# Copyright (c) Streamlit Inc. (2018-2022) Snowflake Inc. (2022-2026)
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import annotations

from textwrap import dedent
from typing import (
    TYPE_CHECKING,
    Any,
    Generic,
    Literal,
    TypeVar,
    cast,
    overload,
)

from typing_extensions import Never

from streamlit.dataframe_util import OptionSequence, convert_anything_to_list
from streamlit.elements.lib.form_utils import current_form_id
from streamlit.elements.lib.layout_utils import (
    WidthWithoutContent,
    create_layout_config,
)
from streamlit.elements.lib.options_selector_utils import (
    SelectWidgetFilterMode,
    create_mappings,
    maybe_coerce_enum,
    resolve_value_against_options,
    validate_select_widget_filter_mode,
)
from streamlit.elements.lib.policies import (
    check_widget_policies,
    maybe_raise_label_warnings,
)
from streamlit.elements.lib.utils import (
    Key,
    LabelVisibility,
    compute_and_register_element_id,
    get_label_visibility_proto_value,
    save_for_app_testing,
    to_key,
)
from streamlit.errors import StreamlitAPIException
from streamlit.proto.Selectbox_pb2 import Selectbox as SelectboxProto
from streamlit.runtime.metrics_util import gather_metrics
from streamlit.runtime.scriptrunner import ScriptRunContext, get_script_run_ctx
from streamlit.runtime.state import (
    BindOption,
    PersistStateOption,
    WidgetArgs,
    WidgetCallback,
    WidgetKwargs,
    get_session_state,
    register_widget,
)
from streamlit.type_util import (
    check_python_comparable,
)

if TYPE_CHECKING:
    from collections.abc import Callable, Sequence

    from streamlit.delta_generator import DeltaGenerator

T = TypeVar("T")


class SelectboxSerde(Generic[T]):
    options: Sequence[T]
    formatted_options: list[str]
    formatted_option_to_option_index: dict[str, int]
    default_option_index: int | None
    format_func: Callable[[Any], str]

    def __init__(
        self,
        options: Sequence[T],
        *,
        formatted_options: list[str],
        formatted_option_to_option_index: dict[str, int],
        default_option_index: int | None = None,
        format_func: Callable[[Any], str] = str,
    ) -> None:
        """Initialize the SelectboxSerde.

        We do not store an option_to_formatted_option mapping because the generic
        options might not be hashable, which would raise a RuntimeError. So we do
        two lookups: option -> index -> formatted_option[index].


        Parameters
        ----------
        options : Sequence[T]
            The sequence of selectable options.
        formatted_options : list[str]
            The string representations of each option. The formatted_options correspond
            to the options sequence by index.
        formatted_option_to_option_index : dict[str, int]
            A mapping from formatted option strings to their corresponding indices in
            the options sequence.
        default_option_index : int or None, optional
            The index of the default option to use when no selection is made.
            If None, no default option is selected.
        format_func : Callable[[Any], str], optional
            Function to format options for comparison. Used to compare values by their
            string representation instead of using == directly. This is necessary because
            widget values are deepcopied, and for custom classes without __eq__, the
            deepcopied instances would fail identity comparison.
        """

        self.options = options
        self.formatted_options = formatted_options
        self.formatted_option_to_option_index = formatted_option_to_option_index
        self.default_option_index = default_option_index
        self.format_func = format_func

    def serialize(self, v: T | str | None) -> str | None:
        if v is None:
            return None
        # Note: We don't short-circuit for empty options here because
        # accept_new_options=True allows user-entered values even with no options.
        # The normal flow below handles this correctly.

