extern crate sdl2;
extern crate std;
extern crate rand;

use super::player;
use super::constants;

pub struct EBullet {
    x: i32,
    y: i32,
    radius: u32,
    real_x: f64,
    real_y: f64,
    d_x: f64,
    d_y: f64,
}

pub struct Enemy {
    pub x: f64,
    pub y: f64,
    v_x: f64,
    v_y: f64,
    a_x: f64,
    a_y: f64,
    target_x: f64,
    target_y: f64,
    radius: u32,
    pub health: i64,
}

pub const STARTING_HEALTH: i64 = 100;

impl EBullet {
    pub fn new(x: i32, d_x: f64, y: i32, d_y: f64) -> EBullet {
        EBullet { x: x, real_x: x as f64, y: y, real_y: y as f64, radius: 10, d_x: d_x, d_y: d_y }
    }

    pub fn act(&mut self) {
        self.real_x += self.d_x;
        self.real_y += self.d_y;
        self.x = self.real_x.round() as i32;
        self.y = self.real_y.round() as i32;
    }
}

pub struct PBullet {
    b: EBullet,
}

impl PBullet {
    pub fn new(x: i32, d_x: f64, y: i32, d_y: f64) -> PBullet {
        PBullet { b: EBullet::new(x, d_x, y, d_y) }
    }
    pub fn act(&mut self) {
        self.b.act()
    }
    pub fn delete(&mut self) {
        self.b.x = -10;
    }
}

fn random_bullet(enemy: &Enemy) -> EBullet {
    let multiplier = 2. + (STARTING_HEALTH as i64 - enemy.health) as f64 / STARTING_HEALTH as f64 * 2.;
    let theta: f64 = rand::random::<f64>()*2.*std::f64::consts::PI/3. + std::f64::consts::PI/6.;
    let dx = f64::cos(theta) * multiplier;
    let dy = f64::sin(theta) * multiplier;
    EBullet::new(enemy.x.round() as i32, dx, enemy.y.round() as i32, dy)
}

fn random_position() -> (f64, f64) {
    (rand::random::<f64>() * (constants::X_DIM - 200) as f64 + 100., rand::random::<f64>() * 100.)
}

fn shorten(x: f64, y: f64, maxlen: f64) -> (f64, f64) {
    let len = f64::sqrt(x*x + y*y);
    if len > maxlen {
        (x / len / 2., y / len / 2.)
    } else {
        (x, y)
    }
}

impl Enemy {
    pub fn new() -> Enemy {
        let (x, y) = random_position();
        Enemy { x: 200., y: 40., v_x: 0., v_y: 0., a_x: 0., a_y: 0., radius: 30, health: STARTING_HEALTH, target_x: x, target_y: y }
    }
    pub fn act(&mut self, count: u64) -> Vec<EBullet> {
        let max_accel = 0.25;
        let max_velocity = 5.;
        let dx = self.target_x - self.x;
        let dy = self.target_y - self.y;
        /* If we've arrived (close and stopped) */
        if (dx*dx + dy*dy).sqrt() < max_velocity / max_accel && (self.v_x*self.v_x + self.v_y*self.v_y).sqrt() < 0.01 {
            /* Then pick a new target */
            let (x, y) = random_position();
            self.target_x = x;
            self.target_y = y;
        }

        let dx = self.target_x - self.x;
        let dy = self.target_y - self.y;
        /* If we're close */
        if (dx*dx + dy*dy).sqrt() < max_velocity / max_accel {
            /* Then slow down */
            let (x, y) = shorten(-self.v_x, -self.v_y, max_accel);
            self.a_x = x;
            self.a_y = y;
        } else {
            /* Otherwise, speed up */
            let (x, y) = shorten(dx, dy, max_accel);
            self.a_x = x;
            self.a_y = y;
        }

