Confluence bridge for Gliffy cannot convert some diagrams

[oanalavinia]

Describe the bug
After migrating from Confluence, I have some gliffy diagrams that don't work (cannot convert them in order to be able to edit). In my case, the diagrams that don't work are gliffy diagrams that were created recently, while some older ones do not have issues (cannot say how new are they)

To Reproduce
Steps to reproduce the behavior:

1. Have 2 pages on your Confluence instance. One page that has a gliffy diagram which was added some time ago (I tested with one from May 2024) , i.e. OldGliffyPage. And one page with a newly added gliffy diagram, i.e. NewGliffyPage (create one and add some shapes)
2. Export the space that contains the 2 pages
3. Use the Confluence Migrator tool to migrate this space
4. Go to OldGliffyPage and try to convert this diagram and observe that this is working
5. Go to NewGliffyPage and observe the result

Expected behavior
The diagram fromNewGliffyPage is converted and I get a success notification displayed

Actual result
The diagram is not converted and I get a Could not convert the diagram notification error displayed

Screenshots
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• OS: Fedora
• Browser Firefox
• XWiki version 16.10.2
• App version 1.26.7

[oanalavinia]

Investigation result:
The problem comes from the drawio's Gliffy importer class we are using. It fails with com.google.gson.JsonSyntaxException: java.lang.NumberFormatException: For input string: "a0f6b805-9eaf-4d4b-a628-dba9779e38b6".
The problem is that drawio removed the gliffy import class from their sources a long time ago . And we are now loading the last available version of that class, which is 13.4.8. Since drawio is currently at 26.1.1, we are now missing some fixes.

I looked at what exactly changed that triggered the issue and it looks like the structure of gliffy diagrams (the JSON we use for conversion) has changed. So the convert will work for older gliffy diagram, but not for diagrams created (or saved?) after this change.
Basically, the gliffy converter code we have tries to convert from JSON to a Diagram class using this structure, but this is no longer used.

In short
The structure of the gliffy diagram has changed in recent versions of the plugin and the convertor we use on our side (taken from drawio before the code was moved to a private repo) is not compatible with it anymore.

The gliffy plugin from Confluence is the one managing the changed format. It's hard to be very precise for when this change was introduced. For example, I checked the plugin version history and I noticed that versions 10.2.0 / 10.3.0 do mention Significant improvements to the Draw.io to Gliffy diagram conversion experience and accuracy., so maybe these are related

Potential fixes

1. Convert the gliffy diagrams to drawio before exporting from confluence
   Confluence has a mass convert feature, to convert all your gliffy diagrams to drawio https://info.seibert.group/display/DRAWIO/Diagramming+in+Confluence+-+Mass+import+from+Gliffy+to+draw.io . This should be done before exporting your space/s for confluence migration
   Alongside this, we should mention on our side we don't support gliffy conversion anymore.
2. Create a Gliffy convertor on our side.
   Started something on this direction Upgrade the gliffy convertor packaged code #10 xwiki-contrib/draw.io#11 , but is more of a POC, there is still work to be done