        # Use format_func to find the formatted option instead of using
        # index_(self.options, v) which relies on == comparison. This is necessary
        # because widget values are deepcopied, and for custom classes without
        # __eq__, the deepcopied instances would fail identity comparison.
        try:
            formatted_value = self.format_func(v)
        except Exception:
            # format_func failed (e.g., v is a string but format_func expects
            # an object with specific attributes). Use str(v) to ensure we return
            # a proper string, not the original object. This handles both cases:
            # - v is already a string -> str(v) returns it unchanged
            # - v is a custom object -> str(v) gives its string representation
            return str(v)

        if formatted_value in self.formatted_option_to_option_index:
            return formatted_value
        # Value not found in options - return the formatted string (not the original
        # object) to maintain type consistency since serialize() must return str|None
        return formatted_value

    def deserialize(self, ui_value: str | None) -> T | str | None:
        # Note: We don't short-circuit for empty options here because
        # accept_new_options=True allows user-entered values even with no options.
        # The normal flow below handles this: ui_value not in options -> return ui_value.

        # Check if the option is pointing to a generic option type T,
        # otherwise return the option itself.
        if ui_value is None:
            return (
                self.options[self.default_option_index]
                if self.default_option_index is not None and len(self.options) > 0
                else None
            )

        option_index = self.formatted_option_to_option_index.get(ui_value)
        return self.options[option_index] if option_index is not None else ui_value


class SelectboxMixin:
    @overload
    def selectbox(
        self,
        label: str,
        options: Sequence[Never],  # Type for empty or Never-inferred options
        index: int = 0,
        format_func: Callable[[Any], str] = str,
        key: Key | None = None,
        help: str | None = None,
        on_change: WidgetCallback | None = None,
        args: WidgetArgs | None = None,
        kwargs: WidgetKwargs | None = None,
        *,  # keyword-only arguments:
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: Literal[False] = False,
        filter_mode: SelectWidgetFilterMode = "fuzzy",
        width: WidthWithoutContent = "stretch",
        bind: BindOption = None,
        persist_state: PersistStateOption = None,
    ) -> None: ...  # Returns None if options is empty and accept_new_options is False

    @overload
    def selectbox(
        self,
        label: str,
        options: OptionSequence[T],
        index: int = 0,
        format_func: Callable[[Any], str] = str,
        key: Key | None = None,
        help: str | None = None,
        on_change: WidgetCallback | None = None,
        args: WidgetArgs | None = None,
        kwargs: WidgetKwargs | None = None,
        *,  # keyword-only arguments:
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: Literal[False] = False,
        filter_mode: SelectWidgetFilterMode = "fuzzy",
        width: WidthWithoutContent = "stretch",
        bind: BindOption = None,
        persist_state: PersistStateOption = None,
    ) -> T: ...

    @overload
    def selectbox(
        self,
        label: str,
        options: OptionSequence[T],
        index: int = 0,
        format_func: Callable[[Any], str] = str,
        key: Key | None = None,
        help: str | None = None,
        on_change: WidgetCallback | None = None,
        args: WidgetArgs | None = None,
        kwargs: WidgetKwargs | None = None,
        *,  # keyword-only arguments:
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: Literal[True] = True,
        filter_mode: SelectWidgetFilterMode = "fuzzy",
        width: WidthWithoutContent = "stretch",
        bind: BindOption = None,
        persist_state: PersistStateOption = None,
    ) -> T | str: ...

    @overload
    def selectbox(
        self,
        label: str,
        options: OptionSequence[T],
        index: None,
        format_func: Callable[[Any], str] = str,
        key: Key | None = None,
        help: str | None = None,
        on_change: WidgetCallback | None = None,
        args: WidgetArgs | None = None,
        kwargs: WidgetKwargs | None = None,
        *,  # keyword-only arguments:
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: Literal[False] = False,
        filter_mode: SelectWidgetFilterMode = "fuzzy",
        width: WidthWithoutContent = "stretch",
        bind: BindOption = None,
        persist_state: PersistStateOption = None,
    ) -> T | None: ...

