# Τεκμηρίωση του Django - 1.10.7

# Πηγαίος κώδικας για το django.utils.text

    from __future__ import unicode_literals

    import re
    import unicodedata
    from gzip import GzipFile
    from io import BytesIO

    from django.utils import six
    from django.utils.encoding import force_text
    from django.utils.functional import SimpleLazyObject, keep_lazy, keep_lazy_text
    from django.utils.safestring import SafeText, mark_safe
    from django.utils.six.moves import html_entities
    from django.utils.translation import pgettext, ugettext as _, ugettext_lazy

    if six.PY2:
        # Import force_unicode even though this module doesn't use it, because some
        # people rely on it being here.
        from django.utils.encoding import force_unicode  # NOQA

    # Capitalizes the first letter of a string.
    def capfirst(x):
        return x and force_text(x)[0].upper() + force_text(x)[1:]
    capfirst = keep_lazy_text(capfirst)

    # Set up regular expressions
    re_words = re.compile(r'<.*?>|((?:\w[-\w]*|&.*?;)+)', re.U | re.S)
    re_chars = re.compile(r'<.*?>|(.)', re.U | re.S)
    re_tag = re.compile(r'<(/)?([^ ]+?)(?:(\s*/)| .*?)?>', re.S)
    re_newlines = re.compile(r'\r\n|\r')  # Used in normalize_newlines
    re_camel_case = re.compile(r'(((?<=[a-z])[A-Z])|([A-Z](?![A-Z]|$)))')

    @keep_lazy_text
    def wrap(text, width):
        """
        A word-wrap function that preserves existing line breaks. Expects that
        existing line breaks are posix newlines.

        All white space is preserved except added line breaks consume the space on
        which they break the line.

        Long words are not wrapped, so the output text may have lines longer than
        ``width``.
        """
        text = force_text(text)

        def _generator():
            for line in text.splitlines(True):  # True keeps trailing linebreaks
                max_width = min((line.endswith('\n') and width + 1 or width), width)
                while len(line) > max_width:
                    space = line[:max_width + 1].rfind(' ') + 1
                    if space == 0:
                        space = line.find(' ') + 1
                        if space == 0:
                            yield line
                            line = ''
                            break
                    yield '%s\n' % line[:space - 1]
                    line = line[space:]
                    max_width = min((line.endswith('\n') and width + 1 or width), width)
                if line:
                    yield line
        return ''.join(_generator())

    class Truncator(SimpleLazyObject):
        """
        An object used to truncate text, either by characters or words.
        """
        def __init__(self, text):
            super(Truncator, self).__init__(lambda: force_text(text))

        def add_truncation_text(self, text, truncate=None):
            if truncate is None:
                truncate = pgettext(
                    'String to return when truncating text',
                    '%(truncated_text)s...')
            truncate = force_text(truncate)
            if '%(truncated_text)s' in truncate:
                return truncate % {'truncated_text': text}
            # The truncation text didn't contain the %(truncated_text)s string
            # replacement argument so just append it to the text.
            if text.endswith(truncate):
                # But don't append the truncation text if the current text already
                # ends in this.
                return text
            return '%s%s' % (text, truncate)

        def chars(self, num, truncate=None, html=False):
            """
            Returns the text truncated to be no longer than the specified number
            of characters.

            Takes an optional argument of what should be used to notify that the
            string has been truncated, defaulting to a translatable string of an
            ellipsis (...).
            """
            self._setup()
            length = int(num)
            text = unicodedata.normalize('NFC', self._wrapped)

            # Calculate the length to truncate to (max length - end_text length)
            truncate_len = length
            for char in self.add_truncation_text('', truncate):
                if not unicodedata.combining(char):
                    truncate_len -= 1
                    if truncate_len == 0:
                        break
            if html:
                return self._truncate_html(length, truncate, text, truncate_len, False)
            return self._text_chars(length, truncate, text, truncate_len)

        def _text_chars(self, length, truncate, text, truncate_len):
            """
            Truncates a string after a certain number of chars.
            """
            s_len = 0
            end_index = None
            for i, char in enumerate(text):
                if unicodedata.combining(char):
                    # Don't consider combining characters
                    # as adding to the string length
                    continue
                s_len += 1
                if end_index is None and s_len > truncate_len:
                    end_index = i
                if s_len > length:
                    # Return the truncated string
                    return self.add_truncation_text(text[:end_index or 0],
                                                    truncate)

            # Return the original string since no truncation was necessary
            return text

        def words(self, num, truncate=None, html=False):
            """
            Truncates a string after a certain number of words. Takes an optional
            argument of what should be used to notify that the string has been
            truncated, defaulting to ellipsis (...).
            """
            self._setup()
            length = int(num)
            if html:
                return self._truncate_html(length, truncate, self._wrapped, length, True)
            return self._text_words(length, truncate)

        def _text_words(self, length, truncate):
            """
            Truncates a string after a certain number of words.

