[WIP] Added pagination to Resource

restkiss/paginator.py

@@ -0,0 +1,168 @@
+import collections
+import warnings
+from math import ceil
+
+
+class UnorderedObjectListWarning(RuntimeWarning):
+    pass
+
+
+class InvalidPage(Exception):
+    pass
+
+
+class PageNotAnInteger(InvalidPage):
+    pass
+
+
+class EmptyPage(InvalidPage):
+    pass
+
+
+class Paginator(object):
+
+    def __init__(self, object_list, per_page, orphans=0,
+                 allow_empty_first_page=True):
+        self.object_list = object_list
+        self._check_object_list_is_ordered()
+        self.per_page = int(per_page)
+        self.orphans = int(orphans)
+        self.allow_empty_first_page = allow_empty_first_page
+
+    def validate_number(self, number):
+        """
+        Validates the given 1-based page number.
+        """
+        try:
+            number = int(number)
+        except (TypeError, ValueError):
+            raise PageNotAnInteger('That page number is not an integer')
+        if number < 1:
+            raise EmptyPage('That page number is less than 1')
+        if number > self.num_pages:
+            if number == 1 and self.allow_empty_first_page:
+                pass
+            else:
+                raise EmptyPage('That page contains no results')
+        return number
+
+    def page(self, number):
+        """
+        Returns a Page object for the given 1-based page number.
+        """
+        number = self.validate_number(number)
+        bottom = (number - 1) * self.per_page
+        top = bottom + self.per_page
+        if top + self.orphans >= self.count:
+            top = self.count
+        return self._get_page(self.object_list[bottom:top], number, self)
+
+    def _get_page(self, *args, **kwargs):
+        """
+        Returns an instance of a single page.
+
+        This hook can be used by subclasses to use an alternative to the
+        standard :cls:`Page` object.
+        """
+        return Page(*args, **kwargs)
+
+    def count(self):
+        """
+        Returns the total number of objects, across all pages.
+        """
+        try:
+            return self.object_list.count()
+        except (AttributeError, TypeError):
+            # AttributeError if object_list has no count() method.
+            # TypeError if object_list.count() requires arguments
+            # (i.e. is of type list).
+            return len(self.object_list)
+
+    def num_pages(self):
+        """
+        Returns the total number of pages.
+        """
+        if self.count == 0 and not self.allow_empty_first_page:
+            return 0
+        hits = max(1, self.count - self.orphans)
+        return int(ceil(hits / float(self.per_page)))
+
+    @property
+    def page_range(self):
+        """
+        Returns a 1-based range of pages for iterating through within
+        a template for loop.
+        """
+        return range(1, self.num_pages + 1)
+
+    def _check_object_list_is_ordered(self):
+        """
+        Warn if self.object_list is unordered (typically a QuerySet).
+        """
+        if hasattr(self.object_list, 'ordered') and not self.object_list.ordered:
+            warnings.warn(
+                'Pagination may yield inconsistent results with an unordered '
+                'object_list: {!r}'.format(self.object_list),
+                UnorderedObjectListWarning
+            )
+
+
+QuerySetPaginator = Paginator   # For backwards-compatibility.
+
+
+class Page(collections.Sequence):
+
+    def __init__(self, object_list, number, paginator):
+        self.object_list = object_list
+        self.number = number
+        self.paginator = paginator
+
+    def __repr__(self):
+        return '<Page %s of %s>' % (self.number, self.paginator.num_pages)
+
+    def __len__(self):
+        return len(self.object_list)
+
+    def __getitem__(self, index):
+        if not isinstance(index, (slice, int)):
+            raise TypeError
+        # The object_list is converted to a list so that if it was a QuerySet
+        # it won't be a database hit per __getitem__.
+        if not isinstance(self.object_list, list):
+            self.object_list = list(self.object_list)
+        return self.object_list[index]
+
+    def has_next(self):
+        return self.number < self.paginator.num_pages
+
+    def has_previous(self):
+        return self.number > 1
+
+    def has_other_pages(self):
+        return self.has_previous() or self.has_next()
+
+    def next_page_number(self):
+        return self.paginator.validate_number(self.number + 1)
+
+    def previous_page_number(self):
+        return self.paginator.validate_number(self.number - 1)
+
+    def start_index(self):
+        """
+        Returns the 1-based index of the first object on this page,
+        relative to total objects in the paginator.
+        """
+        # Special case, return zero if no items.
+        if self.paginator.count == 0:
+            return 0
+        return (self.paginator.per_page * (self.number - 1)) + 1
+
+    def end_index(self):
+        """
+        Returns the 1-based index of the last object on this page,
+        relative to total objects found (hits).
+        """
+        # Special case for the last page because there can be orphans.
+        if self.number == self.paginator.num_pages:
+            return self.paginator.count
+        return self.number * self.paginator.per_page

restkiss/resources.py

@@ -1,9 +1,9 @@
-import six
 import sys
 
 from .constants import OK, CREATED, ACCEPTED, NO_CONTENT
 from .data import Data
-from .exceptions import MethodNotImplemented, Unauthorized
+from .exceptions import MethodNotImplemented, Unauthorized, BadRequest
+from .paginator import Paginator
 from .preparers import Preparer
 from .serializers import JSONSerializer
 from .utils import format_traceback
@@ -268,7 +268,7 @@ def handle(self, endpoint, *args, **kwargs):
         try:
             # Use ``.get()`` so we can also dodge potentially incorrect
             # ``endpoint`` errors as well.
-            if not method in self.http_methods.get(endpoint, {}):
+            if method not in self.http_methods.get(endpoint, {}):
                 raise MethodNotImplemented(
                     "Unsupported method '{0}' for {1} endpoint.".format(
                         method,
@@ -385,7 +385,23 @@ def serialize(self, method, endpoint, data):
             return self.serialize_list(data)
         return self.serialize_detail(data)
 
+    def paginate_data(self, data):
+        page_size = getattr(self, 'page_size', 20)
+        paginator = Paginator(data, page_size)
+
+        try:
+            page_number = int(self.request.GET.get('p', 1))
+        except ValueError:
+            page_number = None
+
+        if page_number not in paginator.page_range:
+            raise BadRequest('Invalid page number')
+
+        self.page = paginator.page(page_number)
+        return self.page.object_list
+
     def serialize_list(self, data):
+
         """
         Given a collection of data (``objects`` or ``dicts``), serializes them.
 
@@ -398,6 +414,9 @@ def serialize_list(self, data):
         if data is None:
             return ''
 
+        if getattr(self, 'paginate', False):
+            data = self.paginate_data(data)
+
         # Check for a ``Data``-like object. We should assume ``True`` (all
         # data gets prepared) unless it's explicitly marked as not.
         if not getattr(data, 'should_prepare', True):