api.py

import os.path
import logging
import cgi
import datetime
import glob
import urllib

from pylons import c, request, response
from pylons.i18n import _, gettext
from paste.util.multidict import MultiDict
from webob.multidict import UnicodeMultiDict

import ckan.rating
import ckan.model as model
import ckan.logic as logic
import ckan.lib.base as base
import ckan.lib.helpers as h
import ckan.lib.search as search
import ckan.lib.navl.dictization_functions
import ckan.lib.jsonp as jsonp
import ckan.lib.munge as munge


log = logging.getLogger(__name__)

# shortcuts
get_action = logic.get_action
NotAuthorized = logic.NotAuthorized
NotFound = logic.NotFound
ValidationError = logic.ValidationError
DataError = ckan.lib.navl.dictization_functions.DataError

IGNORE_FIELDS = ['q']
CONTENT_TYPES = {
    'text': 'text/plain;charset=utf-8',
    'html': 'text/html;charset=utf-8',
    'json': 'application/json;charset=utf-8',
}


class ApiController(base.BaseController):

    _actions = {}

    def __call__(self, environ, start_response):
        # we need to intercept and fix the api version
        # as it will have a "/" at the start
        routes_dict = environ['pylons.routes_dict']
        api_version = routes_dict.get('ver')
        if api_version:
            api_version = api_version[1:]
            routes_dict['ver'] = int(api_version)

        self._identify_user()
        try:
            context = {'model': model, 'user': c.user or c.author}
            logic.check_access('site_read', context)
        except NotAuthorized:
            response_msg = self._finish(403,
                                        _('Not authorized to see this page'))
            # Call start_response manually instead of the parent __call__
            # because we want to end the request instead of continuing.
            response_msg = response_msg.encode('utf8')
            body = '%i %s' % (response.status_int, response_msg)
            start_response(body, response.headers.items())
            return [response_msg]

        # avoid status_code_redirect intercepting error responses
        environ['pylons.status_code_redirect'] = True
        return base.BaseController.__call__(self, environ, start_response)

    def _finish(self, status_int, response_data=None,
                content_type='text'):
        '''When a controller method has completed, call this method
        to prepare the response.
        @return response message - return this value from the controller
                                   method
                 e.g. return self._finish(404, 'Package not found')
        '''
        assert(isinstance(status_int, int))
        response.status_int = status_int
        response_msg = ''
        if response_data is not None:
            response.headers['Content-Type'] = CONTENT_TYPES[content_type]
            if content_type == 'json':
                response_msg = h.json.dumps(response_data)
            else:
                response_msg = response_data
            # Support "JSONP" callback.
            if status_int == 200 and 'callback' in request.params and \
                (request.method == 'GET' or
                 c.logic_function and request.method == 'POST'):
                # escape callback to remove '<', '&', '>' chars
                callback = cgi.escape(request.params['callback'])
                response_msg = self._wrap_jsonp(callback, response_msg)
        return response_msg

    def _finish_ok(self, response_data=None,
                   content_type='json',
                   resource_location=None):
        '''If a controller method has completed successfully then
        calling this method will prepare the response.
        @param resource_location - specify this if a new
           resource has just been created.
        @return response message - return this value from the controller
                                   method
                                   e.g. return self._finish_ok(pkg_dict)
        '''
        if resource_location:
            status_int = 201
            self._set_response_header('Location', resource_location)
        else:
            status_int = 200

        return self._finish(status_int, response_data, content_type)

    def _finish_not_authz(self):
        response_data = _('Access denied')
        return self._finish(403, response_data, 'json')

    def _finish_not_found(self, extra_msg=None):
        response_data = _('Not found')
        if extra_msg:
            response_data = '%s - %s' % (response_data, extra_msg)
        return self._finish(404, response_data, 'json')

    def _finish_bad_request(self, extra_msg=None):
        response_data = _('Bad request')
        if extra_msg:
            response_data = '%s - %s' % (response_data, extra_msg)
        return self._finish(400, response_data, 'json')

    def _wrap_jsonp(self, callback, response_msg):
        return '%s(%s);' % (callback, response_msg)

