"""
"""
from abc import ABCMeta, abstractmethod
from typing import AsyncGenerator, Callable, Iterable, List, Optional, Sequence

from prompt_toolkit.document import Document
from prompt_toolkit.eventloop import (
    aclosing,
    generator_to_async_generator,
    get_event_loop,
)
from prompt_toolkit.filters import FilterOrBool, to_filter
from prompt_toolkit.formatted_text import AnyFormattedText, StyleAndTextTuples

__all__ = [
    "Completion",
    "Completer",
    "ThreadedCompleter",
    "DummyCompleter",
    "DynamicCompleter",
    "CompleteEvent",
    "ConditionalCompleter",
    "merge_completers",
    "get_common_complete_suffix",
]


class Completion:
    """
    :param text: The new string that will be inserted into the document.
    :param start_position: Position relative to the cursor_position where the
        new text will start. The text will be inserted between the
        start_position and the original cursor position.
    :param display: (optional string or formatted text) If the completion has
        to be displayed differently in the completion menu.
    :param display_meta: (Optional string or formatted text) Meta information
        about the completion, e.g. the path or source where it's coming from.
        This can also be a callable that returns a string.
    :param style: Style string.
    :param selected_style: Style string, used for a selected completion.
        This can override the `style` parameter.
    """

    def __init__(
        self,
        text: str,
        start_position: int = 0,
        display: Optional[AnyFormattedText] = None,
        display_meta: Optional[AnyFormattedText] = None,
        style: str = "",
        selected_style: str = "",
    ) -> None:

        from prompt_toolkit.formatted_text import to_formatted_text

        self.text = text
        self.start_position = start_position
        self._display_meta = display_meta

        if display is None:
            display = text

        self.display = to_formatted_text(display)

        self.style = style
        self.selected_style = selected_style

        assert self.start_position <= 0

    def __repr__(self) -> str:
        if isinstance(self.display, str) and self.display == self.text:
            return "{}(text={!r}, start_position={!r})".format(
                self.__class__.__name__,
                self.text,
                self.start_position,
            )
        else:
            return "{}(text={!r}, start_position={!r}, display={!r})".format(
                self.__class__.__name__,
                self.text,
                self.start_position,
                self.display,
            )

    def __eq__(self, other: object) -> bool:
        if not isinstance(other, Completion):
            return False
        return (
            self.text == other.text
            and self.start_position == other.start_position
            and self.display == other.display
            and self._display_meta == other._display_meta
        )

    def __hash__(self) -> int:
        return hash((self.text, self.start_position, self.display, self._display_meta))

    @property
    def display_text(self) -> str:
        "The 'display' field as plain text."
        from prompt_toolkit.formatted_text import fragment_list_to_text

        return fragment_list_to_text(self.display)

    @property
    def display_meta(self) -> StyleAndTextTuples:
        "Return meta-text. (This is lazy when using a callable)."
        from prompt_toolkit.formatted_text import to_formatted_text

        return to_formatted_text(self._display_meta or "")

    @property
    def display_meta_text(self) -> str:
        "The 'meta' field as plain text."
        from prompt_toolkit.formatted_text import fragment_list_to_text

        return fragment_list_to_text(self.display_meta)

    def new_completion_from_position(self, position: int) -> "Completion":
        """
        (Only for internal use!)
        Get a new completion by splitting this one. Used by `Application` when
        it needs to have a list of new completions after inserting the common
        prefix.
        """
        assert position - self.start_position >= 0

        return Completion(
            text=self.text[position - self.start_position :],
            display=self.display,
            display_meta=self._display_meta,
        )


class CompleteEvent:
    """
    Event that called the completer.

    :param text_inserted: When True, it means that completions are requested
        because of a text insert. (`Buffer.complete_while_typing`.)
    :param completion_requested: When True, it means that the user explicitly
        pressed the `Tab` key in order to view the completions.

    These two flags can be used for instance to implement a completer that
    shows some completions when ``Tab`` has been pressed, but not
    automatically when the user presses a space. (Because of
    `complete_while_typing`.)
    """

    def __init__(
        self, text_inserted: bool = False, completion_requested: bool = False
    ) -> None:
        assert not (text_inserted and completion_requested)

        #: Automatic completion while typing.
        self.text_inserted = text_inserted

        #: Used explicitly requested completion by pressing 'tab'.
        self.completion_requested = completion_requested

    def __repr__(self) -> str:
        return "{}(text_inserted={!r}, completion_requested={!r})".format(
            self.__class__.__name__,
            self.text_inserted,
            self.completion_requested,
        )


class Completer(metaclass=ABCMeta):
    """
    Base class for completer implementations.
    """

    @abstractmethod
    def get_completions(
        self, document: Document, complete_event: CompleteEvent
    ) -> Iterable[Completion]:
        """
        This should be a generator that yields :class:`.Completion` instances.

