jinja2/utils.py

# -*- coding: utf-8 -*-
"""
    jinja2.utils
    ~~~~~~~~~~~~

    Utility functions.

    :copyright: 2008 by Armin Ronacher.
    :license: BSD, see LICENSE for more details.
"""
import re
import sys
import errno
try:
    from thread import allocate_lock
except ImportError:
    from dummy_thread import allocate_lock
from collections import deque
from itertools import imap


_word_split_re = re.compile(r'(\s+)')
_punctuation_re = re.compile(
    '^(?P<lead>(?:%s)*)(?P<middle>.*?)(?P<trail>(?:%s)*)$' % (
        '|'.join(imap(re.escape, ('(', '<', '&lt;'))),
        '|'.join(imap(re.escape, ('.', ',', ')', '>', '\n', '&gt;')))
    )
)
_simple_email_re = re.compile(r'^\S+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9._-]+$')
_striptags_re = re.compile(r'(<!--.*?-->|<[^>]*>)')
_entity_re = re.compile(r'&([^;]+);')
_letters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
_digits = '0123456789'

# special singleton representing missing values for the runtime
missing = type('MissingType', (), {'__repr__': lambda x: 'missing'})()


# concatenate a list of strings and convert them to unicode.
# unfortunately there is a bug in python 2.4 and lower that causes
# unicode.join trash the traceback.
_concat = u''.join
try:
    def _test_gen_bug():
        raise TypeError(_test_gen_bug)
        yield None
    _concat(_test_gen_bug())
except TypeError, _error:
    if not _error.args or _error.args[0] is not _test_gen_bug:
        def concat(gen):
            try:
                return _concat(list(gen))
            except:
                # this hack is needed so that the current frame
                # does not show up in the traceback.
                exc_type, exc_value, tb = sys.exc_info()
                raise exc_type, exc_value, tb.tb_next
    else:
        concat = _concat
    del _test_gen_bug, _error


# ironpython without stdlib doesn't have keyword
try:
    from keyword import iskeyword as is_python_keyword
except ImportError:
    _py_identifier_re = re.compile(r'^[a-zA-Z_][a-zA-Z0-9]*$')
    def is_python_keyword(name):
        if _py_identifier_re.search(name) is None:
            return False
        try:
            exec name + " = 42"
        except SyntaxError:
            return False
        return True


# common types.  These do exist in the special types module too which however
# does not exist in IronPython out of the box.
class _C(object):
    def method(self): pass
def _func():
    yield None
FunctionType = type(_func)
GeneratorType = type(_func())
MethodType = type(_C.method)
CodeType = type(_C.method.func_code)
try:
    raise TypeError()
except TypeError:
    _tb = sys.exc_info()[2]
    TracebackType = type(_tb)
    FrameType = type(_tb.tb_frame)
del _C, _tb, _func


def contextfunction(f):
    """This decorator can be used to mark a function or method context callable.
    A context callable is passed the active :class:`Context` as first argument when
    called from the template.  This is useful if a function wants to get access
    to the context or functions provided on the context object.  For example
    a function that returns a sorted list of template variables the current
    template exports could look like this::

        @contextfunction
        def get_exported_names(context):
            return sorted(context.exported_vars)
    """
    f.contextfunction = True
    return f


def environmentfunction(f):
    """This decorator can be used to mark a function or method as environment
    callable.  This decorator works exactly like the :func:`contextfunction`
    decorator just that the first argument is the active :class:`Environment`
    and not context.
    """
    f.environmentfunction = True
    return f


def is_undefined(obj):
    """Check if the object passed is undefined.  This does nothing more than
    performing an instance check against :class:`Undefined` but looks nicer.
    This can be used for custom filters or tests that want to react to
    undefined variables.  For example a custom default filter can look like
    this::

        def default(var, default=''):
            if is_undefined(var):
                return default
            return var
    """
    from jinja2.runtime import Undefined
    return isinstance(obj, Undefined)


def consume(iterable):
    """Consumes an iterable without doing anything with it."""
    for event in iterable:
        pass


def clear_caches():
    """Jinja2 keeps internal caches for environments and lexers.  These are
    used so that Jinja2 doesn't have to recreate environments and lexers all
    the time.  Normally you don't have to care about that but if you are
    messuring memory consumption you may want to clean the caches.
    """
    from jinja2.environment import _spontaneous_environments
    from jinja2.lexer import _lexer_cache
    _spontaneous_environments.clear()
    _lexer_cache.clear()


def import_string(import_name, silent=False):
    """Imports an object based on a string.  This use useful if you want to
    use import paths as endpoints or something similar.  An import path can
    be specified either in dotted notation (``xml.sax.saxutils.escape``)
    or with a colon as object delimiter (``xml.sax.saxutils:escape``).

