コード例 #1
0
    def metadata_needed_for(self, collection_details):
        """Returns identifiers in the collection that could benefit from
        distributor metadata on the circulation manager.
        """
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(
            self._db, client, collection_details
        )

        resolver = IdentifierResolutionCoverageProvider
        unresolved_identifiers = collection.unresolved_catalog(
            self._db, resolver.DATA_SOURCE_NAME, resolver.OPERATION
        )

        # Omit identifiers that currently have metadata pending for
        # the IntegrationClientCoverImageCoverageProvider.
        data_source = DataSource.lookup(
            self._db, collection.name, autocreate=True
        )
        is_awaiting_metadata = self._db.query(
            CoverageRecord.id, CoverageRecord.identifier_id
        ).filter(
            CoverageRecord.data_source_id==data_source.id,
            CoverageRecord.status==CoverageRecord.REGISTERED,
            CoverageRecord.operation==IntegrationClientCoverImageCoverageProvider.OPERATION,
        ).subquery()

        unresolved_identifiers = unresolved_identifiers.outerjoin(
            is_awaiting_metadata,
            Identifier.id==is_awaiting_metadata.c.identifier_id
        ).filter(is_awaiting_metadata.c.id==None)

        # Add a message for each unresolved identifier
        pagination = load_pagination_from_request(default_size=25)
        feed_identifiers = pagination.apply(unresolved_identifiers).all()
        messages = list()
        for identifier in feed_identifiers:
            messages.append(OPDSMessage(
                identifier.urn, HTTP_ACCEPTED, "Metadata needed."
            ))

        title = "%s Metadata Requests for %s" % (collection.protocol, client.url)
        metadata_request_url = self.collection_feed_url(
            'metadata_needed_for', collection
        )

        request_feed = AcquisitionFeed(
            self._db, title, metadata_request_url, [], VerboseAnnotator,
            precomposed_entries=messages
        )

        self.add_pagination_links_to_feed(
            pagination, unresolved_identifiers, request_feed,
            'metadata_needed_for', collection
        )

        return feed_response(request_feed)
コード例 #2
0
    def metadata_needed_for(self, collection_details):
        """Returns identifiers in the collection that could benefit from
        distributor metadata on the circulation manager.
        """
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(self._db, client,
                                             collection_details)

        resolver = IdentifierResolutionCoverageProvider
        unresolved_identifiers = collection.unresolved_catalog(
            self._db, resolver.DATA_SOURCE_NAME, resolver.OPERATION)

        # Omit identifiers that currently have metadata pending for
        # the IntegrationClientCoverImageCoverageProvider.
        data_source = DataSource.lookup(self._db,
                                        collection.name,
                                        autocreate=True)
        is_awaiting_metadata = self._db.query(
            CoverageRecord.id, CoverageRecord.identifier_id).filter(
                CoverageRecord.data_source_id == data_source.id,
                CoverageRecord.status == CoverageRecord.REGISTERED,
                CoverageRecord.operation ==
                IntegrationClientCoverImageCoverageProvider.OPERATION,
            ).subquery()

        unresolved_identifiers = unresolved_identifiers.outerjoin(
            is_awaiting_metadata,
            Identifier.id == is_awaiting_metadata.c.identifier_id).filter(
                is_awaiting_metadata.c.id == None)

        # Add a message for each unresolved identifier
        pagination = load_pagination_from_request(default_size=25)
        feed_identifiers = pagination.apply(unresolved_identifiers).all()
        messages = list()
        for identifier in feed_identifiers:
            messages.append(
                OPDSMessage(identifier.urn, HTTP_ACCEPTED, "Metadata needed."))

