request.py

# -*- coding: utf-8 -*-
# imageio is distributed under the terms of the (new) BSD License.

"""
Definition of the Request object, which acts as a kind of bridge between
what the user wants and what the plugins can.
"""

import os
from io import BytesIO
import zipfile
import tempfile
import shutil
import enum
import warnings

from ..core import urlopen, get_remote_file

from pathlib import Path
from urllib.parse import urlparse
from typing import Optional

# URI types
URI_BYTES = 1
URI_FILE = 2
URI_FILENAME = 3
URI_ZIPPED = 4
URI_HTTP = 5
URI_FTP = 6


class IOMode(str, enum.Enum):
    """Available Image modes

    This is a helper enum for ``Request.Mode`` which is a composite of a
    ``Request.ImageMode`` and ``Request.IOMode``. The IOMode that tells the
    plugin if the resource should be read from or written to. Available values are

    - read ("r"): Read from the specified resource
    - write ("w"): Write to the specified resource

    """

    read = "r"
    write = "w"


class ImageMode(str, enum.Enum):
    """Available Image modes

    This is a helper enum for ``Request.Mode`` which is a composite of a
    ``Request.ImageMode`` and ``Request.IOMode``. The image mode that tells the
    plugin the desired (and expected) image shape. Available values are

    - single_image ("i"): Return a single image extending in two spacial
      dimensions
    - multi_image ("I"): Return a list of images extending in two spacial
      dimensions
    - single_volume ("v"): Return an image extending into multiple dimensions.
      E.g. three spacial dimensions for image stacks, or two spatial and one
      time dimension for videos
    - multi_volume ("V"): Return a list of images extending into multiple
      dimensions.
    - any_mode ("?"): Return an image in any format (the plugin decides the
      appropriate action).

    """

    single_image = "i"
    multi_image = "I"
    single_volume = "v"
    multi_volume = "V"
    any_mode = "?"


@enum.unique
class Mode(str, enum.Enum):
    """The mode to use when interacting with the resource

    ``Request.Mode`` is a composite of ``Request.ImageMode`` and
    ``Request.IOMode``. The image mode that tells the plugin the desired (and
    expected) image shape and the ``Request.IOMode`` tells the plugin the way
    the resource should be interacted with. For a detailed description of the
    available modes, see the documentation for ``Request.ImageMode`` and
    ``Request.IOMode`` respectively.

    Available modes are all combinations of ``Request.IOMode`` and ``Request.ImageMode``:

    - read_single_image ("ri")
    - read_multi_image ("rI")
    - read_single_volume ("rv")
    - read_multi_volume ("rV")
    - read_any ("r?")
    - write_single_image ("wi")
    - write_multi_image ("wI")
    - write_single_volume ("wv")
    - write_multi_volume ("wV")
    - write_any ("w?")

    Examples
    --------
    >>> Request.Mode("rI")  # a list of simple images should be read from the resource
    >>> Request.Mode("wv")  # a single volume should be written to the resource

    """

    read_single_image = "ri"
    read_multi_image = "rI"
    read_single_volume = "rv"
    read_multi_volume = "rV"
    read_any = "r?"
    write_single_image = "wi"
    write_multi_image = "wI"
    write_single_volume = "wv"
    write_multi_volume = "wV"
    write_any = "w?"

    @classmethod
    def _missing_(cls, value):
        """Enable Mode("r") and Mode("w")

        The sunder method ``_missing_`` is called whenever the constructor fails
        to directly look up the corresponding enum value from the given input.
        In our case, we use it to convert the modes "r" and "w" (from the v3
        API) into their legacy versions "r?" and "w?".

        More info on _missing_:
        https://docs.python.org/3/library/enum.html#supported-sunder-names
        """

        if value == "r":
            return cls("r?")
        elif value == "w":
            return cls("w?")
        else:
            raise ValueError(f"{value} is no valid Mode.")

    @property
    def io_mode(self) -> IOMode:
        return IOMode(self.value[0])

    @property
    def image_mode(self) -> ImageMode:
        return ImageMode(self.value[1])

    def __getitem__(self, key):
        """For backwards compatibility with the old non-enum modes"""
        if key == 0:
            return self.io_mode
        elif key == 1:
            return self.image_mode
        else:
            raise IndexError(f"Mode has no item {key}")


SPECIAL_READ_URIS = "<video", "<screen>", "<clipboard>"

