Add Conditional Execution Support with IfNode

example.py

@@ -30,6 +30,7 @@
     MissionRuntimeOptions,
     MissionStepSetData,
     MissionStepPoseWaypoint,
+    MissionStepIf,
     Pose,
 )
 from inorbit_edge_executor.worker_pool import WorkerPool
@@ -121,8 +122,11 @@ async def main():
             "state": "starting",
             "label": "Example inorbit_edge_executor mission",
             "tasks": [
+                {"taskId": "step 0", "label": "Step 0"},
                 {"taskId": "step 1", "label": "Step 1"},
                 {"taskId": "step 2", "label": "Step 2"},
+                {"taskId": "step 3", "label": "Then waypoint A"},
+                {"taskId": "step 4", "label": "Else waypoint B"},
             ],
         },
     )
@@ -135,13 +139,66 @@ async def main():
         definition=MissionDefinition(
             label="A mission definition",
             steps=[
-                MissionStepSetData(
-                    label="set some data", completeTask="step 1", data={"key": "value"}
+                MissionStepSetData.model_validate(
+                    {
+                        "label": "set some data",
+                        "completeTask": "step 0",
+                        "data": {"key": "value"},
+                    }
                 ),
-                MissionStepPoseWaypoint(
-                    label="go to waypoint",
-                    completeTask="step 2",
-                    waypoint=Pose(x=0, y=0, theta=0, frameId="map", waypointId="wp1"),
+                MissionStepSetData.model_validate(
+                    {
+                        "label": "set more data",
+                        "completeTask": "step 1",
+                        "data": {"key2": "value2"},
+                    }
+                ),
+                MissionStepPoseWaypoint.model_validate(
+                    {
+                        "label": "go to waypoint",
+                        "completeTask": "step 2",
+                        "waypoint": {
+                            "x": 0,
+                            "y": 0,
+                            "theta": 0,
+                            "frameId": "map",
+                            "waypointId": "wp1",
+                        },
+                    }
+                ),
+                MissionStepIf.model_validate(
+                    {
+                        "label": "if",
+                        "if": {
+                            "expression": "0 > 1",
+                            "then": [
+                                {
+                                    "label": "go to waypoint A",
+                                    "completeTask": "step 3",
+                                    "waypoint": {
+                                        "x": 0,
+                                        "y": 0,
+                                        "theta": 0,
+                                        "frameId": "map",
+                                        "waypointId": "wpA",
+                                    },
+                                },
+                            ],
+                            "else": [
+                                {
+                                    "label": "go to waypoint B",
+                                    "completeTask": "step 4",
+                                    "waypoint": {
+                                        "x": 0,
+                                        "y": 0,
+                                        "theta": 0,
+                                        "frameId": "map",
+                                        "waypointId": "wpB",
+                                    },
+                                },
+                            ],
+                        },
+                    }
                 ),
             ],
         ),

inorbit_edge_executor/behavior_tree.py

@@ -26,11 +26,13 @@
 from typing import Dict
 from typing import List
 from typing import Union
+from typing import Callable
 
 from async_timeout import timeout
 
 from .datatypes import MissionRuntimeOptions
 from .datatypes import MissionRuntimeSharedMemory
+from .datatypes import MissionStep
 from .datatypes import MissionStepPoseWaypoint
 from .datatypes import MissionStepRunAction
 from .datatypes import MissionStepSetData
@@ -686,6 +688,119 @@ def from_object(cls, context, expression, target=None, **kwargs):
         return WaitExpressionNode(context, expression, target, **kwargs)
 
