pkg: add Package.next_image_partname()

Author: Steve Canny

pptx/package.py

@@ -9,11 +9,12 @@
 
 import os
 
-from pptx.opc.constants import RELATIONSHIP_TYPE as RT
-from pptx.opc.package import OpcPackage
-from pptx.parts.coreprops import CoreProperties
-from pptx.parts.image import Image, ImagePart
-from pptx.util import lazyproperty
+from .opc.constants import RELATIONSHIP_TYPE as RT
+from .opc.package import OpcPackage
+from .opc.packuri import PackURI
+from .parts.coreprops import CoreProperties
+from .parts.image import Image, ImagePart
+from .util import lazyproperty
 
 
 class Package(OpcPackage):
@@ -70,7 +71,19 @@ def next_image_partname(self, ext):
         partname, by sequence number. *ext* is used as the extention on the
         returned partname.
         """
-        raise NotImplementedError
+        def first_available_image_idx():
+            image_idxs = sorted([
+                part.partname.idx for part in self.iter_parts()
+                if part.partname.startswith('/ppt/media/image')
+            ])
+            for i, image_idx in enumerate(image_idxs):
+                idx = i + 1
+                if idx < image_idx:
+                    return idx
+            return len(image_idxs)+1
+
+        idx = first_available_image_idx()
+        return PackURI('/ppt/media/image%d.%s' % (idx, ext))
 
     @property
     def presentation(self):

tests/test_package.py

@@ -10,6 +10,7 @@
 
 from pptx.opc.constants import RELATIONSHIP_TYPE as RT
 from pptx.opc.package import Part, _Relationship
+from pptx.opc.packuri import PackURI
 from pptx.package import _ImageParts, Package
 from pptx.parts.coreprops import CoreProperties
 from pptx.parts.image import Image, ImagePart
@@ -71,6 +72,11 @@ def it_can_save_itself_to_a_pptx_file(self, temp_pptx_path):
         assert slide_layouts is not None
         assert len(slide_layouts) == 11
 
+    def it_knows_the_next_available_image_partname(self, next_fixture):
+        package, ext, expected_value = next_fixture
+        partname = package.next_image_partname(ext)
+        assert partname == expected_value
+
     # fixtures ---------------------------------------------
 
     @pytest.fixture
@@ -80,6 +86,19 @@ def image_part_fixture(self, _image_parts_, image_part_):
         package._image_parts.get_or_add_image_part.return_value = image_part_
         return package, image_file, image_part_
 
+    @pytest.fixture(params=[
+        ((3, 4, 2), 1),
+        ((4, 2, 1), 3),
+        ((2, 3, 1), 4),
+    ])
+    def next_fixture(self, request, iter_parts_):
+        idxs, idx = request.param
+        package = Package()
+        package.iter_parts.return_value = self.i_image_parts(request, idxs)
+        ext = 'foo'
+        expected_value = '/ppt/media/image%d.%s' % (idx, ext)
+        return package, ext, expected_value
+
     @pytest.fixture
     def temp_pptx_path(self, tmpdir):
         return absjoin(str(tmpdir), 'test-pptx.pptx')
@@ -94,6 +113,16 @@ def image_part_(self, request):
     def _image_parts_(self, request):
         return property_mock(request, Package, '_image_parts')
 
+    def i_image_parts(self, request, idxs):
+        def part(idx):
+            partname = PackURI('/ppt/media/image%d.png' % idx)
+            return instance_mock(request, Part, partname=partname)
+        return iter([part(idx) for idx in idxs])
+
+    @pytest.fixture
+    def iter_parts_(self, request):
+        return property_mock(request, Package, 'iter_parts')
+
 
 class Describe_ImageParts(object):