use crate::level::{Level, StructureElement};
use crate::level_generator::LevelGenerator;
use crate::player::Player;
use crate::position::{HasPosition, Position};

pub const LEVELS: usize = 10;

#[derive(PartialEq)]
/// represents a state of a game
pub enum GameState {
    /// the game is ongoing (neither won or lost)
    RUNNING,
    /// the player died
    LOST,
    /// the player reached the Ω
    WON,
}


/// the main structure to hold all information about the ongoing game
pub struct Game {
    /// the player
    player: Player,
    /// the levels of the game
    levels: Vec<Level>,
    pub messages: Vec<String>,
}

impl Game {
    pub fn new(p: Player) -> Game {
        let mut v: Vec<Level> = Vec::with_capacity(LEVELS);
        for d in 0..LEVELS {
            v.push(LevelGenerator::generate(d, d == 0, d == LEVELS - 1).render());
        }
        let mut g = Game {
            player: p,
            levels: v,
            messages: Vec::with_capacity(10),
        };
        let start = {
            g.get_level(0).start
        };
        g.get_mutable_player().get_position().set(0, start.0, start.1);
        g.get_mutable_level(0).discover(&Position::new(0, start.0, start.1));
        g
    }

    /// returns true if the player is standing on the End element
    fn player_reached_goal(&mut self) -> bool {
        match self.next_element(0, 0) {
            None => {}
            Some(a) => {
                match a {
                    StructureElement::End => { return true; }
                    _ => {}
                }
            }
        };
        false
    }
    /// returns the state of the game (depending on player's life and position)
    pub fn get_game_state(&mut self) -> GameState {
        if self.player.is_dead() {
            return GameState::LOST;
        }
        if self.player_reached_goal() {
            return GameState::WON;
        }
        GameState::RUNNING
    }
    pub fn get_player(&self) -> &Player {
        &self.player
    }
    pub fn get_mutable_player(&mut self) -> &mut Player {
        &mut self.player
    }
    pub fn get_level(&self, level: usize) -> &Level { &self.levels[level] }
    pub fn get_mutable_level(&mut self, level: usize) -> &mut Level { &mut self.levels[level] }
    /// check if the player can move in the given direction. This only checks for structure element
    /// limitation as walls.
    fn can_move(&mut self, dx: i16, dy: i16) -> bool {
        let player_pos = &self.player.get_position();
        let level = &mut self.levels[player_pos.get_level()];
        level.can_player_move(&self.player, dx, dy)
    }
    /// returns the position (as tuple) of the next level's start point.
    fn next_start(&self) -> (usize, usize, usize) {
        let level = self.player.get_immutable_position().get_level() + 1;
        let (x, y) = self.levels[level].start;
        (level, x, y)
    }
    /// returns the position (as tuple) of the previous level's end point.
    fn prev_end(&self) -> (usize, usize, usize) {
        let level = self.player.get_immutable_position().get_level() - 1;
        let (x, y) = self.levels[level].end;
        (level, x, y)
    }
    /// get the next structure element sen from the player's position into the given direction.
    fn next_element(&mut self, dx: i16, dy: i16) -> Option<StructureElement> {
        let player_pos = &self.player.get_position();
        let new_x: i16 = player_pos.get_x() as i16 + dx;
        let new_y: i16 = player_pos.get_y() as i16 + dy;
        let player_level = player_pos.get_level();
        let level = &mut self.levels[player_level];
        level.get_element(new_x, new_y).0
    }

    /// move the game's player into the given direction. If on the target field there is a stair,
    /// the player follows the stair up/down to the next level.
    /// Discovery is performed on the new location of the player.
    /// The returned value is the direction that will bring the player back to his original field.
    pub fn move_player(&mut self, mut dx: i16, mut dy: i16) -> (i16, i16) {
        // verify the player can do the move
        if !self.can_move(dx, dy) {
            return (-dx, -dy);
        }

        let player_pos = &self.player.get_position();
        let mut player_level = player_pos.get_level();
        let structure = self.next_element(dx, dy);

        // use stairs if walked onto one
        match structure {
            Some(e) => {
                match e {
                    StructureElement::StairDown => {
                        (dx, dy) = (0, 0);
                        let (next_level, x, y) = self.next_start();
                        player_level = next_level;
                        self.messages.insert(0, format!("you climb down to level {}.", next_level));
                        self.get_mutable_player().get_position().set(next_level, x, y);
                    }
                    StructureElement::StairUp => {
                        (dx, dy) = (0, 0);
                        let (next_level, x, y) = self.prev_end();
                        player_level = next_level;
                        self.messages.insert(0, format!("you climb up to level {}.", next_level));
                        self.get_mutable_player().get_position().set(next_level, x, y);
                    }
                    _ => {}
                }
            }
            _ => {}
        }

        // update position and discover area on new position
        let (new_x, new_y) = self.get_mutable_player().get_position().change(dx, dy);
        self.get_mutable_level(player_level).discover(&Position::new(player_level, new_x, new_y));
        (-dx, -dy)
    }
    pub fn player_fights_monster(&mut self) -> bool {
        let player_pos = &self.player.get_immutable_position();
        let player_level = player_pos.get_level();
        let level = &mut self.levels[player_level];
        let (_, m, _) = level.get_element(player_pos.get_x() as i16, player_pos.get_y() as i16);
        match m {
            None => {}
            Some(m) => {
                // TODO fight the monster
                self.player.change_life(-1);
                m.decrease_life(1);
                self.messages.insert(0, format!("{} hits you.", m.get_name()).to_string());
                self.messages.insert(0, format!("you hit {}.", m.get_name()).to_string());
                // monster died, player gains experience
                if m.is_dead() {
                    self.player.gain_experience(m.get_experience_gain());
                }
                return m.is_dead();
            }
        };
        true
    }
    pub fn player_collects_artifact(&mut self) {
        let player_pos = &self.player.get_immutable_position();
        let player_level = player_pos.get_level();
        let level = &mut self.levels[player_level];
        let (_, _, a) = level.get_element(player_pos.get_x() as i16, player_pos.get_y() as i16);
        match a {
            None => {}
            Some(a) => {
                a.collect(&mut self.player, &mut self.messages);
            }
        }
    }
    /// updates the player's current level. This will remove collected artifacts and dead monsters.
    pub fn update_level(&mut self, ticks: u128) {
        let player_pos = &self.player.get_immutable_position();
        let player_level = player_pos.get_level();
        let level = &mut self.levels[player_level];
        level.update(ticks, &mut self.player, &mut self.messages);
    }
}

#[test]
fn game_has_correct_number_of_levels() {
    let p = Player::new("foo", 42);
    let g = Game::new(p);
    assert_eq!(g.levels.len(), LEVELS);
}

#[test]
fn game_has_player() {
    let p = Player::new("foo", 42);
    let g = Game::new(p);
    assert_eq!(g.get_player().get_name(), "foo");
    assert_eq!(g.get_player().get_immutable_position().get_level(), 0);
}

#[test]
fn game_has_mutable_player() {
    let p = Player::new("foo", 42);
    let mut g = Game::new(p);
    assert_eq!(g.get_player().get_name(), "foo");
    g.get_mutable_player().change_life(-1);
    assert_eq!(g.get_player().get_life(), 41);
}

#[test]
fn game_get_level() {
    let p = Player::new("foo", 42);
    let mut g = Game::new(p);
    g.get_level(0);
    assert_ne!(g.get_level(0).start, (0, 0));
    g.get_mutable_level(0).discover(&Position::new(0, 1, 1));
}