        title = "%s Metadata Requests for %s" % (collection.protocol,
                                                 client.url)
        metadata_request_url = self.collection_feed_url(
            'metadata_needed_for', collection)

        request_feed = AcquisitionFeed(self._db,
                                       title,
                                       metadata_request_url, [],
                                       VerboseAnnotator,
                                       precomposed_entries=messages)

        self.add_pagination_links_to_feed(pagination, unresolved_identifiers,
                                          request_feed, 'metadata_needed_for',
                                          collection)

        return feed_response(request_feed)
コード例 #3
0
    def remove_items(self, collection_details):
        """Removes identifiers from a Collection's catalog"""
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(
            self._db, client, collection_details
        )

        urns = request.args.getlist('urn')
        messages = []
        identifiers_by_urn, failures = Identifier.parse_urns(self._db, urns)

        for urn in failures:
            message = OPDSMessage(
                urn, INVALID_URN.status_code, INVALID_URN.detail
            )
            messages.append(message)

        # Find the IDs of the subset of provided identifiers that are
        # in the catalog, so we know which ones to delete and give a
        # 200 message. Also get a SQLAlchemy clause that selects only
        # those IDs.
        matching_ids, identifier_match_clause = self._in_catalog_subset(
            collection, identifiers_by_urn
        )

        # Use that clause to delete all of the relevant catalog
        # entries.
        delete_stmt = collections_identifiers.delete().where(
            identifier_match_clause
        )
        self._db.execute(delete_stmt)

        # IDs that matched get a 200 message; all others get a 404
        # message.
        for urn, identifier in identifiers_by_urn.items():
            if identifier.id in matching_ids:
                status = HTTP_OK
                description = "Successfully removed"
            else:
                status = HTTP_NOT_FOUND
                description = "Not in catalog"
            message = OPDSMessage(urn, status, description)
            messages.append(message)

        title = "%s Catalog Item Removal for %s" % (collection.protocol, client.url)
        url = self.collection_feed_url("remove", collection, urn=urns)
        removal_feed = AcquisitionFeed(
            self._db, title, url, [], VerboseAnnotator,
            precomposed_entries=messages
        )

        return feed_response(removal_feed)
コード例 #4
0
    def remove_items(self, collection_details):
        """Removes identifiers from a Collection's catalog"""
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(self._db, client,
                                             collection_details)

        urns = request.args.getlist('urn')
        messages = []
        identifiers_by_urn, failures = Identifier.parse_urns(self._db, urns)

        for urn in failures:
            message = OPDSMessage(urn, INVALID_URN.status_code,
                                  INVALID_URN.detail)
            messages.append(message)

        # Find the IDs of the subset of provided identifiers that are
        # in the catalog, so we know which ones to delete and give a
        # 200 message. Also get a SQLAlchemy clause that selects only
        # those IDs.
        matching_ids, identifier_match_clause = self._in_catalog_subset(
            collection, identifiers_by_urn)

        # Use that clause to delete all of the relevant catalog
        # entries.
        delete_stmt = collections_identifiers.delete().where(
            identifier_match_clause)
        self._db.execute(delete_stmt)

        # IDs that matched get a 200 message; all others get a 404
        # message.
        for urn, identifier in identifiers_by_urn.items():
            if identifier.id in matching_ids:
                status = HTTP_OK
                description = "Successfully removed"
            else:
                status = HTTP_NOT_FOUND
                description = "Not in catalog"
            message = OPDSMessage(urn, status, description)
            messages.append(message)

        title = "%s Catalog Item Removal for %s" % (collection.protocol,
                                                    client.url)
        url = self.collection_feed_url("remove", collection, urn=urns)
        removal_feed = AcquisitionFeed(self._db,
                                       title,
                                       url, [],
                                       VerboseAnnotator,
                                       precomposed_entries=messages)

        return feed_response(removal_feed)
コード例 #5
0
 def suppressed(self):
     this_url = self.url_for('suppressed')
     annotator = AdminAnnotator(self.circulation)
     pagination = load_pagination_from_request()
     if isinstance(pagination, ProblemDetail):
         return pagination
     opds_feed = AdminFeed.suppressed(
         _db=self._db, title="Hidden Books",
         url=this_url, annotator=annotator,
         pagination=pagination
     )
     return feed_response(opds_feed)
コード例 #6
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 def complaints(self):
     this_url = self.url_for('complaints')
     annotator = AdminAnnotator(self.circulation)
     pagination = load_pagination_from_request()
     if isinstance(pagination, ProblemDetail):
         return pagination
     opds_feed = AdminFeed.complaints(
         _db=self._db, title="Complaints",
         url=this_url, annotator=annotator,
         pagination=pagination
     )
     return feed_response(opds_feed)    
コード例 #7
0
    def add_items(self, collection_details):
        """Adds identifiers to a Collection's catalog"""
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(
            self._db, client, collection_details
        )
        urns = request.args.getlist('urn')
        messages = []
        identifiers_by_urn, failures = Identifier.parse_urns(self._db, urns)

