get.py

import uuid
import logging

from pylons import config
from pylons.i18n import _
import webhelpers.html
from sqlalchemy.sql import select
from sqlalchemy.orm import aliased
from sqlalchemy import or_, and_, func, desc, case, text

import ckan
import ckan.authz
import ckan.lib.dictization
import ckan.lib.base
import ckan.logic as logic
import ckan.logic.action
import ckan.lib.dictization.model_dictize as model_dictize
import ckan.lib.navl.dictization_functions
import ckan.model.misc as misc
import ckan.plugins as plugins
import ckan.lib.search as search
import ckan.lib.plugins as lib_plugins

log = logging.getLogger('ckan.logic')

# define some shortcuts
validate = ckan.lib.navl.dictization_functions.validate
table_dictize = ckan.lib.dictization.table_dictize
render = ckan.lib.base.render
Authorizer = ckan.authz.Authorizer
check_access = logic.check_access
NotFound = logic.NotFound
ValidationError = logic.ValidationError
get_or_bust = logic.get_or_bust

def _package_list_with_resources(context, package_revision_list):
    package_list = []
    model = context["model"]
    for package in package_revision_list:
        result_dict = model_dictize.package_dictize(package,context)
        package_list.append(result_dict)
    return package_list

def site_read(context,data_dict=None):
    check_access('site_read',context,data_dict)
    return True

def package_list(context, data_dict):
    '''Lists packages by name or id'''

    model = context["model"]
    user = context["user"]
    api = context.get("api_version", 1)
    ref_package_by = 'id' if api == 2 else 'name'

    check_access('package_list', context, data_dict)

    query = model.Session.query(model.PackageRevision)
    query = query.filter(model.PackageRevision.state=='active')
    query = query.filter(model.PackageRevision.current==True)

    packages = query.all()
    return [getattr(p, ref_package_by) for p in packages]

def current_package_list_with_resources(context, data_dict):
    model = context["model"]
    user = context["user"]
    limit = data_dict.get("limit")
    page = int(data_dict.get('page', 1))

    check_access('current_package_list_with_resources', context, data_dict)

    query = model.Session.query(model.PackageRevision)
    query = query.filter(model.PackageRevision.state=='active')
    query = query.filter(model.PackageRevision.current==True)

    query = query.order_by(model.package_revision_table.c.revision_timestamp.desc())
    if limit:
        query = query.limit(int(limit))
        query = query.offset((page-1)*limit)
    pack_rev = query.all()
    return _package_list_with_resources(context, pack_rev)

def revision_list(context, data_dict):

    model = context['model']

    check_access('revision_list', context, data_dict)

    revs = model.Session.query(model.Revision).all()
    return [rev.id for rev in revs]

def package_revision_list(context, data_dict):
    model = context["model"]
    id = data_dict["id"]
    pkg = model.Package.get(id)
    if pkg is None:
        raise NotFound

    check_access('package_revision_list',context, data_dict)

    revision_dicts = []
    for revision, object_revisions in pkg.all_related_revisions:
        revision_dicts.append(model.revision_as_dict(revision,
                                                     include_packages=False,
                                                     include_groups=False))
    return revision_dicts


def related_show(context, data_dict=None):
    """
    Shows a single related item

    context:
        model - The CKAN model module
        user  - The name of the current user

    data_dict:
        id - The ID of the related item we want to show
    """
    model = context['model']
    id = data_dict['id']

    related = model.Related.get(id)
    context['related'] = related

    if related is None:
        raise NotFound

    check_access('related_show',context, data_dict)

    schema = context.get('schema') or ckan.logic.schema.default_related_schema()
    related_dict = model_dictize.related_dictize(related, context)
    related_dict, errors = validate(related_dict, schema, context=context)

    return related_dict


def related_list(context, data_dict=None):
    """
    List the related items for a specific package which should be
    mentioned in the data_dict

    context:
        model - The CKAN model module
        user  - The name of the current user
        session - The current DB session

    data_dict:
        id - The ID of the dataset to which we want to list related items
        or
        dataset - The dataset (package) model
    """
    model = context['model']
    session = context['session']
    dataset = data_dict.get('dataset', None)

    if not dataset:
        dataset = model.Package.get(data_dict.get('id'))

    if not dataset:
        raise NotFound

    check_access('related_show',context, data_dict)

    relateds = model.Related.get_for_dataset(dataset, status='active')
    related_items = (r.related for r in relateds)
    related_list = model_dictize.related_list_dictize( related_items, context)
    return related_list


def member_list(context, data_dict=None):
    """
    Returns a list of (id,type,capacity) tuples that are members of the
    specified group if the user has permission to 'get' the group.

    context:
        model - The CKAN model module
        user  - The name of the current user

    data_dict:
        id - The ID of the group to which we want to list members
        object_type - The optional name of the type being added, all lowercase,
                      e.g. package, or user
        capacity - The optional capacity of objects that we want to retrieve
    """
    model = context['model']
    user = context['user']

    group = model.Group.get(data_dict.get('id',''))
    obj_type = data_dict.get('object_type', None)
    capacity = data_dict.get('capacity', None)