    def _set_response_header(self, name, value):
        try:
            value = str(value)
        except Exception, inst:
            msg = "Couldn't convert '%s' header value '%s' to string: %s" % \
                (name, value, inst)
            raise Exception(msg)
        response.headers[name] = value

    def get_api(self, ver=None):
        response_data = {}
        response_data['version'] = ver
        return self._finish_ok(response_data)

    def snippet(self, snippet_path, ver=None):
        ''' Renders and returns a snippet used by ajax calls '''
        # we only allow snippets in templates/ajax_snippets and it's subdirs
        snippet_path = u'ajax_snippets/' + snippet_path
        return base.render(snippet_path, extra_vars=dict(request.params))

    def action(self, logic_function, ver=None):
        try:
            function = get_action(logic_function)
        except KeyError:
            log.error('Can\'t find logic function: %s' % logic_function)
            return self._finish_bad_request(
                gettext('Action name not known: %s') % str(logic_function))

        context = {'model': model, 'session': model.Session, 'user': c.user,
                   'api_version': ver}
        model.Session()._context = context
        return_dict = {'help': function.__doc__}
        try:
            side_effect_free = getattr(function, 'side_effect_free', False)
            request_data = self._get_request_data(try_url_params=
                                                  side_effect_free)
        except ValueError, inst:
            log.error('Bad request data: %s' % str(inst))
            return self._finish_bad_request(
                gettext('JSON Error: %s') % str(inst))
        if not isinstance(request_data, dict):
            # this occurs if request_data is blank
            log.error('Bad request data - not dict: %r' % request_data)
            return self._finish_bad_request(
                gettext('Bad request data: %s') %
                'Request data JSON decoded to %r but '
                'it needs to be a dictionary.' % request_data)
        try:
            result = function(context, request_data)
            return_dict['success'] = True
            return_dict['result'] = result
        except DataError, e:
            log.error('Format incorrect: %s - %s' % (e.error, request_data))
            #TODO make better error message
            return self._finish(400, _(u'Integrity Error') +
                                ': %s - %s' % (e.error, request_data))
        except NotAuthorized:
            return_dict['error'] = {'__type': 'Authorization Error',
                                    'message': _('Access denied')}
            return_dict['success'] = False
            return self._finish(403, return_dict, content_type='json')
        except NotFound, e:
            return_dict['error'] = {'__type': 'Not Found Error',
                                    'message': _('Not found')}
            if e.extra_msg:
                return_dict['error']['message'] += ': %s' % e.extra_msg
            return_dict['success'] = False
            return self._finish(404, return_dict, content_type='json')
        except ValidationError, e:
            error_dict = e.error_dict
            error_dict['__type'] = 'Validation Error'
            return_dict['error'] = error_dict
            return_dict['success'] = False
            log.error('Validation error: %r' % str(e.error_dict))
            return self._finish(409, return_dict, content_type='json')
        except logic.ParameterError, e:
            return_dict['error'] = {'__type': 'Parameter Error',
                                    'message': '%s: %s' %
                                    (_('Parameter Error'), e.extra_msg)}
            return_dict['success'] = False
            log.error('Parameter error: %r' % e.extra_msg)
            return self._finish(409, return_dict, content_type='json')
        except search.SearchQueryError, e:
            return_dict['error'] = {'__type': 'Search Query Error',
                                    'message': 'Search Query is invalid: %r' %
                                    e.args}
            return_dict['success'] = False
            return self._finish(400, return_dict, content_type='json')
        except search.SearchError, e:
            return_dict['error'] = {'__type': 'Search Error',
                                    'message': 'Search error: %r' % e.args}
            return_dict['success'] = False
            return self._finish(409, return_dict, content_type='json')
        return self._finish_ok(return_dict)

    def _get_action_from_map(self, action_map, register, subregister):
        ''' Helper function to get the action function specified in
            the action map'''

