/*  Copyright (C) 2019 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include "knot/common/log.h"
#include "knot/dnssec/zone-events.h"
#include "knot/updates/zone-update.h"
#include "knot/zone/adjust.h"
#include "knot/zone/serial.h"
#include "knot/zone/zone-diff.h"
#include "contrib/mempattern.h"
#include "contrib/trim.h"
#include "contrib/ucw/lists.h"
#include "contrib/ucw/mempool.h"

#include <urcu.h>

static int init_incremental(zone_update_t *update, zone_t *zone, zone_contents_t *old_contents, bool deep_copy)
{
	if (old_contents == NULL) {
		return KNOT_EINVAL;
	}

	int ret = changeset_init(&update->change, zone->name);
	if (ret != KNOT_EOK) {
		return ret;
	}

	if (deep_copy) {
		update->new_cont_deep_copy = true;
		update->new_cont = old_contents;
	} else {
		update->new_cont_deep_copy = false;
		ret = apply_prepare_zone_copy(old_contents, &update->new_cont);
		if (ret != KNOT_EOK) {
			changeset_clear(&update->change);
			return ret;
		}
	}

	uint32_t apply_flags = update->flags & UPDATE_STRICT ? APPLY_STRICT : 0;
	ret = apply_init_ctx(update->a_ctx, update->new_cont, apply_flags);
	if (ret != KNOT_EOK) {
		changeset_clear(&update->change);
		return ret;
	}

	/* Copy base SOA RR. */
	update->change.soa_from =
		node_create_rrset(old_contents->apex, KNOT_RRTYPE_SOA);
	if (update->change.soa_from == NULL) {
		zone_contents_free(update->new_cont);
		changeset_clear(&update->change);
		return KNOT_ENOMEM;
	}

	return KNOT_EOK;
}

static int init_full(zone_update_t *update, zone_t *zone)
{
	update->new_cont = zone_contents_new(zone->name);
	if (update->new_cont == NULL) {
		return KNOT_ENOMEM;
	}

	update->new_cont_deep_copy = true;

	int ret = apply_init_ctx(update->a_ctx, update->new_cont, 0);
	if (ret != KNOT_EOK) {
		zone_contents_free(update->new_cont);
		return ret;
	}

	return KNOT_EOK;
}

static int replace_soa(zone_contents_t *contents, const knot_rrset_t *rr)
{
	/* SOA possible only within apex. */
	if (!knot_dname_is_equal(rr->owner, contents->apex->owner)) {
		return KNOT_EDENIED;
	}

	knot_rrset_t old_soa = node_rrset(contents->apex, KNOT_RRTYPE_SOA);
	zone_node_t *n = contents->apex;
	int ret = zone_contents_remove_rr(contents, &old_soa, &n);
	if (ret != KNOT_EOK && ret != KNOT_EINVAL) {
		return ret;
	}

	ret = zone_contents_add_rr(contents, rr, &n);
	if (ret == KNOT_ETTL) {
		return KNOT_EOK;
	}

	return ret;
}

int init_base(zone_update_t *update, zone_t *zone, zone_contents_t *old_contents,
              zone_update_flags_t flags)
{
	if (update == NULL || zone == NULL || (old_contents == NULL && (flags & UPDATE_INCREMENTAL))) {
		return KNOT_EINVAL;
	}

	memset(update, 0, sizeof(*update));
	update->zone = zone;

	mm_ctx_mempool(&update->mm, MM_DEFAULT_BLKSIZE);
	update->flags = flags;

	update->a_ctx = calloc(1, sizeof(*update->a_ctx));
	if (update->a_ctx == NULL) {
		return KNOT_ENOMEM;
	}

	int ret = KNOT_EINVAL;
	if (flags & UPDATE_INCREMENTAL) {
		ret = init_incremental(update, zone, old_contents, flags & UPDATE_JOURNAL);
	} else if (flags & UPDATE_FULL) {
		ret = init_full(update, zone);
	}
	if (ret != KNOT_EOK) {
		free(update->a_ctx);
	}