    # User must be able to update the group to remove a member from it
    check_access('group_show', context, data_dict)

    q = model.Session.query(model.Member).\
            filter(model.Member.group_id == group.id).\
            filter(model.Member.state    == "active")

    if obj_type:
        q = q.filter(model.Member.table_name == obj_type)
    if capacity:
        q = q.filter(model.Member.capacity == capacity)

    lookup = {}
    def type_lookup(name):
        if name in lookup:
            return lookup[name]
        if hasattr(model, name.title()):
            lookup[name] = getattr(model,name.title())
            return lookup[name]
        return None

    return [ (m.table_id, type_lookup(m.table_name) ,m.capacity,)
             for m in q.all() ]

def group_list(context, data_dict):
    '''Returns a list of groups'''

    model = context['model']
    user = context['user']
    api = context.get('api_version')
    ref_group_by = 'id' if api == 2 else 'name';
    order_by = data_dict.get('order_by', 'name')
    if order_by not in set(('name', 'packages')):
        raise logic.ParameterError('"order_by" value %r not implemented.' % order_by)
    all_fields = data_dict.get('all_fields',None)

    check_access('group_list',context, data_dict)

    query = model.Session.query(model.Group).join(model.GroupRevision)
    query = query.filter(model.GroupRevision.state=='active')
    query = query.filter(model.GroupRevision.current==True)

    if order_by == 'name':
        sort_by, reverse = 'name', False

    groups = query.all()

    if order_by == 'packages':
        sort_by, reverse = 'packages', True

    group_list = model_dictize.group_list_dictize(groups, context,
                                    lambda x:x[sort_by], reverse)

    if not all_fields:
        group_list = [group[ref_group_by] for group in group_list]

    return group_list

def group_list_authz(context, data_dict):
    '''
    Returns a list of groups which the user is allowed to edit

    If 'available_only' is specified, the existing groups in the package are
    removed.
    '''
    model = context['model']
    user = context['user']
    available_only = data_dict.get('available_only',False)

    check_access('group_list_authz',context, data_dict)

    query = Authorizer().authorized_query(user, model.Group, model.Action.EDIT)
    groups = set(query.all())

    if available_only:
        package = context.get('package')
        if package:
            groups = groups - set(package.get_groups())

    return [{'id':group.id,'name':group.name} for group in groups]

def group_revision_list(context, data_dict):
    model = context['model']
    id = data_dict['id']
    group = model.Group.get(id)
    if group is None:
        raise NotFound

    check_access('group_revision_list',context, data_dict)

    revision_dicts = []
    for revision, object_revisions in group.all_related_revisions:
        revision_dicts.append(model.revision_as_dict(revision,
                                                     include_packages=False,
                                                     include_groups=False))
    return revision_dicts

def licence_list(context, data_dict):
    model = context["model"]

    check_access('licence_list',context, data_dict)

    license_register = model.Package.get_license_register()
    licenses = license_register.values()
    licences = [l.as_dict() for l in licenses]
    return licences

def tag_list(context, data_dict):
    '''Return a list of tag dictionaries.

    If a query is provided in the data_dict with key 'query' or 'q', then only
    tags whose names match the given query will be returned. Otherwise, all
    tags will be returned.

    By default only free tags (tags that don't belong to a vocabulary) are
    returned. If a 'vocabulary_id' is provided in the data_dict then tags
    belonging to the given vocabulary (id or name) will be returned instead.

    '''
    model = context['model']

    vocab_id_or_name = data_dict.get('vocabulary_id')
    query = data_dict.get('query') or data_dict.get('q')
    if query:
        query = query.strip()
    all_fields = data_dict.get('all_fields', None)

    check_access('tag_list', context, data_dict)

    if query:
        tags = _tag_search(context, data_dict)
    else:
        tags = model.Tag.all(vocab_id_or_name)

    tag_list = []
    if tags:
        if all_fields:
            for tag in tags:
                result_dict = model_dictize.tag_dictize(tag, context)
                tag_list.append(result_dict)
        else:
            tag_list.extend([tag.name for tag in tags])

    return tag_list

def user_list(context, data_dict):
    '''Lists the current users'''
    model = context['model']
    user = context['user']

    check_access('user_list',context, data_dict)

    q = data_dict.get('q','')
    order_by = data_dict.get('order_by','name')

    query = model.Session.query(
        model.User,
        model.User.name.label('name'),
        model.User.fullname.label('fullname'),
        model.User.about.label('about'),
        model.User.about.label('email'),
        model.User.created.label('created'),
        select([func.count(model.Revision.id)], or_(
                model.Revision.author==model.User.name,
                model.Revision.author==model.User.openid
                )
        ).label('number_of_edits'),
        select([func.count(model.UserObjectRole.id)], and_(
            model.UserObjectRole.user_id==model.User.id,
            model.UserObjectRole.context=='Package',
            model.UserObjectRole.role=='admin'
            )
        ).label('number_administered_packages')
    )

    if q:
        query = model.User.search(q, query)

    if order_by == 'edits':
        query = query.order_by(desc(
            select([func.count(model.Revision.id)], or_(
                model.Revision.author==model.User.name,
                model.Revision.author==model.User.openid
                ))
        ))
    else:
        query = query.order_by(
            case([(or_(model.User.fullname == None, model.User.fullname == ''),
                   model.User.name)],
                 else_=model.User.fullname)
        )