        # translate old package calls to use dataset
        if register == 'package':
            register = 'dataset'

        action = action_map.get((register, subregister))
        if not action:
            action = action_map.get(register)
        if action:
            return get_action(action)

    def list(self, ver=None, register=None, subregister=None, id=None):
        context = {'model': model, 'session': model.Session,
                   'user': c.user, 'api_version': ver}
        log.debug('listing: %s' % context)
        action_map = {
            'revision': 'revision_list',
            'group': 'group_list',
            'dataset': 'package_list',
            'tag': 'tag_list',
            'related': 'related_list',
            'licenses': 'licence_list',
            ('dataset', 'relationships'): 'package_relationships_list',
            ('dataset', 'revisions'): 'package_revision_list',
            ('dataset', 'activity'): 'package_activity_list',
            ('group', 'activity'): 'group_activity_list',
            ('user', 'activity'): 'user_activity_list',
            ('user', 'dashboard_activity'): 'dashboard_activity_list',
            ('activity', 'details'): 'activity_detail_list',
        }

        action = self._get_action_from_map(action_map, register, subregister)
        if not action:
            return self._finish_bad_request(
                gettext('Cannot list entity of this type: %s') % register)
        try:
            return self._finish_ok(action(context, {'id': id}))
        except NotFound, e:
            extra_msg = e.extra_msg
            return self._finish_not_found(extra_msg)
        except NotAuthorized:
            return self._finish_not_authz()

    def show(self, ver=None, register=None, subregister=None,
             id=None, id2=None):
        action_map = {
            'revision': 'revision_show',
            'group': 'group_show_rest',
            'tag': 'tag_show_rest',
            'related': 'related_show',
            'dataset': 'package_show_rest',
            ('dataset', 'relationships'): 'package_relationships_list',
        }
        for type in model.PackageRelationship.get_all_types():
            action_map[('dataset', type)] = 'package_relationships_list'

        context = {'model': model, 'session': model.Session, 'user': c.user,
                   'api_version': ver}
        data_dict = {'id': id, 'id2': id2, 'rel': subregister}

        log.debug('show: %s' % context)

        action = self._get_action_from_map(action_map, register, subregister)
        if not action:
            return self._finish_bad_request(
                gettext('Cannot read entity of this type: %s') % register)
        try:
            return self._finish_ok(action(context, data_dict))
        except NotFound, e:
            extra_msg = e.extra_msg
            return self._finish_not_found(extra_msg)
        except NotAuthorized:
            return self._finish_not_authz()

    def _represent_package(self, package):
        return package.as_dict(ref_package_by=self.ref_package_by,
                               ref_group_by=self.ref_group_by)

    def create(self, ver=None, register=None, subregister=None,
               id=None, id2=None):

        action_map = {
            'group': 'group_create_rest',
            'dataset': 'package_create_rest',
            'rating': 'rating_create',
            'related': 'related_create',
            ('dataset', 'relationships'): 'package_relationship_create_rest',
        }
        for type in model.PackageRelationship.get_all_types():
            action_map[('dataset', type)] = 'package_relationship_create_rest'

        context = {'model': model, 'session': model.Session, 'user': c.user,
                   'api_version': ver}
        log.debug('create: %s' % (context))
        try:
            request_data = self._get_request_data()
            data_dict = {'id': id, 'id2': id2, 'rel': subregister}
            data_dict.update(request_data)
        except ValueError, inst:
            return self._finish_bad_request(
                gettext('JSON Error: %s') % str(inst))

        action = self._get_action_from_map(action_map, register, subregister)
        if not action:
            return self._finish_bad_request(
                gettext('Cannot create new entity of this type: %s %s') %
                (register, subregister))

        try:
            response_data = action(context, data_dict)
            location = None
            if "id" in data_dict:
                location = str('%s/%s' % (request.path.replace('package',
                                                               'dataset'),
                                          data_dict.get("id")))
            return self._finish_ok(response_data,
                                   resource_location=location)
        except NotAuthorized:
            return self._finish_not_authz()
        except NotFound, e:
            extra_msg = e.extra_msg
            return self._finish_not_found(extra_msg)
        except ValidationError, e:
            log.error('Validation error: %r' % str(e.error_dict))
            return self._finish(409, e.error_dict, content_type='json')
        except DataError, e:
            log.error('Format incorrect: %s - %s' % (e.error, request_data))
            #TODO make better error message
            return self._finish(400, _(u'Integrity Error') +
                                ': %s - %s' % (e.error, request_data))
        except search.SearchIndexError:
            log.error('Unable to add package to search index: %s' %
                      request_data)
            return self._finish(500,
                                _(u'Unable to add package to search index') %
                                request_data)
        except:
            model.Session.rollback()
            raise