    @overload
    def selectbox(
        self,
        label: str,
        options: OptionSequence[T],
        index: None,
        format_func: Callable[[Any], str] = str,
        key: Key | None = None,
        help: str | None = None,
        on_change: WidgetCallback | None = None,
        args: WidgetArgs | None = None,
        kwargs: WidgetKwargs | None = None,
        *,  # keyword-only arguments:
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: Literal[True] = True,
        filter_mode: SelectWidgetFilterMode = "fuzzy",
        width: WidthWithoutContent = "stretch",
        bind: BindOption = None,
        persist_state: PersistStateOption = None,
    ) -> T | str | None: ...

    @overload
    def selectbox(
        self,
        label: str,
        options: OptionSequence[T],
        index: int | None = 0,
        format_func: Callable[[Any], str] = str,
        key: Key | None = None,
        help: str | None = None,
        on_change: WidgetCallback | None = None,
        args: WidgetArgs | None = None,
        kwargs: WidgetKwargs | None = None,
        *,  # keyword-only arguments:
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: bool = False,
        filter_mode: SelectWidgetFilterMode = "fuzzy",
        width: WidthWithoutContent = "stretch",
        bind: BindOption = None,
        persist_state: PersistStateOption = None,
    ) -> T | str | None: ...

    @gather_metrics("selectbox")
    def selectbox(
        self,
        label: str,
        options: OptionSequence[T],
        index: int | None = 0,
        format_func: Callable[[Any], str] = str,
        key: Key | None = None,
        help: str | None = None,
        on_change: WidgetCallback | None = None,
        args: WidgetArgs | None = None,
        kwargs: WidgetKwargs | None = None,
        *,  # keyword-only arguments:
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: bool = False,
        filter_mode: SelectWidgetFilterMode = "fuzzy",
        width: WidthWithoutContent = "stretch",
        bind: BindOption = None,
        persist_state: PersistStateOption = None,
    ) -> T | str | None:
        r"""Display a select widget.

        Parameters
        ----------
        label : str
            A short label explaining to the user what this select widget is for.
            The label can optionally contain GitHub-flavored Markdown of the
            following types: Bold, Italics, Strikethroughs, Inline Code, Links,
            and Images. Images display like icons, with a max height equal to
            the font height.

            Unsupported Markdown elements are unwrapped so only their children
            (text contents) render. Common block-level Markdown (headings,
            lists, blockquotes) is automatically escaped and displays as
            literal text in labels.

            See the ``body`` parameter of |st.markdown|_ for additional,
            supported Markdown directives.

            For accessibility reasons, you should never set an empty label, but
            you can hide it with ``label_visibility`` if needed. In the future,
            we may disallow empty labels by raising an exception.

            .. |st.markdown| replace:: ``st.markdown``
            .. _st.markdown: https://docs.streamlit.io/develop/api-reference/text/st.markdown

        options : Iterable
            Labels for the select options in an ``Iterable``. This can be a
            ``list``, ``set``, or anything supported by ``st.dataframe``. If
            ``options`` is dataframe-like, the first column will be used. Each
            label will be cast to ``str`` internally by default.

        index : int or None
            The index of the preselected option on first render. If ``None``,
            will initialize empty and return ``None`` until the user selects an option.
            Defaults to 0 (the first option).

        format_func : function
            Function to modify the display of the options. It receives
            the raw option as an argument and should output the label to be
            shown for that option. This has no impact on the return value of
            the command.

        key : str, int, or None
            An optional string or integer to use as the unique key for
            the widget. If this is ``None`` (default), a key will be
            generated for the widget based on the values of the other
            parameters. No two widgets may have the same key. Assigning
            a key stabilizes the widget's identity and preserves its
            state across reruns even when other parameters change.

            .. note::
               Changing ``accept_new_options`` resets the widget even when
               a key is provided.

            A key lets you read or update the widget's value via
            ``st.session_state[key]``. For more details, see `Widget
            behavior <https://docs.streamlit.io/develop/concepts/architecture/widget-behavior>`_.

