Function chan_extra_cannot_send

plugins/renepay/chan_extra.c:305–347

Update the knowledge that this (channel,direction) cannot send.*/

/* Update the knowledge that this (channel,direction) cannot send.*/
enum renepay_errorcode
chan_extra_cannot_send(struct chan_extra_map *chan_extra_map,
		       const struct short_channel_id_dir *scidd)
{
	assert(scidd);
	assert(chan_extra_map);
	struct amount_msat x;
	enum renepay_errorcode err;
	struct chan_extra *ce = chan_extra_map_get(chan_extra_map, scidd->scid);
	if (!ce)
		return RENEPAY_CHANNEL_NOT_FOUND;

	/* Note: sent is already included in htlc_total! */
	if (!amount_msat_sub(&x, ce->half[scidd->dir].htlc_total,
			     AMOUNT_MSAT(1)))
		return RENEPAY_AMOUNT_OVERFLOW;

	struct amount_msat known_min, known_max;
	// in case we fail, let's remember the original state
	known_min = ce->half[scidd->dir].known_min;
	known_max = ce->half[scidd->dir].known_max;

	/* If we "knew" the capacity was at least this, we just showed we're
	 * wrong! */
	if (amount_msat_less(x, ce->half[scidd->dir].known_min)) {
		/* Skip to half of x, since we don't know (rounds down) */
		ce->half[scidd->dir].known_min = amount_msat_div(x, 2);
	}

	ce->half[scidd->dir].known_max =
	    amount_msat_min(ce->half[scidd->dir].known_max, x);

	err = chan_extra_adjust_half(ce, !scidd->dir);
	if (err != RENEPAY_NOERROR)
		goto restore_and_fail;
	return err;

restore_and_fail:
	// we fail, thus restore the original state
	ce->half[scidd->dir].known_min = known_min;
	ce->half[scidd->dir].known_max = known_max;
	return err;
}

/* Update the knowledge that this (channel,direction) has liquidity x.*/
// FIXME for being this low level API, I thinkg it's too much to have verbose