    def update(self, ver=None, register=None, subregister=None,
               id=None, id2=None):
        action_map = {
            'dataset': 'package_update_rest',
            'group': 'group_update_rest',
            ('dataset', 'relationships'): 'package_relationship_update_rest',
        }
        for type in model.PackageRelationship.get_all_types():
            action_map[('dataset', type)] = 'package_relationship_update_rest'

        context = {'model': model, 'session': model.Session, 'user': c.user,
                   'api_version': ver, 'id': id}
        log.debug('update: %s' % (context))
        try:
            request_data = self._get_request_data()
            data_dict = {'id': id, 'id2': id2, 'rel': subregister}
            data_dict.update(request_data)
        except ValueError, inst:
            return self._finish_bad_request(
                gettext('JSON Error: %s') % str(inst))

        action = self._get_action_from_map(action_map, register, subregister)
        if not action:
            return self._finish_bad_request(
                gettext('Cannot update entity of this type: %s') %
                register.encode('utf-8'))
        try:
            response_data = action(context, data_dict)
            return self._finish_ok(response_data)
        except NotAuthorized:
            return self._finish_not_authz()
        except NotFound, e:
            extra_msg = e.extra_msg
            return self._finish_not_found(extra_msg)
        except ValidationError, e:
            log.error('Validation error: %r' % str(e.error_dict))
            return self._finish(409, e.error_dict, content_type='json')
        except DataError, e:
            log.error('Format incorrect: %s - %s' % (e.error, request_data))
            #TODO make better error message
            return self._finish(400, _(u'Integrity Error') +
                                ': %s - %s' % (e.error, request_data))
        except search.SearchIndexError:
            log.error('Unable to update search index: %s' % request_data)
            return self._finish(500, _(u'Unable to update search index') %
                                request_data)

    def delete(self, ver=None, register=None, subregister=None,
               id=None, id2=None):
        action_map = {
            'group': 'group_delete',
            'dataset': 'package_delete',
            'related': 'related_delete',
            ('dataset', 'relationships'): 'package_relationship_delete_rest',
        }
        for type in model.PackageRelationship.get_all_types():
            action_map[('dataset', type)] = 'package_relationship_delete_rest'

        context = {'model': model, 'session': model.Session, 'user': c.user,
                   'api_version': ver}

        data_dict = {'id': id, 'id2': id2, 'rel': subregister}

        log.debug('delete %s/%s/%s/%s' % (register, id, subregister, id2))

        action = self._get_action_from_map(action_map, register, subregister)
        if not action:
            return self._finish_bad_request(
                gettext('Cannot delete entity of this type: %s %s') %
                (register, subregister or ''))
        try:
            response_data = action(context, data_dict)
            return self._finish_ok(response_data)
        except NotAuthorized:
            return self._finish_not_authz()
        except NotFound, e:
            extra_msg = e.extra_msg
            return self._finish_not_found(extra_msg)
        except ValidationError, e:
            log.error('Validation error: %r' % str(e.error_dict))
            return self._finish(409, e.error_dict, content_type='json')

    def search(self, ver=None, register=None):

