As part of the new Discord <-> Status Community Import functionality,
we're adding an API that extracts all discord categories and channels
from a previously exported discord export file.
These APIs can be used in clients to show the user what categories and
channels will be imported later on.
There are two APIs:
1. `Messenger.ExtractDiscordCategoriesAndChannels(filesToimport
[]string) (*MessengerResponse, map[string]*discord.ImportError)`
This takes a list of exported discord export (JSON) files (typically one per
channel), reads them, and extracts the categories and channels into
dedicated data structures (`[]DiscordChannel` and `[]DiscordCategory`)
It also returns the oldest message timestamp found in all extracted
channels.
The API is synchronous and returns the extracted data as
a `*MessengerResponse`. This allows to make the API available
status-go's RPC interface.
The error case is a `map[string]*discord.ImportError` where each key
is a file path of a JSON file that we tried to extract data from, and
the value a `discord.ImportError` which holds an error message and an
error code, allowing for distinguishing between "critical" errors and
"non-critical" errors.
2. `Messenger.RequestExtractDiscordCategoriesAndChannels(filesToImport
[]string)`
This is the asynchronous counterpart to
`ExtractDiscordCategoriesAndChannels`. The reason this API has been
added is because discord servers can have a lot of message and
channel data, which causes `ExtractDiscordCategoriesAndChannels` to
block the thread for too long, making apps potentially feel like they
are stuck.
This API runs inside a go routine, eventually calls
`ExtractDiscordCategoriesAndChannels`, and then emits a newly
introduced `DiscordCategoriesAndChannelsExtractedSignal` that clients
can react to.
Failure of extraction has to be determined by the
`discord.ImportErrors` emitted by the signal.
**A note about exported discord history files**
We expect users to export their discord histories via the
[DiscordChatExporter](https://github.com/Tyrrrz/DiscordChatExporter/wiki/GUI%2C-CLI-and-Formats-explained#exportguild)
tool. The tool allows to export the data in different formats, such as
JSON, HTML and CSV.
We expect users to have their data exported as JSON.
Closes: https://github.com/status-im/status-desktop/issues/6690