use lyra_ecs::{query::Entities, relation::{ChildOf, RelationOriginComponent}, Bundle, Entity};
use lyra_reflect::Reflect;

use crate::{SceneGraph, lyra_engine};

/// A node inside of the Scene
#[derive(Clone, PartialEq, Eq, Reflect)]
pub struct SceneNode {
    #[reflect(skip)]
    parent: Option<Entity>,
    #[reflect(skip)]
    entity: Entity
}

impl SceneNode {
    pub fn new(parent: Option<Entity>, entity: Entity) -> Self {
        Self {
            parent,
            entity,
        }
    }

    /// If this node has a parent, retrieves the parent node from the SceneGraph.
    pub fn parent(&self, graph: &SceneGraph) -> Option<SceneNode> {
        if let Some(parent) = self.parent {
            let v = graph.world.view_one::<&RelationOriginComponent<ChildOf>>(parent);
            
            let p_parent = if let Some(pp) = v.get() {
                Some(pp.target())
            } else { None };

            Some(SceneNode::new(p_parent, parent))
        } else {
            None
        }
    }

    pub fn parent_entity(&self) -> Option<Entity> {
        self.parent
    }

    pub fn children(&self, graph: &SceneGraph) -> Vec<SceneNode> {
        let v = graph.world.view::<Entities>()
            .relates_to::<ChildOf>(self.entity);

        v.into_iter().map(|(e, _)| SceneNode::new(Some(self.entity), e)).collect()
    }

    pub fn entity(&self) -> Entity {
        self.entity
    }

    /// Add a child node to this node.
    /// 
    /// The spawned entity backing the scene node will have a `ChildOf` relation targeting
    /// the provided parent node, the `SceneNodeFlag` component is also added to the entity.
    pub fn add_node<B: Bundle>(&self, graph: &mut SceneGraph, bundle: B) -> SceneNode {
        graph.add_node_under(self, bundle)
    }
}

#[cfg(test)]
mod tests {
    use lyra_ecs::{query::{filter::{Has, Not}, Entities}, relation::{ChildOf, RelationOriginComponent}};
    use lyra_math::{Transform, Vec3};
    use lyra_resource::ResHandle;
    
    use crate::{tests::FakeMesh, WorldTransform, SceneGraph};

    #[test]
    fn node_world_transform() {
        let mut scene = SceneGraph::new();

        let a = scene.add_node((WorldTransform::default(), Transform::from_translation(Vec3::new(10.0, 10.0, 10.0)), FakeMesh));
        assert!(a.parent(&scene).unwrap() == scene.root_node);
        
        let b = a.add_node(&mut scene, (WorldTransform::default(), Transform::from_translation(Vec3::new(50.0, 50.0, 50.0)), FakeMesh));
        assert!(b.parent(&scene).unwrap() == a);

        // update global transforms
        let view = scene.world.filtered_view::<(Entities, &mut WorldTransform, &Transform, Option<&ResHandle<SceneGraph>>), Not<Has<RelationOriginComponent<ChildOf>>>>();
        crate::system_update_world_transforms(&scene.world, view).unwrap();

        let tran = scene.world.view_one::<&WorldTransform>(b.entity).get().unwrap();
        assert_eq!(**tran, Transform::from_translation(Vec3::new(60.0, 60.0, 60.0)));
    }
}