        for urn in failures:
            message = OPDSMessage(
                urn, INVALID_URN.status_code, INVALID_URN.detail
            )
            messages.append(message)

        # Find the subset of incoming identifiers that are already
        # in the catalog.
        already_in_catalog, ignore = self._in_catalog_subset(
            collection, identifiers_by_urn
        )

        # Everything else needs to be added to the catalog.
        needs_to_be_added = [
            x for x in identifiers_by_urn.values()
            if x.id not in already_in_catalog
        ]
        collection.catalog_identifiers(needs_to_be_added)

        for urn, identifier in identifiers_by_urn.items():
            if identifier.id in already_in_catalog:
                status = HTTP_OK
                description = "Already in catalog"
            else:
                status = HTTP_CREATED
                description = "Successfully added"

            messages.append(OPDSMessage(urn, status, description))

        title = "%s Catalog Item Additions for %s" % (collection.protocol, client.url)
        url = self.collection_feed_url('add', collection, urn=urns)
        addition_feed = AcquisitionFeed(
            self._db, title, url, [], VerboseAnnotator,
            precomposed_entries=messages
        )

        return feed_response(addition_feed)
コード例 #8
0
    def add_items(self, collection_details):
        """Adds identifiers to a Collection's catalog"""
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(self._db, client,
                                             collection_details)
        urns = request.args.getlist('urn')
        messages = []
        identifiers_by_urn, failures = Identifier.parse_urns(self._db, urns)

        for urn in failures:
            message = OPDSMessage(urn, INVALID_URN.status_code,
                                  INVALID_URN.detail)
            messages.append(message)

        # Find the subset of incoming identifiers that are already
        # in the catalog.
        already_in_catalog, ignore = self._in_catalog_subset(
            collection, identifiers_by_urn)

        # Everything else needs to be added to the catalog.
        needs_to_be_added = [
            x for x in identifiers_by_urn.values()
            if x.id not in already_in_catalog
        ]
        collection.catalog_identifiers(needs_to_be_added)

        for urn, identifier in identifiers_by_urn.items():
            if identifier.id in already_in_catalog:
                status = HTTP_OK
                description = "Already in catalog"
            else:
                status = HTTP_CREATED
                description = "Successfully added"

            messages.append(OPDSMessage(urn, status, description))

        title = "%s Catalog Item Additions for %s" % (collection.protocol,
                                                      client.url)
        url = self.collection_feed_url('add', collection, urn=urns)
        addition_feed = AcquisitionFeed(self._db,
                                        title,
                                        url, [],
                                        VerboseAnnotator,
                                        precomposed_entries=messages)

        return feed_response(addition_feed)
コード例 #9
0
ファイル: controller.py プロジェクト: rskm1/metadata_wrangler
    def add_items(self, collection_details):
        """Adds identifiers to a Collection's catalog"""
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection, ignore = Collection.from_metadata_identifier(
            self._db, collection_details)

        urns = request.args.getlist('urn')
        messages = []
        for urn in urns:
            message = None
            identifier = None
            try:
                identifier, ignore = Identifier.parse_urn(self._db, urn)
            except Exception as e:
                identifier = None

            if not identifier:
                message = OPDSMessage(urn, INVALID_URN.status_code,
                                      INVALID_URN.detail)
            else:
                status = HTTP_OK
                description = "Already in catalog"

                if identifier not in collection.catalog:
                    collection.catalog_identifier(self._db, identifier)
                    status = HTTP_CREATED
                    description = "Successfully added"

