)),
                        (false, false) => Some((Direction::NorthWest, -diff.x)),
                    }
                } else {
                    None
                }
            })
            .filter(|(dir, range)| {
                let diff = dir.as_vec();
                // NB: This is up to range EXCLUSIVE, so if there's
                // anything in the way, even another good shot, skip.
                !(1..*range).any(|distance| {
                    self.map.at(center + diff * distance) != Some(false)
                        && !self
                            .players
                            .iter()
                            .flat_map(|p| p.worms.iter())
                            .any(|w| w.position == center + diff * distance)
                })
            })
            .map(|(dir, _range)| Command::new(Action::Shoot(dir)))
            .collect()
    }
}

#[cfg(test)]
mod test {}