"""Value related classes.

DOM Level 2 CSS CSSValue, CSSPrimitiveValue and CSSValueList are **no longer**
supported and are replaced by these new classes.
"""
__all__ = [
    'PropertyValue',
    'Value',
    'ColorValue',
    'DimensionValue',
    'URIValue',
    'CSSFunction',
    'CSSCalc',
    'CSSVariable',
    'MSValue',
]

from cssutils.prodparser import Choice, PreDef, Prod, ProdParser, Sequence
import cssutils
from cssutils.helper import normalize, pushtoken
import colorsys
import re
import urllib.parse


class PropertyValue(cssutils.util._NewBase):
    """
    An unstructured list like holder for all values defined for a
    :class:`~cssutils.css.Property`. Contains :class:`~cssutils.css.Value`
    or subclass objects. Currently there is no access to the combinators of
    the defined values which might simply be space or comma or slash.

    You may:

    - iterate over all contained Value objects (not the separators like ``,``,
      ``/`` or `` `` though!)
    - get a Value item by index or use ``PropertyValue[index]``
    - find out the number of values defined (unstructured)
    """

    def __init__(self, cssText=None, parent=None, readonly=False):
        """
        :param cssText:
            the parsable cssText of the value
        :param readonly:
            defaults to False
        """
        super().__init__()

        self.parent = parent
        self.wellformed = False

        if cssText is not None:  # may be 0
            if isinstance(cssText, (int, float)):
                cssText = str(cssText)  # if it is a number
            self.cssText = cssText

        self._readonly = readonly

    def __len__(self):
        return len(list(self.__items()))

    def __getitem__(self, index):
        try:
            return list(self.__items())[index]
        except IndexError:
            return None

    def __iter__(self):
        "Generator which iterates over values."
        yield from self.__items()

    def __repr__(self):
        return "cssutils.css.{}({!r})".format(self.__class__.__name__, self.cssText)

    def __str__(self):
        return "<cssutils.css.%s object length=%r cssText=%r at " "0x%x>" % (
            self.__class__.__name__,
            self.length,
            self.cssText,
            id(self),
        )

    def __items(self, seq=None):
        "a generator of Value obects only, no , / or ' '"
        if seq is None:
            seq = self.seq
        return (x.value for x in seq if isinstance(x.value, Value))

    def _setCssText(self, cssText):
        if isinstance(cssText, (int, float)):
            cssText = str(cssText)  # if it is a number
        """
        Format::

            unary_operator
              : '-' | '+'
              ;
            operator
              : '/' S* | ',' S* | /* empty */
              ;
            expr
              : term [ operator term ]*
              ;
            term
              : unary_operator?
                [ NUMBER S* | PERCENTAGE S* | LENGTH S* | EMS S* | EXS S* |
                  ANGLE S* | TIME S* | FREQ S* ]
              | STRING S* | IDENT S* | URI S* | hexcolor | function
              | UNICODE-RANGE S*
              ;
            function
              : FUNCTION S* expr ')' S*
              ;
            /*
             * There is a constraint on the color that it must
             * have either 3 or 6 hex-digits (i.e., [0-9a-fA-F])
             * after the "#"; e.g., "#000" is OK, but "#abcd" is not.
             */
            hexcolor
              : HASH S*
              ;

        :exceptions:
            - :exc:`~xml.dom.SyntaxErr`:
              Raised if the specified CSS string value has a syntax error
              (according to the attached property) or is unparsable.
            - :exc:`~xml.dom.InvalidModificationErr`:
              TODO: Raised if the specified CSS string value represents a
              different type of values than the values allowed by the CSS
              property.
            - :exc:`~xml.dom.NoModificationAllowedErr`:
              Raised if this value is readonly.
        """
        self._checkReadonly()