            Additionally, if ``key`` is provided, it will be used as a
            CSS class name prefixed with ``st-key-``.

        help : str or None
            A tooltip that gets displayed next to the widget label. Streamlit
            only displays the tooltip when ``label_visibility="visible"``. If
            this is ``None`` (default), no tooltip is displayed.

            The tooltip can optionally contain GitHub-flavored Markdown,
            including the Markdown directives described in the ``body``
            parameter of ``st.markdown``.

        on_change : callable
            An optional callback invoked when this selectbox's value changes.

        args : list or tuple
            An optional list or tuple of args to pass to the callback.

        kwargs : dict
            An optional dict of kwargs to pass to the callback.

        placeholder : str or None
            A string to display when no options are selected.
            If this is ``None`` (default), the widget displays placeholder text
            based on the widget's configuration:

            - "Choose an option" is displayed when options are available and
              ``accept_new_options=False``.
            - "Choose or add an option" is displayed when options are available
              and ``accept_new_options=True``.
            - "Add an option" is displayed when no options are available and
              ``accept_new_options=True``.
            - "No options to select" is displayed when no options are available
              and ``accept_new_options=False``. The widget is also disabled in
              this case.

        disabled : bool
            An optional boolean that disables the selectbox if set to ``True``.
            The default is ``False``.

        label_visibility : "visible", "hidden", or "collapsed"
            The visibility of the label. The default is ``"visible"``. If this
            is ``"hidden"``, Streamlit displays an empty spacer instead of the
            label, which can help keep the widget aligned with other widgets.
            If this is ``"collapsed"``, Streamlit displays no label or spacer.

        accept_new_options : bool
            Whether the user can add a selection that isn't included in ``options``.
            If this is ``False`` (default), the user can only select from the
            items in ``options``. If this is ``True``, the user can enter a new
            item that doesn't exist in ``options``.

            When a user enters a new item, it is returned by the widget as a
            string. The new item is not added to the widget's drop-down menu.
            Streamlit will use a case-insensitive match from ``options`` before
            adding a new item.

        filter_mode : "fuzzy", "contains", "prefix", or None
            The matching mode used to filter options while the user types.
            If this is ``"fuzzy"`` (default), options are matched by in-order
            subsequence and sorted by match score. If this is ``"contains"``,
            options are matched by case-insensitive substring. If this is
            ``"prefix"``, options are matched by case-insensitive prefix. If
            this is ``None``, typing is disabled and the options are not
            filtered.

            ``filter_mode=None`` is incompatible with
            ``accept_new_options=True``.

        width : "stretch" or int
            The width of the selectbox widget. This can be one of the
            following:

            - ``"stretch"`` (default): The width of the widget matches the
              width of the parent container.
            - An integer specifying the width in pixels: The widget has a
              fixed width. If the specified width is greater than the width of
              the parent container, the width of the widget matches the width
              of the parent container.

        bind : "query-params" or None
            Binding mode for syncing the widget's value with a URL query
            parameter. If this is ``None`` (default), the widget's value
            is not synced to the URL. When this is set to
            ``"query-params"``, changes to the widget update the URL, and
            the widget can be initialized or updated through a query
            parameter in the URL. This requires ``key`` to be set. The
            key is used as the query parameter name.

            When the widget's value equals its default, the query
            parameter is removed from the URL to keep it clean. A bound
            query parameter can't be set or deleted through
            ``st.query_params``; it can only be programmatically changed
            through ``st.session_state``.

            Invalid query parameter values are ignored and removed
            from the URL. If ``index`` is ``None``, an empty query
            parameter (e.g., ``?my_key=``) clears the widget.

        persist_state : "page", "session", or None
            How long to preserve the widget's value when it isn't rendered.
            If this is ``None`` (default), the value is lost when the widget
            stops being rendered or the user switches pages. If this is
            ``"page"``, the value is preserved only while the user stays on the
            page where the widget is defined (for example, while the widget is
            conditionally hidden); it is discarded on a page switch and is not
            restored if the user returns to the page. If this is ``"session"``,
            the value is preserved for the entire session, including across
            page switches, so it returns when the user navigates back. This
            requires ``key`` to be set. If ``bind="query-params"`` is also set,
            the binding takes precedence: the value is stored in the URL, so it
            persists across page switches regardless of the ``persist_state``
            scope.

