extern crate rand;
extern crate std;

use super::state;
use super::constants;

pub struct Gates {
    x: f64,
    y: f64,
    v_x: f64,
    v_y: f64,
    a_x: f64,
    a_y: f64,
    target_x: f64,
    target_y: f64,
    health: f64,
}

pub struct GatesBullet {
    real_x: f64,
    real_y: f64,
    d_x: f64,
    d_y: f64,
}

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

impl state::Positioned for GatesBullet {
    fn x(&self) -> i32 {
        self.real_x.round() as i32
    }
    fn y(&self) -> i32 {
        self.real_y.round() as i32
    }
    fn radius() -> u32 {
        10
    }
}

impl state::Positioned for Gates {
    fn x(&self) -> i32 {
        self.x.round() as i32
    }
    fn y(&self) -> i32 {
        self.y.round() as i32
    }
    fn radius() -> u32 {
        30
    }
}

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

impl state::StraightBullet for GatesBullet {
    fn real_x(&self) -> f64 {
        self.real_x
    }
    fn real_y(&self) -> f64 {
        self.real_y
    }
    fn set_real_x(&mut self, real_x: f64) {
        self.real_x = real_x;
    }
    fn set_real_y(&mut self, real_y: f64) {
        self.real_y = real_y;
    }
    fn d_x(&self) -> f64 {
        self.d_x
    }
    fn d_y(&self) -> f64 {
        self.d_y
    }
}

fn random_bullet<T: state::Enemy<GatesBullet>>(enemy: &T) -> GatesBullet {
    let multiplier = 2. + 3.*(1. - enemy.health());
    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;
    GatesBullet::new(enemy.x(), dx, enemy.y(), dy)
}

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 Gates {
    fn choose_position(&mut self) {
        let (x, y) = random_position();
        self.target_x = x;
        self.target_y = y;
    }
}

impl state::Enemy<GatesBullet> for Gates {
    fn new() -> Gates {
        Gates { x: 200., y: 40., v_x: 0., v_y: 0., a_x: 0., a_y: 0., target_x: 200., target_y: 40., health: 1. }
    }
    fn act(&mut self, count: u64) -> Vec<GatesBullet> {
        let max_accel = (1. - self.health) * 0.75 + 0.25;
        let max_velocity = (1. - self.health) * 5. + 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 */
            self.choose_position();
        }

        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 >= 0.8 {
                5
            } else if self.health >= 0.7 {
                6
            } else if self.health >= 0.5 {
                7
            } else if self.health >= 0.4 {
                8
            } else if self.health >= 0.3 {
                9
            } else if self.health >= 0.2 {
                10
            } else {
                11
            };
            let mut result = Vec::new();
            for _ in 0..num_bullets {
                result.push(random_bullet(&*self));
            }
            result
        } else {
            Vec::new()
        }
    }
    fn health(&self) -> f64 {
        self.health
    }
    fn set_health(&mut self, health: f64) {
        self.health = health;
    }
    fn injure(&mut self, damage: f64) {
        self.health -= damage;
    }
}

impl state::Drawable for GatesBullet {
    fn center() -> (u32, u32) {
        (20, 20)
    }
}

impl state::Drawable for Gates {
    fn center() -> (u32, u32) {
        (16, 23)
    }
}