    ## hack for pagination
    if context.get('return_query'):
        return query

    users_list = []

    for user in query.all():
        result_dict = model_dictize.user_dictize(user[0], context)
        del result_dict['apikey']
        users_list.append(result_dict)

    return users_list

def package_relationships_list(context, data_dict):

    ##TODO needs to work with dictization layer
    model = context['model']
    user = context['user']
    api = context.get('api_version')

    id = data_dict["id"]
    id2 = data_dict.get("id2")
    rel = data_dict.get("rel")
    ref_package_by = 'id' if api == 2 else 'name';
    pkg1 = model.Package.get(id)
    pkg2 = None
    if not pkg1:
        raise NotFound('First package named in request was not found.')
    if id2:
        pkg2 = model.Package.get(id2)
        if not pkg2:
            raise NotFound('Second package named in address was not found.')

    if rel == 'relationships':
        rel = None

    check_access('package_relationships_list',context, data_dict)

    # TODO: How to handle this object level authz?
    relationships = Authorizer().\
                    authorized_package_relationships(\
                    user, pkg1, pkg2, rel, model.Action.READ)

    if rel and not relationships:
        raise NotFound('Relationship "%s %s %s" not found.'
                                 % (id, rel, id2))

    relationship_dicts = [rel.as_dict(pkg1, ref_package_by=ref_package_by)
                          for rel in relationships]

    return relationship_dicts

def package_show(context, data_dict):

    model = context['model']
    context['session'] = model.Session
    name_or_id = data_dict.get("id") or data_dict['name_or_id']

    pkg = model.Package.get(name_or_id)

    if pkg is None:
        raise NotFound

    context['package'] = pkg

    check_access('package_show', context, data_dict)

    package_dict = model_dictize.package_dictize(pkg, context)

    for item in plugins.PluginImplementations(plugins.IPackageController):
        item.read(pkg)

    package_plugin = lib_plugins.lookup_package_plugin(package_dict['type'])
    try:
        schema = package_plugin.db_to_form_schema_options({
            'type':'show',
            'api': 'api_version' in context,
            'context': context })
    except AttributeError:
        schema = package_plugin.db_to_form_schema()

    if schema and context.get('validate', True):
        package_dict, errors = validate(package_dict, schema, context=context)

    return package_dict

def resource_show(context, data_dict):
    model = context['model']
    id = data_dict['id']

    resource = model.Resource.get(id)
    context['resource'] = resource

    if not resource:
        raise NotFound

    check_access('resource_show', context, data_dict)
    return model_dictize.resource_dictize(resource, context)

def resource_status_show(context, data_dict):

    try:
        import ckan.lib.celery_app as celery_app
    except ImportError:
        return {'message': 'queue is not installed on this instance'}

    model = context['model']
    id = get_or_bust(data_dict, 'id')

    check_access('resource_status_show', context, data_dict)

    # needs to be text query as celery tables are not in our model
    q = text("""select status, date_done, traceback, task_status.*
                from task_status left join celery_taskmeta
                on task_status.value = celery_taskmeta.task_id and key = 'celery_task_id'
                where entity_id = :entity_id """)

    result = model.Session.connection().execute(q, entity_id=id)
    result_list = [table_dictize(row, context) for row in result]

    return result_list


def revision_show(context, data_dict):
    model = context['model']
    api = context.get('api_version')
    id = data_dict['id']
    ref_package_by = 'id' if api == 2 else 'name'

    rev = model.Session.query(model.Revision).get(id)
    if rev is None:
        raise NotFound
    rev_dict = model.revision_as_dict(rev, include_packages=True,
                                      ref_package_by=ref_package_by)
    return rev_dict

def group_show(context, data_dict):
    '''Shows group details'''
    model = context['model']
    id = data_dict['id']

    group = model.Group.get(id)
    context['group'] = group

    if group is None:
        raise NotFound

    check_access('group_show',context, data_dict)

    group_dict = model_dictize.group_dictize(group, context)

    for item in plugins.PluginImplementations(plugins.IGroupController):
        item.read(group)

    group_plugin = lib_plugins.lookup_group_plugin(group_dict['type'])
    try:
        schema = group_plugin.db_to_form_schema_options({
            'type':'show',
            'api': 'api_version' in context,
            'context': context })
    except AttributeError:
        schema = group_plugin.db_to_form_schema()

    if schema:
        package_dict, errors = validate(group_dict, schema, context=context)

    return group_dict

def group_package_show(context, data_dict):
    """
    Shows all packages belonging to a group.
    """
    model = context["model"]
    user = context["user"]
    id = data_dict['id']
    limit = data_dict.get("limit")

    group = model.Group.get(id)
    context['group'] = group
    if group is None:
        raise NotFound

    check_access('group_show', context, data_dict)