	return ret;
}

/* ------------------------------- API -------------------------------------- */

int zone_update_init(zone_update_t *update, zone_t *zone, zone_update_flags_t flags)
{
	return init_base(update, zone, zone->contents, flags);
}

int zone_update_from_differences(zone_update_t *update, zone_t *zone, zone_contents_t *old_cont,
				 zone_contents_t *new_cont, zone_update_flags_t flags, bool ignore_dnssec)
{
	if (update == NULL || zone == NULL || new_cont == NULL ||
	    !(flags & UPDATE_INCREMENTAL) || (flags & UPDATE_FULL)) {
		return KNOT_EINVAL;
	}

	changeset_t diff;
	int ret = changeset_init(&diff, zone->name);
	if (ret != KNOT_EOK) {
		return ret;
	}

	ret = zone_contents_diff(old_cont, new_cont, &diff, ignore_dnssec);
	if (ret != KNOT_EOK && ret != KNOT_ENODIFF && ret != KNOT_ESEMCHECK) {
		changeset_clear(&diff);
		return ret;
	}

	// True if nonempty changes were made but the serial
	// remained the same and has to be incremented.
	bool diff_semcheck = (ret == KNOT_ESEMCHECK);

	ret = init_base(update, zone, old_cont, flags);
	if (ret != KNOT_EOK) {
		changeset_clear(&diff);
		return ret;
	}

	ret = zone_update_apply_changeset(update, &diff);
	changeset_clear(&diff);
	if (ret != KNOT_EOK) {
		zone_update_clear(update);
		return ret;
	}

	if (diff_semcheck) {
		ret = zone_update_increment_soa(update, conf());
		if (ret != KNOT_EOK) {
			zone_update_clear(update);
			return ret;
		}
		log_zone_info(zone->name, "automatic SOA serial increment");
	}

	return KNOT_EOK;
}

int zone_update_from_contents(zone_update_t *update, zone_t *zone_without_contents,
                              zone_contents_t *new_cont, zone_update_flags_t flags)
{
	if (update == NULL || zone_without_contents == NULL || new_cont == NULL) {
		return KNOT_EINVAL;
	}

	memset(update, 0, sizeof(*update));
	update->zone = zone_without_contents;

	mm_ctx_mempool(&update->mm, MM_DEFAULT_BLKSIZE);
	update->flags = flags;

	update->new_cont = new_cont;
	update->new_cont_deep_copy = true;

	update->a_ctx = calloc(1, sizeof(*update->a_ctx));
	if (update->a_ctx == NULL) {
		return KNOT_ENOMEM;
	}

	if (flags & UPDATE_INCREMENTAL) {
		int ret = changeset_init(&update->change, zone_without_contents->name);
		if (ret != KNOT_EOK) {
			free(update->a_ctx);
			return ret;
		}

		update->change.soa_from = node_create_rrset(new_cont->apex, KNOT_RRTYPE_SOA);
		if (update->change.soa_from == NULL) {
			changeset_clear(&update->change);
			free(update->a_ctx);
			return KNOT_ENOMEM;
		}
	}

	uint32_t apply_flags = update->flags & UPDATE_STRICT ? APPLY_STRICT : 0;
	int ret = apply_init_ctx(update->a_ctx, update->new_cont, apply_flags);
	if (ret != KNOT_EOK) {
		changeset_clear(&update->change);
		free(update->a_ctx);
		return ret;
	}

	return KNOT_EOK;
}

const zone_node_t *zone_update_get_node(zone_update_t *update, const knot_dname_t *dname)
{
	if (update == NULL || dname == NULL) {
		return NULL;
	}

	return zone_contents_find_node(update->new_cont, dname);
}

const zone_node_t *zone_update_get_apex(zone_update_t *update)
{
	if (update == NULL) {
		return NULL;
	}

