# 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 collections.abc import Sequence
from textwrap import dedent
from typing import (
    TYPE_CHECKING,
    Any,
    Generic,
    Literal,
    TypeVar,
    cast,
    overload,
)

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 (
    LayoutConfig,
    WidthWithoutContent,
    validate_width,
)
from streamlit.elements.lib.options_selector_utils import (
    convert_to_sequence_and_check_comparable,
    create_mappings,
    get_default_indices,
    maybe_coerce_enum_sequence,
    validate_and_sync_multiselect_value_with_options,
)
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 (
    StreamlitSelectionCountExceedsMaxError,
)
from streamlit.proto.MultiSelect_pb2 import MultiSelect as MultiSelectProto
from streamlit.runtime.metrics_util import gather_metrics
from streamlit.runtime.scriptrunner import ScriptRunContext, get_script_run_ctx
from streamlit.runtime.state import register_widget
from streamlit.type_util import (
    is_iterable,
)

if TYPE_CHECKING:
    from collections.abc import Callable, Sequence

    from streamlit.dataframe_util import OptionSequence
    from streamlit.delta_generator import DeltaGenerator
    from streamlit.runtime.state import (
        WidgetArgs,
        WidgetCallback,
        WidgetKwargs,
    )

T = TypeVar("T")


class MultiSelectSerde(Generic[T]):
    options: Sequence[T]
    formatted_options: list[str]
    formatted_option_to_option_index: dict[str, int]
    default_options_indices: list[int]

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

        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.
        """

        self.options = options
        self.formatted_options = formatted_options
        self.formatted_option_to_option_index = formatted_option_to_option_index
        self.default_options_indices = default_options_indices or []

    def serialize(self, value: list[T | str] | list[T]) -> list[str]:
        converted_value = convert_anything_to_list(value)
        values: list[str] = []
        for v in converted_value:
            try:
                option_index = self.options.index(v)
                values.append(self.formatted_options[option_index])
            except ValueError:  # noqa: PERF203
                # at this point we know that v is a string, otherwise
                # it would have been found in the options
                values.append(cast("str", v))
        return values

    def deserialize(self, ui_value: list[str] | None) -> list[T | str] | list[T]:
        if ui_value is None:
            return [self.options[i] for i in self.default_options_indices]

        values: list[T | str] = []
        for v in ui_value:
            try:
                option_index = self.formatted_options.index(v)
                values.append(self.options[option_index])
            except ValueError:  # noqa: PERF203
                values.append(v)
        return values


def _get_default_count(default: Sequence[Any] | Any | None) -> int:
    if default is None:
        return 0
    if not is_iterable(default):
        return 1
    return len(cast("Sequence[Any]", default))


def _check_max_selections(
    selections: Sequence[Any] | Any | None, max_selections: int | None
) -> None:
    if max_selections is None:
        return

    default_count = _get_default_count(selections)
    if default_count > max_selections:
        raise StreamlitSelectionCountExceedsMaxError(
            current_selections_count=default_count, max_selections_count=max_selections
        )


class MultiSelectMixin:
    @overload
    def multiselect(
        self,
        label: str,
        options: OptionSequence[T],
        default: Any | None = 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:
        max_selections: int | None = None,
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: Literal[False] = False,
        width: WidthWithoutContent = "stretch",
    ) -> list[T]: ...

    @overload
    def multiselect(
        self,
        label: str,
        options: OptionSequence[T],
        default: Any | None = 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:
        max_selections: int | None = None,
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: Literal[True] = True,
        width: WidthWithoutContent = "stretch",
    ) -> list[T | str]: ...

    @overload
    def multiselect(
        self,
        label: str,
        options: OptionSequence[T],
        default: Any | None = 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:
        max_selections: int | None = None,
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: bool = False,
        width: WidthWithoutContent = "stretch",
    ) -> list[T] | list[T | str]: ...

    @gather_metrics("multiselect")
    def multiselect(
        self,
        label: str,
        options: OptionSequence[T],
        default: Any | None = 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:
        max_selections: int | None = None,
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: bool = False,
        width: WidthWithoutContent = "stretch",
    ) -> list[T] | list[T | str]:
        r"""Display a multiselect widget.
        The multiselect widget starts as empty.

        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. Display unsupported elements as literal
            characters by backslash-escaping them. E.g.,
            ``"1\. Not an ordered list"``.

            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.

        default : Iterable of V, V, or None
            List of default values. Can also be a single value.

        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 or int
            An optional string or integer to use as the unique key for the widget.
            If this is omitted, a key will be generated for the widget
            based on its content. No two widgets may have the same 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 widget'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.

        max_selections : int
            The max selections that can be selected at a time.

        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 options" is displayed when options are available and
              ``accept_new_options=False``.
            - "Choose or add options" is displayed when options are available
              and ``accept_new_options=True``.
            - "Add options" 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 multiselect widget 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 selections that aren'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 new
            items that don't exist in ``options``.

            When a user enters and selects a new item, it is included in the
            widget's returned list 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, and a new item
            can't be added if a case-insensitive match is already selected. The
            ``max_selections`` argument is still enforced.

        width : "stretch" or int
            The width of the multiselect 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.

