It's *possible* to do this using various RPC calls, but it's
unfriendly:
1. Call getinfo to get the current block height.
2. Call listfunds to map the UTXOs.
3. Create the PSBT and hope you get all the fields correct.
Instead, this presents an interface just like `fundpsbt`, with identical
returns.
I think it's different enough to justify a new command (though it
shares much internally, of course).
In particular, it's now quite simple to create a command which uses
specified utxos, and then adds more to meet any shortfall.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
It keeps multiple different variables around the loop, but a simple
"are we done yet?" helper makes this clearer and reduces special
cases or all-vs-target.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
fundpsbt forces the caller to manually add their weight * feerate
to the satoshis they ask for. That means no named feerates.
Instead, create a startweight parameter and do the calc for them
internally, and return the feerate we used (and, while we're at it,
the estimated final weight).
This API change is best done now, as it would otherwise have to
be appended as a parameter.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Technically, they could do this themselves, but it's much nicer to have one
place to do it (and it makes sure we get the required information into the
PSBT, which is actually not entirely accessible through listfunds, as that
doesn't want to consult with the HSM for close outputs).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON RPC: new low-level coin selection `fundpsbt` routine.
This is the normal case: you only want to reserve inputs which
are not already reserved. This saves you iterating through the
results and unreserving some if you weren't exclusive.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
reserveinputs marks UTXOs reserved for 12 hours, so we won't select them
for spending: unreserveinputs marks them available again.
Exposes param_psbt() for wider use.
Disabled the test_sign_and_send_psbt since we're altering the API;
the final patch restores it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Rusty Russell