	return zone_update_get_node(update, update->zone->name);
}

uint32_t zone_update_current_serial(zone_update_t *update)
{
	const zone_node_t *apex = zone_update_get_apex(update);
	if (apex != NULL) {
		return knot_soa_serial(node_rdataset(apex, KNOT_RRTYPE_SOA)->rdata);
	} else {
		return 0;
	}
}

static bool zone_update_changed_nsec3param(const zone_update_t *update)
{
	if (update->zone->contents == NULL) {
		return true;
	}

	dnssec_nsec3_params_t *orig = &update->zone->contents->nsec3_params;
	dnssec_nsec3_params_t *upd = &update->new_cont->nsec3_params;
	return dnssec_nsec3_params_match(orig, upd);
}

const knot_rdataset_t *zone_update_from(zone_update_t *update)
{
	if (update == NULL) {
		return NULL;
	}

	if (update->flags & UPDATE_INCREMENTAL) {
		const zone_node_t *apex = update->zone->contents->apex;
		return node_rdataset(apex, KNOT_RRTYPE_SOA);
	}

	return NULL;
}

const knot_rdataset_t *zone_update_to(zone_update_t *update)
{
	if (update == NULL) {
		return NULL;
	}

	if (update->flags & UPDATE_FULL) {
		const zone_node_t *apex = update->new_cont->apex;
		return node_rdataset(apex, KNOT_RRTYPE_SOA);
	} else if (update->flags & UPDATE_INCREMENTAL) {
		if (update->change.soa_to == NULL) {
			return NULL;
		}
		return &update->change.soa_to->rrs;
	}

	return NULL;
}

void zone_update_clear(zone_update_t *update)
{
	if (update == NULL) {
		return;
	}

	if (update->flags & UPDATE_INCREMENTAL) {
		/* Revert any changes on error, do nothing on success. */
		if (update->new_cont_deep_copy) {
			update_cleanup(update->a_ctx);
			zone_contents_deep_free(update->new_cont);
		} else {
			update_rollback(update->a_ctx);
			update_free_zone(update->new_cont);
		}
		changeset_clear(&update->change);
	} else if (update->flags & UPDATE_FULL) {
		assert(update->new_cont_deep_copy);
		zone_contents_deep_free(update->new_cont);
	}
	free(update->a_ctx);
	mp_delete(update->mm.ctx);
	memset(update, 0, sizeof(*update));
}

int zone_update_add(zone_update_t *update, const knot_rrset_t *rrset)
{
	if (update == NULL || rrset == NULL) {
		return KNOT_EINVAL;
	}

	if (update->flags & UPDATE_INCREMENTAL) {
		int ret = changeset_add_addition(&update->change, rrset, CHANGESET_CHECK);
		if (ret != KNOT_EOK) {
			return ret;
		}

		if (rrset->type == KNOT_RRTYPE_SOA) {
			/* replace previous SOA */
			ret = apply_replace_soa(update->a_ctx, &update->change);
			if (ret != KNOT_EOK) {
				changeset_remove_addition(&update->change, rrset);
			}
			return ret;
		}

		ret = apply_add_rr(update->a_ctx, rrset);
		if (ret != KNOT_EOK) {
			changeset_remove_addition(&update->change, rrset);
			return ret;
		}

		return KNOT_EOK;
	} else if (update->flags & UPDATE_FULL) {
		if (rrset->type == KNOT_RRTYPE_SOA) {
			/* replace previous SOA */
			return replace_soa(update->new_cont, rrset);
		}

