use bevy::ecs::component::Component;
use bevy::math::{Vec2, Vec3};

/// Resource that defines world's gravity.
///
/// # Example
///
/// ```
/// # use bevy::prelude::*;
/// # use heron_core::*;
///
/// fn main() {
///     App::new()
///         // ... Add plugins
///         .insert_resource(Gravity::from(Vec3::new(0.0, -9.81, 0.0)))
///         // ... Add systems
///         .run();
/// }
/// ```
#[derive(Debug, Component, Copy, Clone, PartialEq)]
pub struct Gravity(Vec3);

impl Gravity {
    /// Returns the underlying vector
    #[must_use]
    pub fn vector(self) -> Vec3 {
        self.0
    }
}

impl Default for Gravity {
    fn default() -> Self {
        Self::from(Vec3::ZERO)
    }
}

impl From<Vec3> for Gravity {
    fn from(v: Vec3) -> Self {
        Self(v)
    }
}

impl From<Vec2> for Gravity {
    fn from(v: Vec2) -> Self {
        Self::from(v.extend(0.0))
    }
}

impl From<Gravity> for Vec3 {
    fn from(g: Gravity) -> Self {
        g.vector()
    }
}