        /* If we're going too fast */
        if (self.v_x*self.v_x + self.v_y*self.v_y).sqrt() > max_velocity {
            /* Then don't go faster */
            if self.v_x.signum() == self.a_x.signum() {
                self.a_x = 0.;
            }
            if self.v_y.signum() == self.a_y.signum() {
                self.a_y = 0.;
            }
        }

        self.v_x += self.a_x;
        self.x += self.v_x;
        self.v_y += self.a_y;
        self.y += self.v_y;
        if count % 20 == 0 {
            let num_bullets;
            if self.health >= 80 {
                num_bullets = 4;
            } else if self.health >= 50 {
                num_bullets = 5;
            } else if self.health >= 30 {
                num_bullets = 6;
            } else if self.health >= 20 {
                num_bullets = 7;
            } else {
                num_bullets = 8;
            }
            let mut result = Vec::new();
            for _ in 0..num_bullets {
                result.push(random_bullet(&*self));
            }
            result
        } else {
            Vec::new()
        }
    }
    pub fn health(&self) -> i64 {
        self.health
    }
}

pub struct State {
    pub player: player::Player,
    pub enemies: Vec<Enemy>,
    pub bullets: Vec<EBullet>,
    pub player_bullets: Vec<PBullet>,
    pub count: u64,
}

impl State {
    pub fn new() -> State {
        State { player: player::Player::new(), enemies: Vec::new(), bullets: Vec::new(), count: 0, player_bullets: Vec::new() }
    }
}

fn dist(x1: i32, y1: i32, x2: i32, y2: i32) -> f64 {
    let xdist = x1 - x2;
    let ydist = y1 - y2;
    f64::sqrt((xdist*xdist + ydist*ydist) as f64)
}

pub trait Positioned {
    fn x(&self) -> i32;
    fn y(&self) -> i32;
    fn radius(&self) -> u32;
    fn contains(&self, x: i32, y: i32) -> bool {
        let d = dist(self.x(), self.y(), x, y);
        d <= self.radius() as f64
    }
    fn overlaps<T: Positioned>(&self, other: &T) -> bool {
        let sx = self.x();
        let ox = other.x();
        let sy = self.y();
        let oy = other.y();
        let threshold = self.radius() + other.radius();
        if (sx - ox).abs() as u32 >= threshold || (sy - oy).abs() as u32 >= threshold {
            return false;
        }
        let dist = dist(sx, sy, ox, oy);
        dist < threshold as f64
    }
    fn outside(&self) -> bool {
        let x = self.x();
        let y = self.y();
        x < 0 || x > constants::X_DIM as i32 || y < 0 || y > constants::Y_DIM as i32
    }
}

impl Positioned for EBullet {
    fn x(&self) -> i32 {
        self.x
    }
    fn y(&self) -> i32 {
        self.y
    }
    fn radius(&self) -> u32 {
        self.radius
    }
}

impl Positioned for PBullet {
    fn x(&self) -> i32 {
        self.b.x()
    }
    fn y(&self) -> i32 {
        self.b.y()
    }
    fn radius(&self) -> u32 {
        self.b.radius()
    }
}

impl Positioned for Enemy {
    fn x(&self) -> i32 {
        self.x.round() as i32
    }
    fn y(&self) -> i32 {
        self.y.round() as i32
    }
    fn radius(&self) -> u32 {
        self.radius
    }
}

pub trait Drawable : Positioned {
    fn center(&self) -> (u32, u32);
    fn draw(&self, canvas: &mut sdl2::render::WindowCanvas, texture: &sdl2::render::Texture) {
        let tw = texture.query().width;
        let th = texture.query().height;
        let (cx, cy) = self.center();
        let x0 = self.x() - cx as i32;
        let y0 = self.y() - cy as i32;
        canvas.copy(&texture, None, Some(sdl2::rect::Rect::new(x0, y0, tw, th))).unwrap();
    }
}

impl Drawable for Enemy {
    fn center(&self) -> (u32, u32) {
        (0, 0)
    }
}

impl Drawable for EBullet {
    fn center(&self) -> (u32, u32) {
        (20, 20)
    }
}

impl Drawable for PBullet {
    fn center(&self) -> (u32, u32) {
        (16, 22)
    }
}