        # used as operator is , / or S
        nextSor = ',/'
        term = Choice(
            _ColorProd(self, nextSor),
            _DimensionProd(self, nextSor),
            _URIProd(self, nextSor),
            _ValueProd(self, nextSor),
            #                      _Rect(self, nextSor),
            # all other functions
            _CSSVariableProd(self, nextSor),
            _MSValueProd(self, nextSor),
            _CalcValueProd(self, nextSor),
            _CSSFunctionProd(self, nextSor),
        )
        operator = Choice(
            PreDef.S(toSeq=False),
            PreDef.char(
                'comma', ',', toSeq=lambda t, tokens: ('operator', t[1]), optional=True
            ),
            PreDef.char(
                'slash', '/', toSeq=lambda t, tokens: ('operator', t[1]), optional=True
            ),
            optional=True,
        )
        prods = Sequence(
            term,
            Sequence(  # mayEnd this Sequence if whitespace
                operator,
                # TODO: only when setting via other class
                # used by variabledeclaration currently
                PreDef.char('END', ';', stopAndKeep=True, optional=True),
                # TODO: } and !important ends too!
                term,
                minmax=lambda: (0, None),
            ),
        )
        # parse
        ok, seq, store, unused = ProdParser().parse(cssText, 'PropertyValue', prods)
        # must be at least one value!
        ok = ok and len(list(self.__items(seq))) > 0

        for item in seq:
            if hasattr(item.value, 'wellformed') and not item.value.wellformed:
                ok = False
                break

        self.wellformed = ok
        if ok:
            self._setSeq(seq)
        else:
            self._log.error(
                'PropertyValue: Unknown syntax or no value: %s'
                % self._valuestr(cssText)
            )

    cssText = property(
        lambda self: cssutils.ser.do_css_PropertyValue(self),
        _setCssText,
        doc="A string representation of the current value.",
    )

    def item(self, index):
        """
        The value at position `index`. Alternatively simple use
        ``PropertyValue[index]``.

        :param index:
            the parsable cssText of the value
        :exceptions:
            - :exc:`~IndexError`:
              Raised if index if out of bounds
        """
        return self[index]

    length = property(lambda self: len(self), doc="Number of values set.")

    value = property(
        lambda self: cssutils.ser.do_css_PropertyValue(self, valuesOnly=True),
        doc="A string representation of the current value "
        "without any comments used for validation.",
    )


class Value(cssutils.util._NewBase):
    """
    Represents a single CSS value. For now simple values of
    IDENT, STRING, or UNICODE-RANGE values are represented directly
    as Value objects. Other values like e.g. FUNCTIONs are represented by
    subclasses with an extended API.
    """

    IDENT = 'IDENT'
    STRING = 'STRING'
    UNICODE_RANGE = 'UNICODE-RANGE'
    URI = 'URI'

    DIMENSION = 'DIMENSION'
    NUMBER = 'NUMBER'
    PERCENTAGE = 'PERCENTAGE'

    COLOR_VALUE = 'COLOR_VALUE'
    HASH = 'HASH'

    FUNCTION = 'FUNCTION'
    CALC = 'CALC'
    VARIABLE = 'VARIABLE'

    _type = None
    _value = ''

    def __init__(self, cssText=None, parent=None, readonly=False):
        super().__init__()

        self.parent = parent
        self.wellformed = False

        if cssText:
            self.cssText = cssText

    def __repr__(self):
        return "cssutils.css.{}({!r})".format(self.__class__.__name__, self.cssText)

    def __str__(self):
        return (
            "<cssutils.css.{} object type={} value={!r} cssText={!r} at 0x{:x}>".format(
                self.__class__.__name__,
                self.type,
                self.value,
                self.cssText,
                id(self),
            )
        )

    def _setCssText(self, cssText):
        self._checkReadonly()

        prods = Choice(
            PreDef.hexcolor(stop=True),
            PreDef.ident(stop=True),
            PreDef.string(stop=True),
            PreDef.unicode_range(stop=True),
        )
        ok, seq, store, unused = ProdParser().parse(cssText, 'Value', prods)
        self.wellformed = ok
        if ok:
            # only 1 value anyway!
            self._type = seq[0].type
            self._value = seq[0].value

            self._setSeq(seq)

    cssText = property(
        lambda self: cssutils.ser.do_css_Value(self),
        _setCssText,
        doc='String value of this value.',
    )

    type = property(
        lambda self: self._type,  # _setType,
        doc="Type of this value, for now the production type "
        "like e.g. `DIMENSION` or `STRING`. All types are "
        "defined as constants in :class:`~cssutils.css.Value`.",
    )

    def _setValue(self, value):
        # TODO: check!
        self._value = value

    value = property(
        lambda self: self._value,
        _setValue,
        doc="Actual value if possible: An int or float or else " " a string",
    )


class ColorValue(Value):
    """
    A color value like rgb(), rgba(), hsl(), hsla() or #rgb, #rrggbb

