[philo.git] / philo / contrib / sobol / search.py

#encoding: utf-8
import datetime
from hashlib import sha1

from django.conf import settings
from django.contrib.sites.models import Site
from django.core.cache import cache
from django.db.models.options import get_verbose_name as convert_camelcase
from django.utils import simplejson as json
from django.utils.http import urlquote_plus
from django.utils.safestring import mark_safe
from django.utils.text import capfirst
from django.template import loader, Context, Template

from philo.contrib.sobol.utils import make_tracking_querydict, RegistryIterator


if getattr(settings, 'SOBOL_USE_EVENTLET', False):
        try:
                from eventlet.green import urllib2
        except:
                import urllib2
else:
        import urllib2


__all__ = (
        'Result', 'BaseSearch', 'DatabaseSearch', 'URLSearch', 'JSONSearch', 'GoogleSearch', 'SearchRegistry', 'registry', 'get_search_instance'
)


SEARCH_CACHE_SEED = 'philo_sobol_search_results'
USE_CACHE = getattr(settings, 'SOBOL_USE_SEARCH', True)


class RegistrationError(Exception):
        """Raised if there is a problem registering a search with a :class:`SearchRegistry`"""
        pass


class SearchRegistry(object):
        """Holds a registry of search types by slug."""
        
        def __init__(self):
                self._registry = {}
        
        def register(self, search, slug=None):
                """
                Register a search with the registry.
                
                :param search: The search class to register - generally a subclass of :class:`BaseSearch`
                :param slug: The slug which will be used to register the search class. If ``slug`` is ``None``, the search's default slug will be used.
                :raises: :class:`RegistrationError` if a different search is already registered with ``slug``.
                
                """
                slug = slug or search.slug
                if slug in self._registry:
                        registered = self._registry[slug]
                        if registered.__module__ != search.__module__:
                                raise RegistrationError("A different search is already registered as `%s`" % slug)
                else:
                        self._registry[slug] = search
        
        def unregister(self, search, slug=None):
                """
                Unregister a search from the registry.
                
                :param search: The search class to unregister - generally a subclass of :class:`BaseSearch`
                :param slug: If provided, the search will only be removed if it was registered with ``slug``. If not provided, the search class will be unregistered no matter what slug it was registered with.
                :raises: :class:`RegistrationError` if a slug is provided but the search registered with that slug is not ``search``.
                
                """
                if slug is not None:
                        if slug in self._registry and self._registry[slug] == search:
                                del self._registry[slug]
                        raise RegistrationError("`%s` is not registered as `%s`" % (search, slug))
                else:
                        for slug, search in self._registry.items():
                                if search == search:
                                        del self._registry[slug]
        
        def items(self):
                """Returns a list of (slug, search) items in the registry."""
                return self._registry.items()
        
        def iteritems(self):
                """Returns an iterator over the (slug, search) pairs in the registry."""
                return RegistryIterator(self._registry, 'iteritems')
        
        def iterchoices(self):
                """Returns an iterator over (slug, search.verbose_name) pairs for the registry."""
                return RegistryIterator(self._registry, 'iteritems', lambda x: (x[0], x[1].verbose_name))
        
        def __getitem__(self, key):
                """Returns the search registered with ``key``."""
                return self._registry[key]
        
        def __iter__(self):
                """Returns an iterator over the keys in the registry."""
                return self._registry.__iter__()


registry = SearchRegistry()


def _make_cache_key(search, search_arg):
        return sha1(SEARCH_CACHE_SEED + search.slug + search_arg).hexdigest()


def get_search_instance(slug, search_arg):
        """Returns a search instance for the given slug, either from the cache or newly-instantiated."""
        search = registry[slug]
        search_arg = search_arg.lower()
        if USE_CACHE:
                key = _make_cache_key(search, search_arg)
                cached = cache.get(key)
                if cached:
                        return cached
        return search(search_arg)
        


class Result(object):
        """
        :class:`Result` is a helper class that, given a search and a result of that search, is able to correctly render itself with a template defined by the search. Every :class:`Result` will pass a ``title``, a ``url`` (if applicable), and the raw ``result`` returned by the search into the template context when rendering.
        