 
+class IfNode(BehaviorTree):
+    """
+    Node that evaluates an expression once and conditionally executes either a "then" or "else"
+    branch based on the result. The expression is evaluated through REST APIs, normally in the same
+    robot that executes the mission.
+    """
+
+    def __init__(
+        self,
+        context: BehaviorTreeBuilderContext,
+        expression: str,
+        then_branch: BehaviorTree,
+        else_branch: BehaviorTree = None,
+        target: Target = None,
+        retry_wait_secs: float = 3,
+        **kwargs,
+    ):
+        super().__init__(**kwargs)
+        self.expression = expression
+        self.retry_wait_secs = retry_wait_secs
+        self.then_branch = then_branch
+        self.else_branch = else_branch
+        self.target = target
+        if self.target is None:
+            self.robot = context.robot_api
+        else:
+            self.robot = context.robot_api_factory.build(self.target.robot_id)
+
+    async def _execute(self):
+        logger.debug(f"evaluating expression {self.expression} on {self.robot.robot_id}")
+        try:
+            result = None
+            max_attempts = 5
+            for attempt in range(1, max_attempts + 1):
+                try:
+                    logger.debug(
+                        f"Attempt {attempt}/{max_attempts} to evaluate expression: {self.expression}"
+                    )
+                    result = await self.robot.evaluate_expression(self.expression)
+                    break
+                except Exception as e:
+                    logger.warning(
+                        f"Attempt {attempt} failed for expression {self.expression}: {e}"
+                    )
+                    if attempt < max_attempts:
+                        await asyncio.sleep(self.retry_wait_secs)
+                    else:
+                        logger.error(
+                            f"All {max_attempts} attempts failed for expression {self.expression}"
+                        )
+                        raise
+        except Exception as e:
+            logger.error(f"Error evaluating expression {self.expression}: {e}")
+            raise e
+
+        if result:
+            logger.debug(f"expression {self.expression} == true, executing then branch")
+            await self.then_branch.execute()
+            self.state = self.then_branch.state
+            self.last_error = self.then_branch.last_error
+        else:
+            if self.else_branch is not None:
+                logger.debug(f"expression {self.expression} == false, executing else branch")
+                await self.else_branch.execute()
+                self.state = self.else_branch.state
+                self.last_error = self.else_branch.last_error
+            else:
+                logger.debug(f"expression {self.expression} == false, no else branch, succeeding")
+                # No else branch, succeed (no-op)
+                self.state = NODE_STATE_SUCCESS
+                self.last_error = ""
+
+    def reset_execution(self):
+        super().reset_execution()
+        if self.then_branch:
+            self.then_branch.reset_execution()
+        if self.else_branch:
+            self.else_branch.reset_execution()
+
+    def reset_handlers_execution(self):
+        super().reset_handlers_execution()
+        if self.then_branch:
+            self.then_branch.reset_handlers_execution()
+        if self.else_branch:
+            self.else_branch.reset_handlers_execution()
+
+    def collect_nodes(self, nodes_list: List):
+        super().collect_nodes(nodes_list)
+        if self.then_branch:
+            self.then_branch.collect_nodes(nodes_list)
+        if self.else_branch:
+            self.else_branch.collect_nodes(nodes_list)
+
+    def dump_object(self):
+        object = super().dump_object()
+        object["expression"] = self.expression
+        object["then_branch"] = self.then_branch.dump_object()
+        if self.else_branch is not None:
+            object["else_branch"] = self.else_branch.dump_object()
+        if self.target is not None:
+            object["target"] = self.target.dump_object()
+        object["retry_wait_secs"] = self.retry_wait_secs
+        return object
+
+    @classmethod
+    def from_object(cls, context, expression, then_branch, else_branch=None, target=None, **kwargs):
+        then_branch_tree = build_tree_from_object(context, then_branch)
+        else_branch_tree = build_tree_from_object(context, else_branch) if else_branch else None
+        if target is not None:
+            target = Target.from_object(**target)
+        return IfNode(context, expression, then_branch_tree, else_branch_tree, target, **kwargs)
+
+
 class DummyNode(BehaviorTree):
     async def _execute(self):
         pass
@@ -983,6 +1098,11 @@ def from_object(cls, context, node_state, **kwargs):
 
 class NodeFromStepBuilder:
     def __init__(self, context: BehaviorTreeBuilderContext):
+        """
+        Implements the visitor pattern for building behavior tree nodes from mission steps.
+        Args:
+            context: The behavior tree builder context.
+        """
         self.context = context
         self.waypoint_distance_tolerance = WAYPOINT_DISTANCE_TOLERANCE_DEFAULT
         self.waypoint_angular_tolerance = WAYPOINT_ANGULAR_TOLERANCE_DEFAULT
@@ -1001,6 +1121,27 @@ def __init__(self, context: BehaviorTreeBuilderContext):
             if WAYPOINT_ANGULAR_TOLERANCE in args:
                 self.waypoint_angular_tolerance = float(args[WAYPOINT_ANGULAR_TOLERANCE])
 
+    def add_step_node_decorator(
+        self, step_decorator_fn: Callable[[MissionStep, BehaviorTree], BehaviorTree]
+    ):
+        # Patch all visit_* methods so that they call the step decorator around the real core node
+        for attr_name in dir(self):
+            if attr_name.startswith("visit_") and callable(getattr(self, attr_name)):
+                orig_method = getattr(self, attr_name)
+                # Don't double-wrap if it's already wrapped (avoid recursion)
+                if hasattr(orig_method, "__wrapped_with_step_wrapper__"):
+                    continue
+
+                def make_wrapped(orig_method):
+                    def visit_method(step):
+                        core_node = orig_method(step)
+                        return step_decorator_fn(step, core_node)
+
+                    visit_method.__wrapped_with_step_wrapper__ = True
+                    return visit_method
+
+                setattr(self, attr_name, make_wrapped(orig_method))
+
     def visit_wait(self, step: MissionStepWait):
         return WaitNode(self.context, step.timeout_secs, label=step.label)
 
