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

"""

.. note::
    imageio is under construction, some details with regard to the
    Reader and Writer classes may change.

These are the main classes of imageio. They expose an interface for
advanced users and plugin developers. A brief overview:

  * imageio.FormatManager - for keeping track of registered formats.
  * imageio.Format - representation of a file format reader/writer
  * imageio.Format.Reader - object used during the reading of a file.
  * imageio.Format.Writer - object used during saving a file.
  * imageio.Request - used to store the filename and other info.

Plugins need to implement a Format class and register
a format object using ``imageio.formats.add_format()``.

"""

# todo: do we even use the known extensions?

# Some notes:
#
# The classes in this module use the Request object to pass filename and
# related info around. This request object is instantiated in
# imageio.get_reader and imageio.get_writer.

import sys
import warnings
import contextlib

import numpy as np
from pathlib import Path

from . import Array, asarray
from .request import ImageMode
from ..config import known_plugins, known_extensions, PluginConfig, FileExtension
from ..config.plugins import _original_order
from .imopen import imopen

# survived for backwards compatibility
# I don't know if external plugin code depends on it existing
# We no longer do
MODENAMES = ImageMode


def _get_config(plugin):
    """Old Plugin resolution logic.

    Remove once we remove the old format manager.
    """

    extension_name = None

    if Path(plugin).suffix.lower() in known_extensions:
        extension_name = Path(plugin).suffix.lower()
    elif plugin in known_plugins:
        pass
    elif plugin.lower() in known_extensions:
        extension_name = plugin.lower()
    elif "." + plugin.lower() in known_extensions:
        extension_name = "." + plugin.lower()
    else:
        raise IndexError(f"No format known by name `{plugin}`.")

    if extension_name is not None:
        for plugin_name in [
            x
            for file_extension in known_extensions[extension_name]
            for x in file_extension.priority
        ]:
            if known_plugins[plugin_name].is_legacy:
                plugin = plugin_name
                break

    return known_plugins[plugin]


class Format(object):
    """Represents an implementation to read/write a particular file format

    A format instance is responsible for 1) providing information about
    a format; 2) determining whether a certain file can be read/written
    with this format; 3) providing a reader/writer class.

    Generally, imageio will select the right format and use that to
    read/write an image. A format can also be explicitly chosen in all
    read/write functions. Use ``print(format)``, or ``help(format_name)``
    to see its documentation.

    To implement a specific format, one should create a subclass of
    Format and the Format.Reader and Format.Writer classes. See
    :class:`imageio.plugins` for details.

    Parameters
    ----------
    name : str
        A short name of this format. Users can select a format using its name.
    description : str
        A one-line description of the format.
    extensions : str | list | None
        List of filename extensions that this format supports. If a
        string is passed it should be space or comma separated. The
        extensions are used in the documentation and to allow users to
        select a format by file extension. It is not used to determine
        what format to use for reading/saving a file.
    modes : str
        A string containing the modes that this format can handle ('iIvV'),
        “i” for an image, “I” for multiple images, “v” for a volume,
        “V” for multiple volumes.
        This attribute is used in the documentation and to select the
        formats when reading/saving a file.
    """

    def __init__(self, name, description, extensions=None, modes=None):
        """Initialize the Plugin.

        Parameters
        ----------
        name : str
            A short name of this format. Users can select a format using its name.
        description : str
            A one-line description of the format.
        extensions : str | list | None
            List of filename extensions that this format supports. If a
            string is passed it should be space or comma separated. The
            extensions are used in the documentation and to allow users to
            select a format by file extension. It is not used to determine
            what format to use for reading/saving a file.
        modes : str
            A string containing the modes that this format can handle ('iIvV'),
            “i” for an image, “I” for multiple images, “v” for a volume,
            “V” for multiple volumes.
            This attribute is used in the documentation and to select the
            formats when reading/saving a file.
        """

        # Store name and description
        self._name = name.upper()
        self._description = description

        # Store extensions, do some effort to normalize them.
        # They are stored as a list of lowercase strings without leading dots.
        if extensions is None:
            extensions = []
        elif isinstance(extensions, str):
            extensions = extensions.replace(",", " ").split(" ")
        #
        if isinstance(extensions, (tuple, list)):
            self._extensions = tuple(
                ["." + e.strip(".").lower() for e in extensions if e]
            )
        else:
            raise ValueError("Invalid value for extensions given.")

