feat: retention funnel chart tab with treatment line depth (Task C.1)

dash_app/callbacks/chart.py

@@ -267,6 +267,31 @@ def _render_duration(app_state, title):
     return create_duration_figure(data, title, show_directory=show_directory)
 
 
+def _render_funnel(app_state, title):
+    """Build the retention funnel figure from current filter state."""
+    from dash_app.data.queries import get_retention_funnel
+    from visualization.plotly_generator import create_retention_funnel_figure
+
+    filter_id = (app_state or {}).get("date_filter_id", "all_6mo")
+    chart_type = (app_state or {}).get("chart_type", "directory")
+
+    selected_dirs = (app_state or {}).get("selected_directorates") or []
+    selected_trusts = (app_state or {}).get("selected_trusts") or []
+    directory = selected_dirs[0] if len(selected_dirs) == 1 else None
+    trust = selected_trusts[0] if len(selected_trusts) == 1 else None
+
+    try:
+        data = get_retention_funnel(filter_id, chart_type, directory, trust)
+    except Exception:
+        log.exception("Failed to load retention funnel data")
+        return _empty_figure("Failed to load retention funnel data.")
+
+    if not data:
+        return _empty_figure("No retention data available.\nTry adjusting your filters.")
+
+    return create_retention_funnel_figure(data, title)
+
+
 def register_chart_callbacks(app):
     """Register tab switching, pathway data loading, and chart rendering callbacks."""
 
@@ -407,6 +432,9 @@ def register_chart_callbacks(app):
         elif active_tab == "duration":
             fig = _render_duration(app_state, title)
 
+        elif active_tab == "funnel":
+            fig = _render_funnel(app_state, title)
+
         else:
             # Placeholder for charts not yet implemented
             tab_label = dict(TAB_DEFINITIONS).get(active_tab, active_tab)

dash_app/components/chart_card.py

@@ -8,6 +8,7 @@ TAB_DEFINITIONS = [
     ("icicle", "Icicle"),
     ("sankey", "Sankey"),
     ("heatmap", "Heatmap"),
+    ("funnel", "Funnel"),
 ]
 
 # Full set retained for Trust Comparison dashboard (Phase 10.8)

dash_app/data/queries.py

@@ -24,6 +24,7 @@ from data_processing.pathway_queries import (
     get_trust_heatmap as _get_trust_heatmap,
     get_trust_durations as _get_trust_durations,
     get_directorate_summary as _get_directorate_summary,
+    get_retention_funnel as _get_retention_funnel,
 )
 
 DB_PATH = Path(__file__).resolve().parents[2] / "data" / "pathways.db"
@@ -180,3 +181,16 @@ def get_directorate_summary(
 ) -> list[dict]:
     """Per-directorate summary (name, patient count, drug count) for landing cards."""
     return _get_directorate_summary(DB_PATH, date_filter_id, chart_type)
+
+
+# --- Retention funnel (Phase C) ---
+
+
+def get_retention_funnel(
+    date_filter_id: str = "all_6mo",
+    chart_type: str = "directory",
+    directory: Optional[str] = None,
+    trust: Optional[str] = None,
+) -> list[dict]:
+    """Patient retention by treatment line depth."""
+    return _get_retention_funnel(DB_PATH, date_filter_id, chart_type, directory, trust)