Viber data source

[ikesler]

Viber does not provide an open API for retrieving message history. In fact, the history is purely client-side in Viber.
However, Windows desktop Viber client uses an SQLite DB file as the storage of messages. The DB is not encrypted nor secured in any other way. Of course, hacking it is not officially supported and maybe even breaks some license agreements. But who cares? :)

In order to bring Viber messages in Consensus DB we need a client-side application running on Windows system alongside with Viber desktop client. This application should check Viber SQLite DB file periodically for new messages in the chats specified in params. We call this application Agent.

The agent, similarly to Consensus server, runs a set of data source handlers. Right now it is only Viber data source handler. In the future it can be also Skype or some non-messenger stuff (browsing history, etc.).

The agent binary is a part of back end application container in terms build and deployment. A download link is available in the web front end. Agent itself is UI-less and runs in the background. Upon first run it installs itself to an app data directory and configures itself to run on system boot. Agent is being updated automatically, again in the background.

Some trade-offs have been made:

• Custom installer (built-in to the application). The option which comes with .NET out of the box for installing Windows apps is ClickOnce installer. However, it has several drawbacks in .NET 6 (and also 5): cannot build ClickOnce package in Docker and
  unstable support in dotnet CLI (I was able to publish ClickOnce package successfully only from VisualStudio). Involving a third-party installer framework is an overkill for this project.
• Unfortunately, assembly trimming does not play well with Entity Framework and was disabled. It could be very helpful because the size of the agent application does matter.

To do in the future:

• Authentication. Not only for Agent - for the system in general - right now it is single-user.
• Add Quartz.NET to Agent app - same way as we use it on the server side. Schedules should be taken from the API. Right now Viber data source handler is woke up every minute - hardcoded.
• Some sort of Agent web dashboard - which agents are connected to the API, last connection time, version, etc.