img: add ImageParts._next_image_partname

Steve Canny · Steve Canny · commit af1afc04852f · 2013-12-29T01:38:12.000-08:00
diff --git a/docx/package.py b/docx/package.py
@@ -8,6 +8,7 @@
 
 from docx.opc.constants import RELATIONSHIP_TYPE as RT
 from docx.opc.package import OpcPackage
+from docx.opc.packuri import PackURI
 from docx.parts.image import Image, ImagePart
 from docx.shared import lazyproperty
 
@@ -56,6 +57,9 @@ def __init__(self):
     def __contains__(self, item):
         return self._image_parts.__contains__(item)
 
+    def __iter__(self):
+        return self._image_parts.__iter__()
+
     def __len__(self):
         return self._image_parts.__len__()
 
@@ -79,7 +83,7 @@ def _add_image_part(self, image):
         Return an |ImagePart| instance newly created from image and appended
         to the collection.
         """
-        partname = self._next_image_partname
+        partname = self._next_image_partname(image.ext)
         image_part = ImagePart.from_image(image, partname)
         self.append(image_part)
         return image_part
@@ -94,10 +98,17 @@ def _get_by_sha1(self, sha1):
                 return image_part
         return None
 
-    @property
-    def _next_image_partname(self):
+    def _next_image_partname(self, ext):
         """
         The next available image partname, starting from
-        ``/word/media/image1.{ext}`` where unused numbers are reused.
+        ``/word/media/image1{ext}`` where unused numbers are reused. The
+        partname is unique by number, without regard to the extension. *ext*
+        must include the leading period.
         """
-        raise NotImplementedError
+        def image_partname(n):
+            return PackURI('/word/media/image%d%s' % (n, ext))
+        used_numbers = [image_part.partname.idx for image_part in self]
+        for n in range(1, len(self)+1):
+            if not n in used_numbers:
+                return image_partname(n)
+        return image_partname(len(self)+1)
diff --git a/docx/parts/image.py b/docx/parts/image.py
@@ -36,6 +36,15 @@ def content_type(self):
         """
         raise NotImplementedError
 
+    @property
+    def ext(self):
+        """
+        The file extension for the image. If an actual one is available from
+        a load filename it is used. Otherwise a canonical extension is
+        assigned based on the content type.
+        """
+        raise NotImplementedError
+
     @property
     def filename(self):
         """
diff --git a/tests/test_package.py b/tests/test_package.py
@@ -13,7 +13,7 @@
 from docx.parts.image import Image, ImagePart
 
 from .unitutil import (
-    docx_path, class_mock, instance_mock, method_mock, property_mock
+    docx_path, class_mock, instance_mock, method_mock
 )
 
 
@@ -39,6 +39,13 @@ def it_can_add_a_new_image_part(self, add_image_part_fixture):
         image_parts._add_image_part.assert_called_once_with(image_)
         assert image_part is image_part_
 
+    def it_knows_the_next_available_image_partname(
+            self, next_partname_fixture):
+        image_parts, ext, expected_partname = next_partname_fixture
+        assert image_parts._next_image_partname(ext) == expected_partname
+        print('\n%s' % image_parts._next_image_partname(ext))
+        print(expected_partname)
+
     def it_can_really_add_a_new_image_part(
             self, really_add_image_part_fixture):
         image_parts, image_, ImagePart_, partname_, image_part_ = (
@@ -99,13 +106,33 @@ def image_part_(self, request, sha1):
         image_part_.sha1 = sha1
         return image_part_
 
+    def _image_part_with_partname_(self, request, n):
+        partname = self._image_partname(n)
+        return instance_mock(request, ImagePart, partname=partname)
+
+    def _image_partname(self, n):
+        return PackURI('/word/media/image%d.png' % n)
+
     @pytest.fixture
     def new_image_part_(self, request):
         return instance_mock(request, ImagePart)
 
     @pytest.fixture
     def _next_image_partname_(self, request):
-        return property_mock(request, ImageParts, '_next_image_partname')
+        return method_mock(request, ImageParts, '_next_image_partname')
+
+    @pytest.fixture(params=[((2, 3), 1), ((1, 3), 2), ((1, 2), 3)])
+    def next_partname_fixture(self, request):
+        existing_partname_numbers, expected_partname_number = request.param
+        image_parts = ImageParts()
+        for n in existing_partname_numbers:
+            image_part_ = self._image_part_with_partname_(request, n)
+            image_parts.append(image_part_)
+        ext = '.png'
+        expected_image_partname = self._image_partname(
+            expected_partname_number
+        )
+        return image_parts, ext, expected_image_partname
 
     @pytest.fixture
     def partname_(self, request):