        If the generation of completions is something expensive (that takes a
        lot of time), consider wrapping this `Completer` class in a
        `ThreadedCompleter`. In that case, the completer algorithm runs in a
        background thread and completions will be displayed as soon as they
        arrive.

        :param document: :class:`~prompt_toolkit.document.Document` instance.
        :param complete_event: :class:`.CompleteEvent` instance.
        """
        while False:
            yield

    async def get_completions_async(
        self, document: Document, complete_event: CompleteEvent
    ) -> AsyncGenerator[Completion, None]:
        """
        Asynchronous generator for completions. (Probably, you won't have to
        override this.)

        Asynchronous generator of :class:`.Completion` objects.
        """
        for item in self.get_completions(document, complete_event):
            yield item


class ThreadedCompleter(Completer):
    """
    Wrapper that runs the `get_completions` generator in a thread.

    (Use this to prevent the user interface from becoming unresponsive if the
    generation of completions takes too much time.)

    The completions will be displayed as soon as they are produced. The user
    can already select a completion, even if not all completions are displayed.
    """

    def __init__(self, completer: Completer) -> None:
        self.completer = completer

    def get_completions(
        self, document: Document, complete_event: CompleteEvent
    ) -> Iterable[Completion]:
        return self.completer.get_completions(document, complete_event)

    async def get_completions_async(
        self, document: Document, complete_event: CompleteEvent
    ) -> AsyncGenerator[Completion, None]:
        """
        Asynchronous generator of completions.
        """
        # NOTE: Right now, we are consuming the `get_completions` generator in
        #       a synchronous background thread, then passing the results one
        #       at a time over a queue, and consuming this queue in the main
        #       thread (that's what `generator_to_async_generator` does). That
        #       means that if the completer is *very* slow, we'll be showing
        #       completions in the UI once they are computed.

        #       It's very tempting to replace this implementation with the
        #       commented code below for several reasons:

        #       - `generator_to_async_generator` is not perfect and hard to get
        #         right. It's a lot of complexity for little gain. The
        #         implementation needs a huge buffer for it to be efficient
        #         when there are many completions (like 50k+).
        #       - Normally, a completer is supposed to be fast, users can have
        #         "complete while typing" enabled, and want to see the
        #         completions within a second. Handling one completion at a
        #         time, and rendering once we get it here doesn't make any
        #         sense if this is quick anyway.
        #       - Completers like `FuzzyCompleter` prepare all completions
        #         anyway so that they can be sorted by accuracy before they are
        #         yielded. At the point that we start yielding completions
        #         here, we already have all completions.
        #       - The `Buffer` class has complex logic to invalidate the UI
        #         while it is consuming the completions. We don't want to
        #         invalidate the UI for every completion (if there are many),
        #         but we want to do it often enough so that completions are
        #         being displayed while they are produced.

        #       We keep the current behavior mainly for backward-compatibility.
        #       Similarly, it would be better for this function to not return
        #       an async generator, but simply be a coroutine that returns a
        #       list of `Completion` objects, containing all completions at
        #       once.

        #       Note that this argument doesn't mean we shouldn't use
        #       `ThreadedCompleter`. It still makes sense to produce
        #       completions in a background thread, because we don't want to
        #       freeze the UI while the user is typing. But sending the
        #       completions one at a time to the UI maybe isn't worth it.

        # def get_all_in_thread() -> List[Completion]:
        #   return list(self.get_completions(document, complete_event))

        # completions = await get_event_loop().run_in_executor(None, get_all_in_thread)
        # for completion in completions:
        #   yield completion

        async with aclosing(
            generator_to_async_generator(
                lambda: self.completer.get_completions(document, complete_event)
            )
        ) as async_generator:
            async for completion in async_generator:
                yield completion

    def __repr__(self) -> str:
        return f"ThreadedCompleter({self.completer!r})"


class DummyCompleter(Completer):
    """
    A completer that doesn't return any completion.
    """

    def get_completions(
        self, document: Document, complete_event: CompleteEvent
    ) -> Iterable[Completion]:
        return []

    def __repr__(self) -> str:
        return "DummyCompleter()"


class DynamicCompleter(Completer):
    """
    Completer class that can dynamically returns any Completer.

