1 files changed, 66 insertions, 0 deletions
diff --git a/ecs/src/query/options.rs b/ecs/src/query/options.rs
new file mode 100644
index 0000000..d895073
--- /dev/null
+++ b/ecs/src/query/options.rs
@@ -0,0 +1,66 @@
+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)
+    }
+}