            Newlines in the string will be stripped.
            """
            words = self._wrapped.split()
            if len(words) > length:
                words = words[:length]
                return self.add_truncation_text(' '.join(words), truncate)
            return ' '.join(words)

        def _truncate_html(self, length, truncate, text, truncate_len, words):
            """
            Truncates HTML to a certain number of chars (not counting tags and
            comments), or, if words is True, then to a certain number of words.
            Closes opened tags if they were correctly closed in the given HTML.

            Newlines in the HTML are preserved.
            """
            if words and length <= 0:
                return ''

            html4_singlets = (
                'br', 'col', 'link', 'base', 'img',
                'param', 'area', 'hr', 'input'
            )

            # Count non-HTML chars/words and keep note of open tags
            pos = 0
            end_text_pos = 0
            current_len = 0
            open_tags = []

            regex = re_words if words else re_chars

            while current_len <= length:
                m = regex.search(text, pos)
                if not m:
                    # Checked through whole string
                    break
                pos = m.end(0)
                if m.group(1):
                    # It's an actual non-HTML word or char
                    current_len += 1
                    if current_len == truncate_len:
                        end_text_pos = pos
                    continue
                # Check for tag
                tag = re_tag.match(m.group(0))
                if not tag or current_len >= truncate_len:
                    # Don't worry about non tags or tags after our truncate point
                    continue
                closing_tag, tagname, self_closing = tag.groups()
                # Element names are always case-insensitive
                tagname = tagname.lower()
                if self_closing or tagname in html4_singlets:
                    pass
                elif closing_tag:
                    # Check for match in open tags list
                    try:
                        i = open_tags.index(tagname)
                    except ValueError:
                        pass
                    else:
                        # SGML: An end tag closes, back to the matching start tag,
                        # all unclosed intervening start tags with omitted end tags
                        open_tags = open_tags[i + 1:]
                else:
                    # Add it to the start of the open tags list
                    open_tags.insert(0, tagname)

            if current_len <= length:
                return text
            out = text[:end_text_pos]
            truncate_text = self.add_truncation_text('', truncate)
            if truncate_text:
                out += truncate_text
            # Close any tags still open
            for tag in open_tags:
                out += '</%s>' % tag
            # Return string
            return out

    @keep_lazy_text
    def get_valid_filename(s):
        """
        Returns the given string converted to a string that can be used for a clean
        filename. Specifically, leading and trailing spaces are removed; other
        spaces are converted to underscores; and anything that is not a unicode
        alphanumeric, dash, underscore, or dot, is removed.
        >>> get_valid_filename("john's portrait in 2004.jpg")
        'johns_portrait_in_2004.jpg'
        """
        s = force_text(s).strip().replace(' ', '_')
        return re.sub(r'(?u)[^-\w.]', '', s)

    @keep_lazy_text
    def get_text_list(list_, last_word=ugettext_lazy('or')):
        """
        >>> get_text_list(['a', 'b', 'c', 'd'])
        'a, b, c or d'
        >>> get_text_list(['a', 'b', 'c'], 'and')
        'a, b and c'
        >>> get_text_list(['a', 'b'], 'and')
        'a and b'
        >>> get_text_list(['a'])
        'a'
        >>> get_text_list([])
        ''
        """
        if len(list_) == 0:
            return ''
        if len(list_) == 1:
            return force_text(list_[0])
        return '%s %s %s' % (
            # Translators: This string is used as a separator between list elements
            _(', ').join(force_text(i) for i in list_[:-1]),
            force_text(last_word), force_text(list_[-1]))

    @keep_lazy_text
    def normalize_newlines(text):
        """Normalizes CRLF and CR newlines to just LF."""
        text = force_text(text)
        return re_newlines.sub('\n', text)

    @keep_lazy_text
    def phone2numeric(phone):
        """Converts a phone number with letters into its numeric equivalent."""
        char2number = {
            'a': '2', 'b': '2', 'c': '2', 'd': '3', 'e': '3', 'f': '3', 'g': '4',
            'h': '4', 'i': '4', 'j': '5', 'k': '5', 'l': '5', 'm': '6', 'n': '6',
            'o': '6', 'p': '7', 'q': '7', 'r': '7', 's': '7', 't': '8', 'u': '8',
            'v': '8', 'w': '9', 'x': '9', 'y': '9', 'z': '9',
        }
        return ''.join(char2number.get(c, c) for c in phone.lower())

