Mimics what @thomaseizinger did here [1] and here [2].
This has the advantage that the consumer has more freedom to execute
`Action`s without having to implement particular traits. The error
handling required inside this protocol-executing function is also
reduced.
As discussed with Thomas, for this approach to work well, the
trait functions such as `receive_transfer_proof` should be infallible,
and the implementer should be forced to hide IO errors behind a retry
mechanism.
All of these asynchronous calls need to be "raced" against
the abort condition (determined by the `refund_timelock`), which is
missing in the current state of the implementation.
The initial handshake of the protocol has not been included here,
because it may not be easy to integrate this approach with libp2p, but
a couple of messages still need to exchanged. I need @tcharding to
tell me if it's feasible/good to do it like this.
[1]
https://github.com/comit-network/comit-rs/blob/move-nectar-swap-to-comit/nectar/src/swap/comit/herc20_hbit.rs#L57-L184.
[2] e584d2b14f/nectar/src/swap.rs (L716-L751).
Previously we were testing the protocol by manually driving Alice and
Bob's state machines. This logic has now be moved to an async state
transition function that can take any possible state as input. The
state transition function is called in a loop until it returns the
desired state. This allows use to interrupt midway through the protocol
and perform refund and punish tests. This design was chosen over a
generator based implementation because the the generator based
implementation results in a impure state transition function that is
difficult to reason about and prone to bugs.
Test related code was extracted into the tests folder.
The 2b and 4b states were renamed to be consistent with the rest.
Macros were used to reduce code duplication when converting
child states to their parent states and vice versa.
Todos were added were neccessary.
