defaultfilters.py

"""Default variable filters."""
import random as random_module
import re
import types
from decimal import ROUND_HALF_UP, Context, Decimal, InvalidOperation
from functools import wraps
from operator import itemgetter
from pprint import pformat
from urllib.parse import quote

from django.utils import formats
from django.utils.dateformat import format, time_format
from django.utils.encoding import iri_to_uri
from django.utils.html import (
    avoid_wrapping, conditional_escape, escape, escapejs,
    json_script as _json_script, linebreaks, strip_tags, urlize as _urlize,
)
from django.utils.safestring import SafeData, mark_safe
from django.utils.text import (
    Truncator, normalize_newlines, phone2numeric, slugify as _slugify, wrap,
)
from django.utils.timesince import timesince, timeuntil
from django.utils.translation import gettext, ngettext

from .base import Variable, VariableDoesNotExist
from .library import Library

register = Library()


#######################
# STRING DECORATOR    #
#######################

def stringfilter(func):
    """
    Decorator for filters which should only receive strings. The object
    passed as the first positional argument will be converted to a string.
    """
    def _dec(*args, **kwargs):
        args = list(args)
        args[0] = str(args[0])
        if (isinstance(args[0], SafeData) and
                getattr(_dec._decorated_function, 'is_safe', False)):
            return mark_safe(func(*args, **kwargs))
        return func(*args, **kwargs)

    # Include a reference to the real function (used to check original
    # arguments by the template parser, and to bear the 'is_safe' attribute
    # when multiple decorators are applied).
    _dec._decorated_function = getattr(func, '_decorated_function', func)

    return wraps(func)(_dec)


###################
# STRINGS         #
###################

@register.filter(is_safe=True)
@stringfilter
def addslashes(value):
    """
    Add slashes before quotes. Useful for escaping strings in CSV, for
    example. Less useful for escaping JavaScript; use the ``escapejs``
    filter instead.
    """
    return value.replace('\\', '\\\\').replace('"', '\\"').replace("'", "\\'")


@register.filter(is_safe=True)
@stringfilter
def capfirst(value):
    """Capitalize the first character of the value."""
    return value and value[0].upper() + value[1:]


@register.filter("escapejs")
@stringfilter
def escapejs_filter(value):
    """Hex encode characters for use in JavaScript strings."""
    return escapejs(value)


@register.filter(is_safe=True)
def json_script(value, element_id):
    """
    Output value JSON-encoded, wrapped in a <script type="application/json">
    tag.
    """
    return _json_script(value, element_id)


@register.filter(is_safe=True)
def floatformat(text, arg=-1):
    """
    Display a float to a specified number of decimal places.

    If called without an argument, display the floating point number with one
    decimal place -- but only if there's a decimal place to be displayed:

    * num1 = 34.23234
    * num2 = 34.00000
    * num3 = 34.26000
    * {{ num1|floatformat }} displays "34.2"
    * {{ num2|floatformat }} displays "34"
    * {{ num3|floatformat }} displays "34.3"

    If arg is positive, always display exactly arg number of decimal places:

    * {{ num1|floatformat:3 }} displays "34.232"
    * {{ num2|floatformat:3 }} displays "34.000"
    * {{ num3|floatformat:3 }} displays "34.260"

    If arg is negative, display arg number of decimal places -- but only if
    there are places to be displayed:

    * {{ num1|floatformat:"-3" }} displays "34.232"
    * {{ num2|floatformat:"-3" }} displays "34"
    * {{ num3|floatformat:"-3" }} displays "34.260"

    Use the suffix ``g`` to force the result to be grouped
    (appropriately for the locale, if settings.`USE_L10N` is True):

    * {{ 6666.6666|floatformat:"2g" }} displays "6,666.67"
    * {{ 10000|floatformat:"g" }} displays "10,000"

