path: root/scss/functions/core.py

"""Functions from the Sass "standard library", i.e., built into the original
Ruby implementation.
"""

from __future__ import absolute_import

import colorsys
import logging
import math
import operator

import six
from six.moves import xrange

from scss.cssdefs import _variable_re
from scss.functions.library import FunctionLibrary
from scss.types import BooleanValue, ColorValue, List, NumberValue, QuotedStringValue, StringValue, String

log = logging.getLogger(__name__)

CORE_LIBRARY = FunctionLibrary()
register = CORE_LIBRARY.register

# ------------------------------------------------------------------------------
# Color creation

def _constrain(n, lb, ub):
    if n < lb:
        return lb
    elif n > ub:
        return ub
    else:
        return n

def _apply_percentage(n, relto=1):
    """Given a unitless Number, returns its value.  Given a percentage Number,
    returns its value divided by 100%.  Raises TypeError otherwise.

    The optional `relto` gives a value for what "100%" means; percentages will
    be scaled by this value before being returned.
    """
    if not isinstance(n, NumberValue):
        raise TypeError("Expected number, got %r" % (n,))

    if n.is_unitless:
        return n.value
    elif n.unit == '%':
        return n.value * relto / 100.
    else:
        raise TypeError("Expected unitless number or percentage, got %r" % (n,))

def _color_type(color, a, type):
    color = ColorValue(color).value
    a = NumberValue(a).value if a is not None else color[3]
    col = list(color[:3])
    col += [0.0 if a < 0 else 1.0 if a > 1 else a]
    col += [type]
    return ColorValue(col)


@register('rgba', 4)
def rgba(r, g, b, a, type='rgba'):
    channels = []
    for ch in (r, g, b):
        channels.append(_constrain(_apply_percentage(ch, relto=255), 0, 255))

    channels.append(_constrain(_apply_percentage(a), 0, 1))
    channels.append(type)
    return ColorValue(channels)

@register('rgb', 3)
def rgb(r, g, b, type='rgb'):
    return rgba(r, g, b, NumberValue(1.0), type)


@register('rgba', 1)
@register('rgba', 2)
def rgba2(color, a=None):
    return _color_type(color, a, 'rgba')

@register('rgb', 1)
def rgb1(color):
    return _color_type(color, 1.0, 'rgb')


@register('hsla', 4)
def hsla(h, s, l, a, type='hsla'):
    rgb = colorsys.hls_to_rgb(
        _apply_percentage(h, relto=360) % 360 / 360,
        # Ruby sass treats plain numbers for saturation and lightness as though
        # they were percentages, just without the %
        _constrain(_apply_percentage(l, relto=100), 0, 100) / 100,
        _constrain(_apply_percentage(s, relto=100), 0, 100) / 100,
    )

    channels = list(ch * 255 for ch in rgb)
    channels.append(_constrain(_apply_percentage(a), 0, 1))
    channels.append(type)
    return ColorValue(channels)

@register('hsl', 3)
def hsl(h, s, l, type='hsl'):
    return hsla(h, s, l, NumberValue(1), type)


@register('hsla', 1)
@register('hsla', 2)
def hsla2(color, a=None):
    return _color_type(color, a, 'hsla')

@register('hsl', 1)
def hsl1(color):
    return _color_type(color, 1.0, 'hsl')


@register('mix', 2)
@register('mix', 3)
def mix(color1, color2, weight=None):
    """
    Mixes together two colors. Specifically, takes the average of each of the
    RGB components, optionally weighted by the given percentage.
    The opacity of the colors is also considered when weighting the components.

    Specifically, takes the average of each of the RGB components,
    optionally weighted by the given percentage.
    The opacity of the colors is also considered when weighting the components.

    The weight specifies the amount of the first color that should be included
    in the returned color.
    50%, means that half the first color
        and half the second color should be used.
    25% means that a quarter of the first color
        and three quarters of the second color should be used.