@@ -1117,7 +1258,32 @@ def visit_wait_until(self, step: MissionStepWaitUntil):
         )
 
     def visit_if(self, step: MissionStepIf):
-        raise NotImplementedError("visit_if not implemented")
+        # Build the behavior tree nodes for the then branch
+        then_label = f"{step.label} - then" if step.label else "then"
+        then_branch = BehaviorTreeSequential(label=then_label)
+        for then_step in step.then:
+            node = then_step.accept(self)
+            if node:
+                then_branch.add_node(node)
+        # Build the behavior tree nodes for the else branch (if it exists)
+        else_branch = None
+        if step.else_ is not None:
+            else_label = f"{step.label} - else" if step.label else "else"
+            else_branch = BehaviorTreeSequential(label=else_label)
+            for else_step in step.else_:
+                node = else_step.accept(self)
+                if node:
+                    else_branch.add_node(node)
+        # Create the if node
+        if_node = IfNode(
+            context=self.context,
+            expression=step.expression,
+            then_branch=then_branch,
+            else_branch=else_branch,
+            target=step.target,
+            label=step.label,
+        )
+        return if_node
 
 
 # List of accepted node types (classes). With register_accepted_node_types(),
@@ -1128,6 +1294,7 @@ def visit_if(self, step: MissionStepIf):
     WaitNode,
     RunActionNode,
     WaitExpressionNode,
+    IfNode,
     DummyNode,
     TimeoutNode,
     MissionStartNode,
@@ -1181,41 +1348,70 @@ def __init__(self, step_builder_factory: NodeFromStepBuilder = None, *args, **kw
             step_builder_factory if step_builder_factory else NodeFromStepBuilder
         )
 
-    def build_tree_for_mission(self, context: BehaviorTreeBuilderContext) -> BehaviorTree:
-        mission = context.mission
-        tree = BehaviorTreeSequential(label=f"mission {mission.id}")
-        tree.add_node(MissionInProgressNode(context, label="mission start"))
-        step_builder = self._step_builder_factory(context)
-
-        for step, ix in zip(mission.definition.steps, range(len(mission.definition.steps))):
-            # TODO build the right kind of behavior node
-            try:
-                node = step.accept(step_builder)
-            except Exception as e:  # TODO
-                raise Exception(f"Error building step #{ix} [{step}]: {str(e)}")
-            # Before every step, keep robot locked
-            tree.add_node(LockRobotNode(context, label="lock robot"))
-            if step.timeout_secs is not None and type(node) not in (WaitNode, TimeoutNode):
-                node = TimeoutNode(step.timeout_secs, node, label=f"timeout for {step.label}")
+    def _build_step_decorator_for_context(
+        self, context: BehaviorTreeBuilderContext
+    ) -> Callable[[MissionStep, BehaviorTree], BehaviorTreeSequential]:
+        def _step_decorator_fn(
+            step: MissionStep, core_node: BehaviorTree
+        ) -> BehaviorTreeSequential:
+            """
+            Wraps a step node with lock robot, timeout, and task tracking nodes.
+            Returns a BehaviorTreeSequential containing all necessary nodes for the step.
+            """
+            sequential = BehaviorTreeSequential(label=step.label)
+
+            # Always add lock robot node before the step
+            sequential.add_node(LockRobotNode(context, label="lock robot"))
+
+            # Add task started node if complete_task is set
             if step.complete_task is not None:
-                tree.add_node(
+                sequential.add_node(
                     TaskStartedNode(
                         context,
                         step.complete_task,
                         label=f"report task {step.complete_task} started",
                     )
                 )
-            if node:
-                tree.add_node(node)
+
+            # Wrap core node in TimeoutNode if timeout_secs is set and node is not already WaitNode or TimeoutNode
+            if step.timeout_secs is not None and type(core_node) not in (WaitNode, TimeoutNode):
+                core_node = TimeoutNode(
+                    step.timeout_secs, core_node, label=f"timeout for {step.label}"
+                )
+
+            # Add the core node (possibly wrapped in TimeoutNode)
+            if core_node:
+                sequential.add_node(core_node)
+
+            # Add task completed node if complete_task is set
             if step.complete_task is not None:
-                tree.add_node(
+                sequential.add_node(
                     TaskCompletedNode(
                         context,
                         step.complete_task,
                         label=f"report task {step.complete_task} completed",
                     )
                 )
 
+            return sequential
+
+        return _step_decorator_fn
+
+    def build_tree_for_mission(self, context: BehaviorTreeBuilderContext) -> BehaviorTree:
+        mission = context.mission
+        tree = BehaviorTreeSequential(label=f"mission {mission.id}")
+        tree.add_node(MissionInProgressNode(context, label="mission start"))
+        step_builder = self._step_builder_factory(context)
+        step_builder.add_step_node_decorator(self._build_step_decorator_for_context(context))
+
+        for step, ix in zip(mission.definition.steps, range(len(mission.definition.steps))):
+            try:
+                node = step.accept(step_builder)
+            except Exception as e:  # TODO
+                raise Exception(f"Error building step #{ix} [{step}]: {str(e)}")
+            if node:
+                tree.add_node(node)
+
         tree.add_node(MissionCompletedNode(context, label="mission completed"))
         tree.add_node(UnlockRobotNode(context, label="unlock robot after mission completed"))
         # add error handlers