    If the input float is infinity or NaN, display the string representation
    of that value.
    """
    force_grouping = False
    if isinstance(arg, str):
        force_grouping = arg.endswith('g')
        arg = arg.strip('g')
        if not arg:
            arg = -1
    try:
        input_val = repr(text)
        d = Decimal(input_val)
    except InvalidOperation:
        try:
            d = Decimal(str(float(text)))
        except (ValueError, InvalidOperation, TypeError):
            return ''
    try:
        p = int(arg)
    except ValueError:
        return input_val

    try:
        m = int(d) - d
    except (ValueError, OverflowError, InvalidOperation):
        return input_val

    if not m and p < 0:
        return mark_safe(formats.number_format('%d' % (int(d)), 0, force_grouping=force_grouping))

    exp = Decimal(1).scaleb(-abs(p))
    # Set the precision high enough to avoid an exception (#15789).
    tupl = d.as_tuple()
    units = len(tupl[1])
    units += -tupl[2] if m else tupl[2]
    prec = abs(p) + units + 1

    # Avoid conversion to scientific notation by accessing `sign`, `digits`,
    # and `exponent` from Decimal.as_tuple() directly.
    rounded_d = d.quantize(exp, ROUND_HALF_UP, Context(prec=prec))
    sign, digits, exponent = rounded_d.as_tuple()
    digits = [str(digit) for digit in reversed(digits)]
    while len(digits) <= abs(exponent):
        digits.append('0')
    digits.insert(-exponent, '.')
    if sign and rounded_d:
        digits.append('-')
    number = ''.join(reversed(digits))
    return mark_safe(formats.number_format(number, abs(p), force_grouping=force_grouping))


@register.filter(is_safe=True)
@stringfilter
def iriencode(value):
    """Escape an IRI value for use in a URL."""
    return iri_to_uri(value)


@register.filter(is_safe=True, needs_autoescape=True)
@stringfilter
def linenumbers(value, autoescape=True):
    """Display text with line numbers."""
    lines = value.split('\n')
    # Find the maximum width of the line count, for use with zero padding
    # string format command
    width = str(len(str(len(lines))))
    if not autoescape or isinstance(value, SafeData):
        for i, line in enumerate(lines):
            lines[i] = ("%0" + width + "d. %s") % (i + 1, line)
    else:
        for i, line in enumerate(lines):
            lines[i] = ("%0" + width + "d. %s") % (i + 1, escape(line))
    return mark_safe('\n'.join(lines))


@register.filter(is_safe=True)
@stringfilter
def lower(value):
    """Convert a string into all lowercase."""
    return value.lower()


@register.filter(is_safe=False)
@stringfilter
def make_list(value):
    """
    Return the value turned into a list.

    For an integer, it's a list of digits.
    For a string, it's a list of characters.
    """
    return list(value)


@register.filter(is_safe=True)
@stringfilter
def slugify(value):
    """
    Convert to ASCII. Convert spaces to hyphens. Remove characters that aren't
    alphanumerics, underscores, or hyphens. Convert to lowercase. Also strip
    leading and trailing whitespace.
    """
    return _slugify(value)


@register.filter(is_safe=True)
def stringformat(value, arg):
    """
    Format the variable according to the arg, a string formatting specifier.

    This specifier uses Python string formatting syntax, with the exception
    that the leading "%" is dropped.

    See https://docs.python.org/library/stdtypes.html#printf-style-string-formatting
    for documentation of Python string formatting.
    """
    if isinstance(value, tuple):
        value = str(value)
    try:
        return ("%" + str(arg)) % value
    except (ValueError, TypeError):
        return ""


@register.filter(is_safe=True)
@stringfilter
def title(value):
    """Convert a string into titlecase."""
    t = re.sub("([a-z])'([A-Z])", lambda m: m[0].lower(), value.title())
    return re.sub(r'\d([A-Z])', lambda m: m[0].lower(), t)


@register.filter(is_safe=True)
@stringfilter
def truncatechars(value, arg):
    """Truncate a string after `arg` number of characters."""
    try:
        length = int(arg)
    except ValueError:  # Invalid literal for int().
        return value  # Fail silently.
    return Truncator(value).chars(length)


@register.filter(is_safe=True)
@stringfilter
def truncatechars_html(value, arg):
    """
    Truncate HTML after `arg` number of chars.
    Preserve newlines in the HTML.
    """
    try:
        length = int(arg)
    except ValueError:  # invalid literal for int()
        return value  # Fail silently.
    return Truncator(value).chars(length, html=True)


