# Copyright 2018-2022 Streamlit Inc.
#
# 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 streamlit.type_util import Key, to_key
from typing import cast, overload, List, Optional, Union
from textwrap import dedent

import sys

if sys.version_info >= (3, 8):
    from typing import Literal
else:
    from typing_extensions import Literal

import streamlit
from streamlit import config
from streamlit.logger import get_logger
from streamlit.proto.FileUploader_pb2 import FileUploader as FileUploaderProto
from streamlit.scriptrunner import ScriptRunContext, get_script_run_ctx
from streamlit.state import (
    register_widget,
    WidgetArgs,
    WidgetCallback,
    WidgetKwargs,
)
from .form import current_form_id
from ..proto.Common_pb2 import (
    FileUploaderState as FileUploaderStateProto,
    UploadedFileInfo as UploadedFileInfoProto,
)
from ..uploaded_file_manager import UploadedFile, UploadedFileRec
from .utils import check_callback_rules, check_session_state_rules

LOGGER = get_logger(__name__)

SomeUploadedFiles = Optional[Union[UploadedFile, List[UploadedFile]]]


class FileUploaderMixin:
    # Multiple overloads are defined on `file_uploader()` below to represent
    # the different return types of `file_uploader()`.
    # These return types differ according to the value of the `accept_multiple_files` argument.
    # There are 2 associated variables, each with 2 options.
    # 1. The `accept_multiple_files` argument is set as `True`,
    #    or it is set as `False` or omitted, in which case the default value `False`.
    # 2. The `type` argument may or may not be provided as a keyword-only argument.
    # There must be 2x2=4 overloads to cover all the possible arguments,
    # as these overloads must be mutually exclusive for mypy.

    # 1. type is given as not a keyword-only argument
    # 2. accept_multiple_files = True
    @overload
    def file_uploader(
        self,
        label: str,
        type: Optional[Union[str, List[str]]],
        accept_multiple_files: Literal[True],
        key: Optional[Key] = None,
        help: Optional[str] = None,
        on_change: Optional[WidgetCallback] = None,
        args: Optional[WidgetArgs] = None,
        kwargs: Optional[WidgetKwargs] = None,
        *,
        disabled: bool = False,
    ) -> Optional[List[UploadedFile]]:
        ...

    # 1. type is given as not a keyword-only argument
    # 2. accept_multiple_files = False or omitted
    @overload
    def file_uploader(
        self,
        label: str,
        type: Optional[Union[str, List[str]]],
        accept_multiple_files: Literal[False] = False,
        key: Optional[Key] = None,
        help: Optional[str] = None,
        on_change: Optional[WidgetCallback] = None,
        args: Optional[WidgetArgs] = None,
        kwargs: Optional[WidgetKwargs] = None,
        *,
        disabled: bool = False,
    ) -> Optional[UploadedFile]:
        ...

    # The following 2 overloads represent the cases where
    # the `type` argument is a keyword-only argument.
    # See https://github.com/python/mypy/issues/4020#issuecomment-737600893
    # for the related discussions and examples.

    # 1. type is skipped or a keyword argument
    # 2. accept_multiple_files = True
    @overload
    def file_uploader(
        self,
        label: str,
        *,
        accept_multiple_files: Literal[True],
        type: Optional[Union[str, List[str]]] = None,
        key: Optional[Key] = None,
        help: Optional[str] = None,
        on_change: Optional[WidgetCallback] = None,
        args: Optional[WidgetArgs] = None,
        kwargs: Optional[WidgetKwargs] = None,
        disabled: bool = False,
    ) -> Optional[List[UploadedFile]]:
        ...

