from __future__ import annotations

from typing import (
    TYPE_CHECKING,
    AbstractSet,
    Any,
    Dict,
    Iterable,
    Iterator,
    Optional,
    Sized,
)

from attrs import define, field
from fontTools.ufoLib import UFOReader, UFOWriter

from ufoLib2.constants import DEFAULT_LAYER_NAME
from ufoLib2.errors import Error
from ufoLib2.objects.layer import Layer
from ufoLib2.objects.misc import (
    _deepcopy_unlazify_attrs,
    _getstate_unlazify_attrs,
    _setstate_attrs,
)
from ufoLib2.serde import serde
from ufoLib2.typing import T

if TYPE_CHECKING:
    from typing import Type

    from cattrs import Converter

_LAYER_NOT_LOADED = Layer(name="___UFOLIB2_LAZY_LAYER___")


def _must_have_at_least_one_item(self: Any, attribute: Any, value: Sized) -> None:
    if not len(value):
        raise ValueError("value must have at least one item.")


@serde
@define
class LayerSet:
    """Represents a mapping of layer names to Layer objects.

    See http://unifiedfontobject.org/versions/ufo3/layercontents.plist/ for layer
    semantics.

    Behavior:
        LayerSet behaves **partly** like a dictionary of type ``Dict[str, Layer]``,
        but creating and loading layers is done through their own methods. Unless the
        font is loaded eagerly (with ``lazy=False``), the layer objects and their
        glyphs are by default only loaded into memory when accessed.

        To get the number of layers in the font::

            layerCount = len(font.layers)

        To iterate over all layers::

            for layer in font.layers:
                ...

        To check if a specific layer exists::

            exists = "myLayerName" in font.layers

        To get a specific layer::

            font.layers["myLayerName"]

        To delete a specific layer::

            del font.layers["myLayerName"]
    """

    _layers: Dict[str, Layer] = field(
        validator=_must_have_at_least_one_item,
    )

    _defaultLayer: Layer = field(default=_LAYER_NOT_LOADED, eq=False)

    _lazy: Optional[bool] = field(default=None, init=False, eq=False)
    _reader: Optional[UFOReader] = field(default=None, init=False, eq=False)

    def __attrs_post_init__(self) -> None:
        if self._defaultLayer == _LAYER_NOT_LOADED:
            found = False
            for layer in self._layers.values():
                if layer._default:
                    if found:
                        raise ValueError("more than one layer marked as default")
                    found = True
                    self._defaultLayer = layer
            if not found:
                raise ValueError("no layer marked as default")
        else:
            if not any(layer is self._defaultLayer for layer in self._layers.values()):
                raise ValueError(
                    f"default layer {repr(self._defaultLayer)} must be in layer set."
                )
            assert self._defaultLayer._default

    @classmethod
    def default(cls) -> LayerSet:
        """Return a new LayerSet with an empty default Layer."""
        return cls.from_iterable([Layer()])

    @classmethod
    def from_iterable(
        cls, value: Iterable[Layer], defaultLayerName: str = DEFAULT_LAYER_NAME
    ) -> LayerSet:
        """Instantiates a LayerSet from an iterable of :class:`.Layer` objects.

        Args:
            value: an iterable of :class:`.Layer` objects.
            defaultLayerName: the name of the default layer of the ones in ``value``.
        """
        if defaultLayerName != DEFAULT_LAYER_NAME:
            import warnings

            warnings.warn(
                "'defaultLayerName' parameter is deprecated; "
                "use Layer.default attribute instead",
                DeprecationWarning,
            )
        layers: dict[str, Layer] = {}
        defaultLayer = None
        for layer in value:
            if not isinstance(layer, Layer):
                raise TypeError(f"expected 'Layer', found '{type(layer).__name__}'")
            if layer.name in layers:
                raise KeyError(f"duplicate layer name: '{layer.name}'")
            if layer.name == defaultLayerName or layer._default:
                if defaultLayer is not None:
                    raise ValueError("more than one layer marked as default")
                if not layer._default:
                    layer._default = True
                defaultLayer = layer
            layers[layer.name] = layer

        if defaultLayer is None:
            raise ValueError("no layer marked as default")
        assert defaultLayer is not None

        return cls(layers=layers, defaultLayer=defaultLayer)

    @classmethod
    def read(cls, reader: UFOReader, lazy: bool = True) -> LayerSet:
        """Instantiates a LayerSet object from a :class:`fontTools.ufoLib.UFOReader`.