@register.filter(is_safe=True)
@stringfilter
def truncatewords(value, arg):
    """
    Truncate a string after `arg` number of words.
    Remove newlines within the string.
    """
    try:
        length = int(arg)
    except ValueError:  # Invalid literal for int().
        return value  # Fail silently.
    return Truncator(value).words(length, truncate=' …')


@register.filter(is_safe=True)
@stringfilter
def truncatewords_html(value, arg):
    """
    Truncate HTML after `arg` number of words.
    Preserve newlines in the HTML.
    """
    try:
        length = int(arg)
    except ValueError:  # invalid literal for int()
        return value  # Fail silently.
    return Truncator(value).words(length, html=True, truncate=' …')


@register.filter(is_safe=False)
@stringfilter
def upper(value):
    """Convert a string into all uppercase."""
    return value.upper()


@register.filter(is_safe=False)
@stringfilter
def urlencode(value, safe=None):
    """
    Escape a value for use in a URL.

    The ``safe`` parameter determines the characters which should not be
    escaped by Python's quote() function. If not provided, use the default safe
    characters (but an empty string can be provided when *all* characters
    should be escaped).
    """
    kwargs = {}
    if safe is not None:
        kwargs['safe'] = safe
    return quote(value, **kwargs)


@register.filter(is_safe=True, needs_autoescape=True)
@stringfilter
def urlize(value, autoescape=True):
    """Convert URLs in plain text into clickable links."""
    return mark_safe(_urlize(value, nofollow=True, autoescape=autoescape))


@register.filter(is_safe=True, needs_autoescape=True)
@stringfilter
def urlizetrunc(value, limit, autoescape=True):
    """
    Convert URLs into clickable links, truncating URLs to the given character
    limit, and adding 'rel=nofollow' attribute to discourage spamming.

    Argument: Length to truncate URLs to.
    """
    return mark_safe(_urlize(value, trim_url_limit=int(limit), nofollow=True, autoescape=autoescape))


@register.filter(is_safe=False)
@stringfilter
def wordcount(value):
    """Return the number of words."""
    return len(value.split())


@register.filter(is_safe=True)
@stringfilter
def wordwrap(value, arg):
    """Wrap words at `arg` line length."""
    return wrap(value, int(arg))


@register.filter(is_safe=True)
@stringfilter
def ljust(value, arg):
    """Left-align the value in a field of a given width."""
    return value.ljust(int(arg))


@register.filter(is_safe=True)
@stringfilter
def rjust(value, arg):
    """Right-align the value in a field of a given width."""
    return value.rjust(int(arg))


@register.filter(is_safe=True)
@stringfilter
def center(value, arg):
    """Center the value in a field of a given width."""
    return value.center(int(arg))


@register.filter
@stringfilter
def cut(value, arg):
    """Remove all values of arg from the given string."""
    safe = isinstance(value, SafeData)
    value = value.replace(arg, '')
    if safe and arg != ';':
        return mark_safe(value)
    return value


###################
# HTML STRINGS    #
###################

@register.filter("escape", is_safe=True)
@stringfilter
def escape_filter(value):
    """Mark the value as a string that should be auto-escaped."""
    return conditional_escape(value)


@register.filter(is_safe=True)
@stringfilter
def force_escape(value):
    """
    Escape a string's HTML. Return a new string containing the escaped
    characters (as opposed to "escape", which marks the content for later
    possible escaping).
    """
    return escape(value)


@register.filter("linebreaks", is_safe=True, needs_autoescape=True)
@stringfilter
def linebreaks_filter(value, autoescape=True):
    """
    Replace line breaks in plain text with appropriate HTML; a single
    newline becomes an HTML line break (``<br>``) and a new line
    followed by a blank line becomes a paragraph break (``</p>``).
    """
    autoescape = autoescape and not isinstance(value, SafeData)
    return mark_safe(linebreaks(value, autoescape))


@register.filter(is_safe=True, needs_autoescape=True)
@stringfilter
def linebreaksbr(value, autoescape=True):
    """
    Convert all newlines in a piece of plain text to HTML line breaks
    (``<br>``).
    """
    autoescape = autoescape and not isinstance(value, SafeData)
    value = normalize_newlines(value)
    if autoescape:
        value = escape(value)
    return mark_safe(value.replace('\n', '<br>'))