        Returns
        -------
        any
            The selected option or ``None`` if no option is selected.

            This is a copy of the selected option, not the original.

        Examples
        --------
        **Example 1: Use a basic selectbox widget**

        If no index is provided, the first option is selected by default.

        >>> import streamlit as st
        >>>
        >>> option = st.selectbox(
        ...     "How would you like to be contacted?",
        ...     ("Email", "Home phone", "Mobile phone"),
        ... )
        >>>
        >>> st.write("You selected:", option)

        .. output::
           https://doc-selectbox.streamlit.app/
           height: 320px

        **Example 2: Use a selectbox widget with no initial selection**

        To initialize an empty selectbox, use ``None`` as the index value.

        >>> import streamlit as st
        >>>
        >>> option = st.selectbox(
        ...     "How would you like to be contacted?",
        ...     ("Email", "Home phone", "Mobile phone"),
        ...     index=None,
        ...     placeholder="Select contact method...",
        ... )
        >>>
        >>> st.write("You selected:", option)

        .. output::
           https://doc-selectbox-empty.streamlit.app/
           height: 320px

        **Example 3: Let users add a new option**

        To allow users to add a new option that isn't included in the
        ``options`` list, use the ``accept_new_options=True`` parameter. You
        can also customize the placeholder text.

        >>> import streamlit as st
        >>>
        >>> option = st.selectbox(
        ...     "Default email",
        ...     ["foo@example.com", "bar@example.com", "baz@example.com"],
        ...     index=None,
        ...     placeholder="Select a saved email or enter a new one",
        ...     accept_new_options=True,
        ... )
        >>>
        >>> st.write("You selected:", option)

        .. output::
           https://doc-selectbox-accept-new-options.streamlit.app/
           height: 320px

        """
        ctx = get_script_run_ctx()
        return self._selectbox(
            label=label,
            options=options,
            index=index,
            format_func=format_func,
            key=key,
            help=help,
            on_change=on_change,
            args=args,
            kwargs=kwargs,
            placeholder=placeholder,
            disabled=disabled,
            label_visibility=label_visibility,
            accept_new_options=accept_new_options,
            filter_mode=filter_mode,
            width=width,
            bind=bind,
            persist_state=persist_state,
            ctx=ctx,
        )

    def _selectbox(
        self,
        label: str,
        options: OptionSequence[T],
        index: int | None = 0,
        format_func: Callable[[Any], Any] = str,
        key: Key | None = None,
        help: str | None = None,
        on_change: WidgetCallback | None = None,
        args: WidgetArgs | None = None,
        kwargs: WidgetKwargs | None = None,
        *,  # keyword-only arguments:
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: bool = False,
        filter_mode: SelectWidgetFilterMode = "fuzzy",
        width: WidthWithoutContent = "stretch",
        bind: BindOption = None,
        persist_state: PersistStateOption = None,
        ctx: ScriptRunContext | None = None,
    ) -> T | str | None:
        key = to_key(key)

        check_widget_policies(
            self.dg,
            key,
            on_change,
            default_value=None if index == 0 else index,
        )
        maybe_raise_label_warnings(label, label_visibility)

        opt = convert_anything_to_list(options)
        check_python_comparable(opt)

        if not isinstance(index, int) and index is not None:
            raise StreamlitAPIException(
                f"Selectbox Value has invalid type: {type(index).__name__}"
            )

        if index is not None and len(opt) > 0 and not 0 <= index < len(opt):
            raise StreamlitAPIException(
                "Selectbox index must be greater than or equal to 0 "
                "and less than the length of options."
            )