        # Store mode
        self._modes = modes or ""
        if not isinstance(self._modes, str):
            raise ValueError("Invalid value for modes given.")
        for m in self._modes:
            if m not in "iIvV?":
                raise ValueError("Invalid value for mode given.")

    def __repr__(self):
        # Short description
        return "<Format %s - %s>" % (self.name, self.description)

    def __str__(self):
        return self.doc

    @property
    def doc(self):
        """The documentation for this format (name + description + docstring)."""
        # Our docsring is assumed to be indented by four spaces. The
        # first line needs special attention.
        return "%s - %s\n\n    %s\n" % (
            self.name,
            self.description,
            self.__doc__.strip(),
        )

    @property
    def name(self):
        """The name of this format."""
        return self._name

    @property
    def description(self):
        """A short description of this format."""
        return self._description

    @property
    def extensions(self):
        """A list of file extensions supported by this plugin.
        These are all lowercase with a leading dot.
        """
        return self._extensions

    @property
    def modes(self):
        """A string specifying the modes that this format can handle."""
        return self._modes

    def get_reader(self, request):
        """get_reader(request)

        Return a reader object that can be used to read data and info
        from the given file. Users are encouraged to use
        imageio.get_reader() instead.
        """
        select_mode = request.mode[1] if request.mode[1] in "iIvV" else ""
        if select_mode not in self.modes:
            raise RuntimeError(
                f"Format {self.name} cannot read in {request.mode.image_mode} mode"
            )
        return self.Reader(self, request)

    def get_writer(self, request):
        """get_writer(request)

        Return a writer object that can be used to write data and info
        to the given file. Users are encouraged to use
        imageio.get_writer() instead.
        """
        select_mode = request.mode[1] if request.mode[1] in "iIvV" else ""
        if select_mode not in self.modes:
            raise RuntimeError(
                f"Format {self.name} cannot write in {request.mode.image_mode} mode"
            )
        return self.Writer(self, request)

    def can_read(self, request):
        """can_read(request)

        Get whether this format can read data from the specified uri.
        """
        return self._can_read(request)

    def can_write(self, request):
        """can_write(request)

        Get whether this format can write data to the speciefed uri.
        """
        return self._can_write(request)

    def _can_read(self, request):  # pragma: no cover
        """Check if Plugin can read from ImageResource.

        This method is called when the format manager is searching for a format
        to read a certain image. Return True if this format can do it.

        The format manager is aware of the extensions and the modes that each
        format can handle. It will first ask all formats that *seem* to be able
        to read it whether they can. If none can, it will ask the remaining
        formats if they can: the extension might be missing, and this allows
        formats to provide functionality for certain extensions, while giving
        preference to other plugins.

        If a format says it can, it should live up to it. The format would
        ideally check the request.firstbytes and look for a header of some kind.

        Parameters
        ----------
        request : Request
            A request that can be used to access the ImageResource and obtain
            metadata about it.

        Returns
        -------
        can_read : bool
            True if the plugin can read from the ImageResource, False otherwise.

        """
        return None  # Plugins must implement this

    def _can_write(self, request):  # pragma: no cover
        """Check if Plugin can write to ImageResource.

        Parameters
        ----------
        request : Request
            A request that can be used to access the ImageResource and obtain
            metadata about it.

        Returns
        -------
        can_read : bool
            True if the plugin can write to the ImageResource, False otherwise.