@register.filter(is_safe=True)
@stringfilter
def safe(value):
    """Mark the value as a string that should not be auto-escaped."""
    return mark_safe(value)


@register.filter(is_safe=True)
def safeseq(value):
    """
    A "safe" filter for sequences. Mark each element in the sequence,
    individually, as safe, after converting them to strings. Return a list
    with the results.
    """
    return [mark_safe(obj) for obj in value]


@register.filter(is_safe=True)
@stringfilter
def striptags(value):
    """Strip all [X]HTML tags."""
    return strip_tags(value)


###################
# LISTS           #
###################

def _property_resolver(arg):
    """
    When arg is convertible to float, behave like operator.itemgetter(arg)
    Otherwise, behave like Variable(arg).resolve

    >>> _property_resolver(1)('abc')
    'b'
    >>> _property_resolver('1')('abc')
    Traceback (most recent call last):
    ...
    TypeError: string indices must be integers
    >>> class Foo:
    ...     a = 42
    ...     b = 3.14
    ...     c = 'Hey!'
    >>> _property_resolver('b')(Foo())
    3.14
    """
    try:
        float(arg)
    except ValueError:
        return Variable(arg).resolve
    else:
        return itemgetter(arg)


@register.filter(is_safe=False)
def dictsort(value, arg):
    """
    Given a list of dicts, return that list sorted by the property given in
    the argument.
    """
    try:
        return sorted(value, key=_property_resolver(arg))
    except (TypeError, VariableDoesNotExist):
        return ''


@register.filter(is_safe=False)
def dictsortreversed(value, arg):
    """
    Given a list of dicts, return that list sorted in reverse order by the
    property given in the argument.
    """
    try:
        return sorted(value, key=_property_resolver(arg), reverse=True)
    except (TypeError, VariableDoesNotExist):
        return ''


@register.filter(is_safe=False)
def first(value):
    """Return the first item in a list."""
    try:
        return value[0]
    except IndexError:
        return ''


@register.filter(is_safe=True, needs_autoescape=True)
def join(value, arg, autoescape=True):
    """Join a list with a string, like Python's ``str.join(list)``."""
    try:
        if autoescape:
            value = [conditional_escape(v) for v in value]
        data = conditional_escape(arg).join(value)
    except TypeError:  # Fail silently if arg isn't iterable.
        return value
    return mark_safe(data)


@register.filter(is_safe=True)
def last(value):
    """Return the last item in a list."""
    try:
        return value[-1]
    except IndexError:
        return ''


@register.filter(is_safe=False)
def length(value):
    """Return the length of the value - useful for lists."""
    try:
        return len(value)
    except (ValueError, TypeError):
        return 0


@register.filter(is_safe=False)
def length_is(value, arg):
    """Return a boolean of whether the value's length is the argument."""
    try:
        return len(value) == int(arg)
    except (ValueError, TypeError):
        return ''


@register.filter(is_safe=True)
def random(value):
    """Return a random item from the list."""
    return random_module.choice(value)


@register.filter("slice", is_safe=True)
def slice_filter(value, arg):
    """
    Return a slice of the list using the same syntax as Python's list slicing.
    """
    try:
        bits = []
        for x in str(arg).split(':'):
            if not x:
                bits.append(None)
            else:
                bits.append(int(x))
        return value[slice(*bits)]

    except (ValueError, TypeError):
        return value  # Fail silently.


@register.filter(is_safe=True, needs_autoescape=True)
def unordered_list(value, autoescape=True):
    """
    Recursively take a self-nested list and return an HTML unordered list --
    WITHOUT opening and closing <ul> tags.

