from __future__ import absolute_import, division, print_function

import logging
from datetime import datetime
from errno import ENOTEMPTY
from io import BytesIO

from fsspec import AbstractFileSystem

logger = logging.Logger("fsspec.memoryfs")


class MemoryFileSystem(AbstractFileSystem):
    """A filesystem based on a dict of BytesIO objects

    This is a global filesystem so instances of this class all point to the same
    in memory filesystem.
    """

    store = {}  # global, do not overwrite!
    pseudo_dirs = [""]  # global, do not overwrite!
    protocol = "memory"
    root_marker = "/"

    @classmethod
    def _strip_protocol(cls, path):
        if path.startswith("memory://"):
            path = path[len("memory://") :]
        if "::" in path or "://" in path:
            return path.rstrip("/")
        path = path.lstrip("/").rstrip("/")
        return "/" + path if path else ""

    def ls(self, path, detail=True, **kwargs):
        path = self._strip_protocol(path)
        if path in self.store:
            # there is a key with this exact name
            if not detail:
                return [path]
            return [
                {
                    "name": path,
                    "size": self.store[path].size,
                    "type": "file",
                    "created": self.store[path].created.timestamp(),
                }
            ]
        paths = set()
        starter = path + "/"
        out = []
        for p2 in tuple(self.store):
            if p2.startswith(starter):
                if "/" not in p2[len(starter) :]:
                    # exact child
                    out.append(
                        {
                            "name": p2,
                            "size": self.store[p2].size,
                            "type": "file",
                            "created": self.store[p2].created.timestamp(),
                        }
                    )
                elif len(p2) > len(starter):
                    # implied child directory
                    ppath = starter + p2[len(starter) :].split("/", 1)[0]
                    if ppath not in paths:
                        out = out or []
                        out.append(
                            {
                                "name": ppath,
                                "size": 0,
                                "type": "directory",
                            }
                        )
                        paths.add(ppath)
        for p2 in self.pseudo_dirs:
            if p2.startswith(starter):
                if "/" not in p2[len(starter) :]:
                    # exact child pdir
                    if p2 not in paths:
                        out.append({"name": p2, "size": 0, "type": "directory"})
                        paths.add(p2)
                else:
                    # directory implied by deeper pdir
                    ppath = starter + p2[len(starter) :].split("/", 1)[0]
                    if ppath not in paths:
                        out.append({"name": ppath, "size": 0, "type": "directory"})
                        paths.add(ppath)
        if not out:
            if path in self.pseudo_dirs:
                # empty dir
                return []
            raise FileNotFoundError(path)
        if detail:
            return out
        return sorted([f["name"] for f in out])

    def mkdir(self, path, create_parents=True, **kwargs):
        path = self._strip_protocol(path)
        if path in self.store or path in self.pseudo_dirs:
            raise FileExistsError(path)
        if self._parent(path).strip("/") and self.isfile(self._parent(path)):
            raise NotADirectoryError(self._parent(path))
        if create_parents and self._parent(path).strip("/"):
            try:
                self.mkdir(self._parent(path), create_parents, **kwargs)
            except FileExistsError:
                pass
        if path and path not in self.pseudo_dirs:
            self.pseudo_dirs.append(path)

    def makedirs(self, path, exist_ok=False):
        try:
            self.mkdir(path, create_parents=True)
        except FileExistsError:
            if not exist_ok:
                raise

    def pipe_file(self, path, value, **kwargs):
        """Set the bytes of given file

