criteria: add infrastructure

src/criteria/crit_matchers/critm_string.rs

@@ -0,0 +1,46 @@
+use {
+    crate::criteria::{
+        CritLiteralOrRegex, RootMatcherMap,
+        crit_graph::{CritRootCriterion, CritTarget},
+    },
+    std::marker::PhantomData,
+};
+
+pub struct CritMatchString<Target, A> {
+    string: CritLiteralOrRegex,
+    _phantom: PhantomData<(fn(&Target), A)>,
+}
+
+pub trait StringAccess<Target>: Sized + 'static
+where
+    Target: CritTarget,
+{
+    fn with_string(data: &Target, f: impl FnOnce(&str) -> bool) -> bool;
+    fn nodes(
+        roots: &Target::RootMatchers,
+    ) -> &RootMatcherMap<Target, CritMatchString<Target, Self>>;
+}
+
+impl<Target, A> CritMatchString<Target, A> {
+    #[expect(dead_code)]
+    pub fn new(string: CritLiteralOrRegex) -> Self {
+        Self {
+            string,
+            _phantom: Default::default(),
+        }
+    }
+}
+
+impl<Target, A> CritRootCriterion<Target> for CritMatchString<Target, A>
+where
+    Target: CritTarget,
+    A: StringAccess<Target>,
+{
+    fn matches(&self, data: &Target) -> bool {
+        A::with_string(data, |s| self.string.matches(s))
+    }
+
+    fn nodes(roots: &Target::RootMatchers) -> Option<&RootMatcherMap<Target, Self>> {
+        Some(A::nodes(roots))
+    }
+}