    Assume the list is in the proper format. For example, if ``var`` contains:
    ``['States', ['Kansas', ['Lawrence', 'Topeka'], 'Illinois']]``, then
    ``{{ var|unordered_list }}`` returns::

        <li>States
        <ul>
                <li>Kansas
                <ul>
                        <li>Lawrence</li>
                        <li>Topeka</li>
                </ul>
                </li>
                <li>Illinois</li>
        </ul>
        </li>
    """
    if autoescape:
        escaper = conditional_escape
    else:
        def escaper(x):
            return x

    def walk_items(item_list):
        item_iterator = iter(item_list)
        try:
            item = next(item_iterator)
            while True:
                try:
                    next_item = next(item_iterator)
                except StopIteration:
                    yield item, None
                    break
                if isinstance(next_item, (list, tuple, types.GeneratorType)):
                    try:
                        iter(next_item)
                    except TypeError:
                        pass
                    else:
                        yield item, next_item
                        item = next(item_iterator)
                        continue
                yield item, None
                item = next_item
        except StopIteration:
            pass

    def list_formatter(item_list, tabs=1):
        indent = '\t' * tabs
        output = []
        for item, children in walk_items(item_list):
            sublist = ''
            if children:
                sublist = '\n%s<ul>\n%s\n%s</ul>\n%s' % (
                    indent, list_formatter(children, tabs + 1), indent, indent)
            output.append('%s<li>%s%s</li>' % (
                indent, escaper(item), sublist))
        return '\n'.join(output)

    return mark_safe(list_formatter(value))


###################
# INTEGERS        #
###################

@register.filter(is_safe=False)
def add(value, arg):
    """Add the arg to the value."""
    try:
        return int(value) + int(arg)
    except (ValueError, TypeError):
        try:
            return value + arg
        except Exception:
            return ''


@register.filter(is_safe=False)
def get_digit(value, arg):
    """
    Given a whole number, return the requested digit of it, where 1 is the
    right-most digit, 2 is the second-right-most digit, etc. Return the
    original value for invalid input (if input or argument is not an integer,
    or if argument is less than 1). Otherwise, output is always an integer.
    """
    try:
        arg = int(arg)
        value = int(value)
    except ValueError:
        return value  # Fail silently for an invalid argument
    if arg < 1:
        return value
    try:
        return int(str(value)[-arg])
    except IndexError:
        return 0


###################
# DATES           #
###################

@register.filter(expects_localtime=True, is_safe=False)
def date(value, arg=None):
    """Format a date according to the given format."""
    if value in (None, ''):
        return ''
    try:
        return formats.date_format(value, arg)
    except AttributeError:
        try:
            return format(value, arg)
        except AttributeError:
            return ''


@register.filter(expects_localtime=True, is_safe=False)
def time(value, arg=None):
    """Format a time according to the given format."""
    if value in (None, ''):
        return ''
    try:
        return formats.time_format(value, arg)
    except (AttributeError, TypeError):
        try:
            return time_format(value, arg)
        except (AttributeError, TypeError):
            return ''


@register.filter("timesince", is_safe=False)
def timesince_filter(value, arg=None):
    """Format a date as the time since that date (i.e. "4 days, 6 hours")."""
    if not value:
        return ''
    try:
        if arg:
            return timesince(value, arg)
        return timesince(value)
    except (ValueError, TypeError):
        return ''


@register.filter("timeuntil", is_safe=False)
def timeuntil_filter(value, arg=None):
    """Format a date as the time until that date (i.e. "4 days, 6 hours")."""
    if not value:
        return ''
    try:
        return timeuntil(value, arg)
    except (ValueError, TypeError):
        return ''


###################
# LOGIC           #
###################

@register.filter(is_safe=False)
def default(value, arg):
    """If value is unavailable, use given default."""
    return value or arg


@register.filter(is_safe=False)
def default_if_none(value, arg):
    """If value is None, use given default."""
    if value is None:
        return arg
    return value


@register.filter(is_safe=False)
def divisibleby(value, arg):
    """Return True if the value is divisible by the argument."""
    return int(value) % int(arg) == 0


@register.filter(is_safe=False)
def yesno(value, arg=None):
    """
    Given a string mapping values for true, false, and (optionally) None,
    return one of those strings according to the value:

