use std::ptr::NonNull;

use crate::{World, Access};

mod graph;
pub use graph::*;

mod criteria;
pub use criteria::*;

mod batched;
pub use batched::*;

mod fn_sys;
pub use fn_sys::*;

/// A system that does not mutate the world
pub trait System {
    /// A method that indicates the type of access of the world the system requires.
    fn world_access(&self) -> Access;

    /// The actual execution of the system.
    fn execute(&mut self, world: NonNull<World>) -> anyhow::Result<()>;

    /// A setup step of the System, called before `execute` ever runs.
    fn setup(&self, world: NonNull<World>) -> anyhow::Result<()> {
        let _ = world;
        Ok(())
    }

    fn execute_deferred(&mut self, world: NonNull<World>) -> anyhow::Result<()>;
}

pub trait IntoSystem<T> {
    type System: System;

    fn into_system(self) -> Self::System;
}