                message = OPDSMessage(urn, status, description)

            messages.append(message)

        title = "%s Catalog Item Additions for %s" % (collection.protocol,
                                                      client.url)
        url = cdn_url_for("add",
                          collection_metadata_identifier=collection.name,
                          urn=urns)
        addition_feed = AcquisitionFeed(self._db,
                                        title,
                                        url, [],
                                        VerboseAnnotator,
                                        precomposed_entries=messages)

        return feed_response(addition_feed)
コード例 #10
0
ファイル: controller.py プロジェクト: rskm1/metadata_wrangler
    def remove_items(self, collection_details):
        """Removes identifiers from a Collection's catalog"""
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection, ignore = Collection.from_metadata_identifier(
            self._db, collection_details)

        urns = request.args.getlist('urn')
        messages = []
        for urn in urns:
            message = None
            identifier = None
            try:
                identifier, ignore = Identifier.parse_urn(self._db, urn)
            except Exception as e:
                identifier = None

            if not identifier:
                message = OPDSMessage(urn, INVALID_URN.status_code,
                                      INVALID_URN.detail)
            else:
                if identifier in collection.catalog:
                    collection.catalog.remove(identifier)
                    message = OPDSMessage(urn, HTTP_OK, "Successfully removed")
                else:
                    message = OPDSMessage(urn, HTTP_NOT_FOUND,
                                          "Not in catalog")

            messages.append(message)

        title = "%s Catalog Item Removal for %s" % (collection.protocol,
                                                    client.url)
        url = cdn_url_for("remove",
                          collection_metadata_identifier=collection.name,
                          urn=urns)
        removal_feed = AcquisitionFeed(self._db,
                                       title,
                                       url, [],
                                       VerboseAnnotator,
                                       precomposed_entries=messages)

        return feed_response(removal_feed)
コード例 #11
0
    def updates_feed(self):
        collection = self.authenticated_collection_from_request()
        if isinstance(collection, ProblemDetail):
            return collection

        last_update_time = request.args.get('last_update_time', None)
        if last_update_time:
            last_update_time = datetime.strptime(last_update_time, "%Y-%m-%dT%H:%M:%SZ")
        updated_works = collection.works_updated_since(self._db, last_update_time)

        pagination = load_pagination_from_request()
        works = pagination.apply(updated_works).all()
        title = "%s Updates" % collection.name
        def update_url(time=last_update_time, page=None):
            kw = dict(_external=True)
            if time:
                kw.update({'last_update_time' : last_update_time})
            if page:
                kw.update(page.items())
            return cdn_url_for("updates", **kw)
        update_feed = AcquisitionFeed(
            self._db, title, update_url(), works, VerboseAnnotator
        )

        if len(updated_works.all()) > pagination.size + pagination.offset:
            update_feed.add_link_to_feed(
                update_feed.feed, rel="next", 
                href=update_url(page=pagination.next_page)
            )
        if pagination.offset > 0:
            update_feed.add_link_to_feed(
                update_feed.feed, rel="first", 
                href=update_url(page=pagination.first_page)
            )
        previous_page = pagination.previous_page
        if previous_page:
            update_feed.add_link_to_feed(
                update_feed.feed, rel="previous", 
                href=update_url(page=previous_page)
            )

        return feed_response(update_feed)
コード例 #12
0
    def remove_items(self):
        collection = self.authenticated_collection_from_request()
        if isinstance(collection, ProblemDetail):
            return collection

        urns = request.args.getlist('urn')
        messages = []
        for urn in urns:
            message = None
            identifier = None
            try:
                identifier, ignore = Identifier.parse_urn(self._db, urn)
            except Exception as e:
                identifier = None
            if not identifier:
                message = OPDSMessage(
                    urn, INVALID_URN.status_code, INVALID_URN.detail
                )
            else:
                if identifier in collection.catalog:
                    collection.catalog.remove(identifier)
                    message = OPDSMessage(
                        urn, HTTP_OK, "Successfully removed"
                    )
                else:
                    message = OPDSMessage(
                        urn, HTTP_NOT_FOUND, "Not in collection catalog"
                    )
            if message:
                messages.append(message)

