ecs/src/query/options.rs


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use std::collections::HashSet;
use std::marker::PhantomData;

use crate::component::{Component, Id as ComponentId};
use crate::EntityComponent;

/// Query options.
pub trait Options
{
    fn entity_filter<'component>(
        components: impl IntoIterator<Item = &'component EntityComponent>,
    ) -> bool;
}

impl Options for ()
{
    fn entity_filter<'component>(
        _: impl IntoIterator<Item = &'component EntityComponent>,
    ) -> bool
    {
        true
    }
}

pub struct With<ComponentT>
where
    ComponentT: Component,
{
    _pd: PhantomData<ComponentT>,
}

impl<ComponentT> Options for With<ComponentT>
where
    ComponentT: Component,
{
    fn entity_filter<'component>(
        components: impl IntoIterator<Item = &'component EntityComponent>,
    ) -> bool
    {
        let ids_set = components
            .into_iter()
            .map(|component| component.id)
            .collect::<HashSet<_>>();

        ids_set.contains(&ComponentId::of::<ComponentT>())
    }
}

pub struct Not<OptionsT>
where
    OptionsT: Options,
{
    _pd: PhantomData<OptionsT>,
}

impl<OptionsT> Options for Not<OptionsT>
where
    OptionsT: Options,
{
    fn entity_filter<'component>(
        components: impl IntoIterator<Item = &'component EntityComponent>,
    ) -> bool
    {
        !OptionsT::entity_filter(components)
    }
}