        Args:
            path: The path to the UFO to load.
            lazy: If True, load glyphs, data files and images as they are accessed. If
                False, load everything up front.
        """
        layers: dict[str, Layer] = {}
        defaultLayer = None

        defaultLayerName = reader.getDefaultLayerName()

        for layerName in reader.getLayerNames():
            isDefault = layerName == defaultLayerName
            if isDefault or not lazy:
                layer = cls._loadLayer(reader, layerName, lazy, isDefault)
                if isDefault:
                    defaultLayer = layer
                layers[layerName] = layer
            else:
                layers[layerName] = _LAYER_NOT_LOADED

        assert defaultLayer is not None

        self = cls(layers=layers, defaultLayer=defaultLayer)
        self._lazy = lazy
        if lazy:
            self._reader = reader

        return self

    def unlazify(self) -> None:
        """Load all layers into memory."""
        if self._lazy:
            for layer in self:
                layer.unlazify()
        self._lazy = False

    __deepcopy__ = _deepcopy_unlazify_attrs

    __getstate__ = _getstate_unlazify_attrs
    __setstate__ = _setstate_attrs

    @staticmethod
    def _loadLayer(
        reader: UFOReader, layerName: str, lazy: bool = True, default: bool = False
    ) -> Layer:
        glyphSet = reader.getGlyphSet(layerName)
        return Layer.read(layerName, glyphSet, lazy=lazy, default=default)

    def loadLayer(self, layerName: str, lazy: bool = True) -> Layer:
        # XXX: Remove this method and do business via _loadLayer or take this one
        # private.
        assert self._reader is not None
        if layerName not in self._layers:
            raise KeyError(layerName)
        layer = self._loadLayer(self._reader, layerName, lazy)
        self._layers[layerName] = layer
        return layer

    @property
    def defaultLayer(self) -> Layer:
        return self._defaultLayer

    @defaultLayer.setter
    def defaultLayer(self, layer: Layer) -> None:
        if layer is self._defaultLayer:
            return
        if layer not in self._layers.values():
            raise ValueError(
                f"Layer {layer!r} not found in layer set; can't set as default"
            )
        if self._defaultLayer.name == DEFAULT_LAYER_NAME:
            raise ValueError(
                "there's already a layer named 'public.default' which must stay default"
            )
        self._defaultLayer._default = False
        layer._default = True
        self._defaultLayer = layer

    def __contains__(self, name: str) -> bool:
        return name in self._layers

    def __delitem__(self, name: str) -> None:
        if self.defaultLayer is not None:
            if name == self.defaultLayer.name:
                raise KeyError("cannot delete default layer %r" % name)
        del self._layers[name]

    def __getitem__(self, name: str) -> Layer:
        layer_object = self._layers[name]
        if layer_object is _LAYER_NOT_LOADED:
            return self.loadLayer(name)
        return layer_object

    def __iter__(self) -> Iterator[Layer]:
        for layer_name, layer_object in self._layers.items():
            if layer_object is _LAYER_NOT_LOADED:
                yield self.loadLayer(layer_name)
            else:
                yield layer_object

    def __len__(self) -> int:
        return len(self._layers)

    def get(self, name: str, default: T | None = None) -> T | Layer | None:
        try:
            return self[name]
        except KeyError:
            return default

    def keys(self) -> AbstractSet[str]:
        return self._layers.keys()

    def __repr__(self) -> str:
        n = len(self._layers)
        return "<{}.{} ({} layer{}) at {}>".format(
            self.__class__.__module__,
            self.__class__.__name__,
            n,
            "s" if n > 1 else "",
            hex(id(self)),
        )

    @property
    def layerOrder(self) -> list[str]:
        """The font's layer order.

