feat: request assets in a separate thread (#954)

sepal_ui/scripts/thread_controller.py

@@ -0,0 +1,119 @@
+"""Controller for running long-running tasks in a separate thread."""
+
+import threading
+from typing import Callable, List, Optional
+
+import sepal_ui.sepalwidgets as sw
+
+
+class TaskController:
+    def __init__(
+        self,
+        function: Callable,
+        callback: Optional[Callable] = None,
+        alert: Optional[sw.Alert] = None,
+        start_button: Optional[sw.Btn] = None,
+        stop_button: Optional[sw.Btn] = None,
+        disable_components: Optional[List] = None,
+        *function_args,
+        **function_kwargs,
+    ):
+        """Initializes the TaskController.
+
+        Args:
+            function: The long-running function to execute.
+            callback: A function to call with the result after the task completes.
+            alert: An optional alert widget for displaying messages.
+            start_button: An optional button to start the task.
+            stop_button: An optional button to stop the task.
+            disable_components: A list of components to disable while the task is running.
+            *function_args: Positional arguments for the function.
+            **function_kwargs: Keyword arguments for the function.
+        """
+        self.alert = alert
+        self.function = function
+        self.function_args = function_args
+        self.function_kwargs = function_kwargs
+        self.callback = callback
+        self.disable_components = disable_components or []
+
+        self.start_button = start_button
+        self.stop_button = stop_button
+
+        self.task_thread = None
+        self.stop_event = threading.Event()
+
+        # Set up event handlers if buttons are provided
+        if self.start_button is not None:
+            self.start_button.on_event("click", self.start_task)
+        if self.stop_button is not None:
+            self.stop_button.on_event("click", self.stop_task)
+
+    def start_task(self, *args):
+        """Starts the long-running task in a separate thread."""
+        print("Starting task...")
+        if self.task_thread is not None and self.task_thread.is_alive():
+            # Task is already running
+            return
+
+        try:
+            # Clear the stop event
+            self.stop_event.clear()
+
+            # Disable components
+            self.set_components_enabled(False)
+
+            # Reset the alert if provided
+            if self.alert is not None:
+                self.alert.reset()
+
+            # Start the task thread
+            self.task_thread = threading.Thread(target=self._run_task)
+            self.task_thread.start()
+
+            print("Task started.")
+        except Exception as e:
+            print(f"Exception in start_task: {e}")
+
+    def _run_task(self):
+        """Runs the long-running task and handles completion."""
+        try:
+            if self.start_button is not None:
+                self.start_button.loading = True
+
+            # Run the user's function
+            result = self.function(*self.function_args, **self.function_kwargs)
+
+            # Call the callback with the result, if provided
+            if self.callback:
+                self.callback(result)
+
+        except Exception as e:
+            # Handle exceptions and display an error message
+            print(f"Exception in _run_task: {e}")
+            if self.alert is not None:
+                self.alert.append_msg(f"Error occurred: {e}", type_="error")
+        finally:
+            # Re-enable components
+            self.set_components_enabled(True)
+
+            if self.start_button is not None:
+                self.start_button.loading = False
+            if self.stop_button is not None:
+                self.stop_button.loading = False
+
+    def stop_task(self, *args):
+        """Signals the task to stop."""
+        if self.stop_button is not None:
+            self.stop_button.loading = True
+
+        # Signal the task to stop
+        self.stop_event.set()
+
+        if self.alert is not None:
+            self.alert.append_msg("The process was interrupted by the user.", type_="warning")
+
+    def set_components_enabled(self, enabled: bool):
+        """Enables or disables UI components."""
+        for component in self.disable_components:
+            component.disabled = not enabled

sepal_ui/sepalwidgets/inputs.py

@@ -31,6 +31,7 @@
 from sepal_ui.scripts import decorator as sd
 from sepal_ui.scripts import gee
 from sepal_ui.scripts import utils as su
+from sepal_ui.scripts.thread_controller import TaskController
 from sepal_ui.sepalwidgets.btn import Btn
 from sepal_ui.sepalwidgets.sepalwidget import SepalWidget
 
@@ -711,10 +712,8 @@ def __init__(
 
         # load the assets in the combobox
 
-        if not self._initial_assets:
-            self._initial_assets.extend(gee.get_assets(self.folder))
-
-        self._get_items(gee_assets=self._initial_assets)
+        task_controller = TaskController(self._get_items, gee_assets=self._initial_assets)
+        task_controller.start_task()
 
         self._fill_no_data({})
         # add js behaviours
@@ -767,6 +766,9 @@ def _validate(self, change: dict) -> None:
 
     @sd.switch("loading", "disabled")
     def _get_items(self, *args, gee_assets: List[dict] = None) -> Self:
+
+        if not self._initial_assets:
+            self._initial_assets.extend(gee.get_assets(self.folder))
         # init the item list
         items = []