    # From http://www.xhaus.com/alan/python/httpcomp.html#gzip
    # Used with permission.
    def compress_string(s):
        zbuf = BytesIO()
        zfile = GzipFile(mode='wb', compresslevel=6, fileobj=zbuf)
        zfile.write(s)
        zfile.close()
        return zbuf.getvalue()

    class StreamingBuffer(object):
        def __init__(self):
            self.vals = []

        def write(self, val):
            self.vals.append(val)

        def read(self):
            if not self.vals:
                return b''
            ret = b''.join(self.vals)
            self.vals = []
            return ret

        def flush(self):
            return

        def close(self):
            return

    # Like compress_string, but for iterators of strings.
    def compress_sequence(sequence):
        buf = StreamingBuffer()
        zfile = GzipFile(mode='wb', compresslevel=6, fileobj=buf)
        # Output headers...
        yield buf.read()
        for item in sequence:
            zfile.write(item)
            data = buf.read()
            if data:
                yield data
        zfile.close()
        yield buf.read()

    # Expression to match some_token and some_token="with spaces" (and similarly
    # for single-quoted strings).
    smart_split_re = re.compile(r"""
        ((?:
            [^\s'"]*
            (?:
                (?:"(?:[^"\\]|\\.)*" | '(?:[^'\\]|\\.)*')
                [^\s'"]*
            )+
        ) | \S+)
    """, re.VERBOSE)

    def smart_split(text):
        r"""
        Generator that splits a string by spaces, leaving quoted phrases together.
        Supports both single and double quotes, and supports escaping quotes with
        backslashes. In the output, strings will keep their initial and trailing
        quote marks and escaped quotes will remain escaped (the results can then
        be further processed with unescape_string_literal()).

        >>> list(smart_split(r'This is "a person\'s" test.'))
        ['This', 'is', '"a person\\\'s"', 'test.']
        >>> list(smart_split(r"Another 'person\'s' test."))
        ['Another', "'person\\'s'", 'test.']
        >>> list(smart_split(r'A "\"funky\" style" test.'))
        ['A', '"\\"funky\\" style"', 'test.']
        """
        text = force_text(text)
        for bit in smart_split_re.finditer(text):
            yield bit.group(0)

    def _replace_entity(match):
        text = match.group(1)
        if text[0] == '#':
            text = text[1:]
            try:
                if text[0] in 'xX':
                    c = int(text[1:], 16)
                else:
                    c = int(text)
                return six.unichr(c)
            except ValueError:
                return match.group(0)
        else:
            try:
                return six.unichr(html_entities.name2codepoint[text])
            except (ValueError, KeyError):
                return match.group(0)

    _entity_re = re.compile(r"&(#?[xX]?(?:[0-9a-fA-F]+|\w{1,8}));")

    @keep_lazy_text
    def unescape_entities(text):
        return _entity_re.sub(_replace_entity, force_text(text))

    @keep_lazy_text
    def unescape_string_literal(s):
        r"""
        Convert quoted string literals to unquoted strings with escaped quotes and
        backslashes unquoted::

            >>> unescape_string_literal('"abc"')
            'abc'
            >>> unescape_string_literal("'abc'")
            'abc'
            >>> unescape_string_literal('"a \"bc\""')
            'a "bc"'
            >>> unescape_string_literal("'\'ab\' c'")
            "'ab' c"
        """
        if s[0] not in "\"'" or s[-1] != s[0]:
            raise ValueError("Not a string literal: %r" % s)
        quote = s[0]
        return s[1:-1].replace(r'\%s' % quote, quote).replace(r'\\', '\\')

    @keep_lazy(six.text_type, SafeText)
    def slugify(value, allow_unicode=False):
        """
        Convert to ASCII if 'allow_unicode' is False. Convert spaces to hyphens.
        Remove characters that aren't alphanumerics, underscores, or hyphens.
        Convert to lowercase. Also strip leading and trailing whitespace.
        """
        value = force_text(value)
        if allow_unicode:
            value = unicodedata.normalize('NFKC', value)
            value = re.sub('[^\w\s-]', '', value, flags=re.U).strip().lower()
            return mark_safe(re.sub('[-\s]+', '-', value, flags=re.U))
        value = unicodedata.normalize('NFKD', value).encode('ascii', 'ignore').decode('ascii')
        value = re.sub('[^\w\s-]', '', value).strip().lower()
        return mark_safe(re.sub('[-\s]+', '-', value))

    def camel_case_to_spaces(value):
        """
        Splits CamelCase and converts to lower case. Also strips leading and
        trailing whitespace.
        """
        return re_camel_case.sub(r' \1', value).strip().lower()