        title = "%s Catalog Item Removal" % collection.name
        url = cdn_url_for("remove", urn=urns)
        removal_feed = AcquisitionFeed(
            self._db, title, url, [], VerboseAnnotator,
            precomposed_entries=messages
        )

        return feed_response(removal_feed)
コード例 #13
0
ファイル: controller.py プロジェクト: rskm1/metadata_wrangler
    def updates_feed(self, collection_details):
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection, ignore = Collection.from_metadata_identifier(
            self._db, collection_details)

        last_update_time = request.args.get('last_update_time', None)
        if last_update_time:
            last_update_time = datetime.strptime(last_update_time,
                                                 "%Y-%m-%dT%H:%M:%SZ")
        updated_works = collection.works_updated_since(self._db,
                                                       last_update_time)

        pagination = load_pagination_from_request()
        works = pagination.apply(updated_works).all()
        title = "%s Collection Updates for %s" % (collection.protocol,
                                                  client.url)

        def update_url(time=last_update_time, page=None):
            kw = dict(_external=True,
                      collection_metadata_identifier=collection_details)
            if time:
                kw.update({'last_update_time': last_update_time})
            if page:
                kw.update(page.items())
            return cdn_url_for("updates", **kw)

        entries = []
        for work in works[:]:
            entry = work.verbose_opds_entry or work.simple_opds_entry
            entry = etree.fromstring(entry)
            if entry:
                entries.append(entry)
                works.remove(work)

        works = [(work.identifier, work) for work in works]

        update_feed = LookupAcquisitionFeed(self._db,
                                            title,
                                            update_url(),
                                            works,
                                            VerboseAnnotator,
                                            precomposed_entries=entries)

        if len(updated_works.all()) > pagination.size + pagination.offset:
            update_feed.add_link_to_feed(
                update_feed.feed,
                rel="next",
                href=update_url(page=pagination.next_page))
        if pagination.offset > 0:
            update_feed.add_link_to_feed(
                update_feed.feed,
                rel="first",
                href=update_url(page=pagination.first_page))
        previous_page = pagination.previous_page
        if previous_page:
            update_feed.add_link_to_feed(update_feed.feed,
                                         rel="previous",
                                         href=update_url(page=previous_page))

        return feed_response(update_feed)
コード例 #14
0
    def add_with_metadata(self, collection_details):
        """Adds identifiers with their metadata to a Collection's catalog"""
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(
            self._db, client, collection_details
        )

        data_source = DataSource.lookup(
            self._db, collection.name, autocreate=True
        )

        messages = []

        feed = feedparser.parse(request.data)
        entries = feed.get("entries", [])
        entries_by_urn = { entry.get('id') : entry for entry in entries }

        identifiers_by_urn, invalid_urns = Identifier.parse_urns(
            self._db, entries_by_urn.keys()
        )

        messages = list()

        for urn in invalid_urns:
            messages.append(OPDSMessage(
                urn, INVALID_URN.status_code, INVALID_URN.detail
            ))


        for urn, identifier in identifiers_by_urn.items():
            entry = entries_by_urn[urn]
            status = HTTP_OK
            description = "Already in catalog"

            if identifier not in collection.catalog:
                collection.catalog_identifier(identifier)
                status = HTTP_CREATED
                description = "Successfully added"

            message = OPDSMessage(urn, status, description)

            # Get a cover if it exists.
            image_types = set([Hyperlink.IMAGE, Hyperlink.THUMBNAIL_IMAGE])
            images = [l for l in entry.get("links", []) if l.get("rel") in image_types]
            links = [LinkData(image.get("rel"), image.get("href")) for image in images]