		zone_node_t *n = NULL;
		int ret = zone_contents_add_rr(update->new_cont, rrset, &n);
		if (ret == KNOT_ETTL) {
			char buff[KNOT_DNAME_TXT_MAXLEN + 1];
			char *owner = knot_dname_to_str(buff, rrset->owner, sizeof(buff));
			if (owner == NULL) {
				owner = "";
			}
			char type[16] = { '\0' };
			knot_rrtype_to_string(rrset->type, type, sizeof(type));
			log_zone_notice(update->new_cont->apex->owner,
			                "TTL mismatch, owner %s, type %s, "
			                "TTL set to %u", owner, type, rrset->ttl);
			return KNOT_EOK;
		}

		return ret;
	} else {
		return KNOT_EINVAL;
	}
}

int zone_update_remove(zone_update_t *update, const knot_rrset_t *rrset)
{
	if (update == NULL || rrset == NULL) {
		return KNOT_EINVAL;
	}

	if (update->flags & UPDATE_INCREMENTAL) {
		int ret = changeset_add_removal(&update->change, rrset, CHANGESET_CHECK);
		if (ret != KNOT_EOK) {
			return ret;
		}

		if (rrset->type == KNOT_RRTYPE_SOA) {
			/* SOA is replaced with addition */
			return KNOT_EOK;
		}

		ret = apply_remove_rr(update->a_ctx, rrset);
		if (ret != KNOT_EOK) {
			changeset_remove_removal(&update->change, rrset);
			return ret;
		}

		return KNOT_EOK;
	} else if (update->flags & UPDATE_FULL) {
		zone_node_t *n = NULL;
		knot_rrset_t *rrs_copy = knot_rrset_copy(rrset, &update->mm);
		int ret = zone_contents_remove_rr(update->new_cont, rrs_copy, &n);
		knot_rrset_free(rrs_copy, &update->mm);
		return ret;
	} else {
		return KNOT_EINVAL;
	}
}

int zone_update_remove_rrset(zone_update_t *update, knot_dname_t *owner, uint16_t type)
{
	if (update == NULL || owner == NULL) {
		return KNOT_EINVAL;
	}

	if (update->flags & UPDATE_INCREMENTAL) {
		/* Remove the RRSet from the original node */
		const zone_node_t *node = zone_contents_find_node(update->new_cont, owner);
		if (node != NULL) {
			knot_rrset_t rrset = node_rrset(node, type);
			if (rrset.owner == NULL) {
				return KNOT_ENOENT;
			}
			int ret = changeset_add_removal(&update->change, &rrset,
			                                CHANGESET_CHECK);
			if (ret != KNOT_EOK) {
				return ret;
			}

			if (type == KNOT_RRTYPE_SOA) {
				/* SOA is replaced with addition */
				return KNOT_EOK;
			}

			ret = apply_remove_rr(update->a_ctx, &rrset);
			if (ret != KNOT_EOK) {
				return ret;
			}
		} else {
			return KNOT_ENONODE;
		}
	} else if (update->flags & UPDATE_FULL) {
		/* Remove the RRSet from the non-synthesized new node */
		const zone_node_t *node = zone_contents_find_node(update->new_cont, owner);
		if (node == NULL) {
			return KNOT_ENONODE;
		}

		knot_rrset_t rrset = node_rrset(node, type);
		int ret = zone_update_remove(update, &rrset);
		if (ret != KNOT_EOK) {
			return ret;
		}
	}

	return KNOT_EOK;
}

int zone_update_remove_node(zone_update_t *update, const knot_dname_t *owner)
{
	if (update == NULL || owner == NULL) {
		return KNOT_EINVAL;
	}

	if (update->flags & UPDATE_INCREMENTAL) {
		/* Remove all RRSets from the new node */
		const zone_node_t *node = zone_contents_find_node(update->new_cont, owner);
		if (node != NULL) {
			size_t rrset_count = node->rrset_count;
			for (int i = 0; i < rrset_count; ++i) {
				knot_rrset_t rrset = node_rrset_at(node, rrset_count - 1 - i);
				int ret = changeset_add_removal(&update->change, &rrset,
				                                CHANGESET_CHECK);
				if (ret != KNOT_EOK) {
					return ret;
				}

