Syncing across multiple devices (causes NaN errors)

[iteles]

[By the end of writing this issue it appears that the real issue is that timers need to be synced across devices - is this an alpha issue?]

Original title of this issue: If I log in from a different browser/device, causes NaN on any already running timers
I started a timer in my browser for styling the logout button:

I then decided to log into my account on my phone. As the timer starts automatically when I open the app on my phone, I had a second running timer when I logged in (one I didn't care about and would have deleted). This caused the logout button timer I had started in my browser to **render as a NaN on the phone whilst it was still running in the browser):

Once the timer in the browser was stopped, this:
a) rendered correctly in the browser straight away, but on refresh, a blank NaN timer appeared (looks like this might be because the timer on the phone was still running):

b) rendered correctly on the phone after a manual refresh, replacing the NaN timer BUT after a few minutes, the same blank NaN timer which appears in the browser above appears on the phone as well

[nelsonic]

Spotted this too. But... have a related question:

What happens if there is more than one active timer?
i.e. you have one running on your phone and another on your desktop (anonymously) and then you login, should both timers continue running on the different devices?
(@iteles this is the interesting/hard part...)

[nelsonic]

Relates to: #128 (Multiple Concurrent Timers)

[iteles]

If there's more than one active timer, then I feel like the most obvious thing to happen is that they're synced across your devices as soon as you log in - so rather than displaying one active timer, you display two.

This will have UI implications as well, but is not an [alpha] feature. For the next 24 hours we only worry about [alpha] bugs as this will most likely all change as soon as alpha is out the door!

[nelsonic]

So, is _this_ an alpha bug then...?
How many people are going to be using this on two devices from tomorrow?

[iteles]

This was exactly the question I posed at the very top of the issue. I think for alpha we can tell people that they're limited to one device.
Agreed @nelsonic ?

[nelsonic]

Agreed. The plan is to add Socket.IO V. Soon so devices are sync-ed.
for now pick your browser. one timer (at a time ... no multi-tasking)

[nelsonic]

This should not be an issue with Phoenix Channels 👍
See: https://github.com/dwyl/technology-stack#the-pete-stack