libretube/plugins/compressor/js_minifer.py

# -*- coding: utf-8 -*-

"""JavaScript Minifier functions for CSS-JS-Minify."""

import re
from io import StringIO  # pure-Python StringIO supports unicode.
from .css_minifer import condense_semicolons

__all__ = ('js_minify', )


def remove_commented_lines(js):
    """Force remove commented out lines from Javascript."""
    result = ""
    for line in js.splitlines():
        line = re.sub(r"/\*.*\*/", "", line)  # (/*COMMENT */)
        line = re.sub(r"//.*", "", line)  # (//COMMENT)
        result += '\n'+line
    return result


def simple_replacer_js(js):
    """Force strip simple replacements from Javascript."""
    return condense_semicolons(js.replace("debugger;", ";").replace(
        ";}", "}").replace("; ", ";").replace(" ;", ";").rstrip("\n;"))


def js_minify_keep_comments(js):
    """Return a minified version of the Javascript string."""
    ins, outs = StringIO(js), StringIO()
    JavascriptMinify(ins, outs).minify()
    return force_single_line_js(outs.getvalue())


def force_single_line_js(js):
    """Force Javascript to a single line, even if need to add semicolon."""
    return ";".join(js.splitlines()) if len(js.splitlines()) > 1 else js


class JavascriptMinify(object):

    """Minify an input stream of Javascript, writing to an output stream."""

    def __init__(self, instream=None, outstream=None):
        """Init class."""
        self.ins, self.outs = instream, outstream

    def minify(self, instream=None, outstream=None):
        """Minify Javascript using StringIO."""
        if instream and outstream:
            self.ins, self.outs = instream, outstream
        write, read = self.outs.write, self.ins.read
        space_strings = ("abcdefghijklmnopqrstuvwxyz"
                         "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_$\\")
        starters, enders = '{[(+-', '}])+-"\''
        newlinestart_strings = starters + space_strings
        newlineend_strings = enders + space_strings
        do_newline, do_space = False, False
        doing_single_comment, doing_multi_comment = False, False
        previous_before_comment, in_quote = '', ''
        in_re, quote_buf = False, []
        previous = read(1)
        next1 = read(1)
        if previous == '/':
            if next1 == '/':
                doing_single_comment = True
            elif next1 == '*':
                doing_multi_comment = True
            else:
                write(previous)
        elif not previous:
            return
        elif previous >= '!':
            if previous in "'\"":
                in_quote = previous
            write(previous)
            previous_non_space = previous
        else:
            previous_non_space = ' '
        if not next1:
            return
        while True:
            next2 = read(1)
            if not next2:
                last = next1.strip()
                conditional_1 = (doing_single_comment or doing_multi_comment)
                if not conditional_1 and last not in ('', '/'):
                    write(last)
                break
            if doing_multi_comment:
                if next1 == '*' and next2 == '/':
                    doing_multi_comment = False
                    next2 = read(1)
            elif doing_single_comment:
                if next1 in '\r\n':
                    doing_single_comment = False
                    while next2 in '\r\n':
                        next2 = read(1)
                        if not next2:
                            break
                    if previous_before_comment in ')}]':
                        do_newline = True
                    elif previous_before_comment in space_strings:
                        write('\n')
            elif in_quote:
                quote_buf.append(next1)

                if next1 == in_quote:
                    numslashes = 0
                    for c in reversed(quote_buf[:-1]):
                        if c != '\\':
                            break
                        else:
                            numslashes += 1
                    if numslashes % 2 == 0:
                        in_quote = ''
                        write(''.join(quote_buf))
            elif next1 in '\r\n':
                conditional_2 = previous_non_space in newlineend_strings
                if conditional_2 or previous_non_space > '~':
                    while 1:
                        if next2 < '!':
                            next2 = read(1)
                            if not next2:
                                break
                        else:
                            conditional_3 = next2 in newlinestart_strings
                            if conditional_3 or next2 > '~' or next2 == '/':
                                do_newline = True
                            break
            elif next1 < '!' and not in_re:
                conditional_4 = next2 in space_strings or next2 > '~'
                conditional_5 = previous_non_space in space_strings
                conditional_6 = previous_non_space > '~'
                if (conditional_5 or conditional_6) and (conditional_4):
                    do_space = True
            elif next1 == '/':
                if in_re:
                    if previous != '\\':
                        in_re = False
                    write('/')
                elif next2 == '/':
                    doing_single_comment = True
                    previous_before_comment = previous_non_space
                elif next2 == '*':
                    doing_multi_comment = True
                else:
                    in_re = previous_non_space in '(,=:[?!&|'
                    write('/')
            else:
                if do_space:
                    do_space = False
                    write(' ')
                if do_newline:
                    write('\n')
                    do_newline = False
                write(next1)
                if not in_re and next1 in "'\"":
                    in_quote = next1
                    quote_buf = []
            previous = next1
            next1 = next2
            if previous >= '!':
                previous_non_space = previous


def js_minify(js):
    """Minify a JavaScript string."""
    js = remove_commented_lines(js)
    js = js_minify_keep_comments(js)
    return js.strip()