				if (rrset.type == KNOT_RRTYPE_SOA) {
					/* SOA is replaced with addition */
					continue;
				}

				ret = apply_remove_rr(update->a_ctx, &rrset);
				if (ret != KNOT_EOK) {
					return ret;
				}
			}
		} else {
			return KNOT_ENONODE;
		}
	} else if (update->flags & UPDATE_FULL) {
		/* Remove all RRSets from the non-synthesized new node */
		const zone_node_t *node = zone_contents_find_node(update->new_cont, owner);
		if (node == NULL) {
			return KNOT_ENONODE;
		}

		size_t rrset_count = node->rrset_count;
		for (int i = 0; i < rrset_count; ++i) {
			knot_rrset_t rrset = node_rrset_at(node, rrset_count - 1 - i);
			int ret = zone_update_remove(update, &rrset);
			if (ret != KNOT_EOK) {
				return ret;
			}
		}
	}

	return KNOT_EOK;
}

int zone_update_apply_changeset(zone_update_t *update, const changeset_t *changes)
{
	int ret = KNOT_EOK;
	if (update->flags & UPDATE_INCREMENTAL) {
		ret = changeset_merge(&update->change, changes, CHANGESET_CHECK_CANCELOUT);
	}
	if (ret == KNOT_EOK) {
		ret = apply_changeset_directly(update->a_ctx, changes);
	}
	return ret;
}

int zone_update_apply_changeset_fix(zone_update_t *update, changeset_t *changes)
{
	int ret = changeset_cancelout(changes);
	if (ret == KNOT_EOK) {
		ret = changeset_preapply_fix(update->new_cont, changes);
	}
	if (ret == KNOT_EOK) {
		ret = zone_update_apply_changeset(update, changes);
	}
	return ret;
}

int zone_update_apply_changeset_reverse(zone_update_t *update, const changeset_t *changes)
{
	changeset_t reverse;
	reverse.remove = changes->add;
	reverse.add = changes->remove;
	reverse.soa_from = changes->soa_to;
	reverse.soa_to = changes->soa_from;
	return zone_update_apply_changeset(update, &reverse);
}

static int set_new_soa(zone_update_t *update, unsigned serial_policy)
{
	assert(update);

	knot_rrset_t *soa_cpy = node_create_rrset(zone_update_get_apex(update),
	                                          KNOT_RRTYPE_SOA);
	if (soa_cpy == NULL) {
		return KNOT_ENOMEM;
	}

	int ret = zone_update_remove(update, soa_cpy);
	if (ret != KNOT_EOK) {
		knot_rrset_free(soa_cpy, NULL);
		return ret;
	}

	uint32_t old_serial = knot_soa_serial(soa_cpy->rrs.rdata);
	uint32_t new_serial = serial_next(old_serial, serial_policy);
	if (serial_compare(old_serial, new_serial) != SERIAL_LOWER) {
		log_zone_warning(update->zone->name, "updated SOA serial is lower "
		                 "than current, serial %u -> %u",
		                 old_serial, new_serial);
		ret = KNOT_ESOAINVAL;
	} else {
		knot_soa_serial_set(soa_cpy->rrs.rdata, new_serial);

		ret = zone_update_add(update, soa_cpy);
	}
	knot_rrset_free(soa_cpy, NULL);

	return ret;
}

int zone_update_increment_soa(zone_update_t *update, conf_t *conf)
{
	if (update == NULL || conf == NULL) {
		return KNOT_EINVAL;
	}

	conf_val_t val = conf_zone_get(conf, C_SERIAL_POLICY, update->zone->name);
	return set_new_soa(update, conf_opt(&val));
}

static int commit_incremental(conf_t *conf, zone_update_t *update)
{
	assert(update);

	int ret = KNOT_EOK;
	if (zone_update_to(update) == NULL && !changeset_empty(&update->change)) {
		/* No SOA in the update, create one according to the current policy */
		ret = zone_update_increment_soa(update, conf);
		if (ret != KNOT_EOK) {
			zone_update_clear(update);
			return ret;
		}
	}

	if (zone_update_changed_nsec3param(update)) {
		ret = zone_adjust_full(update->new_cont);
	} else {
		ret = zone_adjust_incremental_update(update);
	}
	if (ret != KNOT_EOK) {
		zone_update_clear(update);
		return ret;
	}