    If the `silent` is True the return value will be `None` if the import
    fails.

    :return: imported object
    """
    try:
        if ':' in import_name:
            module, obj = import_name.split(':', 1)
        elif '.' in import_name:
            items = import_name.split('.')
            module = '.'.join(items[:-1])
            obj = items[-1]
        else:
            return __import__(import_name)
        return getattr(__import__(module, None, None, [obj]), obj)
    except (ImportError, AttributeError):
        if not silent:
            raise


def open_if_exists(filename, mode='r'):
    """Returns a file descriptor for the filename if that file exists,
    otherwise `None`.
    """
    try:
        return file(filename, mode)
    except IOError, e:
        if e.errno not in (errno.ENOENT, errno.EISDIR):
            raise


def pformat(obj, verbose=False):
    """Prettyprint an object.  Either use the `pretty` library or the
    builtin `pprint`.
    """
    try:
        from pretty import pretty
        return pretty(obj, verbose=verbose)
    except ImportError:
        from pprint import pformat
        return pformat(obj)


def urlize(text, trim_url_limit=None, nofollow=False):
    """Converts any URLs in text into clickable links. Works on http://,
    https:// and www. links. Links can have trailing punctuation (periods,
    commas, close-parens) and leading punctuation (opening parens) and
    it'll still do the right thing.

    If trim_url_limit is not None, the URLs in link text will be limited
    to trim_url_limit characters.

    If nofollow is True, the URLs in link text will get a rel="nofollow"
    attribute.
    """
    trim_url = lambda x, limit=trim_url_limit: limit is not None \
                         and (x[:limit] + (len(x) >=limit and '...'
                         or '')) or x
    words = _word_split_re.split(text)
    nofollow_attr = nofollow and ' rel="nofollow"' or ''
    for i, word in enumerate(words):
        match = _punctuation_re.match(word)
        if match:
            lead, middle, trail = match.groups()
            if middle.startswith('www.') or (
                '@' not in middle and
                not middle.startswith('http://') and
                len(middle) > 0 and
                middle[0] in _letters + _digits and (
                    middle.endswith('.org') or
                    middle.endswith('.net') or
                    middle.endswith('.com')
                )):
                middle = '<a href="http://%s"%s>%s</a>' % (middle,
                    nofollow_attr, trim_url(middle))
            if middle.startswith('http://') or \
               middle.startswith('https://'):
                middle = '<a href="%s"%s>%s</a>' % (middle,
                    nofollow_attr, trim_url(middle))
            if '@' in middle and not middle.startswith('www.') and \
               not ':' in middle and _simple_email_re.match(middle):
                middle = '<a href="mailto:%s">%s</a>' % (middle, middle)
            if lead + middle + trail != word:
                words[i] = lead + middle + trail
    return u''.join(words)


def generate_lorem_ipsum(n=5, html=True, min=20, max=100):
    """Generate some lorem impsum for the template."""
    from jinja2.constants import LOREM_IPSUM_WORDS
    from random import choice, random, randrange
    words = LOREM_IPSUM_WORDS.split()
    result = []

    for _ in xrange(n):
        next_capitalized = True
        last_comma = last_fullstop = 0
        word = None
        last = None
        p = []

        # each paragraph contains out of 20 to 100 words.
        for idx, _ in enumerate(xrange(randrange(min, max))):
            while True:
                word = choice(words)
                if word != last:
                    last = word
                    break
            if next_capitalized:
                word = word.capitalize()
                next_capitalized = False
            # add commas
            if idx - randrange(3, 8) > last_comma:
                last_comma = idx
                last_fullstop += 2
                word += ','
            # add end of sentences
            if idx - randrange(10, 20) > last_fullstop:
                last_comma = last_fullstop = idx
                word += '.'
                next_capitalized = True
            p.append(word)

        # ensure that the paragraph ends with a dot.
        p = u' '.join(p)
        if p.endswith(','):
            p = p[:-1] + '.'
        elif not p.endswith('.'):
            p += '.'
        result.append(p)

    if not html:
        return u'\n\n'.join(result)
    return Markup(u'\n'.join(u'<p>%s</p>' % escape(x) for x in result))


class Markup(unicode):
    r"""Marks a string as being safe for inclusion in HTML/XML output without
    needing to be escaped.  This implements the `__html__` interface a couple
    of frameworks and web applications use.  :class:`Markup` is a direct
    subclass of `unicode` and provides all the methods of `unicode` just that
    it escapes arguments passed and always returns `Markup`.