    TODO: Color Keywords
    """

    from .colors import COLORS

    type = Value.COLOR_VALUE
    # hexcolor, FUNCTION?
    _colorType = None
    _red = 0
    _green = 0
    _blue = 0
    _alpha = 0

    def __str__(self):
        return (
            "<cssutils.css.%s object type=%s value=%r colorType=%r "
            "red=%s blue=%s green=%s alpha=%s at 0x%x>"
            % (
                self.__class__.__name__,
                self.type,
                self.value,
                self.colorType,
                self.red,
                self.green,
                self.blue,
                self.alpha,
                id(self),
            )
        )

    def _setCssText(self, cssText):  # noqa: C901
        self._checkReadonly()
        types = self._prods  # rename!

        component = Choice(
            PreDef.unary(
                toSeq=lambda t, tokens: (
                    t[0],
                    DimensionValue(pushtoken(t, tokens), parent=self),
                )
            ),
            PreDef.number(
                toSeq=lambda t, tokens: (
                    t[0],
                    DimensionValue(pushtoken(t, tokens), parent=self),
                )
            ),
            PreDef.percentage(
                toSeq=lambda t, tokens: (
                    t[0],
                    DimensionValue(pushtoken(t, tokens), parent=self),
                )
            ),
        )
        noalp = Sequence(
            Prod(
                name='FUNCTION',
                match=lambda t, v: t == types.FUNCTION and v in ('rgb(', 'hsl('),
                toSeq=lambda t, tokens: (t[0], normalize(t[1])),
            ),
            component,
            Sequence(PreDef.comma(optional=True), component, minmax=lambda: (2, 2)),
            PreDef.funcEnd(stop=True),
        )
        witha = Sequence(
            Prod(
                name='FUNCTION',
                match=lambda t, v: t == types.FUNCTION and v in ('rgba(', 'hsla('),
                toSeq=lambda t, tokens: (t[0], normalize(t[1])),
            ),
            component,
            Sequence(PreDef.comma(optional=True), component, minmax=lambda: (3, 3)),
            PreDef.funcEnd(stop=True),
        )
        namedcolor = Prod(
            name='Named Color',
            match=lambda t, v: t == 'IDENT'
            and (normalize(v) in list(self.COLORS.keys())),
            stop=True,
        )

        prods = Choice(PreDef.hexcolor(stop=True), namedcolor, noalp, witha)

        ok, seq, store, unused = ProdParser().parse(cssText, self.type, prods)
        self.wellformed = ok
        if ok:
            t, v = seq[0].type, seq[0].value
            if 'IDENT' == t:
                rgba = self.COLORS[normalize(v)]
            if 'HASH' == t:
                if len(v) == 4:
                    # HASH #rgb
                    rgba = (
                        int(2 * v[1], 16),
                        int(2 * v[2], 16),
                        int(2 * v[3], 16),
                        1.0,
                    )
                else:
                    # HASH #rrggbb
                    rgba = (int(v[1:3], 16), int(v[3:5], 16), int(v[5:7], 16), 1.0)

            elif 'FUNCTION' == t:
                functiontype, raw, check = None, [], ''
                HSL = False

                for item in seq:
                    try:
                        type_ = item.value.type
                    except AttributeError:
                        # type of function, e.g. rgb(
                        if item.type == 'FUNCTION':
                            functiontype = item.value
                            HSL = functiontype in ('hsl(', 'hsla(')
                        continue

                    # save components
                    if type_ == Value.NUMBER:
                        raw.append(item.value.value)
                        check += 'N'
                    elif type_ == Value.PERCENTAGE:
                        if HSL:
                            # save as percentage fraction
                            raw.append(item.value.value / 100.0)
                        else:
                            # save as real value of percentage of 255
                            raw.append(int(255 * item.value.value / 100))
                        check += 'P'

                if HSL:
                    # convert to rgb
                    # h is 360 based (circle)
                    h, s, l_ = raw[0] / 360.0, raw[1], raw[2]
                    # ORDER h l s !!!
                    r, g, b = colorsys.hls_to_rgb(h, l_, s)
                    # back to 255 based
                    rgba = [
                        int(round(r * 255)),
                        int(round(g * 255)),
                        int(round(b * 255)),
                    ]

                    if len(raw) > 3:
                        rgba.append(raw[3])

                else:
                    # rgb, rgba
                    rgba = raw

                if len(rgba) < 4:
                    rgba.append(1.0)

