feat: Add MultiSelect widget to chatmark library

- Implement MultiSelect class in widgets.py
- Update __init__.py to export MultiSelect
- Add support for multiple option selection with checkboxes

lib/chatmark/__init__.py

@@ -1,6 +1,6 @@
 from .form import Form
 from .step import Step
-from .widgets import Button, Checkbox, Radio, TextEditor
+from .widgets import Button, Checkbox, Radio, TextEditor, MultiSelect
 
 __all__ = [
     "Checkbox",
@@ -9,4 +9,5 @@
     "Button",
     "Form",
     "Step",
+    "MultiSelect",
 ]

lib/chatmark/widgets.py

@@ -162,6 +162,94 @@ def _parse_response(self, response: Dict):
 
         self._selections = selections
 
+class multiSelect(Widget):
+    """
+    ChatMark syntax:
+    ```chatmark
+    Which files would you like to commit? I've suggested a few.
+    > {x}(file1) devchat/engine/prompter.py
+    > {x}(file2) devchat/prompt.py
+    > {}(file3) tests/test_cli_prompt.py
+    ```
+
+    Response:
+    ```yaml
+    file1: checked
+    file3: checked
+    ```
+    """
+
+    def __init__(
+        self,
+        options: List[str],
+        check_states: Optional[List[bool]] = None,
+        title: Optional[str] = None,
+        submit_button_name: str = "Submit",
+        cancel_button_name: str = "Cancel",
+    ):
+        """
+        options: options to be selected
+        check_states: initial check states of options, default to all False
+        title: title of the widget
+        """
+        super().__init__(submit_button_name, cancel_button_name)
+
+        if check_states is not None:
+            assert len(options) == len(check_states)
+        else:
+            check_states = [False for _ in options]
+
+        self._options = options
+        self._states = check_states
+        self._title = title
+
+        self._selections: Optional[List[int]] = None
+
+    @property
+    def selections(self) -> Optional[List[int]]:
+        """
+        Get the indices of selected options
+        """
+        return self._selections
+
+    @property
+    def options(self) -> List[str]:
+        """
+        Get the options
+        """
+        return self._options
+
+    def _in_chatmark(self) -> str:
+        """
+        Generate ChatMark syntax for checkbox options
+        Use the index of option to generate id/key
+        """
+        lines = []
+
+        if self._title:
+            lines.append(self._title)
+
+        for idx, (option, state) in enumerate(zip(self._options, self._states)):
+            mark = "{x}" if state else "{}"
+            key = self.gen_id(self._id_prefix, idx)
+            lines.append(f"> {mark}({key}) {option}")
+
+        text = "\n".join(lines)
+        return text
+
+    def _parse_response(self, response: Dict):
+        selections = []
+        for key, value in response.items():
+            prefix, index = self.parse_id(key)
+            # check if the prefix is the same as the widget's
+            if prefix != self._id_prefix:
+                continue
+
+            if value == "checked":
+                selections.append(index)
+
+        self._selections = selections
+
 
 class TextEditor(Widget):
     """