fix: make burst impact coverage envelopes exclusive

app/services/burst_impact.py

@@ -139,9 +139,12 @@ def estimate_burst_impact(network: str, start: datetime, simulation: dict[str, A
         return output
     groups = [{key: group[key] for key in ("group_id", "title", "node_ids")}
               for group in impact["grades"]]
-    geometry = generate_node_coverage(network, groups)
+    # GRADES are ordered from low to high. Keep the numerical classes intact
+    # while removing overlap between their independently derived envelopes.
+    geometry = generate_node_coverage(network, groups, exclusive_groups=True)
     impact["coverage_status"] = geometry["coverage"]["status"]
     geometry["coverage"]["boundary"] = impact["boundary"]
+    geometry["coverage"]["boundary"] += "分档包络互斥展示，重叠区域优先显示较高降压档，不改变节点分档或表示精确水力等值边界。"
     for feature in geometry["map_payload"]["features"]:
         feature["properties"].update(
             impact_phase=impact["phase"], pressure_drop_unit="m",

app/services/node_coverage.py

@@ -6,7 +6,7 @@ from typing import Any
 
 from pyproj import CRS, Transformer
 from shapely import MultiPoint, concave_hull, get_num_coordinates
-from shapely.geometry import mapping
+from shapely.geometry import GeometryCollection, mapping, shape
 from shapely.ops import transform, unary_union
 
 from app.native.wndb.gis.network_views import get_node_coverage_links, get_node_geographic_positions
@@ -17,6 +17,47 @@ SIMPLIFY_METERS = 2.0
 MAX_COVERAGE_NODES = 10000
 
 
+def exclusive_coverage_features(features: list[dict[str, Any]]) -> list[dict[str, Any]]:
+    """Clip display envelopes, with later groups taking precedence; retain input order.
+
+    This changes only derived geometry, never node membership or model values.
+    No post-clipping buffer or simplification may reintroduce an overlap.
+    """
+    occupied = GeometryCollection()
+    result = []
+    summaries = {}
+    for feature in features:
+        properties = feature["properties"]
+        summaries.update(properties.get("coverage_group_summary", {}))
+    for feature in features:
+        properties = feature["properties"]
+        summaries[properties["coverage_group"]] = {
+            key: properties.get(key) for key in ("node_count", "mapped_node_count", "missing_node_count")
+        }
+    for feature in reversed(features):
+        original = shape(feature["geometry"])
+        visible = original.difference(occupied)
+        occupied = unary_union([occupied, original])
+        if visible.is_empty:
+            continue
+        if (visible.geom_type not in {"Polygon", "MultiPolygon"} or not visible.is_valid
+                or get_num_coordinates(visible) > 20000):
+            raise ValueError("Invalid exclusive derived coverage")
+        result.append({
+            **feature,
+            "properties": {**feature["properties"], "overlap_policy": "higher_priority_group_first"},
+            "geometry": mapping(visible),
+        })
+    visible_groups = {feature["properties"]["coverage_group"] for feature in result}
+    summaries = {key: {**value, "display_area_available": key in visible_groups}
+                 for key, value in summaries.items()}
+    for feature in result:
+        # Retain counts even when that group's entire display envelope was
+        # clipped away. Overlay transport deliberately sends only GeoJSON.
+        feature["properties"]["coverage_group_summary"] = summaries
+    return list(reversed(result))
+
+
 def _components(node_ids: list[str], links: list[dict[str, Any]], closed: set[str]) -> list[list[str]]:
     parent = {node_id: node_id for node_id in node_ids}
 
@@ -41,6 +82,7 @@ def build_node_coverage(
     links: list[dict[str, Any]], *, split_by_connectivity: bool = False,
     excluded_link_ids: list[str] | None = None,
     concave_ratio: float = CONCAVE_RATIO, buffer_m: float = BUFFER_METERS,
+    exclusive_groups: bool = False,
 ) -> dict[str, Any]:
     """Keep caller-defined comparison groups and derive geometry without assigning business meaning."""
     coordinates = {}
@@ -99,6 +141,12 @@ def build_node_coverage(
         }
         features.append(feature)
 
+    if exclusive_groups:
+        features = exclusive_coverage_features(features)
+        visible_groups = {feature["properties"]["coverage_group"] for feature in features}
+        for group_id, metadata in groups_metadata.items():
+            metadata["display_area_available"] = group_id in visible_groups
+
     return {
         "status": "partial" if any(group["missing_node_ids"] for group in groups_metadata.values())
         else "ready" if features else "empty",
@@ -106,7 +154,8 @@ def build_node_coverage(
         "parameters": {"concave_ratio": concave_ratio, "buffer_m": buffer_m,
                        "split_by_connectivity": split_by_connectivity,
                        "excluded_link_ids": sorted(closed),
-                       "simplify_m": simplify_m, "projection": "local_azimuthal_equidistant"},
+                       "simplify_m": simplify_m, "projection": "local_azimuthal_equidistant",
+                       "exclusive_groups": exclusive_groups},
         "output_crs": "EPSG:4326", "display_only": True,
         "position_source": "gis.node_geometries",
         "boundary": "节点空间覆盖示意；不推断故障、污染、停水、水力影响或用户服务边界。",