        log.debug('search %s params: %r' % (register, request.params))
        if register == 'revision':
            since_time = None
            if 'since_id' in request.params:
                id = request.params['since_id']
                if not id:
                    return self._finish_bad_request(
                        gettext(u'No revision specified'))
                rev = model.Session.query(model.Revision).get(id)
                if rev is None:
                    return self._finish_not_found(
                        gettext(u'There is no revision with id: %s') % id)
                since_time = rev.timestamp
            elif 'since_time' in request.params:
                since_time_str = request.params['since_time']
                try:
                    since_time = h.date_str_to_datetime(since_time_str)
                except ValueError, inst:
                    return self._finish_bad_request('ValueError: %s' % inst)
            else:
                return self._finish_bad_request(
                    gettext("Missing search term ('since_id=UUID' or " +
                            " 'since_time=TIMESTAMP')"))
            revs = model.Session.query(model.Revision).\
                filter(model.Revision.timestamp > since_time)
            return self._finish_ok([rev.id for rev in revs])
        elif register in ['dataset', 'package', 'resource']:
            try:
                params = MultiDict(self._get_search_params(request.params))
            except ValueError, e:
                return self._finish_bad_request(
                    gettext('Could not read parameters: %r' % e))

            # if using API v2, default to returning the package ID if
            # no field list is specified
            if register in ['dataset', 'package'] and not params.get('fl'):
                params['fl'] = 'id' if ver == 2 else 'name'

            try:
                if register == 'resource':
                    query = search.query_for(model.Resource)

                    # resource search still uses ckan query parser
                    options = search.QueryOptions()
                    for k, v in params.items():
                        if (k in search.DEFAULT_OPTIONS.keys()):
                            options[k] = v
                    options.update(params)
                    options.username = c.user
                    options.search_tags = False
                    options.return_objects = False
                    query_fields = MultiDict()
                    for field, value in params.items():
                        field = field.strip()
                        if field in search.DEFAULT_OPTIONS.keys() or \
                                field in IGNORE_FIELDS:
                            continue
                        values = [value]
                        if isinstance(value, list):
                            values = value
                        for v in values:
                            query_fields.add(field, v)

                    results = query.run(
                        query=params.get('q'),
                        fields=query_fields,
                        options=options
                    )
                else:
                    # For package searches in API v3 and higher, we can pass
                    # parameters straight to Solr.
                    if ver in [1, 2]:
                        # Otherwise, put all unrecognised ones into the q
                        # parameter
                        params = search.\
                            convert_legacy_parameters_to_solr(params)
                    query = search.query_for(model.Package)
                    results = query.run(params)
                return self._finish_ok(results)
            except search.SearchError, e:
                log.exception(e)
                return self._finish_bad_request(
                    gettext('Bad search option: %s') % e)
        else:
            return self._finish_not_found(
                gettext('Unknown register: %s') % register)

    @classmethod
    def _get_search_params(cls, request_params):
        if 'qjson' in request_params:
            try:
                qjson_param = request_params['qjson'].replace('\\\\u', '\\u')
                params = h.json.loads(qjson_param, encoding='utf8')
            except ValueError, e:
                raise ValueError(gettext('Malformed qjson value') + ': %r'
                                 % e)
        elif len(request_params) == 1 and \
            len(request_params.values()[0]) < 2 and \
                request_params.keys()[0].startswith('{'):
            # e.g. {some-json}='1' or {some-json}=''
            params = h.json.loads(request_params.keys()[0], encoding='utf8')
        else:
            params = request_params
        if not isinstance(params, (UnicodeMultiDict, dict)):
            msg = _('Request params must be in form ' +
                    'of a json encoded dictionary.')
            raise ValueError(msg)
        return params

    def markdown(self, ver=None):
        raw_markdown = request.params.get('q', '')
        results = h.render_markdown(raw_markdown)

        return self._finish_ok(results)

    def tag_counts(self, ver=None):
        c.q = request.params.get('q', '')

        context = {'model': model, 'session': model.Session,
                   'user': c.user or c.author}

        tag_names = get_action('tag_list')(context, {})
        results = []
        for tag_name in tag_names:
            tag_count = len(context['model'].Tag.get(tag_name).packages)
            results.append((tag_name, tag_count))
        return self._finish_ok(results)

    def throughput(self, ver=None):
        qos = self._calc_throughput()
        qos = str(qos)
        return self._finish_ok(qos)

    def _calc_throughput(self, ver=None):
        period = 10  # Seconds.
        timing_cache_path = self._get_timing_cache_path()
        call_count = 0
        for t in range(0, period):
            expr = '%s/%s*' % (
                timing_cache_path,
                (datetime.datetime.now() -
                 datetime.timedelta(0, t)).isoformat()[0:19],
            )
            call_count += len(glob.glob(expr))
        # Todo: Clear old records.
        return float(call_count) / period

