router: use `Step` and new `StepBack` traits in `Route` and `Trace`

src/router/route.rs

@@ -8,6 +8,7 @@ use crate::{
         tracer::Tracer,
         Router, RouterAstarStrategy, RouterError, RouterStatus,
     },
+    step::Step,
 };
 
 pub struct Route {
@@ -53,26 +54,6 @@ impl Route {
         }
     }
 
-    pub fn step(
-        &mut self,
-        router: &mut Router<impl AccessRules>,
-    ) -> Result<RouterStatus, RouterError> {
-        let tracer = Tracer::new(router.layout_mut());
-        let target = self.astar.graph.destination();
-        let mut strategy = RouterAstarStrategy::new(tracer, &mut self.trace, target);
-
-        let result = match self.astar.step(&mut strategy)? {
-            AstarStatus::Probing | AstarStatus::Probed | AstarStatus::Visited => {
-                Ok(RouterStatus::Running)
-            }
-            AstarStatus::Finished(_cost, _path, band) => Ok(RouterStatus::Finished(band)),
-        };
-
-        self.ghosts = strategy.probe_ghosts;
-        self.obstacles = strategy.probe_obstacles;
-        result
-    }
-
     pub fn navmesh(&self) -> &Navmesh {
         &self.astar.graph
     }
@@ -89,3 +70,22 @@ impl Route {
         &self.obstacles
     }
 }
+
+impl<'a, R: AccessRules> Step<Router<'a, R>, RouterStatus, RouterError> for Route {
+    fn step(&mut self, router: &mut Router<R>) -> Result<RouterStatus, RouterError> {
+        let tracer = Tracer::new(router.layout_mut());
+        let target = self.astar.graph.destination();
+        let mut strategy = RouterAstarStrategy::new(tracer, &mut self.trace, target);
+
+        let result = match self.astar.step(&mut strategy)? {
+            AstarStatus::Probing | AstarStatus::Probed | AstarStatus::Visited => {
+                Ok(RouterStatus::Running)
+            }
+            AstarStatus::Finished(_cost, _path, band) => Ok(RouterStatus::Finished(band)),
+        };
+
+        self.ghosts = strategy.probe_ghosts;
+        self.obstacles = strategy.probe_obstacles;
+        result
+    }
+}

src/router/router.rs

@@ -18,6 +18,7 @@ use crate::{
     },
     graph::{GetPetgraphIndex, MakeRef},
     layout::Layout,
+    step::{IsFinished, Step, StepBack},
 };
 
 use super::{
@@ -25,7 +26,7 @@ use super::{
     draw::DrawException,
     navmesh::{Navmesh, NavmeshEdgeReference, NavmeshError, NavvertexIndex},
     route::Route,
-    trace::Trace,
+    trace::{Trace, TraceStepInput},
     tracer::{Tracer, TracerException},
 };
 
@@ -42,6 +43,12 @@ pub enum RouterStatus {
     Finished(BandTermsegIndex),
 }
 
+impl IsFinished for RouterStatus {
+    fn finished(&self) -> bool {
+        matches!(self, RouterStatus::Finished(..))
+    }
+}
+
 #[derive(Debug)]
 pub struct RouterAstarStrategy<'a, R: AccessRules> {
     pub tracer: Tracer<'a, R>,
@@ -107,9 +114,12 @@ impl<'a, R: AccessRules> AstarStrategy<Navmesh, f64, BandTermsegIndex>
         let prev_bihead_length = self.bihead_length();
 
         let width = self.trace.width;
-        let result = self
-            .trace
-            .step(&mut self.tracer, navmesh, edge.target(), width);
+        let result = self.trace.step(&mut TraceStepInput {
+            tracer: &mut self.tracer,
+            navmesh,
+            to: edge.target(),
+            width,
+        });
 
         let probe_length = self.bihead_length() - prev_bihead_length;
 
@@ -141,7 +151,7 @@ impl<'a, R: AccessRules> AstarStrategy<Navmesh, f64, BandTermsegIndex>
     }
 
     fn remove_probe(&mut self, _navmesh: &Navmesh) {
-        self.trace.undo_step(&mut self.tracer);
+        self.trace.step_back(&mut self.tracer);
     }
 
     fn estimate_cost(&mut self, navmesh: &Navmesh, vertex: NavvertexIndex) -> f64 {

src/router/trace.rs

@@ -9,11 +9,14 @@ use crate::{
         head::{BareHead, CaneHead, Head},
         rules::AccessRules,
     },
-    router::{
+    step::{Step, StepBack},
+};
+
+use super::{
     draw::Draw,
     navmesh::{BinavvertexNodeIndex, Navmesh, NavvertexIndex},
+    tracer::TracerStatus,
     tracer::{Tracer, TracerException},
-    },
 };
 