	/* Write changes to journal if all went well. */
	conf_val_t val = conf_zone_get(conf, C_JOURNAL_CONTENT, update->zone->name);
	if (conf_opt(&val) != JOURNAL_CONTENT_NONE && !changeset_empty(&update->change)) {
		ret = zone_change_store(conf, update->zone, &update->change);
		if (ret != KNOT_EOK) {
			return ret;
		}
	}

	return KNOT_EOK;
}

static int commit_full(conf_t *conf, zone_update_t *update)
{
	assert(update);

	/* Check if we have SOA. We might consider adding full semantic check here.
	 * But if we wanted full sem-check I'd consider being it controlled by a flag
	 * - to enable/disable it on demand. */
	if (!node_rrtype_exists(update->new_cont->apex, KNOT_RRTYPE_SOA)) {
		return KNOT_ESEMCHECK;
	}

	int ret = zone_adjust_full(update->new_cont);
	if (ret != KNOT_EOK) {
		zone_update_clear(update);
		return ret;
	}

	/* Store new zone contents in journal. */
	conf_val_t val = conf_zone_get(conf, C_JOURNAL_CONTENT, update->zone->name);
	unsigned content = conf_opt(&val);
	if (content == JOURNAL_CONTENT_ALL) {
		ret = zone_in_journal_store(conf, update->zone, update->new_cont);
	} else if (content != JOURNAL_CONTENT_NONE) { // zone_in_journal_store does this automatically
		ret = zone_changes_clear(conf, update->zone);
	}

	return ret;
}

int zone_update_commit(conf_t *conf, zone_update_t *update)
{
	if (conf == NULL || update == NULL) {
		return KNOT_EINVAL;
	}

	int ret = KNOT_EOK;
	if (update->flags & UPDATE_INCREMENTAL) {
		if (changeset_empty(&update->change) &&
		    update->zone->contents != NULL && !update->new_cont_deep_copy) {
			changeset_clear(&update->change);
			return KNOT_EOK;
		}
		ret = commit_incremental(conf, update);
	} else {
		ret = commit_full(conf, update);
	}
	if (ret != KNOT_EOK) {
		return ret;
	}

	/* Check the zone size. */
	conf_val_t val = conf_zone_get(conf, C_MAX_ZONE_SIZE, update->zone->name);
	size_t size_limit = conf_int(&val);

	if (update->new_cont->size > size_limit) {
		/* Recoverable error. */
		return KNOT_EZONESIZE;
	}

	/* Check if the zone was re-signed upon zone load to ensure proper flush
	 * even if the SOA serial wasn't incremented by re-signing. */
	val = conf_zone_get(conf, C_DNSSEC_SIGNING, update->zone->name);
	bool dnssec = conf_bool(&val);
	if (!changeset_empty(&update->change) && dnssec) {
		update->zone->zonefile.resigned = true;
	}

	/* Switch zone contents. */
	zone_contents_t *old_contents;
	old_contents = zone_switch_contents(update->zone, update->new_cont);

	/* Sync RCU. */
	synchronize_rcu();
	if (update->flags & UPDATE_FULL) {
		assert(update->new_cont_deep_copy);
		zone_contents_deep_free(old_contents);
	} else if (update->flags & UPDATE_INCREMENTAL) {
		if (update->new_cont_deep_copy) {
			zone_contents_deep_free(old_contents);
		} else {
			update_free_zone(old_contents);
		}
		changeset_clear(&update->change);
	}
	update_cleanup(update->a_ctx);
	free(update->a_ctx);
	update->a_ctx = NULL;
	update->new_cont = NULL;

