Add API for finding faces

crates/fj-kernel/src/objects/face.rs

@@ -18,6 +18,17 @@ impl Faces {
     pub fn new() -> Self {
         Self::default()
     }
+
+    /// Find the given face
+    pub fn find(&self, face: &Face) -> Option<Face> {
+        for f in self {
+            if f == face {
+                return Some(f.clone());
+            }
+        }
+
+        None
+    }
 }
 
 impl Extend<Face> for Faces {

crates/fj-kernel/src/objects/shell.rs

@@ -47,6 +47,11 @@ impl Shell {
     pub fn into_faces(self) -> Faces {
         self.faces
     }
+
+    /// Find the given face in this shell
+    pub fn find_face(&self, face: &Face) -> Option<Face> {
+        self.faces().find(face)
+    }
 }
 
 impl Default for Shell {

crates/fj-kernel/src/objects/solid.rs

@@ -2,7 +2,7 @@ use std::collections::BTreeSet;
 
 use crate::builder::SolidBuilder;
 
-use super::Shell;
+use super::{Face, Shell};
 
 /// A 3-dimensional shape
 ///
@@ -49,6 +49,17 @@ impl Solid {
     pub fn into_shells(self) -> impl Iterator<Item = Shell> {
         self.shells.into_iter()
     }
+
+    /// Find the given face in this solid
+    pub fn find_face(&self, face: &Face) -> Option<Face> {
+        for shell in self.shells() {
+            if let Some(face) = shell.find_face(face) {
+                return Some(face);
+            }
+        }
+
+        None
+    }
 }
 
 impl Default for Solid {