Open Source Monorail

appengine/monorail/framework/paginate.py

Index: appengine/monorail/framework/paginate.py
diff --git a/appengine/monorail/framework/paginate.py b/appengine/monorail/framework/paginate.py
new file mode 100644
index 0000000000000000000000000000000000000000..fde7ebe9e124d07f71992b01347fbb81e419d1a5
--- /dev/null
+++ b/appengine/monorail/framework/paginate.py
@@ -0,0 +1,126 @@
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is govered by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+"""Classes that help display pagination widgets for result sets."""
+
+import logging
+
+from third_party import ezt
+
+import settings
+from framework import framework_helpers
+
+
+class VirtualPagination(object):
+  """Class to calc Prev and Next pagination links based on result counts."""
+
+  def __init__(self, mr, total_count, items_per_page,
+               list_page_url=None, count_up=True,
+               start_param='start', num_param='num', max_num=None):
+    """Given 'num' and 'start' params, determine Prev and Next links.
+
+    Args:
+      mr: commonly used info parsed from the request.
+      total_count: total number of artifacts that satisfy the query.
+      items_per_page: number of items to display on each page, e.g., 25.
+      list_page_url: URL of the web application page that is displaying
+        the list of artifacts.  Used to build the Prev and Next URLs.
+        If None, no URLs will be built.
+      count_up: if False, count down from total_count.
+      start_param: query string parameter name to use for the start
+        of the pagination page.
+      num_param: query string parameter name to use for the number of items
+        to show on a pagination page.
+      max_num: optional limit on the value of the num param.  If not given,
+        settings.max_artifact_search_results_per_page is used.
+    """
+    self.total_count = total_count
+    self.prev_url = ''
+    self.reload_url = ''
+    self.next_url = ''
+
+    if max_num is None:
+      max_num = settings.max_artifact_search_results_per_page
+
+    self.num = mr.GetPositiveIntParam(num_param, items_per_page)
+    self.num = min(self.num, max_num)
+
+    if count_up:
+      self.start = mr.GetPositiveIntParam(start_param, 0)
+      self.last = min(self.total_count, self.start + self.num)
+      prev_start = max(0, self.start - self.num)
+      next_start = self.start + self.num
+    else:
+      self.start = mr.GetPositiveIntParam(start_param, self.total_count)
+      self.last = max(0, self.start - self.num)
+      prev_start = min(self.total_count, self.start + self.num)
+      next_start = self.start - self.num
+
+    if list_page_url:
+      if mr.project_name:
+        list_servlet_rel_url = '/p/%s%s' % (
+            mr.project_name, list_page_url)
+      else:
+        list_servlet_rel_url = list_page_url
+
+      self.reload_url = framework_helpers.FormatURL(
+          mr, list_servlet_rel_url,
+          **{start_param: self.start, num_param: self.num})
+
+      if prev_start != self.start:
+        self.prev_url = framework_helpers.FormatURL(
+            mr, list_servlet_rel_url,
+            **{start_param: prev_start, num_param: self.num})
+      if ((count_up and next_start < self.total_count) or
+          (not count_up and next_start >= 1)):
+        self.next_url = framework_helpers.FormatURL(
+            mr, list_servlet_rel_url,
+            **{start_param: next_start, num_param: self.num})
+
+    self.visible = ezt.boolean(self.last != self.start)
+
+    # Adjust indices to one-based values for display to users.
+    if count_up:
+      self.start += 1
+    else:
+      self.last += 1
+
+  def DebugString(self):
+    """Return a string that is useful in on-page debugging."""
+    return '%s - %s of %s; prev_url:%s; next_url:%s' % (
+        self.start, self.last, self.total_count, self.prev_url, self.next_url)
+
+
+class ArtifactPagination(VirtualPagination):
+  """Class to calc Prev and Next pagination links based on a results list."""
+
+  def __init__(
+      self, mr, results, items_per_page, list_page_url, total_count=None,
+      limit_reached=False, skipped=0):
+    """Given 'num' and 'start' params, determine Prev and Next links.
+
+    Args:
+      mr: commonly used info parsed from the request.
+      results: a list of artifact ids that satisfy the query.
+      items_per_page: number of items to display on each page, e.g., 25.
+      list_page_url: URL of the web application page that is displaying
+        the list of artifacts.  Used to build the Prev and Next URLs.
+      total_count: specify total result count rather than the length of results
+      limit_reached: optional boolean that indicates that more results could
+        not be fetched because a limit was reached.
+      skipped: optional int number of items that were skipped and left off the
+        front of results.
+    """
+    if total_count is None:
+      total_count = skipped + len(results)
+    super(ArtifactPagination, self).__init__(
+        mr, total_count, items_per_page, list_page_url=list_page_url)
+
+    self.limit_reached = ezt.boolean(limit_reached)
+    # Determine which of those results should be visible on the current page.
+    range_start = self.start - 1 - skipped
+    range_end = range_start + self.num
+    assert 0 <= range_start <= range_end
+    self.visible_results = results[range_start:range_end]