    The `escape` function returns markup objects so that double escaping can't
    happen.  If you want to use autoescaping in Jinja just enable the
    autoescaping feature in the environment.

    The constructor of the :class:`Markup` class can be used for three
    different things:  When passed an unicode object it's assumed to be safe,
    when passed an object with an HTML representation (has an `__html__`
    method) that representation is used, otherwise the object passed is
    converted into a unicode string and then assumed to be safe:

    >>> Markup("Hello <em>World</em>!")
    Markup(u'Hello <em>World</em>!')
    >>> class Foo(object):
    ...  def __html__(self):
    ...   return '<a href="#">foo</a>'
    ... 
    >>> Markup(Foo())
    Markup(u'<a href="#">foo</a>')

    If you want object passed being always treated as unsafe you can use the
    :meth:`escape` classmethod to create a :class:`Markup` object:

    >>> Markup.escape("Hello <em>World</em>!")
    Markup(u'Hello &lt;em&gt;World&lt;/em&gt;!')

    Operations on a markup string are markup aware which means that all
    arguments are passed through the :func:`escape` function:

    >>> em = Markup("<em>%s</em>")
    >>> em % "foo & bar"
    Markup(u'<em>foo &amp; bar</em>')
    >>> strong = Markup("<strong>%(text)s</strong>")
    >>> strong % {'text': '<blink>hacker here</blink>'}
    Markup(u'<strong>&lt;blink&gt;hacker here&lt;/blink&gt;</strong>')
    >>> Markup("<em>Hello</em> ") + "<foo>"
    Markup(u'<em>Hello</em> &lt;foo&gt;')
    """
    __slots__ = ()

    def __new__(cls, base=u'', encoding=None, errors='strict'):
        if hasattr(base, '__html__'):
            base = base.__html__()
        if encoding is None:
            return unicode.__new__(cls, base)
        return unicode.__new__(cls, base, encoding, errors)

    def __html__(self):
        return self

    def __add__(self, other):
        if hasattr(other, '__html__') or isinstance(other, basestring):
            return self.__class__(unicode(self) + unicode(escape(other)))
        return NotImplemented

    def __radd__(self, other):
        if hasattr(other, '__html__') or isinstance(other, basestring):
            return self.__class__(unicode(escape(other)) + unicode(self))
        return NotImplemented

    def __mul__(self, num):
        if isinstance(num, (int, long)):
            return self.__class__(unicode.__mul__(self, num))
        return NotImplemented
    __rmul__ = __mul__

    def __mod__(self, arg):
        if isinstance(arg, tuple):
            arg = tuple(imap(_MarkupEscapeHelper, arg))
        else:
            arg = _MarkupEscapeHelper(arg)
        return self.__class__(unicode.__mod__(self, arg))

    def __repr__(self):
        return '%s(%s)' % (
            self.__class__.__name__,
            unicode.__repr__(self)
        )

    def join(self, seq):
        return self.__class__(unicode.join(self, imap(escape, seq)))
    join.__doc__ = unicode.join.__doc__

    def split(self, *args, **kwargs):
        return map(self.__class__, unicode.split(self, *args, **kwargs))
    split.__doc__ = unicode.split.__doc__

    def rsplit(self, *args, **kwargs):
        return map(self.__class__, unicode.rsplit(self, *args, **kwargs))
    rsplit.__doc__ = unicode.rsplit.__doc__

    def splitlines(self, *args, **kwargs):
        return map(self.__class__, unicode.splitlines(self, *args, **kwargs))
    splitlines.__doc__ = unicode.splitlines.__doc__

    def unescape(self):
        r"""Unescape markup again into an unicode string.  This also resolves
        known HTML4 and XHTML entities:

