// -*- coding: utf-8 -*-
//
// Copyright 2021 Michael Büsch <m@bues.ch>
//
// Licensed under the Apache License version 2.0
// or the MIT license, at your option.
// SPDX-License-Identifier: Apache-2.0 OR MIT
//

use crate::base::PhyType;
use crate::object::PhyObject;
use crate::vector::Vector;
use std::cmp::max;
use std::time::{Duration, Instant};

pub const GRAVITY_MERCURY: PhyType = PhyType::new_f64(3.7);
pub const GRAVITY_VENUS: PhyType = PhyType::new_f64(8.87);
pub const GRAVITY_EARTH: PhyType = PhyType::new_f64(9.80665);
pub const GRAVITY_EARTH_MOON: PhyType = PhyType::new_f64(1.625);
pub const GRAVITY_MARS: PhyType = PhyType::new_f64(3.72076);
pub const GRAVITY_JUPITER: PhyType = PhyType::new_f64(24.79);
pub const GRAVITY_SATURN: PhyType = PhyType::new_f64(10.44);
pub const GRAVITY_URANUS: PhyType = PhyType::new_f64(8.69);
pub const GRAVITY_NEPTUNE: PhyType = PhyType::new_f64(11.15);
pub const GRAVITY_PLUTO: PhyType = PhyType::new_f64(0.620);

#[derive(Debug)]
pub struct WorldContext {
    now: Instant,
    period: Duration,
    gravity: Vector,
}

impl WorldContext {
    pub fn now(&self) -> Instant {
        self.now
    }

    pub fn period_sec(&self) -> PhyType {
        self.period.as_secs_f64().into()
    }

    pub fn gravity(&self) -> Vector {
        self.gravity
    }
}

pub struct World {
    gravity: Vector,
    now: Instant,
}

impl World {
    pub fn new(gravity: Option<PhyType>) -> World {
        let gravity = match gravity {
            Some(gravity) => max(gravity, 0.into()),
            None => GRAVITY_EARTH,
        };
        let gravity = Vector::new(0.into(), 0.into(), -gravity);
        World {
            gravity,
            now: Instant::now(),
        }
    }

    pub fn calc(&mut self, objs: &mut Vec<&mut dyn PhyObject>) {
        let now = Instant::now();
        let period = now - self.now;
        self.now = now;

        let context = WorldContext {
            now,
            period,
            gravity: self.gravity,
        };

        for obj in objs {
            if obj.is_enabled() {
                obj.calc(&context);
            }
        }
    }
}

// vim: ts=4 sw=4 expandtab