                # validate
                checks = {
                    'rgb(': ('NNN', 'PPP'),
                    'rgba(': ('NNNN', 'PPPN'),
                    'hsl(': ('NPP',),
                    'hsla(': ('NPPN',),
                }
                if check not in checks[functiontype]:
                    self._log.error(
                        'ColorValue has invalid %s) parameters: '
                        '%s (N=Number, P=Percentage)' % (functiontype, check)
                    )

            self._colorType = t
            self._red, self._green, self._blue, self._alpha = tuple(rgba)
            self._setSeq(seq)

    cssText = property(
        lambda self: cssutils.ser.do_css_ColorValue(self),
        _setCssText,
        doc="String value of this value.",
    )

    value = property(
        lambda self: cssutils.ser.do_css_CSSFunction(self, True),
        doc='Same as cssText but without comments.',
    )

    type = property(
        lambda self: Value.COLOR_VALUE, doc="Type is fixed to Value.COLOR_VALUE."
    )

    def _getName(self):
        for n, v in list(self.COLORS.items()):
            if v == (self.red, self.green, self.blue, self.alpha):
                return n

    colorType = property(
        lambda self: self._colorType,
        doc="IDENT (red), HASH (#f00) or FUNCTION (rgb(255, 0, 0).",
    )

    name = property(
        _getName, doc='Name of the color if known (in ColorValue.COLORS) ' 'else None'
    )

    red = property(lambda self: self._red, doc='red part as integer between 0 and 255')
    green = property(
        lambda self: self._green, doc='green part as integer between 0 and 255'
    )
    blue = property(
        lambda self: self._blue, doc='blue part as integer between 0 and 255'
    )
    alpha = property(
        lambda self: self._alpha, doc='alpha part as float between 0.0 and 1.0'
    )


class DimensionValue(Value):
    """
    A numerical value with an optional dimension like e.g. "px" or "%".

    Covers DIMENSION, PERCENTAGE or NUMBER values.
    """

    __reUnNumDim = re.compile(r'^([+-]?)(\d*\.\d+|\d+)(.*)$', re.I | re.U | re.X)
    _dimension = None
    _sign = None

    def __str__(self):
        return (
            "<cssutils.css.%s object type=%s value=%r dimension=%r cssText=%r at 0x%x>"
            % (
                self.__class__.__name__,
                self.type,
                self.value,
                self.dimension,
                self.cssText,
                id(self),
            )
        )

    def _setCssText(self, cssText):
        self._checkReadonly()

        prods = Sequence(  # PreDef.unary(),
            Choice(
                PreDef.dimension(stop=True),
                PreDef.number(stop=True),
                PreDef.percentage(stop=True),
            )
        )
        ok, seq, store, unused = ProdParser().parse(cssText, 'DimensionValue', prods)
        self.wellformed = ok
        if ok:
            item = seq[0]

            sign, v, d = self.__reUnNumDim.findall(normalize(item.value))[0]
            if '.' in v:
                val = float(sign + v)
            else:
                val = int(sign + v)

            dim = None
            if d:
                dim = d

            self._sign = sign
            self._value = val
            self._dimension = dim
            self._type = item.type

            self._setSeq(seq)

    cssText = property(
        lambda self: cssutils.ser.do_css_Value(self),
        _setCssText,
        doc="String value of this value including dimension.",
    )

    dimension = property(
        lambda self: self._dimension,  # _setValue,
        doc="Dimension if a DIMENSION or PERCENTAGE value, " "else None",
    )


class URIValue(Value):
    """
    An URI value like ``url(example.png)``.
    """

