fix: Check for visible changes to diagrams

capella2polarion/elements/api_helper.py

@@ -1,12 +1,16 @@
 # Copyright DB Netz AG and contributors
 # SPDX-License-Identifier: Apache-2.0
 """Capella2Polarion specific helper functions to use the API."""
+import base64
 import collections.abc as cabc
+import io
 import logging
+import re
 import typing as t
 
 import polarion_rest_api_client as polarion_api
 from capellambse.model import common
+from PIL import Image, ImageChops
 
 from capella2polarion.elements import serialize
 
@@ -41,6 +45,12 @@ def patch_work_item(
     if new := receiver(obj, ctx):
         wid = ctx["POLARION_ID_MAP"][obj.uuid]
         old: serialize.CapellaWorkItem = ctx["POLARION_WI_MAP"][obj.uuid]
+
+        if _type == "diagram" and has_visual_changes(
+            old.description, new.description
+        ):
+            return
+
         if new == old:
             return
 
@@ -72,6 +82,40 @@ def patch_work_item(
             logger.error("Updating work item %r failed. %s", wi, error.args[0])
 
 
+def decode_diagram(dia: str):
+    """Decode a diagram from a base64 string."""
+    encoded = dia.replace("data:image/", "").split(";base64,", 1)
+
+    decoded = base64.b64decode(encoded[1])
+
+    return encoded[0], decoded
+
+
+def has_visual_changes(old: str, new: str) -> bool:
+    """Return True if the images of the diagrams differ."""
+    type_old, decoded_old = decode_diagram(old)
+    type_new, decoded_new = decode_diagram(new)
+
+    if type_old != type_new:
+        return True
+
+    if type_old == "svg+xml":
+        d_new = decoded_new.decode("utf-8").splitlines()
+        for i, d_old in enumerate(decoded_old.decode("utf-8").splitlines()):
+            if re.sub(r'id=["\'][^"\']*["\']', "", d_old) != re.sub(
+                r'id=["\'][^"\']*["\']', "", d_new[i]
+            ):
+                return True
+        return False
+
+    image_old = Image.open(io.BytesIO(decoded_old))
+    image_new = Image.open(io.BytesIO(decoded_new))
+
+    diff = ImageChops.difference(image_old, image_new)
+
+    return bool(diff.getbbox())
+
+
 def handle_links(
     left: cabc.Iterable[polarion_api.WorkItemLink],
     right: cabc.Iterable[polarion_api.WorkItemLink],

pyproject.toml

@@ -33,6 +33,7 @@ dependencies = [
   "PyYAML",
   "polarion-rest-api-client @ git+https://github.com/DSD-DBS/polarion-rest-api-client.git@feat-add-attachments-workitem-relations",
   "requests",
+  "jinja2",
 ]
 
 [project.urls]

tests/data/svg_diff/example.svg.license

@@ -0,0 +1,2 @@
+Copyright DB Netz AG and contributors
+SPDX-License-Identifier: Apache-2.0

tests/test_elements.py

@@ -3,18 +3,29 @@
 
 from __future__ import annotations
 
+import base64
+import io
 import logging
+import pathlib
 import typing as t
 from unittest import mock
 
 import capellambse
+import jinja2
 import markupsafe
 import polarion_rest_api_client as polarion_api
 import pytest
 from capellambse.model import common
+from PIL import Image
 
 from capella2polarion import elements
-from capella2polarion.elements import diagram, element, helpers, serialize
+from capella2polarion.elements import (
+    api_helper,
+    diagram,
+    element,
+    helpers,
+    serialize,
+)
 
 # pylint: disable-next=relative-beyond-top-level, useless-suppression
 from .conftest import TEST_DIAGRAM_CACHE, TEST_HOST  # type: ignore[import]
@@ -64,6 +75,117 @@
 )
 
 
+class TestAPIHelper:
+    SVG_PATH = (
+        pathlib.Path(__file__).parent / "data" / "svg_diff" / "example.svg"
+    )
+    SVG_PREFIX = "data:image/svg+xml;base64,"
+    PNG_PREFIX = "data:image/png;base64,"
+
+    def encode_png(self, img: Image.Image) -> str:
+        image_buffer = io.BytesIO()
+        img.save(image_buffer, format="PNG")
+        image_buffer.seek(0)
+        encoded = base64.b64encode(image_buffer.read()).decode()
+        image_buffer.close()
+        return f"{self.PNG_PREFIX}{encoded}"
+
+    def test_pixel_diff(self):
+        img1 = Image.new("RGB", (100, 100))
+        img2 = Image.new("RGB", (100, 100))
+        img2.putpixel((0, 0), (255, 0, 0))
+
+        assert (
+            api_helper.has_visual_changes(
+                self.encode_png(img1),
+                self.encode_png(img2),
+            )
+            is True
+        )
+
+        assert (
+            api_helper.has_visual_changes(
+                self.encode_png(img1),
+                self.encode_png(img1),
+            )
+            is False
+        )
+
+    def encode_svg(self, render_params, params) -> str:
+        svg = jinja2.environment.Template(self.SVG_PATH.read_text()).render(
+            **render_params, **params
+        )
+        encoded = base64.b64encode(svg.encode("utf-8")).decode("utf-8")
+        return f"{self.SVG_PREFIX}{encoded}"
+
+    @pytest.mark.parametrize(
+        "render_params,changed_params,expected",
+        [
+            pytest.param(
+                {
+                    "id": "test",
+                    "width": "100",
+                    "height": "100",
+                    "x": "0",
+                    "y": "0",
+                    "fill": "blue",
+                },
+                ({}, {}),
+                False,
+                id="unchanged",
+            ),
+            pytest.param(
+                {
+                    "id": "test",
+                    "width": "100",
+                    "height": "100",
+                    "x": "0",
+                    "y": "0",
+                },
+                ({"fill": "red"}, {"fill": "blue"}),
+                True,
+                id="fill_changed",
+            ),
+            pytest.param(
+                {
+                    "width": "100",
+                    "height": "100",
+                    "x": "0",
+                    "y": "0",
+                    "fill": "blue",
+                },
+                ({"id": "test"}, {"id": "test2"}),
+                False,
+                id="id_changed",
+            ),
+            pytest.param(
+                {
+                    "width": "100",
+                    "height": "100",
+                    "x": "0",
+                    "y": "0",
+                },
+                (
+                    {"id": "test", "fill": "blue"},
+                    {"id": "test2", "fill": "red"},
+                ),
+                True,
+                id="id_and_fill_changed",
+            ),
+        ],
+    )
+    def test_svg_diff(self, render_params, changed_params, expected):
+        old_params, new_params = changed_params
+
+        assert (
+            api_helper.has_visual_changes(
+                self.encode_svg(render_params, old_params),
+                self.encode_svg(render_params, new_params),
+            )
+            is expected
+        )
+
+
 class TestDiagramElements:
     @staticmethod
     @pytest.fixture