How is the current defined?

Is the current defined in terms of F = I*L*B, i.e. a force between two current carrying wires? And then they somehow figure out the continuity equation: integral of current density = -dq/dt ? They somehow figure out that this current is equal to -dq/dt,

Or is the current defined as i = -dq/dt? And then they introduce the current density and just say that "integral of current density = -dq/dt"?

Here:
https://en.wikipedia.org/wiki/Ampere
I see that it is defined in terms of force and a proposed further definition is in terms of q.

But for now it is defined in terms of force. So what is the logical process through which they realized that i is also -dq/dt?

 

For a base unit of 'something' we can describe what the 'something' actually is, and also can describe how the base unit is to be measured.

So which approach 'defines' the base unit?

 

The force approach defines a base unit.
And:

I^2 = (F/Fu)*Iu^2

where Iu is the base unit.