    # 1. type is skipped or a keyword argument
    # 2. accept_multiple_files = False or omitted
    @overload
    def file_uploader(
        self,
        label: str,
        *,
        accept_multiple_files: Literal[False] = False,
        type: Optional[Union[str, List[str]]] = None,
        key: Optional[Key] = None,
        help: Optional[str] = None,
        on_change: Optional[WidgetCallback] = None,
        args: Optional[WidgetArgs] = None,
        kwargs: Optional[WidgetKwargs] = None,
        disabled: bool = False,
    ) -> Optional[UploadedFile]:
        ...

    def file_uploader(
        self,
        label: str,
        type: Optional[Union[str, List[str]]] = None,
        accept_multiple_files: bool = False,
        key: Optional[Key] = None,
        help: Optional[str] = None,
        on_change: Optional[WidgetCallback] = None,
        args: Optional[WidgetArgs] = None,
        kwargs: Optional[WidgetKwargs] = None,
        *,  # keyword-only arguments:
        disabled: bool = False,
    ):
        """Display a file uploader widget.
        By default, uploaded files are limited to 200MB. You can configure
        this using the `server.maxUploadSize` config option. For more info
        on how to set config options, see
        https://docs.streamlit.io/library/advanced-features/configuration#set-configuration-options

        Parameters
        ----------
        label : str
            A short label explaining to the user what this file uploader is for.

        type : str or list of str or None
            Array of allowed extensions. ['png', 'jpg']
            The default is None, which means all extensions are allowed.

        accept_multiple_files : bool
            If True, allows the user to upload multiple files at the same time,
            in which case the return value will be a list of files.
            Default: False

        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. Multiple widgets of the same type may
            not share the same key.

        help : str
            A tooltip that gets displayed next to the file uploader.

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

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

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

        disabled : bool
            An optional boolean, which disables the file uploader if set to
            True. The default is False. This argument can only be supplied by
            keyword.

        Returns
        -------
        None or UploadedFile or list of UploadedFile
            - If accept_multiple_files is False, returns either None or
              an UploadedFile object.
            - If accept_multiple_files is True, returns a list with the
              uploaded files as UploadedFile objects. If no files were
              uploaded, returns an empty list.

            The UploadedFile class is a subclass of BytesIO, and therefore
            it is "file-like". This means you can pass them anywhere where
            a file is expected.

        Examples
        --------
        Insert a file uploader that accepts a single file at a time:

        >>> uploaded_file = st.file_uploader("Choose a file")
        >>> if uploaded_file is not None:
        ...     # To read file as bytes:
        ...     bytes_data = uploaded_file.getvalue()
        ...     st.write(bytes_data)
        >>>
        ...     # To convert to a string based IO:
        ...     stringio = StringIO(uploaded_file.getvalue().decode("utf-8"))
        ...     st.write(stringio)
        >>>
        ...     # To read file as string:
        ...     string_data = stringio.read()
        ...     st.write(string_data)
        >>>
        ...     # Can be used wherever a "file-like" object is accepted:
        ...     dataframe = pd.read_csv(uploaded_file)
        ...     st.write(dataframe)

        Insert a file uploader that accepts multiple files at a time:

        >>> uploaded_files = st.file_uploader("Choose a CSV file", accept_multiple_files=True)
        >>> for uploaded_file in uploaded_files:
        ...     bytes_data = uploaded_file.read()
        ...     st.write("filename:", uploaded_file.name)
        ...     st.write(bytes_data)

        .. output::
           https://share.streamlit.io/streamlit/docs/main/python/api-examples-source/widget.file_uploader.py
           height: 375px

        """
        ctx = get_script_run_ctx()
        return self._file_uploader(
            label=label,
            type=type,
            accept_multiple_files=accept_multiple_files,
            key=key,
            help=help,
            on_change=on_change,
            args=args,
            kwargs=kwargs,
            disabled=disabled,
            ctx=ctx,
        )

    def _file_uploader(
        self,
        label: str,
        type: Optional[Union[str, List[str]]] = None,
        accept_multiple_files: bool = False,
        key: Optional[Key] = None,
        help: Optional[str] = None,
        on_change: Optional[WidgetCallback] = None,
        args: Optional[WidgetArgs] = None,
        kwargs: Optional[WidgetKwargs] = None,
        *,  # keyword-only arguments:
        disabled: bool = False,
        ctx: Optional[ScriptRunContext] = None,
    ):
        key = to_key(key)
        check_callback_rules(self.dg, on_change)
        check_session_state_rules(default_value=None, key=key, writes_allowed=False)

        if type:
            if isinstance(type, str):
                type = [type]