	/* Sync zonefile immediately if configured. */
	val = conf_zone_get(conf, C_ZONEFILE_SYNC, update->zone->name);
	if (conf_int(&val) == 0) {
		zone_events_schedule_now(update->zone, ZONE_EVENT_FLUSH);
	}

	return KNOT_EOK;
}

static int iter_init_tree_iters(zone_update_iter_t *it, zone_update_t *update,
                                bool nsec3)
{
	/* Set zone iterator. */
	zone_contents_t *_contents = update->new_cont;

	/* Begin iteration. We can safely assume _contents is a valid pointer. */
	zone_tree_t *tree = nsec3 ? _contents->nsec3_nodes : _contents->nodes;
	if (zone_tree_it_begin(tree, &it->tree_it) != KNOT_EOK) {
		return KNOT_ENOMEM;
	}

	it->cur_node = zone_tree_it_val(&it->tree_it);

	return KNOT_EOK;
}

static int iter_get_next_node(zone_update_iter_t *it)
{
	zone_tree_it_next(&it->tree_it);
	if (zone_tree_it_finished(&it->tree_it)) {
		zone_tree_it_free(&it->tree_it);
		it->cur_node = NULL;
		return KNOT_ENOENT;
	}

	it->cur_node = zone_tree_it_val(&it->tree_it);

	return KNOT_EOK;
}

static int iter_init(zone_update_iter_t *it, zone_update_t *update, const bool nsec3)
{
	memset(it, 0, sizeof(*it));

	it->update = update;
	it->nsec3 = nsec3;
	int ret = iter_init_tree_iters(it, update, nsec3);
	if (ret != KNOT_EOK) {
		return ret;
	}

	it->cur_node = zone_tree_it_val(&it->tree_it);

	return KNOT_EOK;
}

int zone_update_iter(zone_update_iter_t *it, zone_update_t *update)
{
	if (it == NULL || update == NULL) {
		return KNOT_EINVAL;
	}

	return iter_init(it, update, false);
}

int zone_update_iter_nsec3(zone_update_iter_t *it, zone_update_t *update)
{
	if (it == NULL || update == NULL) {
		return KNOT_EINVAL;
	}

	if (update->flags & UPDATE_FULL) {
		if (update->new_cont->nsec3_nodes == NULL) {
			/* No NSEC3 tree. */
			return KNOT_ENOENT;
		}
	} else {
		if (update->change.add->nsec3_nodes == NULL &&
		    update->change.remove->nsec3_nodes == NULL) {
			/* No NSEC3 changes. */
			return KNOT_ENOENT;
		}
	}

	return iter_init(it, update, true);
}

int zone_update_iter_next(zone_update_iter_t *it)
{
	if (it == NULL) {
		return KNOT_EINVAL;
	}

	if (it->tree_it.it != NULL) {
		int ret = iter_get_next_node(it);
		if (ret != KNOT_EOK && ret != KNOT_ENOENT) {
			return ret;
		}
	}

	return KNOT_EOK;
}

const zone_node_t *zone_update_iter_val(zone_update_iter_t *it)
{
	if (it != NULL) {
		return it->cur_node;
	} else {
		return NULL;
	}
}

void zone_update_iter_finish(zone_update_iter_t *it)
{
	if (it == NULL) {
		return;
	}

	zone_tree_it_free(&it->tree_it);
}

bool zone_update_no_change(zone_update_t *update)
{
	if (update == NULL) {
		return true;
	}

	if (update->flags & UPDATE_INCREMENTAL) {
		return changeset_empty(&update->change);
	} else {
		/* This branch does not make much sense and FULL update will most likely
		 * be a change every time anyway, just return false. */
		return false;
	}
}