File: cssmin.py

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cssmin 0.2.0-1
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#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""`cssmin` - A Python port of the YUI CSS compressor."""

try:
    from StringIO import StringIO # The pure-Python StringIO supports unicode.
except ImportError:
    from io import StringIO
import re


__version__ = '0.2.0'


def remove_comments(css):
    """Remove all CSS comment blocks."""

    iemac = False
    preserve = False
    comment_start = css.find("/*")
    while comment_start >= 0:
        # Preserve comments that look like `/*!...*/`.
        # Slicing is used to make sure we don"t get an IndexError.
        preserve = css[comment_start + 2:comment_start + 3] == "!"

        comment_end = css.find("*/", comment_start + 2)
        if comment_end < 0:
            if not preserve:
                css = css[:comment_start]
                break
        elif comment_end >= (comment_start + 2):
            if css[comment_end - 1] == "\\":
                # This is an IE Mac-specific comment; leave this one and the
                # following one alone.
                comment_start = comment_end + 2
                iemac = True
            elif iemac:
                comment_start = comment_end + 2
                iemac = False
            elif not preserve:
                css = css[:comment_start] + css[comment_end + 2:]
            else:
                comment_start = comment_end + 2
        comment_start = css.find("/*", comment_start)

    return css


def remove_unnecessary_whitespace(css):
    """Remove unnecessary whitespace characters."""

    def pseudoclasscolon(css):

        """
        Prevents 'p :link' from becoming 'p:link'.

        Translates 'p :link' into 'p ___PSEUDOCLASSCOLON___link'; this is
        translated back again later.
        """

        regex = re.compile(r"(^|\})(([^\{\:])+\:)+([^\{]*\{)")
        match = regex.search(css)
        while match:
            css = ''.join([
                css[:match.start()],
                match.group().replace(":", "___PSEUDOCLASSCOLON___"),
                css[match.end():]])
            match = regex.search(css)
        return css

    css = pseudoclasscolon(css)
    # Remove spaces from before things.
    css = re.sub(r"\s+([!{};:>+\(\)\],])", r"\1", css)

    # If there is a `@charset`, then only allow one, and move to the beginning.
    css = re.sub(r"^(.*)(@charset \"[^\"]*\";)", r"\2\1", css)
    css = re.sub(r"^(\s*@charset [^;]+;\s*)+", r"\1", css)

    # Put the space back in for a few cases, such as `@media screen` and
    # `(-webkit-min-device-pixel-ratio:0)`.
    css = re.sub(r"\band\(", "and (", css)

    # Put the colons back.
    css = css.replace('___PSEUDOCLASSCOLON___', ':')

    # Remove spaces from after things.
    css = re.sub(r"([!{}:;>+\(\[,])\s+", r"\1", css)

    return css


def remove_unnecessary_semicolons(css):
    """Remove unnecessary semicolons."""

    return re.sub(r";+\}", "}", css)


def remove_empty_rules(css):
    """Remove empty rules."""

    return re.sub(r"[^\}\{]+\{\}", "", css)


def normalize_rgb_colors_to_hex(css):
    """Convert `rgb(51,102,153)` to `#336699`."""

    regex = re.compile(r"rgb\s*\(\s*([0-9,\s]+)\s*\)")
    match = regex.search(css)
    while match:
        colors = map(lambda s: s.strip(), match.group(1).split(","))
        hexcolor = '#%.2x%.2x%.2x' % tuple(map(int, colors))
        css = css.replace(match.group(), hexcolor)
        match = regex.search(css)
    return css


def condense_zero_units(css):
    """Replace `0(px, em, %, etc)` with `0`."""

    return re.sub(r"([\s:])(0)(px|em|%|in|cm|mm|pc|pt|ex)", r"\1\2", css)


def condense_multidimensional_zeros(css):
    """Replace `:0 0 0 0;`, `:0 0 0;` etc. with `:0;`."""

    css = css.replace(":0 0 0 0;", ":0;")
    css = css.replace(":0 0 0;", ":0;")
    css = css.replace(":0 0;", ":0;")

    # Revert `background-position:0;` to the valid `background-position:0 0;`.
    css = css.replace("background-position:0;", "background-position:0 0;")

    return css


def condense_floating_points(css):
    """Replace `0.6` with `.6` where possible."""

    return re.sub(r"(:|\s)0+\.(\d+)", r"\1.\2", css)


def condense_hex_colors(css):
    """Shorten colors from #AABBCC to #ABC where possible."""

    regex = re.compile(r"([^\"'=\s])(\s*)#([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])([0-9a-fA-F])")
    match = regex.search(css)
    while match:
        first = match.group(3) + match.group(5) + match.group(7)
        second = match.group(4) + match.group(6) + match.group(8)
        if first.lower() == second.lower():
            css = css.replace(match.group(), match.group(1) + match.group(2) + '#' + first)
            match = regex.search(css, match.end() - 3)
        else:
            match = regex.search(css, match.end())
    return css


def condense_whitespace(css):
    """Condense multiple adjacent whitespace characters into one."""

    return re.sub(r"\s+", " ", css)


def condense_semicolons(css):
    """Condense multiple adjacent semicolon characters into one."""

    return re.sub(r";;+", ";", css)


def wrap_css_lines(css, line_length):
    """Wrap the lines of the given CSS to an approximate length."""

    lines = []
    line_start = 0
    for i, char in enumerate(css):
        # It's safe to break after `}` characters.
        if char == '}' and (i - line_start >= line_length):
            lines.append(css[line_start:i + 1])
            line_start = i + 1

    if line_start < len(css):
        lines.append(css[line_start:])
    return '\n'.join(lines)


def cssmin(css, wrap=None):
    css = remove_comments(css)
    css = condense_whitespace(css)
    # A pseudo class for the Box Model Hack
    # (see http://tantek.com/CSS/Examples/boxmodelhack.html)
    css = css.replace('"\\"}\\""', "___PSEUDOCLASSBMH___")
    css = remove_unnecessary_whitespace(css)
    css = remove_unnecessary_semicolons(css)
    css = condense_zero_units(css)
    css = condense_multidimensional_zeros(css)
    css = condense_floating_points(css)
    css = normalize_rgb_colors_to_hex(css)
    css = condense_hex_colors(css)
    if wrap is not None:
        css = wrap_css_lines(css, wrap)
    css = css.replace("___PSEUDOCLASSBMH___", '"\\"}\\""')
    css = condense_semicolons(css)
    return css.strip()


def main():
    import optparse
    import sys

    p = optparse.OptionParser(
        prog="cssmin", version=__version__,
        usage="%prog [--wrap N]",
        description="""Reads raw CSS from stdin, and writes compressed CSS to stdout.""")

    p.add_option(
        '-w', '--wrap', type='int', default=None, metavar='N',
        help="Wrap output to approximately N chars per line.")

    options, args = p.parse_args()
    sys.stdout.write(cssmin(sys.stdin.read(), wrap=options.wrap))


if __name__ == '__main__':
    main()