Add min and max limits to the date batch.

docs/HISTORY.txt

@@ -7,6 +7,9 @@ Changelog
 * Fix a bug when the ``start`` value is higher than the number of
   element in the batch in the regular batch.
 
+* Add two options ``min`` and ``max`` to the date batch in order to
+  define possible limits for it.
+
 1.0 (2011-11-07)
 ----------------
 

src/zeam/utils/batch/date/batch.py

@@ -15,7 +15,8 @@ class DateBatch(ActiveBatch):
 
     def __init__(
         self, collection,
-        start=None, count=BATCH_MONTH, name='', request=None, factory=None):
+        start=None, count=BATCH_MONTH, name='', request=None, factory=None,
+        min=None, max=None):
         if request is not None:
             key = 'bstart'
             if name:
@@ -27,22 +28,52 @@ def __init__(
                     pass
         if start is None:
             start = datetime.now()
+        self.min = min
+        self.max = max
         super(DateBatch, self).__init__(
             collection,
             start=start, count=count, name=name,
             request=request, factory=factory)
 
     def all(self):
-        for month in range(1, 13):
+        start = 1
+        if self.min is not None:
+            if self.min.year == self.start.year:
+                # We are on the starting year.
+                start = self.min.month
+            elif self.min.year > self.start.year:
+                # We are before the starting year
+                start = 13
+        end = 13
+        if self.max is not None:
+            if self.max.year == self.start.year:
+                # We are on the ending year
+                end = self.max.month + 1
+            elif self.max.year < self.start.year:
+                # We are after the ending year
+                end = 1
+        for month in range(start, end):
             yield datetime(self.start.year, month, 1)
 
     def batch_length(self):
         return 12
 
     @property
     def previous(self):
+        if self.min is not None and self.min.year >= self.start.year:
+            # We are before the minimal year.
+            return None
+        if self.max is not None and self.max.year < self.start.year:
+            # We are after the maximal year.
+            return None
         return datetime(self.start.year - 1, 12, 1)
 
     @property
     def next(self):
+        if self.max is not None and self.max.year <= self.start.year:
+            # We are after the maximal year.
+            return None
+        if self.min is not None and self.min.year > self.start.year:
+            # We are before the minimal year.
+            return None
         return datetime(self.start.year + 1, 1, 1)

src/zeam/utils/batch/date/batch.txt

@@ -74,6 +74,58 @@ And you can see all the months:
   2011-11-01 00:00:00
   2011-12-01 00:00:00
 
+Minimal and maximal dates:
+
+  >>> c = DateBatch(getter,
+  ...               start=datetime(2011, 11, 11),
+  ...               min=datetime(2011, 4, 1),
+  ...               max=datetime(2012, 8, 30))
+  >>> c.previous
+  >>> c.next
+  datetime.datetime(2012, 1, 1, 0, 0)
+  >>> for month in c.all():
+  ...     print month
+  2011-04-01 00:00:00
+  2011-05-01 00:00:00
+  2011-06-01 00:00:00
+  2011-07-01 00:00:00
+  2011-08-01 00:00:00
+  2011-09-01 00:00:00
+  2011-10-01 00:00:00
+  2011-11-01 00:00:00
+  2011-12-01 00:00:00
+
+Change the start of the batch to the next one, test again limits:
+
+  >>> c.start = b.next
+  >>> c.previous
+  datetime.datetime(2011, 12, 1, 0, 0)
+  >>> c.next
+  >>> for month in c.all():
+  ...     print month
+  2012-01-01 00:00:00
+  2012-02-01 00:00:00
+  2012-03-01 00:00:00
+  2012-04-01 00:00:00
+  2012-05-01 00:00:00
+  2012-06-01 00:00:00
+  2012-07-01 00:00:00
+  2012-08-01 00:00:00
+
+Or out of the range:
+
+  >>> c.start = datetime(2001, 4, 1)
+  >>> c.previous
+  >>> c.next
+  >>> for month in c.all():
+  ...     print month
+
+  >>> c.start = datetime(2021, 4, 1)
+  >>> c.previous
+  >>> c.next
+  >>> for month in c.all():
+  ...     print month
+
 
 Factory
 -------

src/zeam/utils/batch/date/views.py

@@ -5,6 +5,7 @@
 
 from zope.interface import Interface
 from zope.publisher.interfaces.http import IHTTPRequest
+from zope.cachedescriptors.property import Lazy
 
 from zeam.utils.batch.interfaces import IDateBatch
 from zeam.utils.batch.views import BasicBatching
@@ -33,17 +34,21 @@ def batch(self):
                        url=url_item,
                        style=style)
 
-    @property
+    @Lazy
     def batch_previous(self):
         previous = self._batch.previous
-        previous_tms = previous.strftime("%Y-%m")
-        return dict(year=previous.year, url=self._create_link(previous_tms))
+        if previous is not None:
+            previous_tms = previous.strftime("%Y-%m")
+            return dict(year=previous.year, url=self._create_link(previous_tms))
+        return {}
 
-    @property
+    @Lazy
     def batch_next(self):
         next = self._batch.next
-        next_tms = next.strftime("%Y-%m")
-        return dict(year=next.year, url=self._create_link(next_tms))
+        if next is not None:
+            next_tms = next.strftime("%Y-%m")
+            return dict(year=next.year, url=self._create_link(next_tms))
+        return {}
 
 
 class BatchPages(megrok.pagetemplate.PageTemplate):

src/zeam/utils/batch/date/views_templates/batchpages.pt

@@ -2,7 +2,8 @@
      tal:define="batch_previous batch/batch_previous;
                  batch_next batch/batch_next">
   <a href="#" class="previous"
-     tal:attributes="href batch/batch_previous/url">
+     tal:attributes="href batch_previous/url"
+     tal:condition="batch_previous">
     &lt; <tal:year tal:replace="batch_previous/year" />
   </a>
   <tal:repeat tal:repeat="item batch/batch">
@@ -13,7 +14,8 @@
     </a>
   </tal:repeat>
   <a href="#" class="next"
-     tal:attributes="href batch/batch_next/url">
+     tal:attributes="href batch_next/url"
+     tal:condition="batch_next">
     <tal:year tal:replace="batch_next/year" /> &gt;
   </a>
 </div>

src/zeam/utils/batch/interfaces.py

@@ -60,6 +60,8 @@ class IActiveBatch(IBatchBehavior):
 class IDateBatch(IActiveBatch):
     """Batch element by date.
     """
+    min = Attribute(u"Minimal date where to stop the batch")
+    max = Attribute(u"Maximal date where to stop the batch")
 
 
 class IAlphabeticalBatch(IActiveBatch, IBatch):