        Getter:
            Returns the font's layer order.

        Note:
            The getter always returns a new list, modifications to it do not change
            the LayerSet.

        Setter:
            Sets the font's layer order. The set order value must contain all layers
            that are present in the LayerSet.
        """
        return list(self._layers)

    @layerOrder.setter
    def layerOrder(self, order: list[str]) -> None:
        if set(order) != set(self._layers):
            raise Error(
                "`order` must contain the same layers that are currently present."
            )
        self._layers = {name: self._layers[name] for name in order}

    def newLayer(self, name: str, **kwargs: Any) -> Layer:
        """Creates and returns a named layer.

        Args:
            name: The layer name.
            kwargs: Arguments passed to the constructor of Layer.
        """
        if name in self._layers:
            raise KeyError("layer %r already exists" % name)
        self._layers[name] = layer = Layer(name, **kwargs)
        if layer._default:
            self.defaultLayer = layer
        return layer

    def renameGlyph(self, name: str, newName: str, overwrite: bool = False) -> None:
        """Renames a glyph across all layers.

        Args:
            name: The old name.
            newName: The new name.
            overwrite: If False, raises exception if newName is already taken in any
                layer. If True, overwrites (read: deletes) the old Glyph object.
        """
        # Note: this would be easier if the glyph contained the layers!
        if name == newName:
            return
        # make sure we're copying something
        if not any(name in layer for layer in self):
            raise KeyError("name %r is not in layer set" % name)
        # prepare destination, delete if overwrite=True or error
        for layer in self:
            if newName in layer:
                if overwrite:
                    del layer[newName]
                else:
                    raise KeyError("target name %r already exists" % newName)
        # now do the move
        for layer in self:
            if name in layer:
                layer[newName] = glyph = layer.pop(name)
                glyph._name = newName

    def renameLayer(self, name: str, newName: str, overwrite: bool = False) -> None:
        """Renames a layer.

        Args:
            name: The old name.
            newName: The new name.
            overwrite: If False, raises exception if newName is already taken. If True,
                overwrites (read: deletes) the old Layer object.
        """
        if name == newName:
            return
        if not overwrite and newName in self._layers:
            raise KeyError("target name %r already exists" % newName)
        layer = self[name]
        del self._layers[name]
        self._layers[newName] = layer
        layer._name = newName
        if newName == DEFAULT_LAYER_NAME:
            self.defaultLayer = layer

    def write(self, writer: UFOWriter, saveAs: bool | None = None) -> None:
        """Writes this LayerSet to a :class:`fontTools.ufoLib.UFOWriter`.

        Args:
            writer(fontTools.ufoLib.UFOWriter): The writer to write to.
            saveAs: If True, tells the writer to save out-of-place. If False, tells the
                writer to save in-place. This affects how resources are cleaned before
                writing.
        """
        if saveAs is None:
            saveAs = self._reader is not writer
        # if in-place, remove deleted layers
        layers = self._layers
        if not saveAs:
            for name in set(writer.getLayerNames()).difference(layers):
                writer.deleteGlyphSet(name)
        # write layers
        defaultLayer = self.defaultLayer
        for name, layer in layers.items():
            default = layer is defaultLayer
            if layer is _LAYER_NOT_LOADED:
                if saveAs:
                    layer = self.loadLayer(name, lazy=False)
                else:
                    continue
            glyphSet = writer.getGlyphSet(name, defaultLayer=default)
            layer.write(glyphSet, saveAs=saveAs)
        writer.writeLayerContents(self.layerOrder)

    def _unstructure(self, converter: Converter) -> list[dict[str, Any]]:
        return [converter.unstructure(layer) for layer in self]

    @staticmethod
    def _structure(
        data: list[dict[str, Any]], cls: Type[LayerSet], converter: Converter
    ) -> LayerSet:
        return cls.from_iterable(converter.structure(layer, Layer) for layer in data)