    query = model.Session.query(model.PackageRevision)\
        .filter(model.PackageRevision.state=='active')\
        .filter(model.PackageRevision.current==True)\
        .join(model.Member, model.Member.table_id==model.PackageRevision.id)\
        .join(model.Group, model.Group.id==model.Member.group_id)\
        .filter_by(id=group.id)\
        .order_by(model.PackageRevision.name)

    if limit:
        query = query.limit(limit)

    if context.get('return_query'):
        return query

    result = []
    for pkg_rev in query.all():
        result.append(model_dictize.package_dictize(pkg_rev, context))

    return result

def tag_show(context, data_dict):
    '''Shows tag details'''

    model = context['model']
    id = data_dict['id']

    tag = model.Tag.get(id)
    context['tag'] = tag

    if tag is None:
        raise NotFound

    check_access('tag_show',context, data_dict)

    tag_dict = model_dictize.tag_dictize(tag,context)

    extended_packages = []
    for package in tag_dict['packages']:
        pkg = model.Package.get(package['id'])
        extended_packages.append(model_dictize.package_dictize(pkg,context))

    tag_dict['packages'] = extended_packages

    return tag_dict

def user_show(context, data_dict):
    '''Shows user details'''
    model = context['model']
    user = context['user']

    id = data_dict.get('id',None)
    provided_user = data_dict.get('user_obj',None)
    if id:
        user_obj = model.User.get(id)
        context['user_obj'] = user_obj
        if user_obj is None:
            raise NotFound
    elif provided_user:
        context['user_obj'] = user_obj = provided_user
    else:
        raise NotFound

    check_access('user_show',context, data_dict)

    user_dict = model_dictize.user_dictize(user_obj,context)

    if not (Authorizer().is_sysadmin(unicode(user)) or user == user_obj.name):
        # If not sysadmin or the same user, strip sensible info
        del user_dict['apikey']
        del user_dict['reset_key']

    revisions_q = model.Session.query(model.Revision
            ).filter_by(author=user_obj.name)

    revisions_list = []
    for revision in revisions_q.limit(20).all():
        revision_dict = revision_show(context,{'id':revision.id})
        revision_dict['state'] = revision.state
        revisions_list.append(revision_dict)
    user_dict['activity'] = revisions_list

    user_dict['datasets'] = []
    dataset_q = model.Session.query(model.Package).join(model.PackageRole
            ).filter_by(user=user_obj, role=model.Role.ADMIN
            ).limit(50)

    for dataset in dataset_q:
        try:
            dataset_dict = package_show(context, {'id': dataset.id})
        except logic.NotAuthorized:
            continue
        user_dict['datasets'].append(dataset_dict)

    return user_dict

def package_show_rest(context, data_dict):

    check_access('package_show_rest',context, data_dict)

    logic.get_action('package_show')(context, data_dict)

    pkg = context['package']

    package_dict = model_dictize.package_to_api(pkg, context)

    return package_dict

def group_show_rest(context, data_dict):

    check_access('group_show_rest',context, data_dict)

    logic.get_action('group_show')(context, data_dict)
    group = context['group']

    group_dict = model_dictize.group_to_api(group, context)

    return group_dict

def tag_show_rest(context, data_dict):

    check_access('tag_show_rest',context, data_dict)

    logic.get_action('tag_show')(context, data_dict)
    tag = context['tag']

    tag_dict = model_dictize.tag_to_api(tag, context)

    return tag_dict

def package_autocomplete(context, data_dict):
    '''Returns packages containing the provided string in either the name
    or the title'''

    model = context['model']
    session = context['session']
    user = context['user']
    q = data_dict['q']

    like_q = u"%s%%" % q

    check_access('package_autocomplete', context, data_dict)

    query = model.Session.query(model.PackageRevision)
    query = query.filter(model.PackageRevision.state=='active')
    query = query.filter(model.PackageRevision.current==True)
    query = query.filter(or_(model.PackageRevision.name.ilike(like_q),
                                model.PackageRevision.title.ilike(like_q)))
    query = query.limit(10)

    q_lower = q.lower()
    pkg_list = []
    for package in query:
        if package.name.startswith(q_lower):
            match_field = 'name'
            match_displayed = package.name
        else:
            match_field = 'title'
            match_displayed = '%s (%s)' % (package.title, package.name)
        result_dict = {'name':package.name, 'title':package.title,
                       'match_field':match_field, 'match_displayed':match_displayed}
        pkg_list.append(result_dict)

    return pkg_list

def format_autocomplete(context, data_dict):
    '''Returns formats containing the provided string'''
    model = context['model']
    session = context['session']
    user = context['user']

    check_access('format_autocomplete', context, data_dict)

    q = data_dict.get('q', None)
    if not q:
        return []

    limit = data_dict.get('limit', 5)
    like_q = u'%' + q + u'%'

    query = session.query(model.ResourceRevision.format,
        func.count(model.ResourceRevision.format).label('total'))\
        .filter(and_(
            model.ResourceRevision.state == 'active',
            model.ResourceRevision.current == True
        ))\
        .filter(model.ResourceRevision.format.ilike(like_q))\
        .group_by(model.ResourceRevision.format)\
        .order_by('total DESC')\
        .limit(limit)

