Simplify /clash: single selector, detect collisions within selected set

Drop selector_b — the endpoint now takes the URL's selector= and tests all
matched elements against each other, consistent with the spec's model.
Self-pairs and duplicates are filtered; requires at least 2 matched elements.

https://claude.ai/code/session_01NBsytCd6L7UQPiKbcLn4kn

ifcurl/render_service.py

@@ -106,10 +106,8 @@ def _sandboxed_select(ifc_bytes: bytes, selector: str) -> list[str]:
     return [e.GlobalId for e in matched if hasattr(e, "GlobalId") and e.GlobalId]
 
 
-def _sandboxed_clash(
-    ifc_bytes: bytes, selector_a: str, selector_b: str | None
-) -> list[list[str]]:
-    """Detect geometric clashes between two sets of IFC elements.
+def _sandboxed_clash(ifc_bytes: bytes, selector: str) -> list[list[str]]:
+    """Detect geometric clashes within the elements matched by selector.
 
     Uses ifcopenshell.geom.tree.clash_collision_many for mesh-level
     interpenetration detection (hard clashes only, touching excluded).
@@ -124,32 +122,21 @@ def _sandboxed_clash(
     settings = ifcopenshell.geom.settings()
     settings.set("use-world-coords", True)
 
-    elems_a = list(ifcopenshell.util.selector.filter_elements(model, selector_a))
-    ids_a = {e.id() for e in elems_a}
-
-    if selector_b:
-        elems_b = list(ifcopenshell.util.selector.filter_elements(model, selector_b))
-    else:
-        elems_b = [
-            e
-            for e in model.by_type("IfcProduct")
-            if e.id() not in ids_a and getattr(e, "GlobalId", None)
-        ]
-
-    if not elems_a or not elems_b:
+    elems = list(ifcopenshell.util.selector.filter_elements(model, selector))
+    if len(elems) < 2:
         return []
 
     tree = ifcopenshell.geom.tree()
     tree.add_file(model, settings)
 
-    clashes = tree.clash_collision_many(elems_a, elems_b, allow_touching=False)
+    clashes = tree.clash_collision_many(elems, elems, allow_touching=False)
 
     pairs: list[list[str]] = []
     seen: set[frozenset[str]] = set()
     for c in clashes:
         guid_a = getattr(c.a, "GlobalId", None)
         guid_b = getattr(c.b, "GlobalId", None)
-        if not guid_a or not guid_b:
+        if not guid_a or not guid_b or guid_a == guid_b:
             continue
         key = frozenset((guid_a, guid_b))
         if key not in seen:
@@ -321,20 +308,16 @@ async def select_endpoint(
 @app.post("/clash")
 async def clash_endpoint(
     ifc: UploadFile = File(...),
-    selector_a: str = Form(...),
-    selector_b: str = Form(""),
+    selector: str = Form(...),
 ) -> Response:
-    """Detect clashing element pairs.
+    """Detect clashing element pairs within the selected set.
 
     Returns JSON ``{"pairs": [["guidA", "guidB"], ...]}``.
-    An empty ``selector_b`` means test set A against all other model elements.
     """
     ifc_bytes = await ifc.read()
 
     try:
-        pairs = run_sandboxed(
-            _sandboxed_clash, ifc_bytes, selector_a, selector_b or None
-        )
+        pairs = run_sandboxed(_sandboxed_clash, ifc_bytes, selector)
     except SandboxCrashError as exc:
         raise HTTPException(status_code=422, detail=f"IFC clash detection crashed: {exc}") from exc
     except SandboxTimeoutError as exc:

ifcurl/service.py

@@ -126,9 +126,7 @@ def _select_via_socket(ifc_bytes: bytes, selector: str) -> list[str]:
     return resp.json()["guids"]
 
 
-def _clash_via_socket(
-    ifc_bytes: bytes, selector_a: str, selector_b: str | None
-) -> list[list[str]]:
+def _clash_via_socket(ifc_bytes: bytes, selector: str) -> list[list[str]]:
     """Delegate clash detection to the render service over the Unix socket."""
     import httpx
 
@@ -137,7 +135,7 @@ def _clash_via_socket(
             resp = client.post(
                 "http://render/clash",
                 files={"ifc": ifc_bytes},
-                data={"selector_a": selector_a, "selector_b": selector_b or ""},
+                data={"selector": selector},
                 timeout=_RENDER_TIMEOUT,
             )
     except httpx.TransportError as exc:
@@ -450,8 +448,6 @@ class QueryRequest(BaseModel):
 
 class ClashRequest(BaseModel):
     url: str
-    selector_b: str | None = None
-    """Second element set to test against. When omitted, set A is tested against all other model elements."""
     token: str | None = None
 
 
@@ -829,21 +825,18 @@ def query(request: QueryRequest) -> JSONResponse:
 
 
 @app.get("/clash")
-def clash_get(url: str, selector_b: str | None = None, token: str | None = None) -> JSONResponse:
+def clash_get(url: str, token: str | None = None) -> JSONResponse:
     """GET variant of POST /clash."""
-    return clash(ClashRequest(url=url, selector_b=selector_b, token=token))
+    return clash(ClashRequest(url=url, token=token))
 
 
 @app.post("/clash")
 def clash(request: ClashRequest) -> JSONResponse:
-    """Detect geometric clashes between two sets of elements.
+    """Detect geometric clashes within the elements matched by the selector.
 
-    Set A is defined by the URL's ``selector=`` parameter.  Set B is defined
-    by ``selector_b``; when omitted, set A is tested against all other
-    model elements.
-
-    Uses ifcopenshell hard-clash (interpenetration) detection.  Returns
-    ``{"pairs": [["<guidA>", "<guidB>"], …]}``.
+    The URL's ``selector=`` parameter defines the set of elements to test
+    against each other.  Uses ifcopenshell hard-clash (interpenetration)
+    detection.  Returns ``{"pairs": [["<guidA>", "<guidB>"], …]}``.
     """
     try:
         ifc_url = IfcUrl.parse(request.url)
@@ -877,11 +870,9 @@ def clash(request: ClashRequest) -> JSONResponse:
 
     try:
         if _RENDER_SOCKET:
-            pairs = _clash_via_socket(ifc_bytes, ifc_url.selector, request.selector_b)
+            pairs = _clash_via_socket(ifc_bytes, ifc_url.selector)
         else:
-            pairs = run_sandboxed(
-                _sandboxed_clash, ifc_bytes, ifc_url.selector, request.selector_b
-            )
+            pairs = run_sandboxed(_sandboxed_clash, ifc_bytes, ifc_url.selector)
     except SandboxCrashError as exc:
         raise HTTPException(
             status_code=422, detail=f"IFC clash detection crashed: {exc}"