Function why_max_constrained

plugins/askrene/child/explain_failure.c:35–78

This mirrors get_constraints() */

/* This mirrors get_constraints() */
static const char *why_max_constrained(const tal_t *ctx,
				       const struct route_query *rq,
				       struct short_channel_id_dir *scidd,
				       struct amount_msat amount)
{
	char *ret = NULL;
	const char *reservations;
	const struct layer *constrains = NULL;
	struct amount_msat max = amount;

	/* Figure out the layer that constrains us (most) */
	for (size_t i = 0; i < tal_count(rq->layers); i++) {
		struct amount_msat min = AMOUNT_MSAT(0), new_max = max;

		layer_apply_constraints(rq->layers[i], scidd, &min, &new_max);
		if (!amount_msat_eq(new_max, max))
			constrains = rq->layers[i];
		max = new_max;
	}

	if (constrains) {
		if (!ret)
			ret = tal_strdup(ctx, "");
		else
			tal_append_fmt(&ret, ", ");
		tal_append_fmt(&ret, "layer %s says max is %s",
			       layer_name(constrains),
			       fmt_amount_msat(tmpctx, max));
	}

	reservations = fmt_reservations(tmpctx, rq->reserved, scidd, rq->layers);
	if (reservations) {
		if (!ret)
			ret = tal_strdup(ctx, "");
		else
			tal_append_fmt(&ret, " and ");
		tal_append_fmt(&ret, "already reserved %s", reservations);
	}

	/* This seems unlikely, but don't return NULL. */
	if (!ret)
		ret = tal_fmt(ctx, "is constrained");
	return ret;
}

struct stat {
	size_t num_channels;