            # Create an edition to hold the title and author. LicensePool.calculate_work
            # refuses to create a Work when there's no title, and if we have a title, author
            # and language we can attempt to look up the edition in OCLC.
            title = entry.get("title") or "Unknown Title"
            author = ContributorData(
                sort_name=(entry.get("author") or Edition.UNKNOWN_AUTHOR),
                roles=[Contributor.PRIMARY_AUTHOR_ROLE]
            )
            language = entry.get("dcterms_language")

            presentation = PresentationCalculationPolicy(
                choose_edition=False,
                set_edition_metadata=False,
                classify=False,
                choose_summary=False,
                calculate_quality=False,
                choose_cover=False,
                regenerate_opds_entries=False,
            )
            replace = ReplacementPolicy(presentation_calculation_policy=presentation)
            metadata = Metadata(
                data_source,
                primary_identifier=IdentifierData(identifier.type, identifier.identifier),
                title=title,
                language=language,
                contributors=[author],
                links=links,
            )

            edition, ignore = metadata.edition(self._db)
            metadata.apply(edition, collection, replace=replace)

            messages.append(message)

        title = "%s Catalog Item Additions for %s" % (collection.protocol, client.url)
        url = self.collection_feed_url("add_with_metadata", collection)
        addition_feed = AcquisitionFeed(
            self._db, title, url, [], VerboseAnnotator,
            precomposed_entries=messages
        )

        return feed_response(addition_feed)
コード例 #15
0
    def add_with_metadata(self, collection_details):
        """Adds identifiers with their metadata to a Collection's catalog"""
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(self._db, client,
                                             collection_details)

        data_source = DataSource.lookup(self._db,
                                        collection.name,
                                        autocreate=True)

        messages = []

        feed = feedparser.parse(request.data)
        entries = feed.get("entries", [])
        entries_by_urn = {entry.get('id'): entry for entry in entries}

        identifiers_by_urn, invalid_urns = Identifier.parse_urns(
            self._db, entries_by_urn.keys())

        messages = list()

        for urn in invalid_urns:
            messages.append(
                OPDSMessage(urn, INVALID_URN.status_code, INVALID_URN.detail))

        for urn, identifier in identifiers_by_urn.items():
            entry = entries_by_urn[urn]
            status = HTTP_OK
            description = "Already in catalog"

            if identifier not in collection.catalog:
                collection.catalog_identifier(identifier)
                status = HTTP_CREATED
                description = "Successfully added"

            message = OPDSMessage(urn, status, description)

            # Get a cover if it exists.
            image_types = set([Hyperlink.IMAGE, Hyperlink.THUMBNAIL_IMAGE])
            images = [
                l for l in entry.get("links", [])
                if l.get("rel") in image_types
            ]
            links = [
                LinkData(image.get("rel"), image.get("href"))
                for image in images
            ]

            # Create an edition to hold the title and author. LicensePool.calculate_work
            # refuses to create a Work when there's no title, and if we have a title, author
            # and language we can attempt to look up the edition in OCLC.
            title = entry.get("title") or "Unknown Title"
            author = ContributorData(sort_name=(entry.get("author")
                                                or Edition.UNKNOWN_AUTHOR),
                                     roles=[Contributor.PRIMARY_AUTHOR_ROLE])
            language = entry.get("dcterms_language")

            presentation = PresentationCalculationPolicy(
                choose_edition=False,
                set_edition_metadata=False,
                classify=False,
                choose_summary=False,
                calculate_quality=False,
                choose_cover=False,
                regenerate_opds_entries=False,
            )
            replace = ReplacementPolicy(
                presentation_calculation_policy=presentation)
            metadata = Metadata(
                data_source,
                primary_identifier=IdentifierData(identifier.type,
                                                  identifier.identifier),
                title=title,
                language=language,
                contributors=[author],
                links=links,
            )

            edition, ignore = metadata.edition(self._db)
            metadata.apply(edition, collection, replace=replace)

            messages.append(message)

        title = "%s Catalog Item Additions for %s" % (collection.protocol,
                                                      client.url)
        url = self.collection_feed_url("add_with_metadata", collection)
        addition_feed = AcquisitionFeed(self._db,
                                        title,
                                        url, [],
                                        VerboseAnnotator,
                                        precomposed_entries=messages)

        return feed_response(addition_feed)
コード例 #16
0
class CatalogController(object):
    """A controller to manage a Collection's catalog"""

    log = logging.getLogger("Catalog Controller")

