Enable arc-view to communicate with WoT-enabled Agents

[RobWin]

Story: Enable arc-view to Communicate with WoT-Enabled Agents

Problem Description:

The arc-view component currently lacks the capability to interact with Web of Things (WoT)-enabled Agents, limiting its interoperability within the system. To address this, I propose two potential solutions:

1. Implement a New WebSocket Protocol Binding in dart_wot:

   • Develop a WebSocket protocol binding based on the LMOS WebSocket Subprotocol within the dart_wot library. This enhancement will enable arc-view, which utilizes Dart, to communicate directly with WoT-enabled Agents.

2. Develop a Kotlin-Based Backend for arc-view:

   • Create a backend service using Kotlin that interfaces with WoT-enabled Agents by using kotlin-wot. This backend will handle communication with the Agents and expose a GraphQL API to arc-view, allowing it to maintain its current GraphQL-based API.

[hsudbrock]

I wonder which option we should follow to make progress on adding LMOS protocol (i.e., WoT) to the arc-view.

@RobWin proposed two options in this issue: (1) extend dart_wot with a websocket protocol binding and then use dart_wot in the arc-view, and (2) develop a Kotlin-based backend for the arc-view that bridges arc-graphql to LMOS protocol using a Kotlin-based WoT library. Another option, (3), could also be to migrate the arc-view to Kotlin (similar to what is started in https://github.com/michalharakal/ark-view) and then use a Kotlin-based WoT lib directly in the arc-view.

I think that (1) sounds charming because it does not require a backend, and we could keep a statically compiled webpage for the arc-view. Also, this would allow the centrally hosted version of the arc-view more simple, and would permit it to talk to agents on localhost. On the other hand, (2) sounds charming at least to me because it does not require to touch Dart code, also in the LMOS universe we so far use Kotlin in most places. Moreover, there might be other features we envision for the arc view in the future that might need a backend anyways(?).

From an initial discussion on Discord I took that there are different requirements in tension when choosing the option to go forward with, I try to list them here (not sorted by any ranking, and to be discussed, please add more if you see other requirements):

1. Support agents speaking LMOS protocol in the arc-view (the "obvious" requirement from this ticket).
2. Ability to use the arc-view with agents running both on localhost, on internet, or on some intranet
3. The arc-view should be as simple as possible to use and deploy
4. Prefer Kotlin over Dart as Kotlin is language used mostly in LMOS currently
5. LMOS protocol should be the “default” protocol used for agent development with arc-view in the future
6. It should be possible to run arc-view self-hosted, and to have a centrally hosted arc-view on the internet
7. There might be future arc-view requirements beyond LMOS protocol that might require a backend for arc-view anyways.
8. Effort for adding LMOS protocol support should be as small as possible

Wdyt?

[hsudbrock]

One more update on this: I made an attempt to integrate the dart-wot library into the arc-view directly (as it would be the simpler solution to speak LMOS protocol directly from the arc-view, without needing a "translation layer" in a BFF). I attempted to use it with the http-binding (as a websocket-binding is currently not available).

The result was that this is not possible without adaptations to the dart-wot library, because dart-wot has dependencies on dart-libraries that are not compatible with compiling flutter for the web. On the one hand, dart-wot also supports CoAP, and the used coap library uses features not compatible with web. This could be avoided by moving the CoAP-related parts out of dart-wot's core package (but this would be a change required in dart-wot). On the other hand, after removing all CoAP-related code, dart-wot's http-binding is built on top of the dart:io library, which also is not suitable for web. This could be dealt with by switching to another http-library in dart-wot.

@RobWin linked me with the maintainer of dart-wot on discord, he will give these topics a look in the next days (but is of course also open for PRs).