        # Convert empty string to single space to distinguish from None:
        # - None (default) → "" → Frontend shows contextual placeholders
        # - "" (explicit empty) → " " → Frontend shows empty placeholder
        # - "Custom" → "Custom" → Frontend shows custom placeholder
        if placeholder == "":
            placeholder = " "

        proto_filter_mode = validate_select_widget_filter_mode(
            filter_mode,
            accept_new_options=accept_new_options,
            command="st.selectbox",
        )

        formatted_options, formatted_option_to_option_index = create_mappings(
            opt, format_func
        )

        element_id = compute_and_register_element_id(
            "selectbox",
            user_key=key,
            # Treat the provided key as the main identity. Only include
            # accept_new_options in the identity computation because it can
            # invalidate the current selection and is complex to support.
            key_as_main_identity={"accept_new_options"},
            dg=self.dg,
            label=label,
            options=formatted_options,
            index=index,
            help=help,
            placeholder=placeholder,
            accept_new_options=accept_new_options,
            filter_mode=filter_mode,
            width=width,
        )

        session_state = get_session_state().filtered_state
        if key is not None and key in session_state and session_state[key] is None:
            index = None

        selectbox_proto = SelectboxProto()
        selectbox_proto.id = element_id
        selectbox_proto.label = label
        if index is not None:
            selectbox_proto.default = index
        selectbox_proto.options[:] = formatted_options
        selectbox_proto.form_id = current_form_id(self.dg)
        selectbox_proto.placeholder = placeholder or ""
        selectbox_proto.disabled = disabled
        selectbox_proto.label_visibility.value = get_label_visibility_proto_value(
            label_visibility
        )
        selectbox_proto.accept_new_options = accept_new_options
        selectbox_proto.filter_mode = proto_filter_mode

        if help is not None:
            selectbox_proto.help = dedent(help)

        # Set query param key if bound
        if bind == "query-params" and key is not None:
            selectbox_proto.query_param_key = str(key)

        serde = SelectboxSerde(
            opt,
            formatted_options=formatted_options,
            formatted_option_to_option_index=formatted_option_to_option_index,
            default_option_index=index,
            format_func=format_func,
        )
        widget_state = register_widget(
            selectbox_proto.id,
            on_change_handler=on_change,
            args=args,
            kwargs=kwargs,
            deserializer=serde.deserialize,
            serializer=serde.serialize,
            ctx=ctx,
            value_type="string_value",
            disabled=disabled,
            bind=bind,
            persist_state=persist_state,
            # Clearable when index=None: the widget can be in an empty state,
            # so ?key= (empty URL param) should clear the widget to None.
            clearable=(index is None),
            # Pass formatted_options so _seed_widget_from_url can reject
            # invalid option strings from URLs. Not passed when
            # accept_new_options=True since any string is valid.
            formatted_options=None if accept_new_options else formatted_options,
        )
        widget_state = maybe_coerce_enum(widget_state, options, opt)

        if accept_new_options:
            current_value = widget_state.value
            value_needs_reset = False
        else:
            # Reset the selection only if the stored value no longer matches any
            # option; see resolve_value_against_options for the format_func and
            # wire-label fallback logic.
            current_value, value_needs_reset = resolve_value_against_options(
                widget_state.value,
                opt,
                formatted_option_to_option_index,
                index,
                key,
                format_func,
                widget_state.incoming_serialized_value,
            )

        if value_needs_reset or widget_state.value_changed:
            serialized_value = serde.serialize(current_value)
            if serialized_value is not None:
                selectbox_proto.raw_value = serialized_value
            selectbox_proto.set_value = True

        layout_config = create_layout_config(width=width)

        if ctx:
            save_for_app_testing(ctx, element_id, format_func)
        self.dg._enqueue(
            "selectbox",
            selectbox_proto,
            layout_config=layout_config,
            has_one_shot_effect=value_needs_reset or widget_state.value_changed,
        )
        return current_value

    @property
    def dg(self) -> DeltaGenerator:
        """The associated DeltaGenerator."""
        return cast("DeltaGenerator", self)
