use specs::{Component, VecStorage, NullStorage};

/// Register all the components with the world.
pub fn register(world: &mut specs::World) {
    world.register::<Position>();
    world.register::<Velocity>();
    world.register::<Sprite>();
    world.register::<Background>();
    world.register::<Foreground>();
    world.register::<Decoration>();
    world.register::<Controlled>();
}

/// The `Position` component represents (in world coordinates) a thing
/// that has a position in the world, measured from the top-left of
/// the thing.
#[derive(Component, Debug)]
#[storage(VecStorage)]
pub struct Position {
    pub x: f32,
    pub y: f32,
}

impl Position {
    /// Convert a `Position` to a screen point
    pub fn to_point(&self) -> ggez::nalgebra::Point2<f32> {
        ggez::nalgebra::Point2::new(self.x * 3.0, self.y * 3.0)
    }
}

/// The `Velocity` componenent is present on any entity that moves
/// through the world, and represents its rate of change per
/// time-unit.
#[derive(Component, Debug)]
#[storage(VecStorage)]
pub struct Velocity {
    pub dx: f32,
    pub dy: f32,
}


/// The `Sprite` components represents the current display location of
/// a sprite in the spritesheet.
#[derive(Component, Debug)]
#[storage(VecStorage)]
pub struct Sprite {
    pub u: u8,
    pub v: u8,
}

impl Sprite {
    /// Convert a `Sprite` into the rectangle that specifies the
    /// sprite location on the spritesheet
    pub fn to_rect(&self) -> ggez::graphics::Rect {
        ggez::graphics::Rect {
            x: (1.0 / 32.0) * self.u as f32,
            y: (1.0 / 32.0) * self.v as f32,
            w: 1.0 / 32.0,
            h: 1.0 / 32.0,
        }
    }
}

/// A drawing-phase component: represents tiles that appear in the
/// background of everything.
#[derive(Component, Default, Debug)]
#[storage(NullStorage)]
pub struct Background;

/// A drawing-phase component: represents tiles which appear in the
/// foreground, possibly entities.
#[derive(Component, Default, Debug)]
#[storage(NullStorage)]
pub struct Foreground;

/// A drawing-phase component: represents tiles which appear on top of
/// everything else, such as the tops of trees or roofs of houses.
#[derive(Component, Default, Debug)]
#[storage(NullStorage)]
pub struct Decoration;

/// A component that represents entities which are controlled by the
/// keyboard.
#[derive(Component, Default, Debug)]
#[storage(NullStorage)]
pub struct Controlled;

/// A component that represents entities which can collide with other
/// things.
#[derive(Component, Debug)]
#[storage(VecStorage)]
pub struct Collision {
    pub has_collision: bool
}