criteria: add infrastructure

src/criteria/crit_graph/crit_downstream.rs

@@ -0,0 +1,52 @@
+use {
+    crate::criteria::{
+        CritMatcherId,
+        crit_graph::{CritTarget, crit_upstream::CritUpstreamNode},
+    },
+    std::rc::Rc,
+};
+
+pub struct CritDownstreamData<Target>
+where
+    Target: CritTarget,
+{
+    id: CritMatcherId,
+    pub(super) upstream: Vec<Rc<dyn CritUpstreamNode<Target>>>,
+}
+
+pub trait CritDownstream<Target>: 'static {
+    fn update_matched(self: Rc<Self>, target: &Target, matched: bool);
+}
+
+impl<Target> CritDownstreamData<Target>
+where
+    Target: CritTarget,
+{
+    pub fn new(id: CritMatcherId, upstream: &[Rc<dyn CritUpstreamNode<Target>>]) -> Self {
+        Self {
+            id,
+            upstream: upstream.to_vec(),
+        }
+    }
+
+    pub fn attach(&self, slf: &Rc<impl CritDownstream<Target>>) {
+        for upstream in &self.upstream {
+            upstream.attach(self.id, slf.clone() as _);
+        }
+    }
+
+    pub fn not(&self, mgr: &Target::Mgr) -> Vec<Rc<dyn CritUpstreamNode<Target>>> {
+        self.upstream.iter().map(|n| n.not(mgr)).collect()
+    }
+}
+
+impl<Target> Drop for CritDownstreamData<Target>
+where
+    Target: CritTarget,
+{
+    fn drop(&mut self) {
+        for el in &self.upstream {
+            el.detach(self.id);
+        }
+    }
+}