feat: add drawer callbacks for drug selection, fragment matching, and clear (Task 4.2)

IMPLEMENTATION_PLAN.md

@@ -214,13 +214,13 @@ Drawer selection → update_drug_selection → app-state store → load_pathway_
 - **Checkpoint**: Drawer opens with correct layout, all directorates and drugs visible
 
 ### 4.2 Drawer callbacks
-- [ ] Create `dash_app/callbacks/drawer.py`:
+- [x] Create `dash_app/callbacks/drawer.py`:
   - Open/close drawer: sidebar "Drug Selection" or "Indications" click → open drawer
-  - Drug selection: clicking a drug chip → adds drug to `selected_drugs` in `app-state` → triggers chart reload
-  - Indication selection: clicking an indication accordion item → filters to drugs under that indication
-  - Visual highlights: selected drugs get active styling (e.g., blue background on chips)
-  - Clear filters: resets `selected_drugs` and `selected_directorates` in `app-state`
-  - Use pattern-matching callbacks for dynamic drug chips: `@app.callback(..., Input({"type": "drug-chip", "index": ALL}, "n_clicks"))`
+  - Drug selection: ChipGroup value change → app-state.selected_drugs via update_app_state
+  - Drug fragment click: pattern-matching badge clicks → substring match → update chip selection
+  - Clear filters: resets chip selection → app-state.selected_drugs empties
+  - Fragment matching uses `drug.upper() in fragment.upper()` for substring match
+  - Toggle behavior: clicking already-selected fragment deselects matching drugs
 - **Checkpoint**: Select drug from drawer → chart filters to show that drug → clear resets
 
 ---

dash_app/callbacks/__init__.py

@@ -6,7 +6,9 @@ def register_callbacks(app):
     from dash_app.callbacks.filters import register_filter_callbacks
     from dash_app.callbacks.chart import register_chart_callbacks
     from dash_app.callbacks.kpi import register_kpi_callbacks
+    from dash_app.callbacks.drawer import register_drawer_callbacks
 
     register_filter_callbacks(app)
     register_chart_callbacks(app)
     register_kpi_callbacks(app)
+    register_drawer_callbacks(app)

dash_app/callbacks/drawer.py

@@ -0,0 +1,72 @@
+"""Callbacks for the drug browser drawer: open/close, drug selection, fragment matching, clear."""
+from dash import Input, Output, State, ctx, no_update, ALL
+
+
+def register_drawer_callbacks(app):
+    """Register drawer-related callbacks."""
+
+    @app.callback(
+        Output("drug-drawer", "opened"),
+        Input("sidebar-drug-selection", "n_clicks"),
+        Input("sidebar-indications", "n_clicks"),
+        prevent_initial_call=True,
+    )
+    def open_drawer(_drug_clicks, _indication_clicks):
+        """Open the drawer when sidebar Drug Selection or Indications is clicked."""
+        return True
+
+    @app.callback(
+        Output("all-drugs-chips", "value"),
+        Input({"type": "drug-fragment", "index": ALL}, "n_clicks"),
+        Input("clear-drug-filters", "n_clicks"),
+        State("all-drugs-chips", "value"),
+        State("reference-data", "data"),
+        prevent_initial_call=True,
+    )
+    def handle_fragment_or_clear(fragment_clicks, _clear_clicks, current_chips, ref_data):
+        """Handle drug fragment badge click (substring match) or clear all filters.
+
+        Fragment click: find all full drug names containing the fragment substring,
+        toggle them in the chip selection.
+        Clear click: reset chip selection to empty.
+        """
+        triggered = ctx.triggered_id
+
+        # Clear button
+        if triggered == "clear-drug-filters":
+            return []
+
+        # Fragment badge click — triggered_id is a dict like {"type": "drug-fragment", "index": "DIR|FRAG"}
+        if isinstance(triggered, dict) and triggered.get("type") == "drug-fragment":
+            # Check if any fragment was actually clicked (not just initial render)
+            if not any(n for n in (fragment_clicks or []) if n):
+                return no_update
+
+            fragment_key = triggered["index"]  # e.g. "CARDIOLOGY|ABCIXIMAB"
+            fragment = fragment_key.split("|", 1)[-1] if "|" in fragment_key else fragment_key
+
+            # Get all available drugs from reference data
+            all_drugs = (ref_data or {}).get("available_drugs", [])
+
+            # Find drugs whose names contain this fragment (case-insensitive substring)
+            matching_drugs = [
+                drug for drug in all_drugs
+                if fragment.upper() in drug.upper()
+            ]
+
+            if not matching_drugs:
+                return no_update
+
+            # Toggle: if all matching drugs are already selected, deselect them;
+            # otherwise, add them to selection
+            current = set(current_chips or [])
+            all_selected = all(d in current for d in matching_drugs)
+
+            if all_selected:
+                updated = current - set(matching_drugs)
+            else:
+                updated = current | set(matching_drugs)
+
+            return sorted(updated)
+
+        return no_update

dash_app/callbacks/filters.py

@@ -31,12 +31,13 @@ def register_filter_callbacks(app):
         Input("chart-type-indication", "n_clicks"),
         Input("filter-initiated", "value"),
         Input("filter-last-seen", "value"),
+        Input("all-drugs-chips", "value"),
         State("app-state", "data"),
     )
     def update_app_state(
-        _dir_clicks, _ind_clicks, initiated, last_seen, current_state
+        _dir_clicks, _ind_clicks, initiated, last_seen, selected_drugs, current_state
     ):
-        """Update app-state when chart type toggle or date filters change."""
+        """Update app-state when chart type toggle, date filters, or drug chips change."""
         if not current_state:
             current_state = {
                 "chart_type": "directory",
@@ -66,6 +67,7 @@ def register_filter_callbacks(app):
             "initiated": initiated,
             "last_seen": last_seen,
             "date_filter_id": date_filter_id,
+            "selected_drugs": selected_drugs or [],
         }
 
         # Toggle pill CSS classes