feat: implement Open With functionality for file chooser integration

tests/unit/test_main_window.py

@@ -149,3 +149,74 @@ class TestMainWindowURLWhitelist:
 
         # web_view should have allowed_urls configured
         assert window.web_view.allowed_urls == sample_config.allowed_urls
+
+
+class TestMainWindowOpenWith:
+    """Test Open With chooser behavior."""
+
+    def test_open_with_app_chooser_windows(self, qtbot, sample_config):
+        """Windows should use ShellExecuteW with the openas verb."""
+        window = MainWindow(sample_config)
+        qtbot.addWidget(window)
+
+        test_file = sample_config.allowed_roots[0] / "open_with_test.txt"
+        test_file.write_text("test")
+
+        with patch("webdrop_bridge.ui.main_window.sys.platform", "win32"):
+            with patch("ctypes.windll.shell32.ShellExecuteW", return_value=33) as mock_shell:
+                assert window._open_with_app_chooser(str(test_file)) is True
+                mock_shell.assert_called_once_with(
+                    None,
+                    "openas",
+                    str(test_file),
+                    None,
+                    None,
+                    1,
+                )
+
+    def test_open_with_app_chooser_windows_shellexecute_failure(self, qtbot, sample_config):
+        """Windows should fall back to OpenAs_RunDLL when ShellExecuteW fails."""
+        window = MainWindow(sample_config)
+        qtbot.addWidget(window)
+
+        test_file = sample_config.allowed_roots[0] / "open_with_fallback.txt"
+        test_file.write_text("test")
+
+        with patch("webdrop_bridge.ui.main_window.sys.platform", "win32"):
+            with patch("ctypes.windll.shell32.ShellExecuteW", return_value=31):
+                with patch("webdrop_bridge.ui.main_window.subprocess.Popen") as mock_popen:
+                    assert window._open_with_app_chooser(str(test_file)) is True
+                    mock_popen.assert_called_once_with(
+                        ["rundll32.exe", "shell32.dll,OpenAs_RunDLL", str(test_file)]
+                    )
+
+    def test_open_with_app_chooser_missing_file(self, qtbot, sample_config):
+        """Missing files should fail before platform-specific invocation."""
+        window = MainWindow(sample_config)
+        qtbot.addWidget(window)
+
+        with patch("webdrop_bridge.ui.main_window.sys.platform", "win32"):
+            assert window._open_with_app_chooser("C:/tmp/does_not_exist.txt") is False
+
+    def test_open_with_app_chooser_macos_success(self, qtbot, sample_config):
+        """macOS should return True when osascript exits successfully."""
+        window = MainWindow(sample_config)
+        qtbot.addWidget(window)
+
+        test_file = sample_config.allowed_roots[0] / "open_with_macos.txt"
+        test_file.write_text("test")
+
+        class _Result:
+            returncode = 0
+
+        with patch("webdrop_bridge.ui.main_window.sys.platform", "darwin"):
+            with patch("webdrop_bridge.ui.main_window.subprocess.run", return_value=_Result()):
+                assert window._open_with_app_chooser(str(test_file)) is True
+
+    def test_open_with_app_chooser_unsupported_platform(self, qtbot, sample_config):
+        """Unsupported platforms should return False."""
+        window = MainWindow(sample_config)
+        qtbot.addWidget(window)
+
+        with patch("webdrop_bridge.ui.main_window.sys.platform", "linux"):
+            assert window._open_with_app_chooser("/tmp/test.txt") is False