    For example:

        mix(#f00, #00f) => #7f007f
        mix(#f00, #00f, 25%) => #3f00bf
        mix(rgba(255, 0, 0, 0.5), #00f) => rgba(63, 0, 191, 0.75)

    """
    # This algorithm factors in both the user-provided weight
    # and the difference between the alpha values of the two colors
    # to decide how to perform the weighted average of the two RGB values.
    #
    # It works by first normalizing both parameters to be within [-1, 1],
    # where 1 indicates "only use color1", -1 indicates "only use color 0",
    # and all values in between indicated a proportionately weighted average.
    #
    # Once we have the normalized variables w and a,
    # we apply the formula (w + a)/(1 + w*a)
    # to get the combined weight (in [-1, 1]) of color1.
    # This formula has two especially nice properties:
    #
    #   * When either w or a are -1 or 1, the combined weight is also that number
    #     (cases where w * a == -1 are undefined, and handled as a special case).
    #
    #   * When a is 0, the combined weight is w, and vice versa
    #
    # Finally, the weight of color1 is renormalized to be within [0, 1]
    # and the weight of color2 is given by 1 minus the weight of color1.
    #
    # Algorithm from the Sass project: http://sass-lang.com/

    c1 = ColorValue(color1).value
    c2 = ColorValue(color2).value
    p = _constrain(_apply_percentage(weight), 0, 1) if weight is not None else 0.5

    w = p * 2 - 1
    a = c1[3] - c2[3]

    w1 = ((w if (w * a == -1) else (w + a) / (1 + w * a)) + 1) / 2.0

    w2 = 1 - w1
    q = [w1, w1, w1, p]
    r = [w2, w2, w2, 1 - p]

    return ColorValue([c1[i] * q[i] + c2[i] * r[i] for i in range(4)])


# ------------------------------------------------------------------------------
# Color inspection

@register('red', 1)
def red(color):
    c = ColorValue(color).value
    return NumberValue(c[0])


@register('green', 1)
def green(color):
    c = ColorValue(color).value
    return NumberValue(c[1])


@register('blue', 1)
def blue(color):
    c = ColorValue(color).value
    return NumberValue(c[2])


@register('opacity', 1)
@register('alpha', 1)
def alpha(color):
    c = ColorValue(color).value
    return NumberValue(c[3])


@register('hue', 1)
def hue(color):
    c = ColorValue(color).value
    h, l, s = colorsys.rgb_to_hls(c[0] / 255.0, c[1] / 255.0, c[2] / 255.0)
    return NumberValue(h * 360, unit='deg')


@register('saturation', 1)
def saturation(color):
    c = ColorValue(color).value
    h, l, s = colorsys.rgb_to_hls(c[0] / 255.0, c[1] / 255.0, c[2] / 255.0)
    return NumberValue(s * 100, unit='%')


@register('lightness', 1)
def lightness(color):
    c = ColorValue(color).value
    h, l, s = colorsys.rgb_to_hls(c[0] / 255.0, c[1] / 255.0, c[2] / 255.0)
    return NumberValue(l * 100, unit='%')


@register('ie-hex-str', 1)
def ie_hex_str(color):
    c = ColorValue(color).value
    return String(u'#%02X%02X%02X%02X' % (round(c[3] * 255), round(c[0]), round(c[1]), round(c[2])))


# ------------------------------------------------------------------------------
# Color modification

def __rgba_op(op, color, r, g, b, a):
    color = ColorValue(color)
    c = color.value
    a = [
        None if r is None else NumberValue(r).value,
        None if g is None else NumberValue(g).value,
        None if b is None else NumberValue(b).value,
        None if a is None else NumberValue(a).value,
    ]
    # Do the additions:
    c = [op(c[i], a[i]) if op is not None and a[i] is not None else a[i] if a[i] is not None else c[i] for i in range(4)]
    # Validations:
    r = 255.0, 255.0, 255.0, 1.0
    c = [0.0 if c[i] < 0 else r[i] if c[i] > r[i] else c[i] for i in range(4)]
    color.value = tuple(c)
    return color


@register('fade-in', 2)
@register('fadein', 2)
@register('opacify', 2)
def opacify(color, amount):
    return __rgba_op(operator.__add__, color, 0, 0, 0, amount)


