from django.utils.html import conditional_escape

from django.utils.encoding import smart_unicode, StrAndUnicode, force_unicode

from django.utils.safestring import mark_safe

def flatatt(attrs):

    """

    Convert a dictionary of attributes to a single string.

    The returned string will contain a leading space followed by key="value",

    XML-style pairs.  It is assumed that the keys do not need to be XML-escaped.

    If the passed dictionary is empty, then return an empty string.

    """

    return u''.join([u' %s="%s"' % (k, conditional_escape(v)) for k, v in attrs.items()])

class ErrorDict(dict, StrAndUnicode):

    """

    A collection of errors that knows how to display itself in various formats.

    The dictionary keys are the field names, and the values are the errors.

    """

    def __unicode__(self):

        return self.as_ul()

    def as_ul(self):

        if not self: return u''

        return mark_safe(u'<ul class="errorlist">%s</ul>'

                % ''.join([u'<li>%s%s</li>' % (k, force_unicode(v))

                    for k, v in self.items()]))

    def as_text(self):

        return u'\n'.join([u'* %s\n%s' % (k, u'\n'.join([u'  * %s' % force_unicode(i) for i in v])) for k, v in self.items()])

class ErrorList(list, StrAndUnicode):

    """

    A collection of errors that knows how to display itself in various formats.

    """

    def __unicode__(self):

        return self.as_ul()

    def as_ul(self):

        if not self: return u''

        return mark_safe(u'<ul class="errorlist">%s</ul>'

                % ''.join([u'<li>%s</li>' % conditional_escape(force_unicode(e)) for e in self]))

    def as_text(self):

        if not self: return u''

        return u'\n'.join([u'* %s' % force_unicode(e) for e in self])

    def __repr__(self):

        return repr([force_unicode(e) for e in self])

class ValidationError(Exception):

    def __init__(self, message):

        """

        ValidationError can be passed any object that can be printed (usually

        a string) or a list of objects.

        """

        if isinstance(message, list):

            self.messages = ErrorList([smart_unicode(msg) for msg in message])

        else:

            message = smart_unicode(message)

            self.messages = ErrorList([message])

    def __str__(self):

        # This is needed because, without a __str__(), printing an exception

        # instance would result in this:

        # AttributeError: ValidationError instance has no attribute 'args'

        # See http://www.python.org/doc/current/tut/node10.html#handling

        return repr(self.messages)