        """
        return None  # Plugins must implement this

    # -----

    class _BaseReaderWriter(object):
        """Base class for the Reader and Writer class to implement common
        functionality. It implements a similar approach for opening/closing
        and context management as Python's file objects.
        """

        def __init__(self, format, request):
            self.__closed = False
            self._BaseReaderWriter_last_index = -1
            self._format = format
            self._request = request
            # Open the reader/writer
            self._open(**self.request.kwargs.copy())

        @property
        def format(self):
            """The :class:`.Format` object corresponding to the current
            read/write operation.
            """
            return self._format

        @property
        def request(self):
            """The :class:`.Request` object corresponding to the
            current read/write operation.
            """
            return self._request

        def __enter__(self):
            self._checkClosed()
            return self

        def __exit__(self, type, value, traceback):
            if value is None:
                # Otherwise error in close hide the real error.
                self.close()

        def __del__(self):
            try:
                self.close()
            except Exception:  # pragma: no cover
                pass  # Suppress noise when called during interpreter shutdown

        def close(self):
            """Flush and close the reader/writer.
            This method has no effect if it is already closed.
            """
            if self.__closed:
                return
            self.__closed = True
            self._close()
            # Process results and clean request object
            self.request.finish()

        @property
        def closed(self):
            """Whether the reader/writer is closed."""
            return self.__closed

        def _checkClosed(self, msg=None):
            """Internal: raise an ValueError if reader/writer is closed"""
            if self.closed:
                what = self.__class__.__name__
                msg = msg or ("I/O operation on closed %s." % what)
                raise RuntimeError(msg)

        # To implement

        def _open(self, **kwargs):
            """_open(**kwargs)

            Plugins should probably implement this.

            It is called when reader/writer is created. Here the
            plugin can do its initialization. The given keyword arguments
            are those that were given by the user at imageio.read() or
            imageio.write().
            """
            raise NotImplementedError()

        def _close(self):
            """_close()

            Plugins should probably implement this.

            It is called when the reader/writer is closed. Here the plugin
            can do a cleanup, flush, etc.

            """
            raise NotImplementedError()

    # -----

    class Reader(_BaseReaderWriter):
        """
        The purpose of a reader object is to read data from an image
        resource, and should be obtained by calling :func:`.get_reader`.

        A reader can be used as an iterator to read multiple images,
        and (if the format permits) only reads data from the file when
        new data is requested (i.e. streaming). A reader can also be
        used as a context manager so that it is automatically closed.

        Plugins implement Reader's for different formats. Though rare,
        plugins may provide additional functionality (beyond what is
        provided by the base reader class).
        """

        def get_length(self):
            """get_length()

            Get the number of images in the file. (Note: you can also
            use ``len(reader_object)``.)

            The result can be:
                * 0 for files that only have meta data
                * 1 for singleton images (e.g. in PNG, JPEG, etc.)
                * N for image series
                * inf for streams (series of unknown length)
            """
            return self._get_length()

        def get_data(self, index, **kwargs):
            """get_data(index, **kwargs)

            Read image data from the file, using the image index. The
            returned image has a 'meta' attribute with the meta data.
            Raises IndexError if the index is out of range.

            Some formats may support additional keyword arguments. These are
            listed in the documentation of those formats.
            """
            self._checkClosed()
            self._BaseReaderWriter_last_index = index
            try:
                im, meta = self._get_data(index, **kwargs)
            except StopIteration:
                raise IndexError(index)
            return Array(im, meta)  # Array tests im and meta

        def get_next_data(self, **kwargs):
            """get_next_data(**kwargs)

            Read the next image from the series.