    return [resource.format.lower() for resource in query]

def user_autocomplete(context, data_dict):
    '''Returns users containing the provided string'''
    model = context['model']
    session = context['session']
    user = context['user']
    q = data_dict.get('q',None)
    if not q:
        return []

    check_access('user_autocomplete', context, data_dict)

    limit = data_dict.get('limit',20)

    query = model.User.search(q).limit(limit)

    user_list = []
    for user in query.all():
        result_dict = {}
        for k in ['id', 'name', 'fullname']:
                result_dict[k] = getattr(user,k)

        user_list.append(result_dict)

    return user_list

def package_search(context, data_dict):
    model = context['model']
    session = context['session']
    user = context['user']

    check_access('package_search', context, data_dict)

    # check if some extension needs to modify the search params
    for item in plugins.PluginImplementations(plugins.IPackageController):
        data_dict = item.before_search(data_dict)

    # the extension may have decided that it is not necessary to perform
    # the query
    abort = data_dict.get('abort_search',False)

    results = []
    if not abort:
        # return a list of package ids
        data_dict['fl'] = 'id'

        query = search.query_for(model.Package)
        query.run(data_dict)

        for package in query.results:
            # get the package object
            pkg_query = session.query(model.PackageRevision)\
                .filter(model.PackageRevision.id == package)\
                .filter(and_(
                    model.PackageRevision.state == u'active',
                    model.PackageRevision.current == True
                ))
            pkg = pkg_query.first()

            ## if the index has got a package that is not in ckan then
            ## ignore it.
            if not pkg:
                log.warning('package %s in index but not in database' % package)
                continue

            result_dict = model_dictize.package_dictize(pkg,context)
            results.append(result_dict)

        count = query.count
        facets = query.facets
    else:
        count = 0
        facets = {}
        results = []

    search_results = {
        'count': count,
        'facets': facets,
        'results': results
    }

    # Transform facets into a more useful data structure.
    restructured_facets = {}
    for key, value in search_results['facets'].items():
        restructured_facets[key] = {
                'title': key,
                'items': []
                }
        for key_, value_ in value.items():
            new_facet_dict = {}
            new_facet_dict['name'] = key_
            if key == 'groups':
                group = model.Group.get(key_)
                if group:
                    new_facet_dict['display_name'] = group.display_name
                else:
                    new_facet_dict['display_name'] = key_
            else:
                new_facet_dict['display_name'] = key_
            new_facet_dict['count'] = value_
            restructured_facets[key]['items'].append(new_facet_dict)
    search_results['search_facets'] = restructured_facets

    # check if some extension needs to modify the search results
    for item in plugins.PluginImplementations(plugins.IPackageController):
        search_results = item.after_search(search_results,data_dict)

    # After extensions have had a chance to modify the facets, sort them by
    # display name.
    for facet in search_results['search_facets']:
        search_results['search_facets'][facet]['items'] = sorted(
                search_results['search_facets'][facet]['items'],
                key=lambda facet: facet['display_name'], reverse=True)

    return search_results

def resource_search(context, data_dict):
    model = context['model']
    session = context['session']

    fields = data_dict['fields']
    order_by = data_dict.get('order_by')
    offset = data_dict.get('offset')
    limit = data_dict.get('limit')

    # TODO: should we check for user authentication first?
    q = model.Session.query(model.Resource)
    resource_fields = model.Resource.get_columns()

    for field, terms in fields.items():
        if isinstance(terms, basestring):
            terms = terms.split()
        if field not in resource_fields:
            raise search.SearchError('Field "%s" not recognised in Resource search.' % field)
        for term in terms:
            model_attr = getattr(model.Resource, field)
            if field == 'hash':
                q = q.filter(model_attr.ilike(unicode(term) + '%'))
            elif field in model.Resource.get_extra_columns():
                model_attr = getattr(model.Resource, 'extras')

                like = or_(
                    model_attr.ilike(u'''%%"%s": "%%%s%%",%%''' % (field, term)),
                    model_attr.ilike(u'''%%"%s": "%%%s%%"}''' % (field, term))
                )
                q = q.filter(like)
            else:
                q = q.filter(model_attr.ilike('%' + unicode(term) + '%'))

    if order_by is not None:
        if hasattr(model.Resource, order_by):
            q = q.order_by(getattr(model.Resource, order_by))

    count = q.count()
    q = q.offset(offset)
    q = q.limit(limit)

    results = []
    for result in q:
        if isinstance(result, tuple) and isinstance(result[0], model.DomainObject):
            # This is the case for order_by rank due to the add_column.
            results.append(result[0])
        else:
            results.append(result)

    return {'count': count, 'results': results}

def _tag_search(context, data_dict):
    '''Return a list of tag objects that contain the given string.

    The query string should be provided in the data_dict with key 'query' or
    'q'.

    By default only free tags (tags that don't belong to a vocabulary) are
    searched. If a 'vocabulary_id' is provided in the data_dict then tags
    belonging to the given vocabulary (id or name) will be searched instead.