@register('fade-out', 2)
@register('fadeout', 2)
@register('transparentize', 2)
def transparentize(color, amount):
    return __rgba_op(operator.__sub__, color, 0, 0, 0, amount)


def __hsl_op(op, color, h, s, l):
    color = ColorValue(color)
    c = color.value
    h = None if h is None else NumberValue(h)
    s = None if s is None else NumberValue(s)
    l = None if l is None else NumberValue(l)
    a = [
        None if h is None else h.value / 360.0,
        None if s is None else _apply_percentage(s),
        None if l is None else _apply_percentage(l),
    ]
    # Convert to HSL:
    h, l, s = list(colorsys.rgb_to_hls(c[0] / 255.0, c[1] / 255.0, c[2] / 255.0))
    c = h, s, l
    # Do the additions:
    c = [0.0 if c[i] < 0 else 1.0 if c[i] > 1 else op(c[i], a[i]) if op is not None and a[i] is not None else a[i] if a[i] is not None else c[i] for i in range(3)]
    # Validations:
    c[0] = (c[0] * 360.0) % 360
    r = 360.0, 1.0, 1.0
    c = [0.0 if c[i] < 0 else r[i] if c[i] > r[i] else c[i] for i in range(3)]
    # Convert back to RGB:
    c = colorsys.hls_to_rgb(c[0] / 360.0, 0.99999999 if c[2] == 1 else c[2], 0.99999999 if c[1] == 1 else c[1])
    color.value = (c[0] * 255.0, c[1] * 255.0, c[2] * 255.0, color.value[3])
    return color


@register('lighten', 2)
def lighten(color, amount):
    return __hsl_op(operator.__add__, color, 0, 0, amount)


@register('darken', 2)
def darken(color, amount):
    return __hsl_op(operator.__sub__, color, 0, 0, amount)


@register('saturate', 2)
def saturate(color, amount):
    return __hsl_op(operator.__add__, color, 0, amount, 0)


@register('desaturate', 2)
def desaturate(color, amount):
    return __hsl_op(operator.__sub__, color, 0, amount, 0)


@register('greyscale', 1)
@register('grayscale', 1)
def grayscale(color):
    return __hsl_op(operator.__sub__, color, 0, 100.0, 0)


@register('spin', 2)
@register('adjust-hue', 2)
def adjust_hue(color, degrees):
    return __hsl_op(operator.__add__, color, degrees, 0, 0)


@register('complement', 1)
def complement(color):
    return __hsl_op(operator.__add__, color, 180.0, 0, 0)


@register('invert', 1)
def invert(color):
    """
    Returns the inverse (negative) of a color.
    The red, green, and blue values are inverted, while the opacity is left alone.
    """
    col = ColorValue(color)
    c = list(col.value)
    c[0] = 255.0 - c[0]
    c[1] = 255.0 - c[1]
    c[2] = 255.0 - c[2]
    col.value = tuple(c)
    return col


@register('adjust-lightness', 2)
def adjust_lightness(color, amount):
    return __hsl_op(operator.__add__, color, 0, 0, amount)


@register('adjust-saturation', 2)
def adjust_saturation(color, amount):
    return __hsl_op(operator.__add__, color, 0, amount, 0)


@register('scale-lightness', 2)
def scale_lightness(color, amount):
    return __hsl_op(operator.__mul__, color, 0, 0, amount)


@register('scale-saturation', 2)
def scale_saturation(color, amount):
    return __hsl_op(operator.__mul__, color, 0, amount, 0)


def _asc_color(op, color, saturation=None, lightness=None, red=None, green=None, blue=None, alpha=None):
    if lightness or saturation:
        color = __hsl_op(op, color, 0, saturation, lightness)
    if red or green or blue or alpha:
        color = __rgba_op(op, color, red, green, blue, alpha)
    return color


@register('adjust-color')
def adjust_color(color, saturation=None, lightness=None, red=None, green=None, blue=None, alpha=None):
    return _asc_color(operator.__add__, color, saturation, lightness, red, green, blue, alpha)


@register('scale-color')
def scale_color(color, saturation=None, lightness=None, red=None, green=None, blue=None, alpha=None):
    return _asc_color(operator.__mul__, color, saturation, lightness, red, green, blue, alpha)


@register('change-color')
def change_color(color, saturation=None, lightness=None, red=None, green=None, blue=None, alpha=None):
    return _asc_color(None, color, saturation, lightness, red, green, blue, alpha)


# ------------------------------------------------------------------------------
# String type manipulation

@register('e', 1)
@register('escape', 1)
@register('unquote')
def unquote(*args):
    return StringValue(' '.join([StringValue(s).value for s in args]))


@register('quote')
def quote(*args):
    return QuotedStringValue(' '.join([StringValue(s).value for s in args]))