            # May need a regex or a library to validate file types are valid
            # extensions.
            type = [
                file_type if file_type[0] == "." else f".{file_type}"
                for file_type in type
            ]

        file_uploader_proto = FileUploaderProto()
        file_uploader_proto.label = label
        file_uploader_proto.type[:] = type if type is not None else []
        file_uploader_proto.max_upload_size_mb = config.get_option(
            "server.maxUploadSize"
        )
        file_uploader_proto.multiple_files = accept_multiple_files
        file_uploader_proto.form_id = current_form_id(self.dg)
        if help is not None:
            file_uploader_proto.help = dedent(help)

        def deserialize_file_uploader(
            ui_value: Optional[FileUploaderStateProto], widget_id: str
        ) -> SomeUploadedFiles:
            file_recs = self._get_file_recs(widget_id, ui_value)
            if len(file_recs) == 0:
                return_value: Optional[Union[List[UploadedFile], UploadedFile]] = (
                    [] if accept_multiple_files else None
                )
            else:
                files = [UploadedFile(rec) for rec in file_recs]
                return_value = files if accept_multiple_files else files[0]
            return return_value

        def serialize_file_uploader(files: SomeUploadedFiles) -> FileUploaderStateProto:
            state_proto = FileUploaderStateProto()

            ctx = get_script_run_ctx()
            if ctx is None:
                return state_proto

            # ctx.uploaded_file_mgr._file_id_counter stores the id to use for
            # the *next* uploaded file, so the current highest file id is the
            # counter minus 1.
            state_proto.max_file_id = ctx.uploaded_file_mgr._file_id_counter - 1

            if not files:
                return state_proto
            elif not isinstance(files, list):
                files = [files]

            for f in files:
                file_info: UploadedFileInfoProto = state_proto.uploaded_file_info.add()
                file_info.id = f.id
                file_info.name = f.name
                file_info.size = f.size

            return state_proto

        # FileUploader's widget value is a list of file IDs
        # representing the current set of files that this uploader should
        # know about.
        widget_value, _ = register_widget(
            "file_uploader",
            file_uploader_proto,
            user_key=key,
            on_change_handler=on_change,
            args=args,
            kwargs=kwargs,
            deserializer=deserialize_file_uploader,
            serializer=serialize_file_uploader,
            ctx=ctx,
        )

        # This needs to be done after register_widget because we don't want
        # the following proto fields to affect a widget's ID.
        file_uploader_proto.disabled = disabled

        file_uploader_state = serialize_file_uploader(widget_value)
        uploaded_file_info = file_uploader_state.uploaded_file_info
        if ctx is not None and len(uploaded_file_info) != 0:
            newest_file_id = file_uploader_state.max_file_id
            active_file_ids = [f.id for f in uploaded_file_info]

            ctx.uploaded_file_mgr.remove_orphaned_files(
                session_id=ctx.session_id,
                widget_id=file_uploader_proto.id,
                newest_file_id=newest_file_id,
                active_file_ids=active_file_ids,
            )

        self.dg._enqueue("file_uploader", file_uploader_proto)
        return cast(SomeUploadedFiles, widget_value)

    @staticmethod
    def _get_file_recs(
        widget_id: str, widget_value: Optional[FileUploaderStateProto]
    ) -> List[UploadedFileRec]:
        if widget_value is None:
            return []

        ctx = get_script_run_ctx()
        if ctx is None:
            return []

        uploaded_file_info = widget_value.uploaded_file_info
        if len(uploaded_file_info) == 0:
            return []

        active_file_ids = [f.id for f in uploaded_file_info]

        # Grab the files that correspond to our active file IDs.
        return ctx.uploaded_file_mgr.get_files(
            session_id=ctx.session_id,
            widget_id=widget_id,
            file_ids=active_file_ids,
        )

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