    '''
    model = context['model']

    query = data_dict.get('query') or data_dict.get('q')
    if query:
        query = query.strip()
    terms = [query] if query else []

    fields = data_dict.get('fields', {})
    offset = data_dict.get('offset')
    limit = data_dict.get('limit')

    # TODO: should we check for user authentication first?
    q = model.Session.query(model.Tag)

    if data_dict.has_key('vocabulary_id'):
        # Filter by vocabulary.
        vocab = model.Vocabulary.get(data_dict['vocabulary_id'])
        if not vocab:
            raise NotFound
        q = q.filter(model.Tag.vocabulary_id == vocab.id)
    else:
        # If no vocabulary_name in data dict then show free tags only.
        q = q.filter(model.Tag.vocabulary_id == None)
        # If we're searching free tags, limit results to tags that are
        # currently applied to a package.
        q = q.distinct().join(model.Tag.package_tags)

    for field, value in fields.items():
        if field in ('tag', 'tags'):
            terms.append(value)

    if not len(terms):
        return []

    for term in terms:
        escaped_term = misc.escape_sql_like_special_characters(term, escape='\\')
        q = q.filter(model.Tag.name.ilike('%' + escaped_term + '%'))

    q = q.offset(offset)
    q = q.limit(limit)
    return q.all()

def tag_search(context, data_dict):
    '''Return a list of tag dictionaries that contain the given string.

    The query string should be provided in the data_dict with key 'query' or
    'q'.

    By default only free tags (tags that don't belong to a vocabulary) are
    searched. If a 'vocabulary_id' is provided in the data_dict then tags
    belonging to the given vocabulary (id or name) will be searched instead.

    Returns a dictionary with keys 'count' (the number of tags in the result)
    and 'results' (the list of tag dicts).

    '''
    tags = _tag_search(context, data_dict)
    return {'count': len(tags),
            'results': [table_dictize(tag, context) for tag in tags]}

def tag_autocomplete(context, data_dict):
    '''Return a list of tag names that contain the given string.

    The query string should be provided in the data_dict with key 'query' or
    'q'.

    By default only free tags (tags that don't belong to a vocabulary) are
    searched. If a 'vocabulary_id' is provided in the data_dict then tags
    belonging to the given vocabulary (id or name) will be searched instead.

    '''
    check_access('tag_autocomplete', context, data_dict)
    matching_tags = _tag_search(context, data_dict)
    if matching_tags:
        return [tag.name for tag in matching_tags]
    else:
        return []

def task_status_show(context, data_dict):
    model = context['model']
    id = data_dict.get('id')

    if id:
        task_status = model.TaskStatus.get(id)
    else:
        query = model.Session.query(model.TaskStatus)\
            .filter(and_(
                model.TaskStatus.entity_id == data_dict['entity_id'],
                model.TaskStatus.task_type == data_dict['task_type'],
                model.TaskStatus.key == data_dict['key']
            ))
        task_status = query.first()

    context['task_status'] = task_status

    if task_status is None:
        raise NotFound

    check_access('task_status_show', context, data_dict)

    task_status_dict = model_dictize.task_status_dictize(task_status, context)
    return task_status_dict


def term_translation_show(context, data_dict):
    model = context['model']

    trans_table = model.term_translation_table

    q = select([trans_table])

    if 'terms' not in data_dict:
        raise ValidationError({'terms': 'terms not in data'})

    q = q.where(trans_table.c.term.in_(data_dict['terms']))

    if 'lang_codes' in data_dict:
        q = q.where(trans_table.c.lang_code.in_(data_dict['lang_codes']))

    conn = model.Session.connection()
    cursor = conn.execute(q)

    results = []

    for row in cursor:
        results.append(table_dictize(row, context))

    return results

def get_site_user(context, data_dict):
    check_access('get_site_user', context, data_dict)
    model = context['model']
    site_id = config.get('ckan.site_id', 'ckan_site_user')
    user = model.User.get(site_id)
    if not user:
        apikey = str(uuid.uuid4())
        user = model.User(name=site_id,
                          password=apikey,
                          apikey=apikey)
        model.add_user_to_role(user, model.Role.ADMIN, model.System())
        model.Session.add(user)
        model.Session.flush()
        if not context.get('defer_commit'):
            model.Session.commit()
    return {'name': user.name,
            'apikey': user.apikey}

def roles_show(context, data_dict):
    '''Returns the roles that users (and authorization groups) have on a
    particular domain_object.

