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 string
try:
    from thread import allocate_lock
except ImportError:
    from dummy_thread import allocate_lock
from collections import deque
from copy import deepcopy
from itertools import imap


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


# 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.
try:
    def _test_gen_bug():
        raise TypeError(_test_gen_bug)
        yield None
    u''.join(_test_gen_bug())
except TypeError, _error:
    if _error.args and _error.args[0] is _test_gen_bug:
        concat = u''.join
    else:
        def concat(gen):
            try:
                return u''.join(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
    del _test_gen_bug, _error


def contextfunction(f):
    """This decorator can be used to mark a callable as context callable.  A
    context callable is passed the active context as first argument if it
    was directly stored in the context.
    """
    f.contextfunction = True
    return f


def environmentfunction(f):
    """This decorator can be used to mark a callable as environment callable.
    A environment callable is passed the current environment as first argument
    if it was directly stored in the context.
    """
    f.environmentfunction = True
    return f


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 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 string.letters + string.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):
    """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.

    The `escape` function returns markup objects so that double escaping can't
    happen.  If you want to use autoescaping in Jinja just set the finalizer
    of the environment to `escape`.
    """
    __slots__ = ()

    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 not isinstance(num, (int, long)):
            return NotImplemented
        return self.__class__(unicode.__mul__(self, num))
    __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 make_wrapper(name):
        orig = getattr(unicode, name)
        def func(self, *args, **kwargs):
            args = list(args)
            for idx, arg in enumerate(args):
                if hasattr(arg, '__html__') or isinstance(arg, basestring):
                    args[idx] = escape(arg)
            for name, arg in kwargs.iteritems():
                if hasattr(arg, '__html__') or isinstance(arg, basestring):
                    kwargs[name] = escape(arg)
            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'):
        locals().update(
            partition=make_wrapper('partition'),
            rpartition=make_wrapper('rpartition')
        )
    del method, make_wrapper


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(repr(escape(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 around 200) but doesn't
    # scale.  But as long as it's only used for the database connections in
    # a non request fallback it's fine.

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

        # 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 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 __iter__(self):
        """Iterate over all values in the cache dict, ordered by
        the most recent usage.
        """
        return reversed(self._queue)

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

    __copy__ = copy


# 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.
        """
        if hasattr(s, '__html__'):
            return s.__html__()
        return Markup(unicode(s)
            .replace('&', '&amp;')
            .replace('>', '&gt;')
            .replace('<', '&lt;')
            .replace('"', '&quot;')
        )

    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)