    ==========  ======================  ==================================
    Value       Argument                Outputs
    ==========  ======================  ==================================
    ``True``    ``"yeah,no,maybe"``     ``yeah``
    ``False``   ``"yeah,no,maybe"``     ``no``
    ``None``    ``"yeah,no,maybe"``     ``maybe``
    ``None``    ``"yeah,no"``           ``"no"`` (converts None to False
                                        if no mapping for None is given.
    ==========  ======================  ==================================
    """
    if arg is None:
        # Translators: Please do not add spaces around commas.
        arg = gettext('yes,no,maybe')
    bits = arg.split(',')
    if len(bits) < 2:
        return value  # Invalid arg.
    try:
        yes, no, maybe = bits
    except ValueError:
        # Unpack list of wrong size (no "maybe" value provided).
        yes, no, maybe = bits[0], bits[1], bits[1]
    if value is None:
        return maybe
    if value:
        return yes
    return no


###################
# MISC            #
###################

@register.filter(is_safe=True)
def filesizeformat(bytes_):
    """
    Format the value like a 'human-readable' file size (i.e. 13 KB, 4.1 MB,
    102 bytes, etc.).
    """
    try:
        bytes_ = int(bytes_)
    except (TypeError, ValueError, UnicodeDecodeError):
        value = ngettext("%(size)d byte", "%(size)d bytes", 0) % {'size': 0}
        return avoid_wrapping(value)

    def filesize_number_format(value):
        return formats.number_format(round(value, 1), 1)

    KB = 1 << 10
    MB = 1 << 20
    GB = 1 << 30
    TB = 1 << 40
    PB = 1 << 50

    negative = bytes_ < 0
    if negative:
        bytes_ = -bytes_  # Allow formatting of negative numbers.

    if bytes_ < KB:
        value = ngettext("%(size)d byte", "%(size)d bytes", bytes_) % {'size': bytes_}
    elif bytes_ < MB:
        value = gettext("%s KB") % filesize_number_format(bytes_ / KB)
    elif bytes_ < GB:
        value = gettext("%s MB") % filesize_number_format(bytes_ / MB)
    elif bytes_ < TB:
        value = gettext("%s GB") % filesize_number_format(bytes_ / GB)
    elif bytes_ < PB:
        value = gettext("%s TB") % filesize_number_format(bytes_ / TB)
    else:
        value = gettext("%s PB") % filesize_number_format(bytes_ / PB)

    if negative:
        value = "-%s" % value
    return avoid_wrapping(value)


@register.filter(is_safe=False)
def pluralize(value, arg='s'):
    """
    Return a plural suffix if the value is not 1, '1', or an object of
    length 1. By default, use 's' as the suffix:

    * If value is 0, vote{{ value|pluralize }} display "votes".
    * If value is 1, vote{{ value|pluralize }} display "vote".
    * If value is 2, vote{{ value|pluralize }} display "votes".

    If an argument is provided, use that string instead:

    * If value is 0, class{{ value|pluralize:"es" }} display "classes".
    * If value is 1, class{{ value|pluralize:"es" }} display "class".
    * If value is 2, class{{ value|pluralize:"es" }} display "classes".

    If the provided argument contains a comma, use the text before the comma
    for the singular case and the text after the comma for the plural case:

    * If value is 0, cand{{ value|pluralize:"y,ies" }} display "candies".
    * If value is 1, cand{{ value|pluralize:"y,ies" }} display "candy".
    * If value is 2, cand{{ value|pluralize:"y,ies" }} display "candies".
    """
    if ',' not in arg:
        arg = ',' + arg
    bits = arg.split(',')
    if len(bits) > 2:
        return ''
    singular_suffix, plural_suffix = bits[:2]

    try:
        return singular_suffix if float(value) == 1 else plural_suffix
    except ValueError:  # Invalid string that's not a number.
        pass
    except TypeError:  # Value isn't a string or a number; maybe it's a list?
        try:
            return singular_suffix if len(value) == 1 else plural_suffix
        except TypeError:  # len() of unsized object.
            pass
    return ''


@register.filter("phone2numeric", is_safe=True)
def phone2numeric_filter(value):
    """Take a phone number and converts it in to its numerical equivalent."""
    return phone2numeric(value)


@register.filter(is_safe=True)
def pprint(value):
    """A wrapper around pprint.pprint -- for debugging, really."""
    try:
        return pformat(value)
    except Exception as e:
        return "Error in formatting: %s: %s" % (e.__class__.__name__, e)