Copy 'wifiOnly` option from react-native-blob-util (aka rn-fetch-blob)

[cristianoccazinsp]

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When connecting, uploading and downloading data from IoT devices, sometimes we need to be able to only perform a network request through a specific network interface (e.g., WiFi).
A long time ago I implemented this feature for rn-fetch-blob (joltup/rn-fetch-blob#497), and I'm planning to migrate to this library, but this feature is a must for us.

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Copying code from joltup/rn-fetch-blob#497 is probably a good start. A very simple flag to force WiFi and never falling back to mobile data.

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[edeckers]

Hi @cristianoccazinsp, thank you for suggesting this feature! And glad to hear I'm helping a rn-fetch-blob user out, that was one of the most important reasons for me to start this library :)

At first I was kind of torn on whether or not to add the feature you're suggesting, because I figured detecting if wifi is on shouldn't be a consideration for react-native-blob-courier, and should be detected through react-native-netinfo before starting the transfer instead. But then I read your code and found your StackOverflow-post and realized that the goal of the feature you're suggesting is to actually force the download over wifi even when other connections are available. To be fair, you actually wrote that in the last line of your feature request, but I was thrown off by the naming of the wifiOnly flag.

Considering that, this feature is in scope and think it would be a nice addition to the library. I would like to enhance the suggested interface a little to make it more extensible though.

Instead of:

{
   (...)
   wifiOnly: <boolean>,
   (...)
}

I propose something like this:

{
  (...),
  channelPreference?: [<cellular | wifi | other | ... >], // ordered list of preferred channels [1]
  (...)
}

Does this make sense and would this work for you?

[1] https://github.com/react-native-netinfo/react-native-netinfo#netinfostatetype

[cristianoccazinsp]

@edeckers that interface looks better. When I added the feature I was in a hurry to get it working so that was the easiest option.

Keep in mind this feature was intended to be able to connect to IoT devices, which are most of the time connected through WiFi in a local address (e.g., 192.168.1.1), so in my use case I would never use cellular data to connect to it.

Either way, what you propose should work great.

[edeckers]

Thank you for elaborating. I'll try to add the new interface in January.

If you want to take a shot at it yourself before that: I accept PR's! Just make sure to adhere to the interface we discussed here and to include relevant tests for TypeScript, Kotlin and Swift and we should be alright.