            Some formats may support additional keyword arguments. These are
            listed in the documentation of those formats.
            """
            return self.get_data(self._BaseReaderWriter_last_index + 1, **kwargs)

        def set_image_index(self, index, **kwargs):
            """set_image_index(index)

            Set the internal pointer such that the next call to
            get_next_data() returns the image specified by the index
            """
            self._checkClosed()
            n = self.get_length()
            self._BaseReaderWriter_last_index = min(max(index - 1, -1), n)

        def get_meta_data(self, index=None):
            """get_meta_data(index=None)

            Read meta data from the file. using the image index. If the
            index is omitted or None, return the file's (global) meta data.

            Note that ``get_data`` also provides the meta data for the returned
            image as an attribute of that image.

            The meta data is a dict, which shape depends on the format.
            E.g. for JPEG, the dict maps group names to subdicts and each
            group is a dict with name-value pairs. The groups represent
            the different metadata formats (EXIF, XMP, etc.).
            """
            self._checkClosed()
            meta = self._get_meta_data(index)
            if not isinstance(meta, dict):
                raise ValueError(
                    "Meta data must be a dict, not %r" % meta.__class__.__name__
                )
            return meta

        def iter_data(self):
            """iter_data()

            Iterate over all images in the series. (Note: you can also
            iterate over the reader object.)

            """
            self._checkClosed()
            n = self.get_length()
            i = 0
            while i < n:
                try:
                    im, meta = self._get_data(i)
                except StopIteration:
                    return
                except IndexError:
                    if n == float("inf"):
                        return
                    raise
                yield Array(im, meta)
                i += 1

        # Compatibility

        def __iter__(self):
            return self.iter_data()

        def __len__(self):
            n = self.get_length()
            if n == float("inf"):
                n = sys.maxsize
            return n

        # To implement

        def _get_length(self):
            """_get_length()

            Plugins must implement this.

            The returned scalar specifies the number of images in the series.
            See Reader.get_length for more information.
            """
            raise NotImplementedError()

        def _get_data(self, index):
            """_get_data()

            Plugins must implement this, but may raise an IndexError in
            case the plugin does not support random access.

            It should return the image and meta data: (ndarray, dict).
            """
            raise NotImplementedError()

        def _get_meta_data(self, index):
            """_get_meta_data(index)

            Plugins must implement this.

            It should return the meta data as a dict, corresponding to the
            given index, or to the file's (global) meta data if index is
            None.
            """
            raise NotImplementedError()

    # -----

    class Writer(_BaseReaderWriter):
        """
        The purpose of a writer object is to write data to an image
        resource, and should be obtained by calling :func:`.get_writer`.

        A writer will (if the format permits) write data to the file
        as soon as new data is provided (i.e. streaming). A writer can
        also be used as a context manager so that it is automatically
        closed.

        Plugins implement Writer's for different formats. Though rare,
        plugins may provide additional functionality (beyond what is
        provided by the base writer class).
        """

        def append_data(self, im, meta=None):
            """append_data(im, meta={})

            Append an image (and meta data) to the file. The final meta
            data that is used consists of the meta data on the given
            image (if applicable), updated with the given meta data.
            """
            self._checkClosed()
            # Check image data
            if not isinstance(im, np.ndarray):
                raise ValueError("append_data requires ndarray as first arg")
            # Get total meta dict
            total_meta = {}
            if hasattr(im, "meta") and isinstance(im.meta, dict):
                total_meta.update(im.meta)
            if meta is None:
                pass
            elif not isinstance(meta, dict):
                raise ValueError("Meta must be a dict.")
            else:
                total_meta.update(meta)

            # Decouple meta info
            im = asarray(im)
            # Call
            return self._append_data(im, total_meta)

        def set_meta_data(self, meta):
            """set_meta_data(meta)

            Sets the file's (global) meta data. The meta data is a dict which
            shape depends on the format. E.g. for JPEG the dict maps
            group names to subdicts, and each group is a dict with
            name-value pairs. The groups represents the different
            metadata formats (EXIF, XMP, etc.).