        :param search: An instance of a :class:`BaseSearch` subclass or an object that implements the same API.
        :param result: An arbitrary result from the ``search``.
        
        """
        def __init__(self, search, result):
                self.search = search
                self.result = result
        
        def get_title(self):
                """Returns the title of the result by calling :meth:`BaseSearch.get_result_title` on the raw result."""
                return self.search.get_result_title(self.result)
        
        def get_url(self):
                """Returns the url of the result or an empty string by calling :meth:`BaseSearch.get_result_querydict` on the raw result and then encoding the querydict returned."""
                qd = self.search.get_result_querydict(self.result)
                if qd is None:
                        return ""
                return "?%s" % qd.urlencode()
        
        def get_template(self):
                """Returns the template for the result by calling :meth:`BaseSearch.get_result_template` on the raw result."""
                return self.search.get_result_template(self.result)
        
        def get_extra_context(self):
                """Returns any extra context for the result by calling :meth:`BaseSearch.get_result_extra_context` on the raw result."""
                return self.search.get_result_extra_context(self.result)
        
        def get_context(self):
                """
                Returns the context dictionary for the result. This is used both in rendering the result and in the AJAX return value for :meth:`.SearchView.ajax_api_view`. The context will contain everything from :meth:`get_extra_context` as well as the following keys:
                
                title
                        The result of calling :meth:`get_title`
                url
                        The result of calling :meth:`get_url`
                result
                        The raw result which the :class:`Result` was instantiated with.
                
                """
                context = self.get_extra_context()
                context.update({
                        'title': self.get_title(),
                        'url': self.get_url(),
                        'result': self.result
                })
                return context
        
        def render(self):
                """Returns the template from :meth:`get_template` rendered with the context from :meth:`get_context`."""
                t = self.get_template()
                c = Context(self.get_context())
                return t.render(c)
        
        def __unicode__(self):
                """Returns :meth:`render`"""
                return self.render()


class BaseSearchMetaclass(type):
        def __new__(cls, name, bases, attrs):
                if 'verbose_name' not in attrs:
                        attrs['verbose_name'] = capfirst(' '.join(convert_camelcase(name).rsplit(' ', 1)[:-1]))
                if 'slug' not in attrs:
                        attrs['slug'] = name.lower()
                return super(BaseSearchMetaclass, cls).__new__(cls, name, bases, attrs)


class BaseSearch(object):
        """
        Defines a generic search api. Accessing :attr:`results` will attempt to retrieve cached results and, if that fails, will initiate a new search and store the results in the cache. Each search has a ``verbose_name`` and a ``slug``. If these are not provided as attributes, they will be automatically generated based on the name of the class.
        
        :param search_arg: The string which is being searched for.
        
        """
        __metaclass__ = BaseSearchMetaclass
        #: The number of results to return from the complete list. Default: 10
        result_limit = 10
        #: How long the items for the search should be cached (in minutes). Default: 48 hours.
        _cache_timeout = 60*48
        #: The path to the template which will be used to render the :class:`Result`\ s for this search.
        result_template = "sobol/search/basesearch.html"
        
        def __init__(self, search_arg):
                self.search_arg = search_arg
        
        @property
        def results(self):
                """Retrieves cached results or initiates a new search via :meth:`get_results` and caches the results."""
                if not hasattr(self, '_results'):
                        try:
                                # Cache one extra result so we can see if there are
                                # more results to be had.
                                limit = self.result_limit
                                if limit is not None:
                                        limit += 1
                                results = self.get_results(limit)
                        except:
                                if settings.DEBUG:
                                        raise
                                #  On exceptions, don't set any cache; just return.
                                return []
                        
                        self._results = results
                        
                        if USE_CACHE:
                                key = _make_cache_key(self, self.search_arg)
                                cache.set(key, self, self._cache_timeout)
                
                return self._results
        
        def get_results(self, limit=None, result_class=Result):
                """
                Calls :meth:`search` and parses the return value into :class:`Result` instances.
                