    @jsonp.jsonpify
    def user_autocomplete(self):
        q = request.params.get('q', '')
        limit = request.params.get('limit', 20)
        user_list = []
        if q:
            context = {'model': model, 'session': model.Session,
                       'user': c.user or c.author}

            data_dict = {'q': q, 'limit': limit}

            user_list = get_action('user_autocomplete')(context, data_dict)
        return user_list

    @jsonp.jsonpify
    def group_autocomplete(self):
        q = request.params.get('q', '')
        t = request.params.get('type', None)
        limit = request.params.get('limit', 20)
        try:
            limit = int(limit)
        except:
            limit = 20
        limit = min(50, limit)

        query = model.Group.search_by_name_or_title(q, t)

        def convert_to_dict(user):
            out = {}
            for k in ['id', 'name', 'title']:
                out[k] = getattr(user, k)
            return out

        query = query.limit(limit)
        out = map(convert_to_dict, query.all())
        return out

    def is_slug_valid(self):

        def package_exists(val):
            if model.Session.query(model.Package) \
                .autoflush(False).filter_by(name=val).count():
                return True
            return False

        def group_exists(val):
            if model.Session.query(model.Group) \
                    .autoflush(False).filter_by(name=val).count():
                return True
            return False

        slug = request.params.get('slug') or ''
        slugtype = request.params.get('type') or ''
        # TODO: We need plugins to be able to register new disallowed names
        disallowed = ['new', 'edit', 'search']
        if slugtype == u'package':
            response_data = dict(valid=not (package_exists(slug)
                                 or slug in disallowed))
            return self._finish_ok(response_data)
        if slugtype == u'group':
            response_data = dict(valid=not (group_exists(slug) or
                                 slug in disallowed))
            return self._finish_ok(response_data)
        return self._finish_bad_request('Bad slug type: %s' % slugtype)

    def dataset_autocomplete(self):
        q = request.params.get('incomplete', '')
        limit = request.params.get('limit', 10)
        package_dicts = []
        if q:
            context = {'model': model, 'session': model.Session,
                       'user': c.user or c.author}

            data_dict = {'q': q, 'limit': limit}

            package_dicts = get_action('package_autocomplete')(context,
                                                               data_dict)

        resultSet = {'ResultSet': {'Result': package_dicts}}
        return self._finish_ok(resultSet)

    def tag_autocomplete(self):
        q = request.params.get('incomplete', '')
        limit = request.params.get('limit', 10)
        tag_names = []
        if q:
            context = {'model': model, 'session': model.Session,
                       'user': c.user or c.author}

            data_dict = {'q': q, 'limit': limit}

            tag_names = get_action('tag_autocomplete')(context, data_dict)

        resultSet = {
            'ResultSet': {
                'Result': [{'Name': tag} for tag in tag_names]
            }
        }
        return self._finish_ok(resultSet)

    def format_autocomplete(self):
        q = request.params.get('incomplete', '')
        limit = request.params.get('limit', 5)
        formats = []
        if q:
            context = {'model': model, 'session': model.Session,
                       'user': c.user or c.author}
            data_dict = {'q': q, 'limit': limit}
            formats = get_action('format_autocomplete')(context, data_dict)

        resultSet = {
            'ResultSet': {
                'Result': [{'Format': format} for format in formats]
            }
        }
        return self._finish_ok(resultSet)

    def munge_package_name(self):
        name = request.params.get('name')
        munged_name = munge.munge_name(name)
        return self._finish_ok(munged_name)

    def munge_title_to_package_name(self):
        name = request.params.get('title') or request.params.get('name')
        munged_name = munge.munge_title_to_name(name)
        return self._finish_ok(munged_name)