            Note that some meta formats may not be supported for
            writing, and individual fields may be ignored without
            warning if they are invalid.
            """
            self._checkClosed()
            if not isinstance(meta, dict):
                raise ValueError("Meta must be a dict.")
            else:
                return self._set_meta_data(meta)

        # To implement

        def _append_data(self, im, meta):
            # Plugins must implement this
            raise NotImplementedError()

        def _set_meta_data(self, meta):
            # Plugins must implement this
            raise NotImplementedError()


class FormatManager(object):
    """
    The FormatManager is a singleton plugin factory.

    The format manager supports getting a format object using indexing (by
    format name or extension). When used as an iterator, this object
    yields all registered format objects.

    See also :func:`.help`.
    """

    @property
    def _formats(self):
        available_formats = list()

        for config in known_plugins.values():
            with contextlib.suppress(ImportError):
                # if an exception is raised, then format not installed
                if config.is_legacy and config.format is not None:
                    available_formats.append(config)

        return available_formats

    def __repr__(self):
        return f"<imageio.FormatManager with {len(self._formats)} registered formats>"

    def __iter__(self):
        return iter(x.format for x in self._formats)

    def __len__(self):
        return len(self._formats)

    def __str__(self):
        ss = []
        for config in self._formats:
            ext = config.legacy_args["extensions"]
            desc = config.legacy_args["description"]
            s = f"{config.name} - {desc} [{ext}]"
            ss.append(s)
        return "\n".join(ss)

    def __getitem__(self, name):
        warnings.warn(
            "The usage of `FormatManager` is deprecated and it will be "
            "removed in Imageio v3. Use `iio.imopen` instead.",
            DeprecationWarning,
            stacklevel=2,
        )

        if not isinstance(name, str):
            raise ValueError(
                "Looking up a format should be done by name or by extension."
            )

        if name == "":
            raise ValueError("No format matches the empty string.")

        # Test if name is existing file
        if Path(name).is_file():
            # legacy compatibility - why test reading here??
            try:
                return imopen(name, "r", legacy_mode=True)._format
            except ValueError:
                # no plugin can read the file
                pass

        config = _get_config(name.upper())

        try:
            return config.format
        except ImportError:
            raise ImportError(
                f"The `{config.name}` format is not installed. "
                f"Use `pip install imageio[{config.install_name}]` to install it."
            )

    def sort(self, *names):
        """sort(name1, name2, name3, ...)

        Sort the formats based on zero or more given names; a format with
        a name that matches one of the given names will take precedence
        over other formats. A match means an equal name, or ending with
        that name (though the former counts higher). Case insensitive.

        Format preference will match the order of the given names: using
        ``sort('TIFF', '-FI', '-PIL')`` would prefer the FreeImage formats
        over the Pillow formats, but prefer TIFF even more. Each time
        this is called, the starting point is the default format order,
        and calling ``sort()`` with no arguments will reset the order.

        Be aware that using the function can affect the behavior of
        other code that makes use of imageio.

        Also see the ``IMAGEIO_FORMAT_ORDER`` environment variable.
        """

        warnings.warn(
            "`FormatManager` is deprecated and it will be removed in ImageIO v3."
            " Migrating `FormatManager.sort` depends on your use-case:\n"
            "\t- modify `iio.config.known_plugins` to specify the search order for "
            "unrecognized formats.\n"
            "\t- modify `iio.config.known_extensions[<extension>].priority`"
            " to control a specific extension.",
            DeprecationWarning,
            stacklevel=2,
        )

        # Check and sanitize input
        for name in names:
            if not isinstance(name, str):
                raise TypeError("formats.sort() accepts only string names.")
            if any(c in name for c in ".,"):
                raise ValueError(
                    "Names given to formats.sort() should not "
                    "contain dots `.` or commas `,`."
                )

        should_reset = len(names) == 0
        if should_reset:
            names = _original_order

        sane_names = [name.strip().upper() for name in names if name != ""]

