feat(actions): implement ActionExecutor with xdotool and pyautogui backends

merlin/actions/executor.py

@@ -0,0 +1,96 @@
+"""
+ActionExecutor — translate action name strings into OS input events.
+
+Backends:
+  xdotool   — Linux X11; requires xdotool package installed
+  pyautogui — cross-platform fallback
+  auto      — detects xdotool at init, falls back to pyautogui
+"""
+
+from __future__ import annotations
+
+import logging
+import os
+import shutil
+import subprocess
+from typing import Literal
+
+# Suppress pyautogui DISPLAY errors on headless systems
+if not os.environ.get("DISPLAY"):
+    os.environ["DISPLAY"] = ":0"
+
+import pyautogui
+
+logger = logging.getLogger(__name__)
+
+Backend = Literal["xdotool", "pyautogui", "auto"]
+
+_XDOTOOL_CLICK: dict[str, list[str]] = {
+    "left_click": ["xdotool", "click", "1"],
+    "right_click": ["xdotool", "click", "3"],
+    "double_click": ["xdotool", "click", "--repeat", "2", "1"],
+    "middle_click": ["xdotool", "click", "2"],
+    "scroll_up": ["xdotool", "click", "4"],
+    "scroll_down": ["xdotool", "click", "5"],
+}
+
+_XDOTOOL_KEY: dict[str, str] = {
+    "key_enter": "Return",
+    "key_escape": "Escape",
+    "key_space": "space",
+    "key_tab": "Tab",
+}
+
+
+class ActionExecutor:
+    def __init__(self, backend: Backend = "auto") -> None:
+        if backend == "auto":
+            self._backend: Backend = (
+                "xdotool" if shutil.which("xdotool") else "pyautogui"
+            )
+        else:
+            self._backend = backend
+
+    def execute(self, action: str) -> None:
+        """Execute a named action. Silently ignores unknown action names."""
+        try:
+            if self._backend == "xdotool":
+                self._xdotool(action)
+            else:
+                self._pyautogui(action)
+        except Exception as exc:
+            logger.warning("ActionExecutor error for action=%r: %s", action, exc)
+
+    def _xdotool(self, action: str) -> None:
+        if action in _XDOTOOL_CLICK:
+            subprocess.run(_XDOTOOL_CLICK[action], capture_output=True)
+        elif action in _XDOTOOL_KEY:
+            subprocess.run(
+                ["xdotool", "key", _XDOTOOL_KEY[action]], capture_output=True
+            )
+        elif action.startswith("drag_start"):
+            subprocess.run(["xdotool", "mousedown", "1"], capture_output=True)
+        elif action.startswith("drag_end"):
+            subprocess.run(["xdotool", "mouseup", "1"], capture_output=True)
+        else:
+            logger.warning("xdotool: unknown action %r", action)
+
+    def _pyautogui(self, action: str) -> None:
+        if action == "left_click":
+            pyautogui.click()
+        elif action == "right_click":
+            pyautogui.rightClick()
+        elif action == "double_click":
+            pyautogui.doubleClick()
+        elif action == "scroll_up":
+            pyautogui.scroll(3)
+        elif action == "scroll_down":
+            pyautogui.scroll(-3)
+        elif action == "key_enter":
+            pyautogui.press("enter")
+        elif action == "key_escape":
+            pyautogui.press("escape")
+        elif action == "key_space":
+            pyautogui.press("space")
+        else:
+            logger.warning("pyautogui: unknown action %r", action)

tests/test_actions/test_executor.py

@@ -0,0 +1,48 @@
+from unittest.mock import patch, MagicMock
+from merlin.actions.executor import ActionExecutor
+
+
+@patch("merlin.actions.executor.subprocess")
+def test_left_click_calls_xdotool(mock_sub):
+    ex = ActionExecutor(backend="xdotool")
+    ex.execute("left_click")
+    mock_sub.run.assert_called_once_with(["xdotool", "click", "1"], capture_output=True)
+
+
+@patch("merlin.actions.executor.subprocess")
+def test_right_click_calls_xdotool(mock_sub):
+    ex = ActionExecutor(backend="xdotool")
+    ex.execute("right_click")
+    mock_sub.run.assert_called_once_with(["xdotool", "click", "3"], capture_output=True)
+
+
+@patch("merlin.actions.executor.subprocess")
+def test_double_click_calls_xdotool(mock_sub):
+    ex = ActionExecutor(backend="xdotool")
+    ex.execute("double_click")
+    mock_sub.run.assert_called_once_with(
+        ["xdotool", "click", "--repeat", "2", "1"], capture_output=True
+    )
+
+
+@patch("merlin.actions.executor.subprocess")
+def test_key_enter(mock_sub):
+    ex = ActionExecutor(backend="xdotool")
+    ex.execute("key_enter")
+    mock_sub.run.assert_called_once_with(
+        ["xdotool", "key", "Return"], capture_output=True
+    )
+
+
+@patch("merlin.actions.executor.subprocess")
+def test_unknown_action_does_not_raise(mock_sub):
+    ex = ActionExecutor(backend="xdotool")
+    ex.execute("nonexistent_action")
+    mock_sub.run.assert_not_called()
+
+
+@patch("merlin.actions.executor.pyautogui")
+def test_pyautogui_fallback_left_click(mock_pag):
+    ex = ActionExecutor(backend="pyautogui")
+    ex.execute("left_click")
+    mock_pag.click.assert_called_once()