"""associate url's path to view identifier / rql queries

It currently handle url's path with the forms

* <publishing_method>

* minimal REST publishing:

  * <eid>

  * <etype>[/<attribute name>/<attribute value>]*

* folder navigation

You can actually control URL (more exactly path) resolution using URL path

evaluator.

XXX actionpath and folderpath execute a query whose results is lost

because of redirecting instead of direct traversal

:organization: Logilab

:copyright: 2001-2008 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr

"""

__docformat__ = "restructuredtext en"

from rql import TypeResolverException

from cubicweb import RegistryException, typed_eid

from cubicweb.web import NotFound, Redirect

from cubicweb.web.component import SingletonComponent, Component

class PathDontMatch(Exception):

    """exception used by url evaluators to notify they can't evaluate

    a path

    """

class URLPublisherComponent(SingletonComponent):

    """associate url's path to view identifier / rql queries,

    by applying a chain of urlpathevaluator components.

    An evaluator is a URLPathEvaluator subclass with a .evaluate_path

    method taking the request object and the path to publish as

    argument.  It will either returns a publishing method identifier

    and a rql query on success or raises a `PathDontMatch` exception

    on failure. URL evaluators are called according to their `priority`

    attribute, with 0 as the greatest priority and greater values as

    lower priority.  The first evaluator returning a result or raising

    something else than `PathDontMatch` will stop the handlers chain.

    """

    id = 'urlpublisher'

    def __init__(self, default_method='view'):

        super(URLPublisherComponent, self).__init__()

        self.default_method = default_method

        evaluators = []        

        for evaluatorcls in self.vreg.registry_objects('components',

                                                       'urlpathevaluator'):

            # instantiation needed

            evaluator = evaluatorcls(self)

            evaluators.append(evaluator)

        self.evaluators = sorted(evaluators, key=lambda x: x.priority)

    def process(self, req, path):

        """given an url (essentialy caracterized by a path on the server,

        but additional information may be found in the request object), return

        a publishing method identifier (eg controller) and an optional result

        set

        :type req: `cubicweb.web.Request`

        :param req: the request object

        :type path: str

        :param path: the path of the resource to publish

        :rtype: tuple(str, `cubicweb.common.utils.ResultSet` or None)

        :return: the publishing method identifier and an optional result set

        :raise NotFound: if no handler is able to decode the given path

        """

        parts = [part for part in path.split('/')

                 if part != ''] or (self.default_method,)

        if req.form.get('rql'):

            if parts[0] in self.vreg.registry('controllers'):

                return parts[0], None

            return 'view', None

        for evaluator in self.evaluators:

            try:

                pmid, rset = evaluator.evaluate_path(req, parts[:])

                break

            except PathDontMatch:

                continue

        else:

            raise NotFound(path)

        if pmid is None:

            pmid = self.default_method

        return pmid, rset

class URLPathEvaluator(Component):

    __abstract__ = True

    id = 'urlpathevaluator'

    def __init__(self, urlpublisher):

        self.urlpublisher = urlpublisher

class RawPathEvaluator(URLPathEvaluator):

    """handle path of the form::

        <publishing_method>?parameters...

    """

    priority = 0

    def evaluate_path(self, req, parts):

        if len(parts) == 1 and parts[0] in self.vreg.registry('controllers'):

            return parts[0], None

        raise PathDontMatch()

class EidPathEvaluator(URLPathEvaluator):

    """handle path with the form::

        <eid>

    """

    priority = 1

    def evaluate_path(self, req, parts):

        if len(parts) != 1:

            raise PathDontMatch()

        try:

            rset = req.execute('Any X WHERE X eid %(x)s',

                               {'x': typed_eid(parts[0])}, 'x')

        except ValueError:

            raise PathDontMatch()

        if rset.rowcount == 0:

            raise NotFound()

        return None, rset

class RestPathEvaluator(URLPathEvaluator):

    """handle path with the form::

        <etype>[[/<attribute name>]/<attribute value>]*

    """

    priority = 2

    def __init__(self, urlpublisher):

        super(RestPathEvaluator, self).__init__(urlpublisher)

        self.etype_map = {}

        for etype in self.schema.entities():

            etype = str(etype)

            self.etype_map[etype.lower()] = etype

    def evaluate_path(self, req, parts):

        if not (0 < len(parts) < 4):

            raise PathDontMatch()

        try:

            etype = self.etype_map[parts.pop(0).lower()]

        except KeyError:

            raise PathDontMatch()

        cls = self.vreg.etype_class(etype)

        if parts:

            if len(parts) == 2:

                attrname = parts.pop(0).lower()

                try:

                    cls.e_schema.subject_relation(attrname)

                except KeyError:

                    raise PathDontMatch()

            else:

                attrname = cls._rest_attr_info()[0]

            value = req.url_unquote(parts.pop(0))

            rset = self.attr_rset(req, etype, attrname, value)

        else:

            rset = self.cls_rset(req, cls)

        if rset.rowcount == 0:

            raise NotFound()

        return None, rset

    def cls_rset(self, req, cls):

        return req.execute(cls.fetch_rql(req.user))

    def attr_rset(self, req, etype, attrname, value):

        rql = u'Any X WHERE X is %s, X %s %%(x)s' % (etype, attrname)

        if attrname == 'eid':

            try:

                rset = req.execute(rql, {'x': typed_eid(value)}, 'x')

            except (ValueError, TypeResolverException):

                # conflicting eid/type

                raise PathDontMatch()

        else:

            rset = req.execute(rql, {'x': value})

        return rset

class URLRewriteEvaluator(URLPathEvaluator):

    """tries to find a rewrite rule to apply

    URL rewrite rule definitions are stored in URLRewriter objects

    """

    priority = 3

    def evaluate_path(self, req, parts):

        # uri <=> req._twreq.path or req._twreq.uri

        uri = req.url_unquote('/' + '/'.join(parts))

        vobjects = sorted(self.vreg.registry_objects('urlrewriting'),

                          key=lambda x: x.priority,

                          reverse=True)

        for rewritercls in vobjects:

            rewriter = rewritercls()

            try:

                # XXX we might want to chain url rewrites

                return rewriter.rewrite(req, uri)

            except KeyError:

                continue

        raise PathDontMatch()

class ActionPathEvaluator(URLPathEvaluator):

    """handle path with the form::

    <any evaluator path>/<action>

    """

    priority = 4

    def evaluate_path(self, req, parts):

        if len(parts) < 2:

            raise PathDontMatch()

        # remove last part and see if this is something like an actions

        # if so, call

        try:

            requested = parts.pop(-1)

            actions = self.vreg.registry_objects('actions', requested)

        except RegistryException:

            raise PathDontMatch()

        for evaluator in self.urlpublisher.evaluators:

            if evaluator is self or evaluator.priority == 0:

                continue

            try:

                pmid, rset = evaluator.evaluate_path(req, parts[:])

            except PathDontMatch:

                continue

            else:

                try:

                    action = self.vreg.select(actions, req, rset)

                except RegistryException:

                    raise PathDontMatch()

                else:

                    # XXX avoid redirect

                    raise Redirect(action.url())

        raise PathDontMatch()