yuzutech
[feature request] make it possible to get supported diagram types via REST
Description
Right now when visiting a self-hosted instance of kroki, it is not possible to get the supported diagram types via REST as some kind of JSON-response. All you can get is a HTML-page that lists the types (via HelloHandler). This makes it hard to auto-detect which diagram type is supported.
Proposal
In order to check which diagram types are supported, there needs to be some REST endpoint to get this information. Inside the server you already have some kind of registry: https://github.com/yuzutech/kroki/blob/d4294d10e70afd25db646466b759eb173cff58a4/server/src/main/java/io/kroki/server/Server.java#L100
Outcome
Not only would it enable the CLI to have some kind of diagram type discovery (which is already reported/requested at https://github.com/yuzutech/kroki-cli/issues/15), but it also would support the integration of other tools, which need to check if the diagram-type could be generated by kroki.
I guess you could use https://kroki.io/health API?
Please keep in mind that this API (currently) returns all supported diagram types. It won't actually check if a diagram type is actually available. For instance, if you don't start the Mermaid companion container, the /health API will still return mermaid.
If we want to return the actual list then we will need to setup a mechanism to check at runtime which diagram types are actually available. It might also be useful to get which output formats are supported per diagram type.
Yes, I could use https://kroki.io/health ... although from the name it does suggest a different use-case.
Regarding the validity of that list, thats another topic. To solve that, my first idea was to have some kind of "bootstrap process" on first server-boot, like calling each "companion container" once with a small example, but it is more a discovery but a "health"-check. What do you think @Mogztter , should this be another issue to be created?
EDIT: I'm right now trying to make some kind of pandoc-filter that converts inline-diagrams in markdown files to images using KROKI as the URL. But to make it "detect" which diagrams are supported to get converted, I was looking for that kind of list. I will start with that health-thing as some kind of proof-of-concept. My main goal is to have some kind of Markdown-to-PDF thing as part of my documentation hosted in a private Gitlab instance.