mailbox-list-index-notify.c

/* Copyright (c) 2013-2016 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "ioloop.h"
#include "str.h"
#include "mail-index-private.h"
#include "mail-transaction-log-private.h"
#include "mail-storage-private.h"
#include "mailbox-list-notify.h"
#include "mailbox-list-notify-tree.h"
#include "mailbox-list-index.h"

#include <sys/stat.h>

#define NOTIFY_DELAY_MSECS 500

enum ilist_ext_type {
	ILIST_EXT_NONE,
	ILIST_EXT_BASE,
	ILIST_EXT_MSGS,
	ILIST_EXT_HIGHESTMODSEQ,
	ILIST_EXT_UNKNOWN
};

struct mailbox_list_notify_rename {
	uint32_t old_uid, new_uid;
};

struct mailbox_list_inotify_entry {
	uint32_t uid;
	guid_128_t guid;
	bool expunge;
};

struct mailbox_list_notify_index {
	struct mailbox_list_notify notify;

	struct mailbox_tree_context *subscriptions;
	struct mailbox_list_notify_tree *tree;
	struct mail_index_view *view, *old_view;
	struct mail_index_view_sync_ctx *sync_ctx;
	enum ilist_ext_type cur_ext;
	uint32_t cur_ext_id;

	void (*wait_callback)(void *context);
	void *wait_context;
	struct io *io_wait, *io_wait_inbox;
	struct timeout *to_wait, *to_notify;

	ARRAY_TYPE(seq_range) new_uids, expunged_uids, changed_uids;
	ARRAY_TYPE(const_string) new_subscriptions, new_unsubscriptions;
	ARRAY(struct mailbox_list_notify_rename) renames;
	struct seq_range_iter new_uids_iter, expunged_uids_iter;
	struct seq_range_iter changed_uids_iter;
	unsigned int new_uids_n, expunged_uids_n, changed_uids_n;
	unsigned int rename_idx, subscription_idx, unsubscription_idx;

	struct mailbox_list_notify_rec notify_rec;
	string_t *rec_name;

	char *list_log_path, *inbox_log_path;
	struct stat list_last_st, inbox_last_st;

	unsigned int initialized:1;
	unsigned int read_failed:1;
	unsigned int inbox_event_pending:1;
};

int mailbox_list_index_notify_init(struct mailbox_list *list,
				   enum mailbox_list_notify_event mask,
				   struct mailbox_list_notify **notify_r)
{
	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT(list);
	struct mailbox_list_notify_index *inotify;
	const char *index_dir;

	if (ilist == NULL) {
		/* can't do this without mailbox list indexes */
		return -1;
	}

	(void)mailbox_list_index_refresh(list);

	inotify = i_new(struct mailbox_list_notify_index, 1);
	inotify->notify.list = list;
	inotify->notify.mask = mask;
	inotify->view = mail_index_view_open(ilist->index);
	inotify->old_view = mail_index_view_dup_private(inotify->view);
	inotify->tree = mailbox_list_notify_tree_init(list);
	i_array_init(&inotify->new_uids, 8);
	i_array_init(&inotify->expunged_uids, 8);
	i_array_init(&inotify->changed_uids, 16);
	i_array_init(&inotify->renames, 16);
	i_array_init(&inotify->new_subscriptions, 16);
	i_array_init(&inotify->new_unsubscriptions, 16);
	inotify->rec_name = str_new(default_pool, 64);
	if ((mask & (MAILBOX_LIST_NOTIFY_SUBSCRIBE |
		     MAILBOX_LIST_NOTIFY_UNSUBSCRIBE)) != 0) {
		(void)mailbox_list_iter_subscriptions_refresh(list);
		mailbox_tree_sort(list->subscriptions);
		inotify->subscriptions = mailbox_tree_dup(list->subscriptions);
	}
	inotify->list_log_path = i_strdup(ilist->index->log->filepath);
	if ((list->ns->flags & NAMESPACE_FLAG_INBOX_ANY) != 0 &&
	    mailbox_list_get_path(list, "INBOX", MAILBOX_LIST_PATH_TYPE_INDEX,
				  &index_dir) > 0) {
		/* FIXME: annoyingly hardcoded filename. */
		inotify->inbox_log_path = i_strdup_printf(
			"%s/"MAIL_INDEX_PREFIX".log", index_dir);
	}