        # enforce order for every extension that uses it
        flat_extensions = [
            ext for ext_list in known_extensions.values() for ext in ext_list
        ]
        for extension in flat_extensions:
            if should_reset:
                extension.reset()
                continue

            for name in reversed(sane_names):
                for plugin in [x for x in extension.default_priority]:
                    if plugin.endswith(name):
                        extension.priority.remove(plugin)
                        extension.priority.insert(0, plugin)

        old_order = known_plugins.copy()
        known_plugins.clear()

        for name in sane_names:
            plugin = old_order.pop(name, None)
            if plugin is not None:
                known_plugins[name] = plugin

        known_plugins.update(old_order)

    def add_format(self, iio_format, overwrite=False):
        """add_format(format, overwrite=False)

        Register a format, so that imageio can use it. If a format with the
        same name already exists, an error is raised, unless overwrite is True,
        in which case the current format is replaced.
        """

        warnings.warn(
            "`FormatManager` is deprecated and it will be removed in ImageIO v3."
            "To migrate `FormatManager.add_format` add the plugin directly to "
            "`iio.config.known_plugins`.",
            DeprecationWarning,
            stacklevel=2,
        )

        if not isinstance(iio_format, Format):
            raise ValueError("add_format needs argument to be a Format object")
        elif not overwrite and iio_format.name in self.get_format_names():
            raise ValueError(
                f"A Format named {iio_format.name} is already registered, use"
                " `overwrite=True` to replace."
            )

        config = PluginConfig(
            name=iio_format.name.upper(),
            class_name=iio_format.__class__.__name__,
            module_name=iio_format.__class__.__module__,
            is_legacy=True,
            install_name="unknown",
            legacy_args={
                "name": iio_format.name,
                "description": iio_format.description,
                "extensions": " ".join(iio_format.extensions),
                "modes": iio_format.modes,
            },
        )

        known_plugins[config.name] = config

        for extension in iio_format.extensions:
            # be conservative and always treat it as a unique file format
            ext = FileExtension(
                extension=extension,
                priority=[config.name],
                name="Unique Format",
                description="A format inserted at runtime."
                f" It is being read by the `{config.name}` plugin.",
            )
            known_extensions.setdefault(extension, list()).append(ext)

    def search_read_format(self, request):
        """search_read_format(request)

        Search a format that can read a file according to the given request.
        Returns None if no appropriate format was found. (used internally)
        """

        try:
            # in legacy_mode imopen returns a LegacyPlugin
            return imopen(request, request.mode.io_mode, legacy_mode=True)._format
        except AttributeError:
            warnings.warn(
                "ImageIO now uses a v3 plugin when reading this format."
                " Please migrate to the v3 API (preferred) or use imageio.v2.",
                DeprecationWarning,
                stacklevel=2,
            )
            return None
        except ValueError:
            # no plugin can read this request
            # but the legacy API doesn't raise
            return None

    def search_write_format(self, request):
        """search_write_format(request)

        Search a format that can write a file according to the given request.
        Returns None if no appropriate format was found. (used internally)
        """

        try:
            # in legacy_mode imopen returns a LegacyPlugin
            return imopen(request, request.mode.io_mode, legacy_mode=True)._format
        except AttributeError:
            warnings.warn(
                "ImageIO now uses a v3 plugin when writing this format."
                " Please migrate to the v3 API (preferred) or use imageio.v2.",
                DeprecationWarning,
                stacklevel=2,
            )
            return None
        except ValueError:
            # no plugin can write this request
            # but the legacy API doesn't raise
            return None

    def get_format_names(self):
        """Get the names of all registered formats."""

        warnings.warn(
            "`FormatManager` is deprecated and it will be removed in ImageIO v3."
            "To migrate `FormatManager.get_format_names` use `iio.config.known_plugins.keys()` instead.",
            DeprecationWarning,
            stacklevel=2,
        )

        return [f.name for f in self._formats]

    def show(self):
        """Show a nicely formatted list of available formats"""
        print(self)