        >>> Markup("Main &raquo; <em>About</em>").unescape()
        u'Main \xbb <em>About</em>'
        """
        from jinja2.constants import HTML_ENTITIES
        def handle_match(m):
            name = m.group(1)
            if name in HTML_ENTITIES:
                return unichr(HTML_ENTITIES[name])
            try:
                if name[:2] in ('#x', '#X'):
                    return unichr(int(name[2:], 16))
                elif name.startswith('#'):
                    return unichr(int(name[1:]))
            except ValueError:
                pass
            return u''
        return _entity_re.sub(handle_match, unicode(self))

    def striptags(self):
        r"""Unescape markup into an unicode string and strip all tags.  This
        also resolves known HTML4 and XHTML entities.  Whitespace is
        normalized to one:

        >>> Markup("Main &raquo;  <em>About</em>").striptags()
        u'Main \xbb About'
        """
        stripped = u' '.join(_striptags_re.sub('', self).split())
        return Markup(stripped).unescape()

    @classmethod
    def escape(cls, s):
        """Escape the string.  Works like :func:`escape` with the difference
        that for subclasses of :class:`Markup` this function would return the
        correct subclass.
        """
        rv = escape(s)
        if rv.__class__ is not cls:
            return cls(rv)
        return rv

    def make_wrapper(name):
        orig = getattr(unicode, name)
        def func(self, *args, **kwargs):
            args = _escape_argspec(list(args), enumerate(args))
            _escape_argspec(kwargs, kwargs.iteritems())
            return self.__class__(orig(self, *args, **kwargs))
        func.__name__ = orig.__name__
        func.__doc__ = orig.__doc__
        return func

    for method in '__getitem__', '__getslice__', 'capitalize', \
                  'title', 'lower', 'upper', 'replace', 'ljust', \
                  'rjust', 'lstrip', 'rstrip', 'center', 'strip', \
                  'translate', 'expandtabs', 'swapcase', 'zfill':
        locals()[method] = make_wrapper(method)

    # new in python 2.5
    if hasattr(unicode, 'partition'):
        partition = make_wrapper('partition'),
        rpartition = make_wrapper('rpartition')

    # new in python 2.6
    if hasattr(unicode, 'format'):
        format = make_wrapper('format')

    del method, make_wrapper


def _escape_argspec(obj, iterable):
    """Helper for various string-wrapped functions."""
    for key, value in iterable:
        if hasattr(value, '__html__') or isinstance(value, basestring):
            obj[key] = escape(value)
    return obj


class _MarkupEscapeHelper(object):
    """Helper for Markup.__mod__"""

    def __init__(self, obj):
        self.obj = obj

    __getitem__ = lambda s, x: _MarkupEscapeHelper(s.obj[x])
    __unicode__ = lambda s: unicode(escape(s.obj))
    __str__ = lambda s: str(escape(s.obj))
    __repr__ = lambda s: str(escape(repr(s.obj)))
    __int__ = lambda s: int(s.obj)
    __float__ = lambda s: float(s.obj)


class LRUCache(object):
    """A simple LRU Cache implementation."""

    # this is fast for small capacities (something below 1000) but doesn't
    # scale.  But as long as it's only used as storage for templates this
    # won't do any harm.

    def __init__(self, capacity):
        self.capacity = capacity
        self._mapping = {}
        self._queue = deque()
        self._postinit()

    def _postinit(self):
        # alias all queue methods for faster lookup
        self._popleft = self._queue.popleft
        self._pop = self._queue.pop
        if hasattr(self._queue, 'remove'):
            self._remove = self._queue.remove
        self._wlock = allocate_lock()
        self._append = self._queue.append

    def _remove(self, obj):
        """Python 2.4 compatibility."""
        for idx, item in enumerate(self._queue):
            if item == obj:
                del self._queue[idx]
                break

    def __getstate__(self):
        return {
            'capacity':     self.capacity,
            '_mapping':     self._mapping,
            '_queue':       self._queue
        }

    def __setstate__(self, d):
        self.__dict__.update(d)
        self._postinit()

    def __getnewargs__(self):
        return (self.capacity,)

    def copy(self):
        """Return an shallow copy of the instance."""
        rv = self.__class__(self.capacity)
        rv._mapping.update(self._mapping)
        rv._queue = deque(self._queue)
        return rv

    def get(self, key, default=None):
        """Return an item from the cache dict or `default`"""
        try:
            return self[key]
        except KeyError:
            return default

    def setdefault(self, key, default=None):
        """Set `default` if the key is not in the cache otherwise
        leave unchanged. Return the value of this key.
        """
        try:
            return self[key]
        except KeyError:
            self[key] = default
            return default

