UI: Execution pagination on client side

* added execution list
  client side pagination
  which rely on the server api
* both next and previous iteration
  are supported
* items per page are coherent to
  user settings

Screenshots:
http://pasteboard.co/2p5A512S.png
http://pasteboard.co/2p5Cd1qW.png

Partially implements blueprint: mistral-dashboard-executions-screen

Change-Id: If13482d8fe62e4989dd1a62874c88c08c3e43d54

mistraldashboard/api.py

@@ -14,8 +14,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import itertools
+
 from django.conf import settings
 from django.utils.translation import ugettext_lazy as _
+
+from horizon.utils import functions as utils
 from horizon.utils import memoized
 
 from mistralclient.api import client as mistral_client
@@ -51,10 +55,50 @@ def execution_create(request, **data):
 
 
 @handle_errors(_("Unable to retrieve executions."), [])
-def execution_list(request):
-    """Returns all executions."""
+def execution_list(request, marker='', sort_keys='',
+                   sort_dirs='', paginate=False):
+    """Retrieve a listing of executions.
 
-    return mistralclient(request).executions.list()
+    :param request: Request data
+    :param marker: Pagination marker for large data sets: execution id
+    :param sort_keys: Columns to sort results by. Default: created_at
+    :param sort_dirs: Sorting Directions (asc/desc). Default:asc
+    :param paginate: If true will perform pagination based on settings
+    """
+
+    limit = getattr(settings, 'API_RESULT_LIMIT', 1000)
+    page_size = utils.get_page_size(request)
+
+    if paginate:
+        request_size = page_size + 1
+    else:
+        request_size = limit
+
+    executions_iter = mistralclient(request).executions.list(
+        marker, limit, sort_keys, sort_dirs
+    )
+
+    has_prev_data = has_more_data = False
+
+    if paginate:
+        executions = list(itertools.islice(executions_iter, request_size))
+        # first and middle page condition
+        if len(executions) > page_size:
+            executions.pop(-1)
+            has_more_data = True
+            # middle page condition
+            if marker is not None:
+                has_prev_data = True
+        # first page condition when reached via prev back
+        elif sort_dirs == 'asc' and marker is not None:
+            has_more_data = True
+        # last page condition
+        elif marker is not None:
+            has_prev_data = True
+    else:
+        executions = list(executions_iter)
+
+    return executions, has_more_data, has_prev_data
 
 
 def execution_get(request, execution_id):
@@ -67,14 +111,14 @@ def execution_get(request, execution_id):
 
 
 def execution_update(request, execution_id, field, value):
-
-    """update specific execution field, either state or description
+    """update specific execution field, either state or description.
 
     :param request: Request data
     :param execution_id: Execution ID
     :param field: flag - either Execution state or description
     :param value: new update value
     """
+
     if field == "state":
         return mistralclient(request).\
             executions.update(execution_id, value)

mistraldashboard/executions/views.py

@@ -74,8 +74,53 @@ class IndexView(tables.DataTableView):
     table_class = ExecutionsTable
     template_name = 'mistral/executions/index.html'
 
+    def has_prev_data(self, table):
+        return self._prev
+
+    def has_more_data(self, table):
+        return self._more
+
     def get_data(self):
-        return api.execution_list(self.request)
+        executions = []
+        prev_marker = self.request.GET.get(
+            ExecutionsTable._meta.prev_pagination_param,
+            None
+        )
+
+        if prev_marker is not None:
+            sort_dir = 'asc'
+            marker = prev_marker
+        else:
+            sort_dir = 'desc'
+            marker = self.request.GET.get(
+                ExecutionsTable._meta.pagination_param,
+                None
+            )
+
+        try:
+            executions, self._more, self._prev = api.execution_list(
+                request=self.request,
+                marker=marker,
+                sort_dirs=sort_dir,
+                paginate=True
+            )
+
+            if prev_marker is not None:
+                executions = sorted(
+                    executions,
+                    key=lambda execution: getattr(
+                        execution, 'created_at'
+                    ),
+                    reverse=True
+                )
+
+        except Exception:
+            self._prev = False
+            self._more = False
+            msg = _('Unable to retrieve executions list.')
+            exceptions.handle(self.request, msg)
+
+        return executions
 
 
 class DetailView(generic.TemplateView):