        Returns
        -------
        list
            A list of the selected options.

            The list contains copies of the selected options, not the originals.

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

        You can declare one or more initial selections with the ``default``
        parameter.

        >>> import streamlit as st
        >>>
        >>> options = st.multiselect(
        ...     "What are your favorite colors?",
        ...     ["Green", "Yellow", "Red", "Blue"],
        ...     default=["Yellow", "Red"],
        ... )
        >>>
        >>> st.write("You selected:", options)

        .. output::
           https://doc-multiselect.streamlit.app/
           height: 350px

        **Example 2: Let users to add new options**

        To allow users to enter and select new options that aren't included in
        the ``options`` list, use the ``accept_new_options`` parameter. To
        prevent users from adding an unbounded number of new options, use the
        ``max_selections`` parameter.

        >>> import streamlit as st
        >>>
        >>> options = st.multiselect(
        ...     "What are your favorite cat names?",
        ...     ["Jellybeans", "Fish Biscuit", "Madam President"],
        ...     max_selections=5,
        ...     accept_new_options=True,
        ... )
        >>>
        >>> st.write("You selected:", options)

        .. output::
           https://doc-multiselect-accept-new-options.streamlit.app/
           height: 350px

        """
        # 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 = " "

        ctx = get_script_run_ctx()
        return self._multiselect(
            label=label,
            options=options,
            default=default,
            format_func=format_func,
            key=key,
            help=help,
            on_change=on_change,
            args=args,
            kwargs=kwargs,
            max_selections=max_selections,
            placeholder=placeholder,
            disabled=disabled,
            label_visibility=label_visibility,
            accept_new_options=accept_new_options,
            width=width,
            ctx=ctx,
        )

    def _multiselect(
        self,
        label: str,
        options: OptionSequence[T],
        default: Any | None = 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:
        max_selections: int | None = None,
        placeholder: str | None = None,
        disabled: bool = False,
        label_visibility: LabelVisibility = "visible",
        accept_new_options: bool = False,
        width: WidthWithoutContent = "stretch",
        ctx: ScriptRunContext | None = None,
    ) -> list[T] | list[T | str]:
        key = to_key(key)

        widget_name = "multiselect"
        check_widget_policies(
            self.dg,
            key,
            on_change,
            default_value=default,
        )
        maybe_raise_label_warnings(label, label_visibility)

        indexable_options = convert_to_sequence_and_check_comparable(options)
        formatted_options, formatted_option_to_option_index = create_mappings(
            indexable_options, format_func
        )

        default_values = get_default_indices(indexable_options, default)

        # 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 = " "

        form_id = current_form_id(self.dg)
        element_id = compute_and_register_element_id(
            widget_name,
            user_key=key,
            key_as_main_identity={
                "max_selections",
                "accept_new_options",
            },
            dg=self.dg,
            label=label,
            options=formatted_options,
            default=default_values,
            help=help,
            max_selections=max_selections,
            placeholder=placeholder,
            accept_new_options=accept_new_options,
            width=width,
        )

        proto = MultiSelectProto()
        proto.id = element_id
        proto.default[:] = default_values
        proto.form_id = form_id
        proto.disabled = disabled
        proto.label = label
        proto.max_selections = max_selections or 0
        proto.placeholder = placeholder or ""
        proto.label_visibility.value = get_label_visibility_proto_value(
            label_visibility
        )
        proto.options[:] = formatted_options
        if help is not None:
            proto.help = dedent(help)
        proto.accept_new_options = accept_new_options

        serde = MultiSelectSerde(
            indexable_options,
            formatted_options=formatted_options,
            formatted_option_to_option_index=formatted_option_to_option_index,
            default_options_indices=default_values,
        )

        widget_state = register_widget(
            proto.id,
            on_change_handler=on_change,
            args=args,
            kwargs=kwargs,
            deserializer=serde.deserialize,
            serializer=serde.serialize,
            ctx=ctx,
            value_type="string_array_value",
        )

        _check_max_selections(widget_state.value, max_selections)

        widget_state = maybe_coerce_enum_sequence(
            widget_state, options, indexable_options
        )

        if accept_new_options:
            # accept_new_options is True, so we keep the user-entered values.
            current_values = widget_state.value
            value_needs_reset = False
        else:
            # Validate the current values against the new options.
            # If values are no longer valid (not in options), filter them out.
            # This handles the case where options change dynamically and the
            # previously selected values are no longer available.
            current_values, value_needs_reset = (
                validate_and_sync_multiselect_value_with_options(
                    widget_state.value, indexable_options, key
                )
            )

        if value_needs_reset or widget_state.value_changed:
            proto.raw_values[:] = serde.serialize(current_values)
            proto.set_value = True

        validate_width(width)
        layout_config = LayoutConfig(width=width)

        if ctx:
            save_for_app_testing(ctx, element_id, format_func)

        self.dg._enqueue(widget_name, proto, layout_config=layout_config)

        return current_values

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