import os
from pathlib import Path
from tempfile import TemporaryDirectory
from typing import TYPE_CHECKING, Optional

from ..cloudpath import CloudPath, NoStatError, register_path_class


if TYPE_CHECKING:
    from .gsclient import GSClient


@register_path_class("gs")
class GSPath(CloudPath):
    """Class for representing and operating on Google Cloud Storage URIs, in the style of the
    Python standard library's [`pathlib` module](https://docs.python.org/3/library/pathlib.html).
    Instances represent a path in GS with filesystem path semantics, and convenient methods allow
    for basic operations like joining, reading, writing, iterating over contents, etc. This class
    almost entirely mimics the [`pathlib.Path`](https://docs.python.org/3/library/pathlib.html#pathlib.Path)
    interface, so most familiar properties and methods should be available and behave in the
    expected way.

    The [`GSClient`](../gsclient/) class handles authentication with GCP. If a client instance is
    not explicitly specified on `GSPath` instantiation, a default client is used. See `GSClient`'s
    documentation for more details.
    """

    cloud_prefix: str = "gs://"
    client: "GSClient"

    @property
    def drive(self) -> str:
        return self.bucket

    def mkdir(self, parents=False, exist_ok=False):
        # not possible to make empty directory on cloud storage
        pass

    def touch(self, exist_ok: bool = True):
        if self.exists():
            if not exist_ok:
                raise FileExistsError(f"File exists: {self}")
            self.client._move_file(self, self)
        else:
            tf = TemporaryDirectory()
            p = Path(tf.name) / "empty"
            p.touch()

            self.client._upload_file(p, self)

            tf.cleanup()

    def stat(self):
        meta = self.client._get_metadata(self)
        if meta is None:
            raise NoStatError(
                f"No stats available for {self}; it may be a directory or not exist."
            )

        try:
            mtime = meta["updated"].timestamp()
        except KeyError:
            mtime = 0

        return os.stat_result(
            (
                None,  # mode
                None,  # ino
                self.cloud_prefix,  # dev,
                None,  # nlink,
                None,  # uid,
                None,  # gid,
                meta.get("size", 0),  # size,
                None,  # atime,
                mtime,  # mtime,
                None,  # ctime,
            )
        )

    @property
    def bucket(self) -> str:
        return self._no_prefix.split("/", 1)[0]

    @property
    def blob(self) -> str:
        key = self._no_prefix_no_drive

        # key should never have starting slash for
        # use with google-cloud-storage, etc.
        if key.startswith("/"):
            key = key[1:]

        return key

    @property
    def etag(self):
        return self.client._get_metadata(self).get("etag")

    @property
    def md5(self) -> Optional[str]:
        meta = self.client._get_metadata(self)
        if not meta:
            return None
        return meta.get("md5_hash", None)