    If you specify a user (or authorization group) then the resulting roles
    will be filtered by those of that user (or authorization group).

    domain_object can be a package/group/authorization_group name or id.
    '''
    model = context['model']
    session = context['session']
    domain_object_ref = data_dict['domain_object']
    user_ref = data_dict.get('user')
    authgroup_ref = data_dict.get('authorization_group')

    domain_object = ckan.logic.action.get_domain_object(model, domain_object_ref)
    if isinstance(domain_object, model.Package):
        query = session.query(model.PackageRole).join('package')
    elif isinstance(domain_object, model.Group):
        query = session.query(model.GroupRole).join('group')
    elif isinstance(domain_object, model.AuthorizationGroup):
        query = session.query(model.AuthorizationGroupRole).join('authorization_group')
    else:
        raise NotFound(_('Cannot list entity of this type: %s') % type(domain_object).__name__)
    # Filter by the domain_obj
    query = query.filter_by(id=domain_object.id)

    # Filter by the user / authorized_group
    if user_ref:
        user = model.User.get(user_ref)
        if not user:
            raise NotFound(_('unknown user:') + repr(user_ref))
        query = query.join('user').filter_by(id=user.id)
    if authgroup_ref:
        authgroup = model.AuthorizationGroup.get(authgroup_ref)
        if not authgroup:
            raise NotFound('unknown authorization group:' + repr(authgroup_ref))
        # we need an alias as we join to model.AuthorizationGroup table twice
        ag = aliased(model.AuthorizationGroup)
        query = query.join(ag, model.AuthorizationGroupRole.authorized_group) \
                .filter_by(id=authgroup.id)

    uors = query.all()

    uors_dictized = [table_dictize(uor, context) for uor in uors]

    result = {'domain_object_type': type(domain_object).__name__,
              'domain_object_id': domain_object.id,
              'roles': uors_dictized}
    if user_ref:
        result['user'] = user.id
    if authgroup_ref:
        result['authorization_group'] = authgroup.id

    return result

def status_show(context, data_dict):
    '''Provides information about the operation of this CKAN instance.'''
    return {
        'site_title': config.get('ckan.site_title'),
        'site_description': config.get('ckan.site_description'),
        'site_url': config.get('ckan.site_url'),
        'ckan_version': ckan.__version__,
        'error_emails_to': config.get('email_to'),
        'locale_default': config.get('ckan.locale_default'),
        'extensions': config.get('ckan.plugins').split(),
        }

def vocabulary_list(context, data_dict):
    model = context['model']
    vocabulary_objects = model.Session.query(model.Vocabulary).all()
    return model_dictize.vocabulary_list_dictize(vocabulary_objects, context)

def vocabulary_show(context, data_dict):
    model = context['model']
    vocab_id = data_dict.get('id')
    if not vocab_id:
        raise ValidationError({'id': _('id not in data')})
    vocabulary = model.vocabulary.Vocabulary.get(vocab_id)
    if vocabulary is None:
        raise NotFound(_('Could not find vocabulary "%s"') % vocab_id)
    vocabulary_dict = model_dictize.vocabulary_dictize(vocabulary, context)
    return vocabulary_dict

def user_activity_list(context, data_dict):
    '''Return a user\'s public activity stream as a list of dicts.'''
    model = context['model']
    user_id = data_dict['id']
    query = model.Session.query(model.Activity)
    query = query.filter_by(user_id=user_id)
    query = query.order_by(desc(model.Activity.timestamp))
    query = query.limit(15)
    activity_objects = query.all()
    return model_dictize.activity_list_dictize(activity_objects, context)

def package_activity_list(context, data_dict):
    '''Return a package\'s public activity stream as a list of dicts.'''
    model = context['model']
    package_id = data_dict['id']
    query = model.Session.query(model.Activity)
    query = query.filter_by(object_id=package_id)
    query = query.order_by(desc(model.Activity.timestamp))
    query = query.limit(15)
    activity_objects = query.all()
    return model_dictize.activity_list_dictize(activity_objects, context)

def group_activity_list(context, data_dict):
    '''Return a group\'s public activity stream as a list of dicts.'''
    model = context['model']
    group_id = data_dict['id']
    query = model.Session.query(model.Activity)
    query = query.filter_by(object_id=group_id)
    query = query.order_by(desc(model.Activity.timestamp))
    query = query.limit(15)
    activity_objects = query.all()
    return model_dictize.activity_list_dictize(activity_objects, context)

def recently_changed_packages_activity_list(context, data_dict):
    '''Return an activity stream of all recently added or updated packages as
    a list of dicts.

    '''
    model = context['model']
    query = model.Session.query(model.Activity)
    query = query.filter(model.Activity.activity_type.endswith('package'))
    query = query.order_by(desc(model.Activity.timestamp))
    query = query.limit(15)
    activity_objects = query.all()
    return model_dictize.activity_list_dictize(activity_objects, context)

def activity_detail_list(context, data_dict):
    '''Return an activity\'s list of activity detail items, as a list of dicts.
    '''
    model = context['model']
    activity_id = data_dict['id']
    activity_detail_objects = model.Session.query(
        model.activity.ActivityDetail).filter_by(activity_id=activity_id).all()
    return model_dictize.activity_detail_list_dictize(activity_detail_objects, context)

def render_new_package_activity(context, activity):
    return render('activity_streams/new_package.html',
        extra_vars = {'activity': activity})

def render_deleted_package_activity(context, activity):
    return render('activity_streams/deleted_package.html',
        extra_vars = {'activity': activity})

def render_new_resource_activity(context, activity, detail):
    return render('activity_streams/new_resource.html',
        extra_vars = {'activity': activity, 'detail': detail})