    _type = Value.URI
    _uri = Value._value

    def __str__(self):
        return "<cssutils.css.{} object type={} value={!r} uri={!r} cssText={!r} at 0x{:x}>".format(
            self.__class__.__name__,
            self.type,
            self.value,
            self.uri,
            self.cssText,
            id(self),
        )

    def _setCssText(self, cssText):
        self._checkReadonly()

        prods = Sequence(PreDef.uri(stop=True))

        ok, seq, store, unused = ProdParser().parse(cssText, 'URIValue', prods)
        self.wellformed = ok
        if ok:
            # only 1 value only anyway
            self._type = seq[0].type
            self._value = seq[0].value

            self._setSeq(seq)

    cssText = property(
        lambda self: cssutils.ser.do_css_Value(self),
        _setCssText,
        doc='String value of this value.',
    )

    def _setUri(self, uri):
        # TODO: check?
        self._value = uri

    uri = property(
        lambda self: self._value,
        _setUri,
        doc="Actual URL without delimiters or the empty string",
    )

    def absoluteUri(self):
        """Actual URL, made absolute if possible, else same as `uri`."""
        # Ancestry: PropertyValue, Property, CSSStyleDeclaration, CSSStyleRule,
        # CSSStyleSheet
        try:
            # TODO: better way?
            styleSheet = self.parent.parent.parent.parentRule.parentStyleSheet
        except AttributeError:
            return self.uri
        else:
            return urllib.parse.urljoin(styleSheet.href, self.uri)

    absoluteUri = property(absoluteUri, doc=absoluteUri.__doc__)


class CSSFunction(Value):
    """
    A function value.
    """

    _functionName = 'Function'

    def _productions(self):
        """Return definition used for parsing."""
        types = self._prods  # rename!

        itemProd = Choice(
            _ColorProd(self),
            _DimensionProd(self),
            _URIProd(self),
            _ValueProd(self),
            _CalcValueProd(self),
            _CSSVariableProd(self),
            _CSSFunctionProd(self),
        )
        funcProds = Sequence(
            Prod(
                name='FUNCTION',
                match=lambda t, v: t == types.FUNCTION,
                toSeq=lambda t, tokens: (t[0], normalize(t[1])),
            ),
            Choice(
                Sequence(
                    itemProd,
                    Sequence(
                        PreDef.comma(optional=True), itemProd, minmax=lambda: (0, None)
                    ),
                    PreDef.funcEnd(stop=True),
                ),
                PreDef.funcEnd(stop=True),
            ),
        )
        return funcProds

    def _setCssText(self, cssText):
        self._checkReadonly()
        ok, seq, store, unused = ProdParser().parse(
            cssText, self.type, self._productions()
        )
        self.wellformed = ok
        if ok:
            self._setSeq(seq)

    cssText = property(
        lambda self: cssutils.ser.do_css_CSSFunction(self),
        _setCssText,
        doc="String value of this value.",
    )

    value = property(
        lambda self: cssutils.ser.do_css_CSSFunction(self, True),
        doc='Same as cssText but without comments.',
    )

    type = property(lambda self: Value.FUNCTION, doc="Type is fixed to Value.FUNCTION.")


class MSValue(CSSFunction):
    """An IE specific Microsoft only function value which is much looser
    in what is syntactically allowed."""

    _functionName = 'MSValue'

    def _productions(self):
        """Return definition used for parsing."""
        types = self._prods  # rename!

        func = Prod(
            name='MSValue-Sub',
            match=lambda t, v: t == self._prods.FUNCTION,
            toSeq=lambda t, tokens: (
                MSValue._functionName,
                MSValue(pushtoken(t, tokens), parent=self),
            ),
        )

        funcProds = Sequence(
            Prod(
                name='FUNCTION',
                match=lambda t, v: t == types.FUNCTION,
                toSeq=lambda t, tokens: (t[0], t[1]),
            ),
            Sequence(
                Choice(
                    _ColorProd(self),
                    _DimensionProd(self),
                    _URIProd(self),
                    _ValueProd(self),
                    _MSValueProd(self),
                    # _CalcValueProd(self),
                    _CSSVariableProd(self),
                    func,
                    # _CSSFunctionProd(self),
                    Prod(
                        name='MSValuePart',
                        match=lambda t, v: v != ')',
                        toSeq=lambda t, tokens: (t[0], t[1]),
                    ),
                ),
                minmax=lambda: (0, None),
            ),
            PreDef.funcEnd(stop=True),
        )
        return funcProds

    def _setCssText(self, cssText):
        super()._setCssText(cssText)

    cssText = property(
        lambda self: cssutils.ser.do_css_MSValue(self),
        _setCssText,
        doc="String value of this value.",
    )


class CSSCalc(CSSFunction):
    """The CSSCalc function represents a CSS calc() function.