# The user can use this string in a write call to get the data back as bytes.
RETURN_BYTES = "<bytes>"

# Example images that will be auto-downloaded
EXAMPLE_IMAGES = {
    "astronaut.png": "Image of the astronaut Eileen Collins",
    "camera.png": "A grayscale image of a photographer",
    "checkerboard.png": "Black and white image of a chekerboard",
    "wood.jpg": "A (repeatable) texture of wooden planks",
    "bricks.jpg": "A (repeatable) texture of stone bricks",
    "clock.png": "Photo of a clock with motion blur (Stefan van der Walt)",
    "coffee.png": "Image of a cup of coffee (Rachel Michetti)",
    "chelsea.png": "Image of Stefan's cat",
    "wikkie.png": "Image of Almar's cat",
    "coins.png": "Image showing greek coins from Pompeii",
    "horse.png": "Image showing the silhouette of a horse (Andreas Preuss)",
    "hubble_deep_field.png": "Photograph taken by Hubble telescope (NASA)",
    "immunohistochemistry.png": "Immunohistochemical (IHC) staining",
    "moon.png": "Image showing a portion of the surface of the moon",
    "page.png": "A scanned page of text",
    "text.png": "A photograph of handdrawn text",
    "chelsea.zip": "The chelsea.png in a zipfile (for testing)",
    "chelsea.bsdf": "The chelsea.png in a BSDF file(for testing)",
    "newtonscradle.gif": "Animated GIF of a newton's cradle",
    "cockatoo.mp4": "Video file of a cockatoo",
    "stent.npz": "Volumetric image showing a stented abdominal aorta",
    "meadow_cube.jpg": "A cubemap image of a meadow, e.g. to render a skybox.",
}


class Request(object):
    """ImageResource handling utility.

    Represents a request for reading or saving an image resource. This
    object wraps information to that request and acts as an interface
    for the plugins to several resources; it allows the user to read
    from filenames, files, http, zipfiles, raw bytes, etc., but offer
    a simple interface to the plugins via ``get_file()`` and
    ``get_local_filename()``.

    For each read/write operation a single Request instance is used and passed
    to the can_read/can_write method of a format, and subsequently to
    the Reader/Writer class. This allows rudimentary passing of
    information between different formats and between a format and
    associated reader/writer.

    Parameters
    ----------
    uri : {str, bytes, file}
        The resource to load the image from.
    mode : str
        The first character is "r" or "w", indicating a read or write
        request. The second character is used to indicate the kind of data:
        "i" for an image, "I" for multiple images, "v" for a volume,
        "V" for multiple volumes, "?" for don't care.

    """

    def __init__(self, uri, mode, *, extension=None, format_hint: str = None, **kwargs):
        # General
        self.raw_uri = uri
        self._uri_type = None
        self._filename = None
        self._extension = None
        self._format_hint = None
        self._kwargs = kwargs
        self._result = None  # Some write actions may have a result

        # To handle the user-side
        self._filename_zip = None  # not None if a zipfile is used
        self._bytes = None  # Incoming bytes
        self._zipfile = None  # To store a zipfile instance (if used)

        # To handle the plugin side
        self._file = None  # To store the file instance
        self._file_is_local = False  # whether the data needs to be copied at end
        self._filename_local = None  # not None if using tempfile on this FS
        self._firstbytes = None  # For easy header parsing

        # To store formats that may be able to fulfil this request
        # self._potential_formats = []

        # Check mode
        try:
            self._mode = Mode(mode)
        except ValueError:
            raise ValueError(f"Invalid Request.Mode: {mode}")

        # Parse what was given
        self._parse_uri(uri)

        # Set extension
        if extension is not None:
            if extension[0] != ".":
                raise ValueError(
                    "`extension` should be a file extension starting with a `.`,"
                    f" but is `{extension}`."
                )
            self._extension = extension
        elif self._filename is not None:
            if self._uri_type in (URI_FILENAME, URI_ZIPPED):
                path = self._filename
            else:
                path = urlparse(self._filename).path
            ext = Path(path).suffix.lower()
            self._extension = ext if ext != "" else None

        if format_hint is not None:
            warnings.warn(
                "The usage of `format_hint` is deprecated and will be removed "
                "in ImageIO v3. Use `extension` instead.",
                DeprecationWarning,
            )

        if format_hint is not None and format_hint[0] != ".":
            raise ValueError(
                "`format_hint` should be a file extension starting with a `.`,"
                f" but is `{format_hint}`."
            )

        self.format_hint = format_hint

    def _parse_uri(self, uri):
        """Try to figure our what we were given"""
        is_read_request = self.mode.io_mode is IOMode.read
        is_write_request = self.mode.io_mode is IOMode.write