        Avoids copies of the data if possible
        """
        self.open(path, "wb", data=value)

    def rmdir(self, path):
        path = self._strip_protocol(path)
        if path == "":
            # silently avoid deleting FS root
            return
        if path in self.pseudo_dirs:
            if not self.ls(path):
                self.pseudo_dirs.remove(path)
            else:
                raise OSError(ENOTEMPTY, "Directory not empty", path)
        else:
            raise FileNotFoundError(path)

    def exists(self, path, **kwargs):
        path = self._strip_protocol(path)
        return path in self.store or path in self.pseudo_dirs

    def info(self, path, **kwargs):
        path = self._strip_protocol(path)
        if path in self.pseudo_dirs or any(
            p.startswith(path + "/") for p in list(self.store) + self.pseudo_dirs
        ):
            return {
                "name": path,
                "size": 0,
                "type": "directory",
            }
        elif path in self.store:
            filelike = self.store[path]
            return {
                "name": path,
                "size": filelike.size,
                "type": "file",
                "created": getattr(filelike, "created", None),
            }
        else:
            raise FileNotFoundError(path)

    def _open(
        self,
        path,
        mode="rb",
        block_size=None,
        autocommit=True,
        cache_options=None,
        **kwargs,
    ):
        path = self._strip_protocol(path)
        if path in self.pseudo_dirs:
            raise IsADirectoryError(path)
        parent = path
        while len(parent) > 1:
            parent = self._parent(parent)
            if self.isfile(parent):
                raise FileExistsError(parent)
        if mode in ["rb", "ab", "rb+"]:
            if path in self.store:
                f = self.store[path]
                if mode == "ab":
                    # position at the end of file
                    f.seek(0, 2)
                else:
                    # position at the beginning of file
                    f.seek(0)
                return f
            else:
                raise FileNotFoundError(path)
        if mode == "wb":
            m = MemoryFile(self, path, kwargs.get("data"))
            if not self._intrans:
                m.commit()
            return m

    def cp_file(self, path1, path2, **kwargs):
        path1 = self._strip_protocol(path1)
        path2 = self._strip_protocol(path2)
        if self.isfile(path1):
            self.store[path2] = MemoryFile(
                self, path2, self.store[path1].getvalue()
            )  # implicit copy
        elif self.isdir(path1):
            if path2 not in self.pseudo_dirs:
                self.pseudo_dirs.append(path2)
        else:
            raise FileNotFoundError(path1)

    def cat_file(self, path, start=None, end=None, **kwargs):
        path = self._strip_protocol(path)
        try:
            return bytes(self.store[path].getbuffer()[start:end])
        except KeyError:
            raise FileNotFoundError(path)

    def _rm(self, path):
        path = self._strip_protocol(path)
        try:
            del self.store[path]
        except KeyError as e:
            raise FileNotFoundError(path) from e

    def modified(self, path):
        path = self._strip_protocol(path)
        try:
            return self.store[path].modified
        except KeyError:
            raise FileNotFoundError(path)

    def created(self, path):
        path = self._strip_protocol(path)
        try:
            return self.store[path].created
        except KeyError:
            raise FileNotFoundError(path)

    def rm(self, path, recursive=False, maxdepth=None):
        if isinstance(path, str):
            path = self._strip_protocol(path)
        else:
            path = [self._strip_protocol(p) for p in path]
        paths = self.expand_path(path, recursive=recursive, maxdepth=maxdepth)
        for p in reversed(paths):
            # If the expanded path doesn't exist, it is only because the expanded
            # path was a directory that does not exist in self.pseudo_dirs. This
            # is possible if you directly create files without making the
            # directories first.
            if not self.exists(p):
                continue
            if self.isfile(p):
                self.rm_file(p)
            else:
                self.rmdir(p)


class MemoryFile(BytesIO):
    """A BytesIO which can't close and works as a context manager

    Can initialise with data. Each path should only be active once at any moment.

    No need to provide fs, path if auto-committing (default)
    """

    def __init__(self, fs=None, path=None, data=None):
        logger.debug("open file %s", path)
        self.fs = fs
        self.path = path
        self.created = datetime.utcnow()
        self.modified = datetime.utcnow()
        if data:
            super().__init__(data)
            self.seek(0)

    @property
    def size(self):
        return self.getbuffer().nbytes

    def __enter__(self):
        return self

    def close(self):
        pass

    def discard(self):
        pass

    def commit(self):
        self.fs.store[self.path] = self
        self.modified = datetime.utcnow()
