experiment(layout): diagnose mandatory leads and test bounded flat separation

crates/oa-core/src/routing.rs

@@ -6,7 +6,9 @@ use crate::{
     RelationBody, RelationKind, Size,
 };
 mod attachments;
+mod leads;
 pub use attachments::{attachment_from_point, attachment_point, semantic_port_endpoint};
+pub use leads::{LeadBlocker, LeadEndpoint, LeadIncompatibility, lead_incompatibilities};
 use std::cmp::Ordering;
 use std::collections::{BTreeMap, BTreeSet, BinaryHeap};
 use std::fmt;
@@ -420,6 +422,73 @@ fn endpoints(
     .collect()
 }
 
+fn effective_route<'a>(
+    project: &Project,
+    diagram: &Diagram,
+    edge: &ProjectedEdge,
+    stored: Option<&'a crate::EdgeRoute>,
+) -> (
+    bool,
+    Option<&'a crate::EdgeRoute>,
+    [Option<EdgeAttachment>; 2],
+) {
+    let promoted = projection::edge_endpoint_placements(project, diagram, edge.id)
+        .is_some_and(|(source, target)| source != edge.source || target != edge.target);
+    let route = if promoted { None } else { stored };
+    let attachments = [EdgeEnd::Source, EdgeEnd::Target].map(|end| {
+        semantic_port_endpoint(project, edge.id, end)
+            .is_none()
+            .then(|| route.and_then(|r| r.attachment(end)))
+            .flatten()
+    });
+    (promoted, route, attachments)
+}
+#[allow(clippy::too_many_arguments)]
+fn edge_endpoints(
+    project: &Project,
+    diagram: &Diagram,
+    edge: &ProjectedEdge,
+    source: &ProjectedNode,
+    target: &ProjectedNode,
+    view: &ProjectedView,
+    attachments: [Option<EdgeAttachment>; 2],
+) -> [Vec<Endpoint>; 2] {
+    [
+        endpoints(
+            project,
+            diagram,
+            source,
+            semantic_port_endpoint(project, edge.id, EdgeEnd::Source).or(edge.source_port),
+            view,
+            attachments[0],
+        ),
+        endpoints(
+            project,
+            diagram,
+            target,
+            semantic_port_endpoint(project, edge.id, EdgeEnd::Target).or(edge.target_port),
+            view,
+            attachments[1],
+        ),
+    ]
+}
+fn allowed_endpoint_pair(edge: &ProjectedEdge, a: Endpoint, b: Endpoint, coincident: bool) -> bool {
+    !(edge.source == edge.target
+        && edge.source_port.is_none()
+        && edge.target_port.is_none()
+        && a.point == b.point
+        && a.stub == b.stub
+        && !coincident)
+}
+fn lead_pair_clear(edge: &ProjectedEdge, a: Endpoint, b: Endpoint, obstacles: &[Rect]) -> bool {
+    !obstacles
+        .iter()
+        .any(|r| r.id != edge.source && r.crosses(a.point, a.stub))
+        && !obstacles
+            .iter()
+            .any(|r| r.id != edge.target && r.crosses(b.point, b.stub))
+}
+
 fn ancestors(id: Id, nodes: &BTreeMap<Id, &ProjectedNode>, out: &mut BTreeSet<Id>) {
     let mut current = nodes.get(&id).and_then(|n| n.visual_parent);
     let mut seen = BTreeSet::new();
@@ -512,16 +581,8 @@ fn route_diagram_impl(
             continue;
         };
         let stored = authored.get(&edge.id).copied();
-        let promoted = projection::edge_endpoint_placements(project, diagram, edge.id)
-            .is_some_and(|(source, target)| source != edge.source || target != edge.target);
-        let custom_suspended = promoted;
-        let route = if promoted { None } else { stored };
-        let attachments = [EdgeEnd::Source, EdgeEnd::Target].map(|end| {
-            semantic_port_endpoint(project, edge.id, end)
-                .is_none()
-                .then(|| route.and_then(|r| r.attachment(end)))
-                .flatten()
-        });
+        let (custom_suspended, route, attachments) =
+            effective_route(project, diagram, edge, stored);
         let pins = route.map_or_else(Vec::new, |r| r.waypoints.clone());
         let obstacles = edge_obstacles(edge, &nodes, &rectangles, &headers);
 
@@ -559,24 +620,11 @@ fn route_diagram_impl(
                 });
             }
         }
+        let ends = edge_endpoints(project, diagram, edge, source, target, view, attachments);
         let (points, pin_lengths, failure) = route_edge(
             edge,
-            &endpoints(
-                project,
-                diagram,
-                source,
-                semantic_port_endpoint(project, edge.id, EdgeEnd::Source).or(edge.source_port),
-                view,
-                attachments[0],
-            ),
-            &endpoints(
-                project,
-                diagram,
-                target,
-                semantic_port_endpoint(project, edge.id, EdgeEnd::Target).or(edge.target_port),
-                view,
-                attachments[1],
-            ),
+            &ends[0],
+            &ends[1],
             &pins,
             &obstacles,
             &previous,
@@ -793,13 +841,7 @@ fn route_edge(
         for &b in target_ends {
             // A real self-relation must leave and return at distinct anchors.
             // Reusing one anchor makes the cheapest path a degenerate stub.
-            if edge.source == edge.target
-                && edge.source_port.is_none()
-                && edge.target_port.is_none()
-                && a.point == b.point
-                && a.stub == b.stub
-                && !coincident
-            {
+            if !allowed_endpoint_pair(edge, a, b, coincident) {
                 continue;
             }
             let estimate = manhattan(a.stub, pins.first().copied().unwrap_or(b.stub))
@@ -823,13 +865,7 @@ fn route_edge(
             }) {
                 continue;
             }
-            if obstacles
-                .iter()
-                .any(|r| r.id != edge.source && r.crosses(a.point, a.stub))
-                || obstacles
-                    .iter()
-                    .any(|r| r.id != edge.target && r.crosses(b.point, b.stub))
-            {
+            if !lead_pair_clear(edge, a, b, obstacles) {
                 continue;
             }
             let mut points = vec![a.point, a.stub];