    def munge_tag(self):
        tag = request.params.get('tag') or request.params.get('name')
        munged_tag = munge.munge_tag(tag)
        return self._finish_ok(munged_tag)

    def format_icon(self):
        f = request.params.get('format')
        out = {
            'format': f,
            'icon': h.icon_url(h.format_icon(f))
        }
        return self._finish_ok(out)

    def status(self):
        context = {'model': model, 'session': model.Session}
        data_dict = {}
        status = get_action('status_show')(context, data_dict)
        return self._finish_ok(status)

    def i18n_js_translations(self, lang):
        ''' translation strings for front end '''
        ckan_path = os.path.join(os.path.dirname(__file__), '..')
        source = os.path.abspath(os.path.join(ckan_path, 'public',
                                 'base', 'i18n', '%s.js' % lang))
        response.headers['Content-Type'] = CONTENT_TYPES['json']
        if not os.path.exists(source):
            return '{}'
        f = open(source, 'r')
        return(f)

    @classmethod
    def _get_request_data(cls, try_url_params=False):
        '''Returns a dictionary, extracted from a request.

        If there is no data, None or "" is returned.
        ValueError will be raised if the data is not a JSON-formatted dict.

        The data is retrieved as a JSON-encoded dictionary from the request
        body.  Or, if the `try_url_params` argument is True and the request is
        a GET request, then an attempt is made to read the data from the url
        parameters of the request.

        try_url_params
            If try_url_params is False, then the data_dict is read from the
            request body.

            If try_url_params is True and the request is a GET request then the
            data is read from the url parameters.  The resulting dict will only
            be 1 level deep, with the url-param fields being the keys.  If a
            single key has more than one value specified, then the value will
            be a list of strings, otherwise just a string.

        '''
        def make_unicode(entity):
            '''Cast bare strings and strings in lists or dicts to Unicode. '''
            if isinstance(entity, str):
                return unicode(entity)
            elif isinstance(entity, list):
                new_items = []
                for item in entity:
                    new_items.append(make_unicode(item))
                return new_items
            elif isinstance(entity, dict):
                new_dict = {}
                for key, val in entity.items():
                    new_dict[key] = make_unicode(val)
                return new_dict
            else:
                return entity

        cls.log.debug('Retrieving request params: %r' % request.params)
        cls.log.debug('Retrieving request POST: %r' % request.POST)
        cls.log.debug('Retrieving request GET: %r' % request.GET)
        request_data = None
        if request.POST:
            try:
                keys = request.POST.keys()
                # Parsing breaks if there is a = in the value, so for now
                # we will check if the data is actually all in a single key
                if keys and request.POST[keys[0]] in [u'1', u'']:
                    request_data = keys[0]
                else:
                    request_data = urllib.unquote_plus(request.body)
            except Exception, inst:
                msg = "Could not find the POST data: %r : %s" % \
                      (request.POST, inst)
                raise ValueError(msg)

        elif try_url_params and request.GET:
            return request.GET.mixed()

        else:
            try:
                if request.method in ['POST', 'PUT']:
                    request_data = request.body
                else:
                    request_data = None
            except Exception, inst:
                msg = "Could not extract request body data: %s" % \
                      (inst)
                raise ValueError(msg)
            cls.log.debug('Retrieved request body: %r' % request.body)
            if not request_data:
                if not try_url_params:
                    msg = "No request body data"
                    raise ValueError(msg)
                else:
                    request_data = {}
        if request_data:
            try:
                request_data = h.json.loads(request_data, encoding='utf8')
            except ValueError, e:
                raise ValueError('Error decoding JSON data. '
                                 'Error: %r '
                                 'JSON data extracted from the request: %r' %
                                 (e, request_data))
            if not isinstance(request_data, dict):
                raise ValueError('Request data JSON decoded to %r but '
                                 'it needs to be a dictionary.' % request_data)
            # ensure unicode values
            for key, val in request_data.items():
                # if val is str then assume it is ascii, since json converts
                # utf8 encoded JSON to unicode
                request_data[key] = make_unicode(val)
        cls.log.debug('Request data extracted: %r' % request_data)
        return request_data