    No further API is provided. For multiplication and division no check
    if one operand is a NUMBER is made.
    """

    _functionName = 'CSSCalc'

    def __str__(self):
        return "<cssutils.css.{} object at 0x{:x}>".format(
            self.__class__.__name__, id(self)
        )

    def _setCssText(self, cssText):
        self._checkReadonly()

        types = self._prods  # rename!

        _operator = Choice(
            Prod(
                name='Operator */',
                match=lambda t, v: v in '*/',
                toSeq=lambda t, tokens: (t[0], t[1]),
            ),
            Sequence(
                PreDef.S(),
                Choice(
                    Sequence(
                        Prod(
                            name='Operator */',
                            match=lambda t, v: v in '*/',
                            toSeq=lambda t, tokens: (t[0], t[1]),
                        ),
                        PreDef.S(optional=True),
                    ),
                    Sequence(
                        Prod(
                            name='Operator +-',
                            match=lambda t, v: v in '+-',
                            toSeq=lambda t, tokens: (t[0], t[1]),
                        ),
                        PreDef.S(),
                    ),
                    PreDef.funcEnd(stop=True, mayEnd=True),
                ),
            ),
        )

        _operant = lambda: Choice(  # noqa:E731
            _DimensionProd(self), _CalcValueProd(self), _CSSVariableProd(self)
        )

        prods = Sequence(
            Prod(
                name='CALC',
                match=lambda t, v: t == types.FUNCTION and normalize(v) == 'calc(',
            ),
            PreDef.S(optional=True),
            _operant(),
            Sequence(_operator, _operant(), minmax=lambda: (0, None)),
            PreDef.funcEnd(stop=True),
        )

        # store: name of variable
        ok, seq, store, unused = ProdParser().parse(
            cssText, 'CSSCalc', prods, checkS=True
        )
        self.wellformed = ok
        if ok:
            self._setSeq(seq)

    cssText = property(
        lambda self: cssutils.ser.do_css_CSSCalc(self),
        _setCssText,
        doc="String representation of calc function.",
    )

    type = property(lambda self: Value.CALC, doc="Type is fixed to Value.CALC.")


class CSSVariable(CSSFunction):
    """The CSSVariable represents a CSS variables like ``var(varname)``.

    A variable has a (nonnormalized!) `name` and a `value` which is
    tried to be resolved from any available CSSVariablesRule definition.
    """

    _functionName = 'CSSVariable'
    _name = None
    _fallback = None

    def __str__(self):
        return "<cssutils.css.{} object name={!r} value={!r} at 0x{:x}>".format(
            self.__class__.__name__,
            self.name,
            self.value,
            id(self),
        )

    def _setCssText(self, cssText):
        self._checkReadonly()

        types = self._prods  # rename!
        prods = Sequence(
            Prod(
                name='var',
                match=lambda t, v: t == types.FUNCTION and normalize(v) == 'var(',
            ),
            PreDef.ident(toStore='ident'),
            Sequence(
                PreDef.comma(),
                Choice(
                    _ColorProd(self, toStore='fallback'),
                    _DimensionProd(self, toStore='fallback'),
                    _URIProd(self, toStore='fallback'),
                    _ValueProd(self, toStore='fallback'),
                    _CalcValueProd(self, toStore='fallback'),
                    _CSSVariableProd(self, toStore='fallback'),
                    _CSSFunctionProd(self, toStore='fallback'),
                ),
                minmax=lambda: (0, 1),
            ),
            PreDef.funcEnd(stop=True),
        )

        # store: name of variable
        store = {'ident': None, 'fallback': None}
        ok, seq, store, unused = ProdParser().parse(cssText, 'CSSVariable', prods)
        self.wellformed = ok

        if ok:
            self._name = store['ident'].value
            try:
                self._fallback = store['fallback'].value
            except KeyError:
                self._fallback = None

            self._setSeq(seq)

    cssText = property(
        lambda self: cssutils.ser.do_css_CSSVariable(self),
        _setCssText,
        doc="String representation of variable.",
    )

    # TODO: writable? check if var (value) available?
    name = property(
        lambda self: self._name,
        doc="The name identifier of this variable referring to "
        "a value in a "
        ":class:`cssutils.css.CSSVariablesDeclaration`.",
    )

    fallback = property(
        lambda self: self._fallback, doc="The fallback Value of this variable"
    )

    type = property(lambda self: Value.VARIABLE, doc="Type is fixed to Value.VARIABLE.")

    def _getValue(self):
        "Find contained sheet and @variables there"
        rel = self
        while True:
            # find node which has parentRule to get to StyleSheet
            if hasattr(rel, 'parent'):
                rel = rel.parent
            else:
                break
        try:
            variables = rel.parentRule.parentStyleSheet.variables
        except AttributeError:
            return None
        else:
            try:
                return variables[self.name]
            except KeyError:
                return None

    value = property(_getValue, doc='The resolved actual value or None.')