 #[derive(Debug)]
@@ -32,33 +35,6 @@ impl Trace {
         }
     }
 
-    #[debug_ensures(ret.is_ok() -> matches!(self.head, Head::Cane(..)))]
-    #[debug_ensures(ret.is_ok() -> self.path.len() == old(self.path.len() + 1))]
-    #[debug_ensures(ret.is_err() -> self.path.len() == old(self.path.len()))]
-    pub fn step(
-        &mut self,
-        tracer: &mut Tracer<impl AccessRules>,
-        navmesh: &Navmesh,
-        to: NavvertexIndex,
-        width: f64,
-    ) -> Result<(), TracerException> {
-        self.head = self.wrap(tracer, navmesh, self.head, to, width)?.into();
-        self.path.push(to);
-
-        Ok::<(), TracerException>(())
-    }
-
-    #[debug_ensures(self.path.len() == old(self.path.len() - 1))]
-    pub fn undo_step(&mut self, tracer: &mut Tracer<impl AccessRules>) {
-        if let Head::Cane(head) = self.head {
-            self.head = Draw::new(tracer.layout).undo_cane(head).unwrap();
-        } else {
-            panic!();
-        }
-
-        self.path.pop();
-    }
-
     fn wrap(
         &mut self,
         tracer: &mut Tracer<impl AccessRules>,
@@ -116,3 +92,49 @@ impl Trace {
         navmesh.node_weight(navvertex).unwrap().maybe_cw
     }
 }
+
+pub struct TraceStepInput<'a: 'b, 'b, R: AccessRules> {
+    pub tracer: &'b mut Tracer<'a, R>,
+    pub navmesh: &'b Navmesh,
+    pub to: NavvertexIndex,
+    pub width: f64,
+}
+
+impl<'a, 'b, R: AccessRules> Step<TraceStepInput<'a, 'b, R>, TracerStatus, TracerException>
+    for Trace
+{
+    #[debug_ensures(ret.is_ok() -> matches!(self.head, Head::Cane(..)))]
+    #[debug_ensures(ret.is_ok() -> self.path.len() == old(self.path.len() + 1))]
+    #[debug_ensures(ret.is_err() -> self.path.len() == old(self.path.len()))]
+    fn step(
+        &mut self,
+        input: &mut TraceStepInput<'a, 'b, R>,
+    ) -> Result<TracerStatus, TracerException> {
+        self.head = self
+            .wrap(
+                input.tracer,
+                input.navmesh,
+                self.head,
+                input.to,
+                input.width,
+            )?
+            .into();
+        self.path.push(input.to);
+
+        Ok(TracerStatus::Running)
+    }
+}
+
+impl<'a, R: AccessRules> StepBack<Tracer<'a, R>, TracerStatus, TracerException> for Trace {
+    #[debug_ensures(self.path.len() == old(self.path.len() - 1))]
+    fn step_back(&mut self, tracer: &mut Tracer<'a, R>) -> Result<TracerStatus, TracerException> {
+        if let Head::Cane(head) = self.head {
+            self.head = Draw::new(tracer.layout).undo_cane(head).unwrap();
+        } else {
+            panic!();
+        }
+
+        self.path.pop();
+        Ok(TracerStatus::Running)
+    }
+}

src/router/tracer.rs

@@ -4,11 +4,13 @@ use thiserror::Error;
 use crate::{
     drawing::{band::BandTermsegIndex, dot::FixedDotIndex, rules::AccessRules},
     layout::Layout,
-    router::{
+    step::{IsFinished, Step, StepBack},
+};
+
+use super::{
     draw::{Draw, DrawException},
     navmesh::{Navmesh, NavvertexIndex},
-        trace::Trace,
-    },
+    trace::{Trace, TraceStepInput},
 };
 
 #[derive(Error, Debug, Clone, Copy)]
@@ -19,6 +21,17 @@ pub enum TracerException {
     CannotWrap,
 }
 
+pub enum TracerStatus {
+    Running,
+    Finished,
+}
+
+impl IsFinished for TracerStatus {
+    fn finished(&self) -> bool {
+        matches!(self, TracerStatus::Finished)
+    }
+}
+
 #[derive(Debug)]
 pub struct Tracer<'a, R: AccessRules> {
     pub layout: &'a mut Layout<R>,
@@ -78,7 +91,12 @@ impl<'a, R: AccessRules> Tracer<'a, R> {
         width: f64,
     ) -> Result<(), TracerException> {
         for (i, vertex) in path.iter().enumerate() {
-            if let Err(err) = trace.step(self, navmesh, *vertex, width) {
+            if let Err(err) = trace.step(&mut TraceStepInput {
+                tracer: self,
+                navmesh,
+                to: *vertex,
+                width,
+            }) {
                 self.undo_path(trace, i);
                 return Err(err.into());
             }
@@ -90,7 +108,7 @@ impl<'a, R: AccessRules> Tracer<'a, R> {
     #[debug_ensures(trace.path.len() == old(trace.path.len() - step_count))]
     pub fn undo_path(&mut self, trace: &mut Trace, step_count: usize) {
         for _ in 0..step_count {
-            trace.undo_step(self);
+            let _ = trace.step_back(self);
         }
     }
 }

src/step.rs

@@ -2,6 +2,10 @@ pub trait IsFinished {
     fn finished(&self) -> bool;
 }
 
-pub trait Step<C, S: IsFinished, E> {
-    fn step(&mut self, context: &mut C) -> Result<S, E>;
+pub trait Step<I, S: IsFinished, E> {
+    fn step(&mut self, input: &mut I) -> Result<S, E>;
+}
+
+pub trait StepBack<I, S: IsFinished, E> {
+    fn step_back(&mut self, input: &mut I) -> Result<S, E>;
 }