def render_changed_resource_activity(context, activity, detail):
    return render('activity_streams/changed_resource.html',
        extra_vars = {'activity': activity, 'detail': detail})

def render_deleted_resource_activity(context, activity, detail):
    return render('activity_streams/deleted_resource.html',
        extra_vars = {'activity': activity, 'detail': detail})

def render_added_tag_activity(context, activity, detail):
    return render('activity_streams/added_tag.html',
            extra_vars = {'activity': activity, 'detail': detail})

def render_removed_tag_activity(context, activity, detail):
    return render('activity_streams/removed_tag.html',
            extra_vars = {'activity': activity, 'detail': detail})

def render_new_package_extra_activity(context, activity, detail):
    return render('activity_streams/new_package_extra.html',
        extra_vars = {'activity': activity, 'detail': detail})

def render_changed_package_extra_activity(context, activity, detail):
    return render('activity_streams/changed_package_extra.html',
        extra_vars = {'activity': activity, 'detail': detail})

def render_deleted_package_extra_activity(context, activity, detail):
    return render('activity_streams/deleted_package_extra.html',
        extra_vars = {'activity': activity, 'detail': detail})

def render_changed_package_activity(context, activity):
    details = activity_detail_list(context=context,
        data_dict={'id': activity['id']})

    if len(details) == 1:
        # If an activity has only one activity detail we try to find an
        # activity detail renderer to use instead of rendering the normal
        # 'changed package' template.
        detail = details[0]
        activity_detail_renderers = {
            'Resource': {
              'new': render_new_resource_activity,
              'changed': render_changed_resource_activity,
              'deleted': render_deleted_resource_activity
              },
            'tag': {
              'added': render_added_tag_activity,
              'removed': render_removed_tag_activity,
              },
            'PackageExtra': {
                'new': render_new_package_extra_activity,
                'changed': render_changed_package_extra_activity,
                'deleted': render_deleted_package_extra_activity
              },
            }
        object_type = detail['object_type']
        if activity_detail_renderers.has_key(object_type):
            activity_type = detail['activity_type']
            if activity_detail_renderers[object_type].has_key(activity_type):
                renderer = activity_detail_renderers[object_type][activity_type]
                return renderer(context, activity, detail)

    return render('activity_streams/changed_package.html',
        extra_vars = {'activity': activity})

def render_new_user_activity(context, activity):
    return render('activity_streams/new_user.html',
        extra_vars = {'activity': activity})

def render_changed_user_activity(context, activity):
    return render('activity_streams/changed_user.html',
        extra_vars = {'activity': activity})

def render_new_group_activity(context, activity):
    return render('activity_streams/new_group.html',
        extra_vars = {'activity': activity})

def render_changed_group_activity(context, activity):
    return render('activity_streams/changed_group.html',
        extra_vars = {'activity': activity})

def render_deleted_group_activity(context, activity):
    return render('activity_streams/deleted_group.html',
        extra_vars = {'activity': activity})

# Global dictionary mapping activity types to functions that render activity
# dicts to HTML snippets for including in HTML pages.
activity_renderers = {
  'new package' : render_new_package_activity,
  'changed package' : render_changed_package_activity,
  'deleted package' : render_deleted_package_activity,
  'new user' : render_new_user_activity,
  'changed user' : render_changed_user_activity,
  'new group' : render_new_group_activity,
  'changed group' : render_changed_group_activity,
  'deleted group' : render_deleted_group_activity,
  }

def _activity_list_to_html(context, activity_stream):
    html = []
    for activity in activity_stream:
        activity_type = activity['activity_type']
        if not activity_renderers.has_key(activity_type):
            raise NotImplementedError, ("No activity renderer for activity "
                "type '%s'" % str(activity_type))
        activity_html = activity_renderers[activity_type](context, activity)
        html.append(activity_html)
    return webhelpers.html.literal('\n'.join(html))

def user_activity_list_html(context, data_dict):
    '''Return an HTML rendering of a user\'s public activity stream.

    The activity stream is rendered as a snippet of HTML meant to be included
    in an HTML page.

    '''
    activity_stream = user_activity_list(context, data_dict)
    return _activity_list_to_html(context, activity_stream)

def package_activity_list_html(context, data_dict):
    '''Return an HTML rendering of a package\'s public activity stream.

    The activity stream is rendered as a snippet of HTML meant to be included
    in an HTML page.

    '''
    activity_stream = package_activity_list(context, data_dict)
    return _activity_list_to_html(context, activity_stream)

def group_activity_list_html(context, data_dict):
    '''Return an HTML rendering of a group\'s public activity stream.

    The activity stream is rendered as a snippet of HTML meant to be included
    in an HTML page.

    '''
    activity_stream = group_activity_list(context, data_dict)
    return _activity_list_to_html(context, activity_stream)

def recently_changed_packages_activity_list_html(context, data_dict):
    '''Return an HTML rendering of the activity stream of all recently added
    or updated packages.

    The activity stream is rendered as a snippet of HTML meant to be included
    in an HTML page.

    '''
    activity_stream = recently_changed_packages_activity_list(context,
            data_dict)
    return _activity_list_to_html(context, activity_stream)