    :param get_completer: Callable that returns a :class:`.Completer` instance.
    """

    def __init__(self, get_completer: Callable[[], Optional[Completer]]) -> None:
        self.get_completer = get_completer

    def get_completions(
        self, document: Document, complete_event: CompleteEvent
    ) -> Iterable[Completion]:
        completer = self.get_completer() or DummyCompleter()
        return completer.get_completions(document, complete_event)

    async def get_completions_async(
        self, document: Document, complete_event: CompleteEvent
    ) -> AsyncGenerator[Completion, None]:
        completer = self.get_completer() or DummyCompleter()

        async for completion in completer.get_completions_async(
            document, complete_event
        ):
            yield completion

    def __repr__(self) -> str:
        return f"DynamicCompleter({self.get_completer!r} -> {self.get_completer()!r})"


class ConditionalCompleter(Completer):
    """
    Wrapper around any other completer that will enable/disable the completions
    depending on whether the received condition is satisfied.

    :param completer: :class:`.Completer` instance.
    :param filter: :class:`.Filter` instance.
    """

    def __init__(self, completer: Completer, filter: FilterOrBool) -> None:
        self.completer = completer
        self.filter = to_filter(filter)

    def __repr__(self) -> str:
        return f"ConditionalCompleter({self.completer!r}, filter={self.filter!r})"

    def get_completions(
        self, document: Document, complete_event: CompleteEvent
    ) -> Iterable[Completion]:
        # Get all completions in a blocking way.
        if self.filter():
            yield from self.completer.get_completions(document, complete_event)

    async def get_completions_async(
        self, document: Document, complete_event: CompleteEvent
    ) -> AsyncGenerator[Completion, None]:

        # Get all completions in a non-blocking way.
        if self.filter():
            async with aclosing(
                self.completer.get_completions_async(document, complete_event)
            ) as async_generator:
                async for item in async_generator:
                    yield item


class _MergedCompleter(Completer):
    """
    Combine several completers into one.
    """

    def __init__(self, completers: Sequence[Completer]) -> None:
        self.completers = completers

    def get_completions(
        self, document: Document, complete_event: CompleteEvent
    ) -> Iterable[Completion]:
        # Get all completions from the other completers in a blocking way.
        for completer in self.completers:
            yield from completer.get_completions(document, complete_event)

    async def get_completions_async(
        self, document: Document, complete_event: CompleteEvent
    ) -> AsyncGenerator[Completion, None]:

        # Get all completions from the other completers in a non-blocking way.
        for completer in self.completers:
            async with aclosing(
                completer.get_completions_async(document, complete_event)
            ) as async_generator:
                async for item in async_generator:
                    yield item


def merge_completers(
    completers: Sequence[Completer], deduplicate: bool = False
) -> Completer:
    """
    Combine several completers into one.

    :param deduplicate: If `True`, wrap the result in a `DeduplicateCompleter`
        so that completions that would result in the same text will be
        deduplicated.
    """
    if deduplicate:
        from .deduplicate import DeduplicateCompleter

        return DeduplicateCompleter(_MergedCompleter(completers))

    return _MergedCompleter(completers)


def get_common_complete_suffix(
    document: Document, completions: Sequence[Completion]
) -> str:
    """
    Return the common prefix for all completions.
    """
    # Take only completions that don't change the text before the cursor.
    def doesnt_change_before_cursor(completion: Completion) -> bool:
        end = completion.text[: -completion.start_position]
        return document.text_before_cursor.endswith(end)

    completions2 = [c for c in completions if doesnt_change_before_cursor(c)]

    # When there is at least one completion that changes the text before the
    # cursor, don't return any common part.
    if len(completions2) != len(completions):
        return ""

    # Return the common prefix.
    def get_suffix(completion: Completion) -> str:
        return completion.text[-completion.start_position :]

    return _commonprefix([get_suffix(c) for c in completions2])


def _commonprefix(strings: Iterable[str]) -> str:
    # Similar to os.path.commonprefix
    if not strings:
        return ""

    else:
        s1 = min(strings)
        s2 = max(strings)

        for i, c in enumerate(s1):
            if c != s2[i]:
                return s1[:i]

        return s1
