criteria: add infrastructure

src/criteria/crit_graph/crit_middle.rs

@@ -0,0 +1,111 @@
+use {
+    crate::criteria::{
+        CritUpstreamNode,
+        crit_graph::{
+            CritDownstream, CritDownstreamData, CritTarget, CritUpstreamData,
+            crit_target::CritMgr,
+            crit_upstream::{CritUpstreamNodeBase, CritUpstreamNodeData},
+        },
+        crit_per_target_data::{CritDestroyListenerBase, CritPerTargetData},
+    },
+    std::rc::Rc,
+};
+
+pub struct CritMiddle<Target, T>
+where
+    Target: CritTarget,
+    T: CritMiddleCriterion<Target>,
+{
+    upstream: CritDownstreamData<Target>,
+    downstream: CritUpstreamData<Target, CritMiddleData<T::Data>>,
+    criterion: T,
+}
+
+#[derive(Default)]
+pub struct CritMiddleData<T> {
+    matches: usize,
+    data: T,
+}
+
+pub trait CritMiddleCriterion<Target>: Sized + 'static {
+    type Data: Default;
+    type Not: CritMiddleCriterion<Target>;
+
+    fn update_matched(&self, target: &Target, node: &mut Self::Data, matched: bool) -> bool;
+    fn pull(&self, upstream: &[Rc<dyn CritUpstreamNode<Target>>], target: &Target) -> bool;
+    fn not(&self) -> Self::Not;
+}
+
+impl<Target, T> CritMiddle<Target, T>
+where
+    Target: CritTarget,
+    T: CritMiddleCriterion<Target>,
+{
+    pub fn new(
+        mgr: &Target::Mgr,
+        upstream: &[Rc<dyn CritUpstreamNode<Target>>],
+        criterion: T,
+    ) -> Rc<Self> {
+        let id = mgr.id();
+        let slf = Rc::new_cyclic(|slf| Self {
+            upstream: CritDownstreamData::new(id, upstream),
+            downstream: CritUpstreamData::new(slf, id),
+            criterion,
+        });
+        slf.upstream.attach(&slf);
+        slf
+    }
+}
+
+impl<Target, T> CritDownstream<Target> for CritMiddle<Target, T>
+where
+    Target: CritTarget,
+    T: CritMiddleCriterion<Target>,
+{
+    fn update_matched(self: Rc<Self>, target: &Target, matched: bool) {
+        let mut node = self.downstream.get_or_create(target);
+        let change = self
+            .criterion
+            .update_matched(target, &mut node.data, matched);
+        let matches = match matched {
+            true => node.matches + 1,
+            false => node.matches - 1,
+        };
+        node.matches = matches;
+        self.downstream
+            .update_matched(target, node, change, matches == 0);
+    }
+}
+
+impl<Target, T> CritUpstreamNodeBase<Target> for CritMiddle<Target, T>
+where
+    Target: CritTarget,
+    T: CritMiddleCriterion<Target>,
+{
+    type Data = CritMiddleData<T::Data>;
+
+    fn data(&self) -> &CritUpstreamData<Target, Self::Data> {
+        &self.downstream
+    }
+
+    fn not(&self, mgr: &Target::Mgr) -> Rc<dyn CritUpstreamNode<Target>> {
+        let upstream = self.upstream.not(mgr);
+        CritMiddle::new(mgr, &upstream, self.criterion.not())
+    }
+
+    fn pull(&self, target: &Target) -> bool {
+        self.criterion.pull(&self.upstream.upstream, target)
+    }
+}
+
+impl<Target, T> CritDestroyListenerBase<Target> for CritMiddle<Target, T>
+where
+    Target: CritTarget,
+    T: CritMiddleCriterion<Target>,
+{
+    type Data = CritUpstreamNodeData<Target, CritMiddleData<T::Data>>;
+
+    fn data(&self) -> &CritPerTargetData<Target, Self::Data> {
+        &self.downstream.nodes
+    }
+}