        if isinstance(uri, str):
            # Explicit
            if uri.startswith("imageio:"):
                if is_write_request:
                    raise RuntimeError("Cannot write to the standard images.")
                fn = uri.split(":", 1)[-1].lower()
                fn, _, zip_part = fn.partition(".zip/")
                if zip_part:
                    fn += ".zip"
                if fn not in EXAMPLE_IMAGES:
                    raise ValueError("Unknown standard image %r." % fn)
                self._uri_type = URI_FILENAME
                self._filename = get_remote_file("images/" + fn, auto=True)
                if zip_part:
                    self._filename += "/" + zip_part
            elif uri.startswith("http://") or uri.startswith("https://"):
                self._uri_type = URI_HTTP
                self._filename = uri
            elif uri.startswith("ftp://") or uri.startswith("ftps://"):
                self._uri_type = URI_FTP
                self._filename = uri
            elif uri.startswith("file://"):
                self._uri_type = URI_FILENAME
                self._filename = uri[7:]
            elif uri.startswith(SPECIAL_READ_URIS) and is_read_request:
                self._uri_type = URI_BYTES
                self._filename = uri
            elif uri.startswith(RETURN_BYTES) and is_write_request:
                self._uri_type = URI_BYTES
                self._filename = uri
            else:
                self._uri_type = URI_FILENAME
                self._filename = uri

        elif isinstance(uri, memoryview) and is_read_request:
            self._uri_type = URI_BYTES
            self._filename = "<bytes>"
            self._bytes = uri.tobytes()
        elif isinstance(uri, bytes) and is_read_request:
            self._uri_type = URI_BYTES
            self._filename = "<bytes>"
            self._bytes = uri
        elif isinstance(uri, Path):
            self._uri_type = URI_FILENAME
            self._filename = str(uri)
        # Files
        elif is_read_request:
            if hasattr(uri, "read") and hasattr(uri, "close"):
                self._uri_type = URI_FILE
                self._filename = "<file>"
                self._file = uri  # Data must be read from here
        elif is_write_request:
            if hasattr(uri, "write") and hasattr(uri, "close"):
                self._uri_type = URI_FILE
                self._filename = "<file>"
                self._file = uri  # Data must be written here

        # Expand user dir
        if self._uri_type == URI_FILENAME and self._filename.startswith("~"):
            self._filename = os.path.expanduser(self._filename)

        # Check if a zipfile
        if self._uri_type == URI_FILENAME:
            # Search for zip extension followed by a path separater
            for needle in [".zip/", ".zip\\"]:
                zip_i = self._filename.lower().find(needle)
                if zip_i > 0:
                    zip_i += 4
                    zip_path = self._filename[:zip_i]
                    if os.path.isdir(zip_path):
                        pass  # is an existing dir (see #548)
                    elif is_write_request or os.path.isfile(zip_path):
                        self._uri_type = URI_ZIPPED
                        self._filename_zip = (
                            zip_path,
                            self._filename[zip_i:].lstrip("/\\"),
                        )
                        break

        # Check if we could read it
        if self._uri_type is None:
            uri_r = repr(uri)
            if len(uri_r) > 60:
                uri_r = uri_r[:57] + "..."
            raise IOError("Cannot understand given URI: %s." % uri_r)

        # Check if this is supported
        noWriting = [URI_HTTP, URI_FTP]
        if is_write_request and self._uri_type in noWriting:
            raise IOError("imageio does not support writing to http/ftp.")

        # Deprecated way to load standard images, give a sensible error message
        if is_read_request and self._uri_type in [URI_FILENAME, URI_ZIPPED]:
            fn = self._filename
            if self._filename_zip:
                fn = self._filename_zip[0]
            if (not os.path.exists(fn)) and (fn in EXAMPLE_IMAGES):
                raise IOError(
                    "No such file: %r. This file looks like one of "
                    "the standard images, but from imageio 2.1, "
                    "standard images have to be specified using "
                    '"imageio:%s".' % (fn, fn)
                )

        # Make filename absolute
        if self._uri_type in [URI_FILENAME, URI_ZIPPED]:
            if self._filename_zip:
                self._filename_zip = (
                    os.path.abspath(self._filename_zip[0]),
                    self._filename_zip[1],
                )
            else:
                self._filename = os.path.abspath(self._filename)

        # Check whether file name is valid
        if self._uri_type in [URI_FILENAME, URI_ZIPPED]:
            fn = self._filename
            if self._filename_zip:
                fn = self._filename_zip[0]
            if is_read_request:
                # Reading: check that the file exists (but is allowed a dir)
                if not os.path.exists(fn):
                    raise FileNotFoundError("No such file: '%s'" % fn)
            else:
                # Writing: check that the directory to write to does exist
                dn = os.path.dirname(fn)
                if not os.path.exists(dn):
                    raise FileNotFoundError("The directory %r does not exist" % dn)

    @property
    def filename(self):
        """Name of the ImageResource.


