talker challenge

Goal

Chatbot capable of automatically keeping up to date with Swagger API, written in F#, running on .Net Core 2.2 and deployable to Linux Debian 9.

Steps

• use Mattermost-preview docker image
• understand it's basic HTTP API
• get acquainted with F# project and dependencies
• use SwaggerProvider to have easy access to Mattermost API
• develop bot conversation logic
• choose release and deployment options

Shortcommings

• mattermost complete installation seems to be a bit too complex (requires databases and proxy servers, notoriously nontrivial to configure)
  • use the mattermost-preview docker image, which comes vendored with said preconfigured depedencies
• SwaggerProvider dependency problem, incompatible with .Net Core 2.2
  • use beta version
• SwaggerProvider documentation and examples seem to be broken
  • exploratory approach to available members/methods
• long compilation/analysis time for simple programs (on VSCode+Ionide)
  • yaml file has to be parsed on every change, iteration cicles delayed
  • try out new approach: hand made API calls
• direct HTTP calls work as expected, but unsure how to subscribe to mentions/messages
  • found WebSocket API, not sure if FSharp.Data HTTP client is able to work with WebSockets
  • there is a 'posts' api, with a filter to get messages only after certain post ID, which could be used for long-pooling messages
• api for bots not quite clear, and default config on preview image is to disallow bot creation
  • user creation and management is sufficiently simple so that a bot could use a proper user account
  • users do not have permission to send posts via api, and couldn't find a way to turn it on (not even making the user admin)
• found (and understood) webhook api
  • with incoming webhooks, bearing the right token, one can send messages via api
    • though preview doesn't seem to support declaring users, so all messages come as from 'admin'
  • with outgoing webhooks, a message starting with a predefined keyword can trigger a post request, so as to notify of an incoming message
    • trouble understanding docker networks, once set up (testing curls from within mattermost container), it became clear mattermost-previview dosen't support outgoing webhooks
  • the right way would be to have a full installation, but setting it up at this point is time prohibitive

What I should have done

• set up a complete installation builder for mattermost
• write a boot script that generates admin, teams, groups, incoming and outgoing webhooks, enables bot accounts, create such, and save tokens in config file
• run a http server, which receives post requests from mattermost
  • bot dispatch made by route, since multiple endpoints can be set up
  • bots work as simple state machines, where a message triggers a response, which is just a json post request to mattermost

What I ended up doing

• hardcoded endpoints ☹️
• learned some F# 🤓
• long pooling for messages 🙁
• bot instances run asynchronously, in parallel 🙂

in the end, even if not fulfilling the whole spec, i'm happy to deliver something, and to say i now know more than when i started