// lib.rs
use kiwi_ecs::*;

pub fn main() {
  let mut world = World::new();
}

#[derive(Component)]
struct Position {
  x: u32,
  y: u32
}

#[flags]
enum Flags {
  Player,
  Enemy,
  Ground,
}

// spawn_entity macro accepts the world as the first parameter, and the 
// components to add to the entity as the other parameters
let entity_id = spawn_entity!(world, Position { x: 0, y: 0 });

world.set_flag(entity_id, Flags::Player);

// immutable system
#[system(pos: Position)]
fn print_positions(world: &World) {
  println!("{:?}", pos);
}

// mutable system
#[system(pos: Position, vel: Vel)]
fn move_entities(world: &mut World) {
  pos.x += vel.x;
  pos.y += vel.y
}

// query entity ids as well
#[system(id: EntityId, pos: Position)]
/// prints all entities ids having the position component
fn print_entity_ids(world: &World) {
  println!("{id}");
}

pub fn main() {
  let mut world = World::new();
  
  //--snip
  
  // Call the systems
  print_positions(&world);
  move_entities(&mut world);
  print_entity_ids(&world);
}

pub fn main() {
  let mut world = World::new();
  
  //--snip
  
  let query_result = query!(world, Position);
  let query_result = query_mut!(world, Position, Velocity);
  let query_result = query!(world, EntityId, Position);
  
  // You can now loop over the components
  query_result.for_each(|components| {
    // ...
  });
}

#[system(id: EntityId, pos: Position)]
fn on_player(world: &World) {
  if world.has_flag(id, Flags::Player) {
    // ...
  }
}

let query_result = query!(world, EntityId, Position)
  .filter(|(id, _pos)| world.has_flag(*id, Flags::Player));

#[system(try, id: EntityId, pos: Position)]
fn a_system_with_a_fallible_condition(world: &World) -> Result<(), String> {
  let mesh = get_mesh(id)?; // fallible function
  render(mesh, pos)?;
}