        The uri for which reading/saving was requested. This
        can be a filename, an http address, or other resource
        identifier. Do not rely on the filename to obtain the data,
        but use ``get_file()`` or ``get_local_filename()`` instead.
        """
        return self._filename

    @property
    def extension(self) -> str:
        """The (lowercase) extension of the requested filename.
        Suffixes in url's are stripped. Can be None if the request is
        not based on a filename.
        """
        return self._extension

    @property
    def format_hint(self) -> Optional[str]:
        return self._format_hint

    @format_hint.setter
    def format_hint(self, format: str) -> None:
        self._format_hint = format
        if self._extension is None:
            self._extension = format

    @property
    def mode(self):
        """The mode of the request. The first character is "r" or "w",
        indicating a read or write request. The second character is
        used to indicate the kind of data:
        "i" for an image, "I" for multiple images, "v" for a volume,
        "V" for multiple volumes, "?" for don't care.
        """
        return self._mode

    @property
    def kwargs(self):
        """The dict of keyword arguments supplied by the user."""
        return self._kwargs

    # For obtaining data

    def get_file(self):
        """get_file()
        Get a file object for the resource associated with this request.
        If this is a reading request, the file is in read mode,
        otherwise in write mode. This method is not thread safe. Plugins
        should not close the file when done.

        This is the preferred way to read/write the data. But if a
        format cannot handle file-like objects, they should use
        ``get_local_filename()``.
        """
        want_to_write = self.mode.io_mode is IOMode.write

        # Is there already a file?
        # Either _uri_type == URI_FILE, or we already opened the file,
        # e.g. by using firstbytes
        if self._file is not None:
            return self._file

        if self._uri_type == URI_BYTES:
            if want_to_write:
                # Create new file object, we catch the bytes in finish()
                self._file = BytesIO()
                self._file_is_local = True
            else:
                self._file = BytesIO(self._bytes)

        elif self._uri_type == URI_FILENAME:
            if want_to_write:
                self._file = open(self.filename, "wb")
            else:
                self._file = open(self.filename, "rb")

        elif self._uri_type == URI_ZIPPED:
            # Get the correct filename
            filename, name = self._filename_zip
            if want_to_write:
                # Create new file object, we catch the bytes in finish()
                self._file = BytesIO()
                self._file_is_local = True
            else:
                # Open zipfile and open new file object for specific file
                self._zipfile = zipfile.ZipFile(filename, "r")
                self._file = self._zipfile.open(name, "r")
                self._file = SeekableFileObject(self._file)

        elif self._uri_type in [URI_HTTP or URI_FTP]:
            assert not want_to_write  # This should have been tested in init
            timeout = os.getenv("IMAGEIO_REQUEST_TIMEOUT")
            if timeout is None or not timeout.isdigit():
                timeout = 5
            self._file = urlopen(self.filename, timeout=float(timeout))
            self._file = SeekableFileObject(self._file)

        return self._file

    def get_local_filename(self):
        """get_local_filename()
        If the filename is an existing file on this filesystem, return
        that. Otherwise a temporary file is created on the local file
        system which can be used by the format to read from or write to.
        """

        if self._uri_type == URI_FILENAME:
            return self._filename
        else:
            # Get filename
            if self.extension is not None:
                ext = self.extension
            else:
                ext = os.path.splitext(self._filename)[1]
            self._filename_local = tempfile.mktemp(ext, "imageio_")
            # Write stuff to it?
            if self.mode.io_mode == IOMode.read:
                with open(self._filename_local, "wb") as file:
                    shutil.copyfileobj(self.get_file(), file)
            return self._filename_local

    def finish(self) -> None:
        """Wrap up this request.

        Finishes any pending reads or writes, closes any open files and frees
        any resources allocated by this request.
        """

        if self.mode.io_mode == IOMode.write:
            # See if we "own" the data and must put it somewhere
            bytes = None
            if self._filename_local:
                bytes = Path(self._filename_local).read_bytes()
            elif self._file_is_local:
                self._file_is_local = False
                bytes = self._file.getvalue()

            # Put the data in the right place
            if bytes is not None:
                if self._uri_type == URI_BYTES:
                    self._result = bytes  # Picked up by imread function
                elif self._uri_type == URI_FILE:
                    self._file.write(bytes)
                elif self._uri_type == URI_ZIPPED:
                    zf = zipfile.ZipFile(self._filename_zip[0], "a")
                    zf.writestr(self._filename_zip[1], bytes)
                    zf.close()
                # elif self._uri_type == URI_FILENAME: -> is always direct
                # elif self._uri_type == URI_FTP/HTTP: -> write not supported