                :param limit: Passed directly to :meth:`search`.
                :param result_class: The class used to represent the results. This will be instantiated with the :class:`BaseSearch` instance and the raw result from the search.
                
                """
                results = self.search(limit)
                return [result_class(self, result) for result in results]
        
        def search(self, limit=None):
                """Returns an iterable of up to ``limit`` results. The :meth:`get_result_title`, :meth:`get_result_url`, :meth:`get_result_template`, and :meth:`get_result_extra_context` methods will be used to interpret the individual items that this function returns, so the result can be an object with attributes as easily as a dictionary with keys. However, keep in mind that the raw results will be stored with django's caching mechanisms and will be converted to JSON."""
                raise NotImplementedError
        
        def get_result_title(self, result):
                """Returns the title of the ``result``. Must be implemented by subclasses."""
                raise NotImplementedError
        
        def get_result_url(self, result):
                """Returns the actual URL for the ``result`` or ``None`` if there is no URL. Must be implemented by subclasses."""
                raise NotImplementedError
        
        def get_result_querydict(self, result):
                """Returns a querydict for tracking selection of the result, or ``None`` if there is no URL for the result."""
                url = self.get_result_url(result)
                if url is None:
                        return None
                return make_tracking_querydict(self.search_arg, url)
        
        def get_result_template(self, result):
                """Returns the template to be used for rendering the ``result``."""
                return loader.get_template(self.result_template)
        
        def get_result_extra_context(self, result):
                """Returns any extra context to be used when rendering the ``result``."""
                return {}
        
        def has_more_results(self):
                """Returns ``True`` if there are more results than :attr:`result_limit` and ``False`` otherwise."""
                return len(self.results) > self.result_limit
        
        @property
        def more_results_url(self):
                """Returns the actual url for more results. This should be accessed through :attr:`more_results_querydict` in the template so that the click can be tracked."""
                raise NotImplementedError
        
        @property
        def more_results_querydict(self):
                """Returns a :class:`QueryDict` for tracking whether people click on a 'more results' link."""
                return make_tracking_querydict(self.search_arg, self.more_results_url)
        
        def __unicode__(self):
                return self.verbose_name


class DatabaseSearch(BaseSearch):
        """Implements :meth:`~BaseSearch.search` and :meth:`get_queryset` methods to handle database queries."""
        #: The model which should be searched by the :class:`DatabaseSearch`.
        model = None
        
        def search(self, limit=None):
                if not hasattr(self, '_qs'):
                        self._qs = self.get_queryset()
                        if limit is not None:
                                self._qs = self._qs[:limit]
                
                return self._qs
        
        def get_queryset(self):
                """Returns a :class:`QuerySet` of all instances of :attr:`model`. This method should be overridden by subclasses to specify how the search should actually be implemented for the model."""
                return self.model._default_manager.all()


class URLSearch(BaseSearch):
        """Defines a generic interface for searches that require accessing a certain url to get search results."""
        #: The base URL which will be accessed to get the search results.
        search_url = ''
        #: The url-encoded query string to be used for fetching search results from :attr:`search_url`. Must have one ``%s`` to contain the search argument.
        query_format_str = "%s"

        @property
        def url(self):
                """The URL where the search gets its results. Composed from :attr:`search_url` and :attr:`query_format_str`."""
                return self.search_url + self.query_format_str % urlquote_plus(self.search_arg)

        @property
        def more_results_url(self):
                return self.url
        
        def parse_response(self, response, limit=None):
                """Handles the ``response`` from accessing :attr:`url` (with :func:`urllib2.urlopen`) and returns a list of up to ``limit`` results."""
                raise NotImplementedError
        
        def search(self, limit=None):
                return self.parse_response(urllib2.urlopen(self.url), limit=limit)


class JSONSearch(URLSearch):
        """Makes a GET request and parses the results as JSON. The default behavior assumes that the response contains a list of results."""
        def parse_response(self, response, limit=None):
                return json.loads(response.read())[:limit]


class GoogleSearch(JSONSearch):
        """An example implementation of a :class:`JSONSearch`."""
        search_url = "http://ajax.googleapis.com/ajax/services/search/web"
        _cache_timeout = 60
        verbose_name = "Google search (current site)"
        result_template = "sobol/search/googlesearch.html"
        
