Lazy load history view with pagination. refs #149

realms/modules/wiki/models.py

@@ -1,3 +1,5 @@
+import collections
+import itertools
 import os
 import posixpath
 import re
@@ -98,37 +100,14 @@ class WikiPage(object):
         cache.set(cache_key, info)
         return info
 
-    def get_history(self, limit=100):
+    @property
+    def history(self):
         """Get page history.
 
-        :param limit: Limit history size.
         :return: list -- List of dicts
 
         """
-        if not len(self.wiki.repo.open_index()):
-            # Index is empty, no commits
-            return []
-
-        versions = []
-
-        walker = self.wiki.repo.get_walker(paths=[self.filename], max_entries=limit)
-        for entry in walker:
-            change_type = None
-            for change in entry.changes():
-                if change.old.path == self.filename:
-                    change_type = change.type
-                elif change.new.path == self.filename:
-                    change_type = change.type
-            author_name, author_email = entry.commit.author.rstrip('>').split('<')
-            versions.append(dict(
-                author=author_name.strip(),
-                author_email=author_email,
-                time=entry.commit.author_time,
-                message=entry.commit.message,
-                sha=entry.commit.id,
-                type=change_type))
-
-        return versions
+        return PageHistory(self, self._cache_key('history'))
 
     @property
     def partials(self):
@@ -319,3 +298,75 @@ class WikiPage(object):
             # We'll get a KeyError if self.sha isn't in the repo, or if self.filename isn't in the tree of our commit
             return False
         return True
+
+
+class PageHistory(collections.Sequence):
+    """Acts like a list, but dynamically loads and caches history revisions as requested."""
+    def __init__(self, page, cache_key):
+        self.page = page
+        self.cache_key = cache_key
+        self._store = cache.get(cache_key) or []
+        if not self._store:
+            self._iter_rest = self._get_rest()
+        elif self._store[-1] == 'TAIL':
+            self._iter_rest = None
+        else:
+            self._iter_rest = self._get_rest(self._store[-1]['sha'])
+
+    def __iter__(self):
+        # Iterate over the revisions already cached
+        for r in self._store:
+            if r == 'TAIL':
+                return
+            yield r
+        # Iterate over the revisions yet to be discovered
+        if self._iter_rest:
+            try:
+                for r in self._iter_rest:
+                    self._store.append(r)
+                    yield r
+                self._store.append('TAIL')
+            finally:
+                # Make sure we cache the results whether or not the iteration was completed
+                cache.set(self.cache_key, self._store)
+
+    def _get_rest(self, start_sha=None):
+        if not len(self.page.wiki.repo.open_index()):
+            # Index is empty, no commits
+            return
+        walker = iter(self.page.wiki.repo.get_walker(paths=[self.page.filename], include=start_sha, follow=True))
+        if start_sha:
+            # If we are not starting from HEAD, we already have the start commit
+            print(next(walker))
+        filename = self.page.filename
+        for entry in walker:
+            change_type = None
+            for change in entry.changes():
+                if change.new.path == filename:
+                    filename = change.old.path
+                    change_type = change.type
+                    break
+
+            author_name, author_email = entry.commit.author.rstrip('>').split('<')
+            r = dict(author=author_name.strip(),
+                     author_email=author_email,
+                     time=entry.commit.author_time,
+                     message=entry.commit.message,
+                     sha=entry.commit.id,
+                     type=change_type)
+            yield r
+
+    def __getitem__(self, index):
+        if isinstance(index, slice):
+            return list(itertools.islice(self, index.start, index.stop, index.step))
+        else:
+            try:
+                return next(itertools.islice(self, index, index+1))
+            except StopIteration:
+                raise IndexError
+
+    def __len__(self):
+        if not self._store or self._store[-1] != 'TAIL':
+            # Force generation of all revisions
+            list(self)
+        return len(self._store) - 1  # Don't include the TAIL sentinel

realms/modules/wiki/views.py

@@ -64,11 +64,22 @@ def revert():
 def history(name):
     if current_app.config.get('PRIVATE_WIKI') and current_user.is_anonymous():
         return current_app.login_manager.unauthorized()
-
+    ITEMS_PER_PAGE = 15
+    page = int(request.args.get('page', 1))
+    start_index = (page - 1) * ITEMS_PER_PAGE
     hist = g.current_wiki.get_page(name).get_history()
-    for item in hist:
+    # Grab one extra item to see if there is a next page
+    items = hist[start_index:start_index+ITEMS_PER_PAGE+1]
+    more = False
+    if len(items) > ITEMS_PER_PAGE:
+        more = True
+        items.pop()
+    if page > 1 and not items:
+        abort(404)
+    for item in items:
         item['gravatar'] = gravatar_url(item['author_email'])
-    return render_template('wiki/history.html', name=name, history=hist)
+    return render_template('wiki/history.html', name=name, history=items,
+                           pagination={'page': page, 'more': more})
 
 
 @blueprint.route("/_edit/<path:name>")

realms/templates/wiki/history.html

@@ -28,6 +28,22 @@
       </tr>
     {% endfor %}
   </table>
+  <!-- TODO: make this pagination look good -->
+  {% if pagination.page > 1 or pagination.more %}
+    <div>
+      {% if pagination.page > 1 %}
+        <a href="{{ url_for('.history', name=name, page=pagination.page - 1) }}">&lt;</a>
+      {% else %}
+        &lt;
+      {% endif %}
+      {{ pagination.page }}
+      {% if pagination.more %}
+        <a href="{{ url_for('.history', name=name, page=pagination.page + 1) }}">&gt;</a>
+      {% else %}
+        &gt;
+      {% endif %}
+    </div>
+  {% endif %}
   <p>
     <a class="btn btn-default btn-sm compare-revisions">Compare Revisions</a>
   </p>