        # Close open files that we know of (and are responsible for)
        if self._file and self._uri_type != URI_FILE:
            self._file.close()
            self._file = None
        if self._zipfile:
            self._zipfile.close()
            self._zipfile = None

        # Remove temp file
        if self._filename_local:
            try:
                os.remove(self._filename_local)
            except Exception:  # pragma: no cover
                warnings.warn(
                    "Failed to delete the temporary file at "
                    f"`{self._filename_local}`. Please report this issue."
                )
            self._filename_local = None

        # Detach so gc can clean even if a reference of self lingers
        self._bytes = None

    def get_result(self):
        """For internal use. In some situations a write action can have
        a result (bytes data). That is obtained with this function.
        """
        # Is there a reason to disallow reading multiple times?
        self._result, res = None, self._result
        return res

    @property
    def firstbytes(self):
        """The first 256 bytes of the file. These can be used to
        parse the header to determine the file-format.
        """
        if self._firstbytes is None:
            self._read_first_bytes()
        return self._firstbytes

    def _read_first_bytes(self, N=256):
        if self._bytes is not None:
            self._firstbytes = self._bytes[:N]
        else:
            # Prepare
            try:
                f = self.get_file()
            except IOError:
                if os.path.isdir(self.filename):  # A directory, e.g. for DICOM
                    self._firstbytes = bytes()
                    return
                raise
            try:
                i = f.tell()
            except Exception:
                i = None
            # Read
            self._firstbytes = read_n_bytes(f, N)
            # Set back
            try:
                if i is None:
                    raise Exception("cannot seek with None")
                f.seek(i)
            except Exception:
                # Prevent get_file() from reusing the file
                self._file = None
                # If the given URI was a file object, we have a problem,
                if self._uri_type == URI_FILE:
                    raise IOError("Cannot seek back after getting firstbytes!")


def read_n_bytes(f, N):
    """read_n_bytes(file, n)

    Read n bytes from the given file, or less if the file has less
    bytes. Returns zero bytes if the file is closed.
    """
    bb = bytes()
    while len(bb) < N:
        extra_bytes = f.read(N - len(bb))
        if not extra_bytes:
            break
        bb += extra_bytes
    return bb


class SeekableFileObject:
    """A readonly wrapper file object that add support for seeking, even if
    the wrapped file object does not. The allows us to stream from http and
    still use Pillow.
    """

    def __init__(self, f):
        self.f = f
        self._i = 0  # >=0 but can exceed buffer
        self._buffer = b""
        self._have_all = False
        self.closed = False

    def read(self, n=None):
        # Fix up n
        if n is None:
            pass
        else:
            n = int(n)
            if n < 0:
                n = None

        # Can and must we read more?
        if not self._have_all:
            more = b""
            if n is None:
                more = self.f.read()
                self._have_all = True
            else:
                want_i = self._i + n
                want_more = want_i - len(self._buffer)
                if want_more > 0:
                    more = self.f.read(want_more)
                    if len(more) < want_more:
                        self._have_all = True
            self._buffer += more

        # Read data from buffer and update pointer
        if n is None:
            res = self._buffer[self._i :]
        else:
            res = self._buffer[self._i : self._i + n]
        self._i += len(res)

        return res

    def tell(self):
        return self._i

    def seek(self, i, mode=0):
        # Mimic BytesIO behavior

        # Get the absolute new position
        i = int(i)
        if mode == 0:
            if i < 0:
                raise ValueError("negative seek value " + str(i))
            real_i = i
        elif mode == 1:
            real_i = max(0, self._i + i)  # negative ok here
        elif mode == 2:
            if not self._have_all:
                self.read()
            real_i = max(0, len(self._buffer) + i)
        else:
            raise ValueError("invalid whence (%s, should be 0, 1 or 2)" % i)

        # Read some?
        if real_i <= len(self._buffer):
            pass  # no need to read
        elif not self._have_all:
            assert real_i > self._i  # if we don't have all, _i cannot be > _buffer
            self.read(real_i - self._i)  # sets self._i

        self._i = real_i
        return self._i

    def close(self):
        self.closed = True
        self.f.close()

    def isatty(self):
        return False

    def seekable(self):
        return True


class InitializationError(Exception):
    """The plugin could not initialize from the given request.

    This is a _internal_ error that is raised by plugins that fail to handle
    a given request. We use this to differentiate incompatibility between
    a plugin and a request from an actual error/bug inside a plugin.

    """

    pass