        @property
        def query_format_str(self):
                default_args = self.default_args
                if default_args:
                        default_args += " "
                return "?v=1.0&q=%s%%s" % urlquote_plus(default_args).replace('%', '%%')
        
        @property
        def default_args(self):
                """Unquoted default arguments for the :class:`GoogleSearch`."""
                return "site:%s" % Site.objects.get_current().domain
        
        def parse_response(self, response, limit=None):
                responseData = json.loads(response.read())['responseData']
                results, cursor = responseData['results'], responseData['cursor']
                
                if results:
                        self._more_results_url = cursor['moreResultsUrl']
                        self._estimated_result_count = cursor['estimatedResultCount']
                
                return results[:limit]
        
        @property
        def url(self):
                # Google requires that an ajax request have a proper Referer header.
                return urllib2.Request(
                        super(GoogleSearch, self).url,
                        None,
                        {'Referer': "http://%s" % Site.objects.get_current().domain}
                )
        
        @property
        def has_more_results(self):
                if self.results and len(self.results) < self._estimated_result_count:
                        return True
                return False
        
        @property
        def more_results_url(self):
                return self._more_results_url
        
        def get_result_title(self, result):
                return result['titleNoFormatting']
        
        def get_result_url(self, result):
                return result['unescapedUrl']


registry.register(GoogleSearch)


try:
        from BeautifulSoup import BeautifulSoup, SoupStrainer, BeautifulStoneSoup
except:
        pass
else:
        __all__ += ('ScrapeSearch', 'XMLSearch',)
        class ScrapeSearch(URLSearch):
                """A base class for scrape-style searching, available if :mod:`BeautifulSoup` is installed."""
                #: Arguments to be passed into a :class:`SoupStrainer`.
                strainer_args = []
                #: Keyword arguments to be passed into a :class:`SoupStrainer`.
                strainer_kwargs = {}
                
                @property
                def strainer(self):
                        """
                        Caches and returns a :class:`SoupStrainer` initialized with :attr:`strainer_args` and :attr:`strainer_kwargs`. This strainer will be used to parse only certain parts of the document.
                        
                        .. seealso:: `BeautifulSoup: Improving Performance by Parsing Only Part of the Document <http://www.crummy.com/software/BeautifulSoup/documentation.html#Improving%20Performance%20by%20Parsing%20Only%20Part%20of%20the%20Document>`_
                        
                        """
                        if not hasattr(self, '_strainer'):
                                self._strainer = SoupStrainer(*self.strainer_args, **self.strainer_kwargs)
                        return self._strainer
                
                def parse_response(self, response, limit=None):
                        strainer = self.strainer
                        soup = BeautifulSoup(response, parseOnlyThese=strainer)
                        return self.parse_results(soup.findAll(recursive=False, limit=limit))
                
                def parse_results(self, results):
                        """
                        Provides a hook for parsing the results of straining. This has no default behavior and must be implemented by subclasses because the results absolutely must be parsed to properly extract the information.
                        
                        .. seealso:: `BeautifulSoup: Improving Memory Usage with extract <http://www.crummy.com/software/BeautifulSoup/documentation.html#Improving%20Memory%20Usage%20with%20extract>`_
                        """
                        raise NotImplementedError
        
        
        class XMLSearch(ScrapeSearch):
                """A base class for searching XML results."""
                #: Self-closing tag names to be used when interpreting the XML document
                #:
                #: .. seealso:: `BeautifulSoup: Parsing XML <http://www.crummy.com/software/BeautifulSoup/documentation.html#Parsing%20XML>`_
                self_closing_tags = []
                
                def parse_response(self, response, limit=None):
                        strainer = self.strainer
                        soup = BeautifulStoneSoup(response, selfClosingTags=self.self_closing_tags, parseOnlyThese=strainer)
                        return self.parse_results(soup.findAll(recursive=False, limit=limit))