# ------------------------------------------------------------------------------
# Number functions

@register('percentage', 1)
def percentage(value):
    if not isinstance(value, NumberValue):
        raise TypeError("Expected number, got %r" % (value,))

    if not value.is_unitless:
        raise TypeError("Expected unitless number, got %r" % (value,))

    return value * NumberValue(100, unit='%')

CORE_LIBRARY.add(NumberValue.wrap_python_function(abs), 'abs', 1)
CORE_LIBRARY.add(NumberValue.wrap_python_function(round), 'round', 1)
CORE_LIBRARY.add(NumberValue.wrap_python_function(math.ceil), 'ceil', 1)
CORE_LIBRARY.add(NumberValue.wrap_python_function(math.floor), 'floor', 1)


# ------------------------------------------------------------------------------
# List functions
def __parse_separator(separator, default_from=None):
    if separator is None:
        return None
    separator = StringValue(separator).value
    if separator == 'comma':
        return True
    elif separator == 'space':
        return False
    elif separator == 'auto':
        if not default_from:
            return True
        elif len(default_from) < 2:
            return True
        else:
            return default_from.use_comma
    else:
        raise ValueError('Separator must be auto, comma, or space')


# TODO get the compass bit outta here
@register('-compass-list-size')
@register('length')
def _length(*lst):
    if len(lst) == 1 and isinstance(lst[0], (list, tuple, List)):
        lst = lst[0]
    return NumberValue(len(lst))


# TODO get the compass bit outta here
@register('-compass-nth', 2)
@register('nth', 2)
def nth(lst, n):
    """
    Return the Nth item in the string
    """
    n = NumberValue(n).value
    lst = List(lst).value
    try:
        n = int(float(n)) - 1
        n = n % len(lst)
    except:
        if n.lower() == 'first':
            n = 0
        elif n.lower() == 'last':
            n = -1
    try:
        ret = lst[n]
    except KeyError:
        lst = [v for k, v in sorted(lst.items()) if isinstance(k, int)]
        try:
            ret = lst[n]
        except:
            ret = ''
    return ret.__class__(ret)


@register('join', 2)
@register('join', 3)
def join(lst1, lst2, separator=None):
    ret = []
    ret.extend(List.from_maybe(lst1))
    ret.extend(List.from_maybe(lst2))

    use_comma = __parse_separator(separator, default_from=lst1)
    return List(ret, use_comma=use_comma)


@register('min')
def min_(*lst):
    if len(lst) == 1 and isinstance(lst[0], (list, tuple, List)):
        lst = lst[0]
    return min(lst)


@register('max')
def max_(*lst):
    if len(lst) == 1 and isinstance(lst[0], (list, tuple, List)):
        lst = lst[0]
    return max(lst)


@register('append', 2)
@register('append', 3)
def append(lst, val, separator=None):
    ret = []
    ret.extend(List.from_maybe(lst))
    ret.append(val)

    use_comma = __parse_separator(separator, default_from=lst)
    return List(ret, use_comma=use_comma)


@register('index', 2)
def index(lst, val):
    for i in xrange(len(lst)):
        if lst.value[i] == val:
            return NumberValue(i + 1)
    return BooleanValue(False)


# ------------------------------------------------------------------------------
# Meta functions

@register('type-of', 1)
def _type_of(obj):  # -> bool, number, string, color, list
    return String(obj.sass_type_name)


@register('unit', 1)
def unit(number):  # -> px, em, cm, etc.
    numer = '*'.join(number.unit_numer)
    denom = '*'.join(number.unit_denom)

    if denom:
        ret = numer + '/' + denom
    else:
        ret = numer
    return StringValue(ret)


@register('unitless', 1)
def unitless(value):
    if not isinstance(value, NumberValue):
        raise TypeError("Expected number, got %r" % (value,))

    return BooleanValue(value.is_unitless)


@register('comparable', 2)
def comparable(number1, number2):
    left = number1.to_base_units()
    right = number2.to_base_units()
    return BooleanValue(
        left.unit_numer == right.unit_numer
        and left.unit_denom == right.unit_denom)


# ------------------------------------------------------------------------------
# Miscellaneous

@register('if', 2)
@register('if', 3)
def if_(condition, if_true, if_false=''):
    condition = bool(False if not condition or isinstance(condition, six.string_types) and (condition in ('0', 'false', 'undefined') or _variable_re.match(condition)) else condition)
    return if_true.__class__(if_true) if condition else if_true.__class__(if_false)