Remember the selected time period within the user's session.

I chose to set the session data with the /chart instead of the /chart_data endpoints (for sensors and assets), because the former endpoint can be called without the need to call the latter (using include_data=true). Right now both the sensor and asset page are calling the /chart endpoint with each date pick.

flexmeasures/api/dev/sensors.py

@@ -18,6 +18,7 @@
 from flexmeasures.data.models.generic_assets import GenericAsset
 from flexmeasures.data.models.time_series import Sensor
 from flexmeasures.data.services.annotations import prepare_annotations_for_chart
+from flexmeasures.ui.utils.view_utils import set_time_range_for_session
 
 
 class SensorAPI(FlaskView):
@@ -55,6 +56,7 @@ def get_chart(self, id: int, sensor: Sensor, **kwargs):
 
         .. :quickref: Chart; Download a chart with time series
         """
+        set_time_range_for_session()
         return json.dumps(sensor.chart(**kwargs))
 
     @route("/<id>/chart_data/")

flexmeasures/api/v3_0/assets.py

@@ -15,6 +15,7 @@
 from flexmeasures.data.schemas.generic_assets import GenericAssetSchema as AssetSchema
 from flexmeasures.api.common.schemas.generic_assets import AssetIdField
 from flexmeasures.api.common.schemas.users import AccountIdField
+from flexmeasures.ui.utils.view_utils import set_time_range_for_session
 
 
 asset_schema = AssetSchema()
@@ -282,6 +283,7 @@ def get_chart(self, id: int, asset: GenericAsset, **kwargs):
 
         .. :quickref: Chart; Download a chart with time series
         """
+        set_time_range_for_session()
         return json.dumps(asset.chart(**kwargs))
 
     @route("/<id>/chart_data/")

flexmeasures/ui/templates/crud/asset.html

@@ -279,13 +279,26 @@ <h3>All sensors for {{ asset.name }}</h3>
           start.setHours(0,0,0,0) // get start of first day
           end.setHours(0,0,0,0) // get start of last day
 
-          // Initialize picker to the last 2 days of sensor data
-          var nearEnd = new Date(end)//.setDate(end.getDate() - 1)
-          nearEnd.setDate(nearEnd.getDate() - 1)
-          picker.setDateRange(
-            nearEnd,
-            end,
-          );
+          {% if event_starts_after and event_ends_before %}
+                // Initialize picker to the date selection specified in the session
+                var sessionStart = new Date('{{ event_starts_after }}');
+                var sessionEnd = new Date('{{ event_ends_before }}')
+                sessionEnd.setSeconds(sessionEnd.getSeconds() - 1); // -1 second in case most recent event ends at midnight
+                sessionStart.setHours(0,0,0,0) // get start of first day
+                sessionEnd.setHours(0,0,0,0) // get start of last day
+                picker.setDateRange(
+                  sessionStart,
+                  sessionEnd,
+                );
+              {% else %}
+                // Initialize picker to the last 2 days of sensor data
+                var nearEnd = new Date(end)//.setDate(end.getDate() - 1)
+                nearEnd.setDate(nearEnd.getDate() - 1)
+                picker.setDateRange(
+                  nearEnd,
+                  end,
+                );
+              {% endif %}
 
           // No use looking for data in years outside timerange of sensor data
           picker.setOptions({

flexmeasures/ui/templates/views/sensors.html

@@ -154,13 +154,26 @@
               start.setHours(0,0,0,0) // get start of first day
               end.setHours(0,0,0,0) // get start of last day
 
-              // Initialize picker to the last 2 days of sensor data
-              var nearEnd = new Date(end)//.setDate(end.getDate() - 1)
-              nearEnd.setDate(nearEnd.getDate() - 1)
-              picker.setDateRange(
-                nearEnd,
-                end,
-              );
+              {% if event_starts_after and event_ends_before %}
+                // Initialize picker to the date selection specified in the session
+                var sessionStart = new Date('{{ event_starts_after }}');
+                var sessionEnd = new Date('{{ event_ends_before }}')
+                sessionEnd.setSeconds(sessionEnd.getSeconds() - 1); // -1 second in case most recent event ends at midnight
+                sessionStart.setHours(0,0,0,0) // get start of first day
+                sessionEnd.setHours(0,0,0,0) // get start of last day
+                picker.setDateRange(
+                  sessionStart,
+                  sessionEnd,
+                );
+              {% else %}
+                // Initialize picker to the last 2 days of sensor data
+                var nearEnd = new Date(end)//.setDate(end.getDate() - 1)
+                nearEnd.setDate(nearEnd.getDate() - 1)
+                picker.setDateRange(
+                  nearEnd,
+                  end,
+                );
+              {% endif %}
 
               // No use looking for data in years outside timerange of sensor data
               picker.setOptions({

flexmeasures/ui/utils/view_utils.py

@@ -47,6 +47,9 @@ def render_flexmeasures_template(html_filename: str, **variables):
     if "end_time" in session:
         variables["end_time"] = session["end_time"]
 
+    variables["event_starts_after"] = session.get("event_starts_after")
+    variables["event_ends_before"] = session.get("event_ends_before")
+
     variables["page"] = html_filename.split("/")[-1].replace(".html", "")
     if "show_datepicker" not in variables:
         variables["show_datepicker"] = variables["page"] in ("analytics", "portfolio")
@@ -113,10 +116,17 @@ def clear_session():
 
 
 def set_time_range_for_session():
-    """Set period (start_date, end_date and resolution) on session if they are not yet set.
-    The datepicker sends times as tz-aware UTC strings.
+    """Set period on session if they are not yet set.
+    The daterangepicker sends times as tz-aware UTC strings.
     We re-interpret them as being in the server's timezone.
-    Also set the forecast horizon, if given."""
+    Also set the forecast horizon, if given.
+
+    TODO: event_[stars|ends]_before are used on the new asset and sensor pages.
+          We simply store the UTC strings.
+          It might be that the other settings & logic can be deprecated when we clean house.
+          Tip: grep for timerangeEnd, where end_time is used in our base template,
+               and then used in the daterangepicker. We seem to use litepicker now.
+    """
     if "start_time" in request.values:
         session["start_time"] = time_utils.localized_datetime(
             iso8601.parse_date(request.values.get("start_time"))
@@ -129,6 +139,8 @@ def set_time_range_for_session():
         ):  # session storage seems to lose tz info and becomes UTC
             session["start_time"] = time_utils.as_server_time(session["start_time"])
 
+    session["event_starts_after"] = request.values.get("event_starts_after")
+    session["event_ends_before"] = request.values.get("event_ends_before")
     if "end_time" in request.values:
         session["end_time"] = time_utils.localized_datetime(
             iso8601.parse_date(request.values.get("end_time"))