Add manual channel jog helpers for OT-2 (#767)

Co-authored-by: hazlamshamin <hazlamshamin@github.com>

Author: hazlamshamin

pylabrobot/liquid_handling/backends/opentrons_backend.py

@@ -1,5 +1,5 @@
 import uuid
-from typing import Dict, List, Optional, Union, cast
+from typing import Dict, List, Optional, Tuple, Union, cast
 
 from pylabrobot import utils
 from pylabrobot.liquid_handling.backends.backend import (
@@ -579,6 +579,61 @@ async def list_connected_modules(self) -> List[dict]:
     """List all connected temperature modules."""
     return cast(List[dict], ot_api.modules.list_connected_modules())
 
+  def _pipette_id_for_channel(self, channel: int) -> str:
+    pipettes = []
+    if self.left_pipette is not None:
+      pipettes.append(self.left_pipette["pipetteId"])
+    if self.right_pipette is not None:
+      pipettes.append(self.right_pipette["pipetteId"])
+    if channel < 0 or channel >= len(pipettes):
+      raise NoChannelError(f"Channel {channel} not available on this OT-2 setup.")
+    return pipettes[channel]
+
+  def _current_channel_position(self, channel: int) -> Tuple[str, Coordinate]:
+    """Return the pipette id and current coordinate for a given channel."""
+
+    pipette_id = self._pipette_id_for_channel(channel)
+    try:
+      res = ot_api.lh.save_position(pipette_id=pipette_id)
+      pos = res["data"]["result"]["position"]
+      current = Coordinate(pos["x"], pos["y"], pos["z"])
+    except Exception as exc:  # noqa: BLE001
+      raise RuntimeError("Failed to query current pipette position") from exc
+
+    return pipette_id, current
+
+  async def prepare_for_manual_channel_operation(self, channel: int):
+    """Validate channel exists (no-op otherwise for OT-2)."""
+
+    _ = self._pipette_id_for_channel(channel)
+
+  async def move_channel_x(self, channel: int, x: float):
+    """Move a channel to an absolute x coordinate using savePosition to seed pose."""
+
+    pipette_id, current = self._current_channel_position(channel)
+    target = Coordinate(x=x, y=current.y, z=current.z)
+    await self.move_pipette_head(
+      location=target, minimum_z_height=self.traversal_height, pipette_id=pipette_id
+    )
+
+  async def move_channel_y(self, channel: int, y: float):
+    """Move a channel to an absolute y coordinate using savePosition to seed pose."""
+
+    pipette_id, current = self._current_channel_position(channel)
+    target = Coordinate(x=current.x, y=y, z=current.z)
+    await self.move_pipette_head(
+      location=target, minimum_z_height=self.traversal_height, pipette_id=pipette_id
+    )
+
+  async def move_channel_z(self, channel: int, z: float):
+    """Move a channel to an absolute z coordinate using savePosition to seed pose."""
+
+    pipette_id, current = self._current_channel_position(channel)
+    target = Coordinate(x=current.x, y=current.y, z=z)
+    await self.move_pipette_head(
+      location=target, minimum_z_height=self.traversal_height, pipette_id=pipette_id
+    )
+
   async def move_pipette_head(
     self,
     location: Coordinate,