lgtm 2

server-rs/src/routes/postcode_stats.rs

@@ -10,13 +10,13 @@ use tracing::{info, warn};
 use crate::auth::OptionalUser;
 use crate::consts::POSTCODE_SEARCH_OFFSET;
 use crate::licensing::{check_license_point, resolve_share_code};
-use crate::parsing::{
-    parse_field_set, parse_filters_with_poi, row_passes_filters, row_passes_poi_filters,
-};
+use crate::parsing::{parse_filters_with_poi, row_passes_filters, row_passes_poi_filters};
 use crate::state::SharedState;
 use crate::utils::normalize_postcode;
 
-use super::hexagon_stats::HexagonStatsResponse;
+use super::hexagon_stats::{
+    parse_area_stats_field_set, top_filter_exclusions, HexagonStatsResponse,
+};
 use super::stats;
 use super::travel_time::{load_travel_data, parse_optional_travel, row_passes_travel_filters};
 
@@ -24,8 +24,9 @@ use super::travel_time::{load_travel_data, parse_optional_travel, row_passes_tra
 pub struct PostcodeStatsParams {
     pub postcode: String,
     pub filters: Option<String>,
-    /// Comma-separated feature names to include in stats response.
-    /// Only listed features are computed; if absent or empty, no features are returned.
+    /// `;;`-separated feature names to include in stats response.
+    /// Only listed features are computed. If absent, area stats default to
+    /// displayable groups; if empty, no feature stats are returned.
     pub fields: Option<String>,
     /// Pipe-separated travel time entries: `mode:slug|mode:slug:min:max`.
     /// Optional min:max applies as a filter (exclude properties outside range).
@@ -80,7 +81,7 @@ pub async fn get_postcode_stats(
     let filters_str = params.filters;
     let has_poi_filters = !parsed_poi_filters.is_empty();
 
-    let (fields_specified, field_set) = parse_field_set(params.fields.as_deref());
+    let (fields_specified, field_set) = parse_area_stats_field_set(params.fields.as_deref());
     let travel_entries = parse_optional_travel(params.travel.as_deref())
         .map_err(|err| (StatusCode::BAD_REQUEST, err).into_response())?;
 
@@ -100,26 +101,26 @@ pub async fn get_postcode_stats(
         let min_lon = centroid_lon as f64 - offset;
         let max_lon = centroid_lon as f64 + offset;
 
+        let mut area_rows: Vec<usize> = Vec::new();
         let mut matching_rows: Vec<usize> = Vec::new();
         state
             .grid
             .for_each_in_bounds(min_lat, min_lon, max_lat, max_lon, |row_idx| {
                 let row = row_idx as usize;
                 let row_postcode = state.data.postcode(row);
-                if row_postcode == postcode_str
-                    && row_passes_filters(
-                        row,
-                        &parsed_filters,
-                        &parsed_enum_filters,
-                        feature_data,
-                        num_features,
-                    )
-                    && (!has_poi_filters
-                        || row_passes_poi_filters(
-                            row,
-                            &parsed_poi_filters,
-                            &state.data.poi_metrics,
-                        ))
+                if row_postcode != postcode_str {
+                    return;
+                }
+
+                area_rows.push(row);
+                if row_passes_filters(
+                    row,
+                    &parsed_filters,
+                    &parsed_enum_filters,
+                    feature_data,
+                    num_features,
+                ) && (!has_poi_filters
+                    || row_passes_poi_filters(row, &parsed_poi_filters, &state.data.poi_metrics))
                 {
                     if has_travel
                         && !row_passes_travel_filters(row_postcode, &travel_entries, &travel_data)
@@ -131,6 +132,19 @@ pub async fn get_postcode_stats(
             });
 
         let total_count = matching_rows.len();
+        let filter_exclusions = if total_count == 0 {
+            top_filter_exclusions(
+                &area_rows,
+                &parsed_filters,
+                &parsed_enum_filters,
+                &parsed_poi_filters,
+                &travel_entries,
+                &travel_data,
+                &state.data,
+            )
+        } else {
+            Vec::new()
+        };
 
         let price_history =
             stats::extract_price_history(&matching_rows, &state.data, &state.feature_name_to_index);
@@ -168,6 +182,7 @@ pub async fn get_postcode_stats(
             enum_features: enum_features_out,
             price_history,
             central_postcode: None,
+            filter_exclusions,
         })
     })
     .await