# helper for productions
def _ValueProd(parent, nextSor=False, toStore=None):
    return Prod(
        name='Value',
        match=lambda t, v: t in ('IDENT', 'STRING', 'UNICODE-RANGE'),
        nextSor=nextSor,
        toStore=toStore,
        toSeq=lambda t, tokens: ('Value', Value(pushtoken(t, tokens), parent=parent)),
    )


def _DimensionProd(parent, nextSor=False, toStore=None):
    return Prod(
        name='Dimension',
        match=lambda t, v: t in ('DIMENSION', 'NUMBER', 'PERCENTAGE'),
        nextSor=nextSor,
        toStore=toStore,
        toSeq=lambda t, tokens: (
            'DIMENSION',
            DimensionValue(pushtoken(t, tokens), parent=parent),
        ),
    )


def _URIProd(parent, nextSor=False, toStore=None):
    return Prod(
        name='URIValue',
        match=lambda t, v: t == 'URI',
        toStore=toStore,
        nextSor=nextSor,
        toSeq=lambda t, tokens: (
            'URIValue',
            URIValue(pushtoken(t, tokens), parent=parent),
        ),
    )


reHexcolor = re.compile(r'^\#(?:[0-9abcdefABCDEF]{3}|[0-9abcdefABCDEF]{6})$')


def _ColorProd(parent, nextSor=False, toStore=None):
    return Prod(
        name='ColorValue',
        match=lambda t, v: (t == 'HASH' and reHexcolor.match(v))
        or (t == 'FUNCTION' and normalize(v) in ('rgb(', 'rgba(', 'hsl(', 'hsla('))
        or (t == 'IDENT' and normalize(v) in list(ColorValue.COLORS.keys())),
        nextSor=nextSor,
        toStore=toStore,
        toSeq=lambda t, tokens: (
            'ColorValue',
            ColorValue(pushtoken(t, tokens), parent=parent),
        ),
    )


def _CSSFunctionProd(parent, nextSor=False, toStore=None):
    return PreDef.function(
        nextSor=nextSor,
        toStore=toStore,
        toSeq=lambda t, tokens: (
            CSSFunction._functionName,
            CSSFunction(pushtoken(t, tokens), parent=parent),
        ),
    )


def _CalcValueProd(parent, nextSor=False, toStore=None):
    return Prod(
        name=CSSCalc._functionName,
        match=lambda t, v: t == PreDef.types.FUNCTION and normalize(v) == 'calc(',
        toStore=toStore,
        toSeq=lambda t, tokens: (
            CSSCalc._functionName,
            CSSCalc(pushtoken(t, tokens), parent=parent),
        ),
        nextSor=nextSor,
    )


def _CSSVariableProd(parent, nextSor=False, toStore=None):
    return PreDef.variable(
        nextSor=nextSor,
        toStore=toStore,
        toSeq=lambda t, tokens: (
            CSSVariable._functionName,
            CSSVariable(pushtoken(t, tokens), parent=parent),
        ),
    )


def _MSValueProd(parent, nextSor=False):
    return Prod(
        name=MSValue._functionName,
        match=lambda t, v: (  # t == self._prods.FUNCTION and (
            normalize(v)
            in (
                'expression(',
                'alpha(',
                'blur(',
                'chroma(',
                'dropshadow(',
                'fliph(',
                'flipv(',
                'glow(',
                'gray(',
                'invert(',
                'mask(',
                'shadow(',
                'wave(',
                'xray(',
            )
            or v.startswith('progid:DXImageTransform.Microsoft.')
        ),
        nextSor=nextSor,
        toSeq=lambda t, tokens: (
            MSValue._functionName,
            MSValue(pushtoken(t, tokens), parent=parent),
        ),
    )


def MediaQueryValueProd(parent):
    return Choice(
        _ColorProd(parent),
        _DimensionProd(parent),
        _ValueProd(parent),
    )