    # Setting a default updates feed size lower than the Pagination.DEFAULT_SIZE
    # of 50. Because the updates feed paginates works and isbns separately,
    # this not-quite-half should keep the feed at about the expected size
    # overall without impacting non-ISBN collections too much.
    UPDATES_SIZE = 35

    TIMESTAMP_FORMAT = "%Y-%m-%dT%H:%M:%SZ"

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

    @classmethod
    def collection_feed_url(cls,
                            endpoint,
                            collection,
                            page=None,
                            **param_kwargs):
        kw = dict(_external=True,
                  collection_metadata_identifier=collection.name)
        kw.update(param_kwargs)
        if page:
            kw.update(page.items())
        return cdn_url_for(endpoint, **kw)

    @classmethod
    def add_pagination_links_to_feed(cls, pagination, query, feed, endpoint,
                                     collection, **url_param_kwargs):
        """Adds links for pagination to a given collection's feed."""
        def href_for(page):
            return cls.collection_feed_url(endpoint,
                                           collection,
                                           page=page,
                                           **url_param_kwargs)

        if fast_query_count(query) > (pagination.size + pagination.offset):
            feed.add_link_to_feed(feed.feed,
                                  rel="next",
                                  href=href_for(pagination.next_page))

        if pagination.offset > 0:
            feed.add_link_to_feed(feed.feed,
                                  rel="first",
                                  href=href_for(pagination.first_page))

        previous_page = pagination.previous_page
        if previous_page:
            feed.add_link_to_feed(feed.feed,
                                  rel="previous",
                                  href=href_for(previous_page))

    def updates_feed(self, collection_details):
        client = authenticated_client_from_request(self._db)
        if isinstance(client, ProblemDetail):
            return client

        collection = collection_from_details(self._db, client,
                                             collection_details)

        last_update_time = request.args.get('last_update_time', None)
        if last_update_time:
            try:
                last_update_time = datetime.strptime(last_update_time,
                                                     self.TIMESTAMP_FORMAT)
            except ValueError, e:
                message = 'The timestamp "%s" is not in the expected format (%s)'
                return INVALID_INPUT.detailed(
                    message % (last_update_time, self.TIMESTAMP_FORMAT))

        pagination = load_pagination_from_request(
            default_size=self.UPDATES_SIZE)

        precomposed_entries = []
        # Add entries for Works associated with the collection's catalog.
        updated_works = collection.works_updated_since(self._db,
                                                       last_update_time)
        works = pagination.apply(updated_works).all()
        annotator = VerboseAnnotator()
        works_for_feed = []
        for work, licensepool, identifier in works:
            entry = work.verbose_opds_entry or work.simple_opds_entry
            if entry:
                # A cached OPDS entry for this Work already
                # exists. annotate it with LicensePool and
                # Identifier-specific information. We have to do this
                # ourselves because we're asking LookupAcquisitionFeed
                # to treat these as precomposed entries, meaning
                # they must be complete as-is.
                entry = etree.fromstring(entry)
                annotator.annotate_work_entry(work, licensepool, None,
                                              identifier, None, entry)
                precomposed_entries.append(entry)
            else:
                # There is no cached OPDS entry. We'll create one later.
                works_for_feed.append((work, identifier))

        title = "%s Collection Updates for %s" % (collection.protocol,
                                                  client.url)
        url_params = dict()
        if last_update_time:
            url_params = dict(last_update_time=last_update_time.strftime(
                self.TIMESTAMP_FORMAT))
        url = self.collection_feed_url('updates', collection, **url_params)

        update_feed = LookupAcquisitionFeed(
            self._db,
            title,
            url,
            works_for_feed,
            annotator,
            precomposed_entries=precomposed_entries)

        self.add_pagination_links_to_feed(pagination, updated_works,
                                          update_feed, 'updates', collection,
                                          **url_params)

        return feed_response(update_feed)