    def clear(self):
        """Clear the cache."""
        self._wlock.acquire()
        try:
            self._mapping.clear()
            self._queue.clear()
        finally:
            self._wlock.release()

    def __contains__(self, key):
        """Check if a key exists in this cache."""
        return key in self._mapping

    def __len__(self):
        """Return the current size of the cache."""
        return len(self._mapping)

    def __repr__(self):
        return '<%s %r>' % (
            self.__class__.__name__,
            self._mapping
        )

    def __getitem__(self, key):
        """Get an item from the cache. Moves the item up so that it has the
        highest priority then.

        Raise an `KeyError` if it does not exist.
        """
        rv = self._mapping[key]
        if self._queue[-1] != key:
            self._remove(key)
            self._append(key)
        return rv

    def __setitem__(self, key, value):
        """Sets the value for an item. Moves the item up so that it
        has the highest priority then.
        """
        self._wlock.acquire()
        try:
            if key in self._mapping:
                self._remove(key)
            elif len(self._mapping) == self.capacity:
                del self._mapping[self._popleft()]
            self._append(key)
            self._mapping[key] = value
        finally:
            self._wlock.release()

    def __delitem__(self, key):
        """Remove an item from the cache dict.
        Raise an `KeyError` if it does not exist.
        """
        self._wlock.acquire()
        try:
            del self._mapping[key]
            self._remove(key)
        finally:
            self._wlock.release()

    def items(self):
        """Return a list of items."""
        result = [(key, self._mapping[key]) for key in list(self._queue)]
        result.reverse()
        return result

    def iteritems(self):
        """Iterate over all items."""
        return iter(self.items())

    def values(self):
        """Return a list of all values."""
        return [x[1] for x in self.items()]

    def itervalue(self):
        """Iterate over all values."""
        return iter(self.values())

    def keys(self):
        """Return a list of all keys ordered by most recent usage."""
        return list(self)

    def iterkeys(self):
        """Iterate over all keys in the cache dict, ordered by
        the most recent usage.
        """
        return reversed(tuple(self._queue))

    __iter__ = iterkeys

    def __reversed__(self):
        """Iterate over the values in the cache dict, oldest items
        coming first.
        """
        return iter(tuple(self._queue))

    __copy__ = copy


# register the LRU cache as mutable mapping if possible
try:
    from collections import MutableMapping
    MutableMapping.register(LRUCache)
except ImportError:
    pass


class Cycler(object):
    """A cycle helper for templates."""

    def __init__(self, *items):
        if not items:
            raise RuntimeError('at least one item has to be provided')
        self.items = items
        self.reset()

    def reset(self):
        """Resets the cycle."""
        self.pos = 0

    @property
    def current(self):
        """Returns the current item."""
        return self.items[self.pos]

    def next(self):
        """Goes one item ahead and returns it."""
        rv = self.current
        self.pos = (self.pos + 1) % len(self.items)
        return rv


class Joiner(object):
    """A joining helper for templates."""

    def __init__(self, sep=u', '):
        self.sep = sep
        self.used = False

    def __call__(self):
        if not self.used:
            self.used = True
            return u''
        return self.sep


# we have to import it down here as the speedups module imports the
# markup type which is define above.
try:
    from jinja2._speedups import escape, soft_unicode
except ImportError:
    def escape(s):
        """Convert the characters &, <, >, ' and " in string s to HTML-safe
        sequences.  Use this if you need to display text that might contain
        such characters in HTML.  Marks return value as markup string.
        """
        if hasattr(s, '__html__'):
            return s.__html__()
        return Markup(unicode(s)
            .replace('&', '&amp;')
            .replace('>', '&gt;')
            .replace('<', '&lt;')
            .replace("'", '&#39;')
            .replace('"', '&#34;')
        )

    def soft_unicode(s):
        """Make a string unicode if it isn't already.  That way a markup
        string is not converted back to unicode.
        """
        if not isinstance(s, unicode):
            s = unicode(s)
        return s


# partials
try:
    from functools import partial
except ImportError:
    class partial(object):
        def __init__(self, _func, *args, **kwargs):
            self._func = _func
            self._args = args
            self._kwargs = kwargs
        def __call__(self, *args, **kwargs):
            kwargs.update(self._kwargs)
            return self._func(*(self._args + args), **kwargs)