from abc import ABC, abstractmethod
from collections.abc import AsyncGenerator, Awaitable, Callable
from dataclasses import dataclass
from typing import Optional, Type, TypeVar, BinaryIO, Union

T = TypeVar("T")

Fetcher = Callable[[str], Awaitable[Optional[Union[str, BinaryIO]]]]

# Like public Fetcher type above but does not allow 'str' outputs.
IOFetcher = Callable[[str], Awaitable[Optional[BinaryIO]]]


ICON_FOLDER = "📂"
ICON_PACKAGE = "📦"
ICON_OPTICAL = "📀"
ICON_QCOW = "🐮"
ICON_OTHER = "  "


class ContentError(Exception):
    """An error raised when indexed content appears to be invalid.

    Errors of this type are raised when repo-autoindex is able to successfully
    retrieve content and determine a repository type but fails to parse
    repository metadata. For example, a corrupt yum repository may cause this
    error to be raised.
    """


class FetcherError(Exception):
    # Internal-only error used to separate exceptions raised by fetchers from
    # exceptions raised by anything else.
    pass


@dataclass
class GeneratedIndex:
    """A single HTML index page generated by repo-autoindex."""

    content: str
    """The content of this index page (an HTML document)."""

    relative_dir: str = "."
    """The directory of this index page, relative to the root of the indexed
    repository.
    """


@dataclass
class IndexEntry:
    href: str
    text: str
    time: str = ""
    size: str = ""
    padding: str = ""
    icon: str = ICON_OTHER

    @property
    def sort_key(self):
        # Returns a suggested sort key for displaying entries in
        # a UI.

        priority = 0

        # Folders should come first
        if self.href.endswith("/"):
            priority -= 1
            # And special folders like ".." even earlier
            if self.href.startswith("."):
                priority -= 1

        # Entries sort by the priority we calculated, and then by name
        return (priority, self.href)


class Repo(ABC):
    def __init__(
        self,
        base_url: str,
        entry_point_content: str,
        fetcher: IOFetcher,
    ):
        self.base_url = base_url
        self.entry_point_content = entry_point_content
        self.fetcher = fetcher

    @abstractmethod
    def render_index(
        self, index_href_suffix: str
    ) -> AsyncGenerator[GeneratedIndex, None]:
        pass  # pragma: no cover

    @classmethod
    @abstractmethod
    async def probe(cls: Type[T], fetcher: IOFetcher, url: str) -> Optional[T]:
        """Determine if a specified URL seems to point at a repository of this type.

        If so, returns an initialized Repo of a concrete subtype. If not, returns None.
        """
        pass  # pragma: no cover