	*notify_r = &inotify->notify;
	return 1;
}

void mailbox_list_index_notify_deinit(struct mailbox_list_notify *notify)
{
	struct mailbox_list_notify_index *inotify =
		(struct mailbox_list_notify_index *)notify;
	bool b;

	if (inotify->subscriptions != NULL)
		mailbox_tree_deinit(&inotify->subscriptions);
	if (inotify->io_wait != NULL)
		io_remove(&inotify->io_wait);
	if (inotify->io_wait_inbox != NULL)
		io_remove(&inotify->io_wait_inbox);
	if (inotify->to_wait != NULL)
		timeout_remove(&inotify->to_wait);
	if (inotify->to_notify != NULL)
		timeout_remove(&inotify->to_notify);
	if (inotify->sync_ctx != NULL)
		(void)mail_index_view_sync_commit(&inotify->sync_ctx, &b);
	mail_index_view_close(&inotify->view);
	mail_index_view_close(&inotify->old_view);
	mailbox_list_notify_tree_deinit(&inotify->tree);
	array_free(&inotify->new_subscriptions);
	array_free(&inotify->new_unsubscriptions);
	array_free(&inotify->new_uids);
	array_free(&inotify->expunged_uids);
	array_free(&inotify->changed_uids);
	array_free(&inotify->renames);
	str_free(&inotify->rec_name);
	i_free(inotify->list_log_path);
	i_free(inotify->inbox_log_path);
	i_free(inotify);
}

static struct mailbox_list_index_node *
notify_lookup_guid(struct mailbox_list_notify_index *inotify,
		   struct mail_index_view *view,
		   uint32_t uid, enum mailbox_status_items items,
		   struct mailbox_status *status_r, guid_128_t guid_r)
{
	struct mailbox_list_index *ilist =
		INDEX_LIST_CONTEXT(inotify->notify.list);
	struct mailbox_list_index_node *index_node;
	uint32_t seq;

	if (!mail_index_lookup_seq(view, uid, &seq))
		return NULL;

	index_node = mailbox_list_index_lookup_uid(ilist, uid);
	if (index_node == NULL) {
		/* re-parse the index list using the given view. we could be
		   jumping here between old and new view. */
		(void)mailbox_list_index_parse(inotify->notify.list,
					       view, FALSE);
		index_node = mailbox_list_index_lookup_uid(ilist, uid);
		if (index_node == NULL)
			return NULL;
	}

	/* get GUID */
	memset(status_r, 0, sizeof(*status_r));
	memset(guid_r, 0, GUID_128_SIZE);
	(void)mailbox_list_index_status(inotify->notify.list, view, seq,
					items, status_r, guid_r, NULL);
	return index_node;
}

static void notify_update_stat(struct mailbox_list_notify_index *inotify)
{
	bool call = FALSE;

	if (stat(inotify->list_log_path, &inotify->list_last_st) < 0 &&
	    errno != ENOENT) {
		i_error("stat(%s) failed: %m", inotify->list_log_path);
		call = TRUE;
	}
	if (inotify->inbox_log_path != NULL) {
		if (stat(inotify->inbox_log_path, &inotify->inbox_last_st) < 0 &&
		    errno != ENOENT) {
			i_error("stat(%s) failed: %m", inotify->inbox_log_path);
			call = TRUE;
		}
	}
	if (call)
		mailbox_list_index_notify_wait(&inotify->notify, NULL, NULL);
}

static void
mailbox_list_index_notify_sync_init(struct mailbox_list_notify_index *inotify)
{
	struct mail_index_view_sync_rec sync_rec;

	notify_update_stat(inotify);
	(void)mail_index_refresh(inotify->view->index);

	/* sync the view so that map extensions gets updated */
	inotify->sync_ctx = mail_index_view_sync_begin(inotify->view, 0);
	mail_transaction_log_view_mark(inotify->view->log_view);
	while (mail_index_view_sync_next(inotify->sync_ctx, &sync_rec)) ;
	mail_transaction_log_view_rewind(inotify->view->log_view);

	inotify->cur_ext = ILIST_EXT_NONE;
	inotify->cur_ext_id = (uint32_t)-1;
}

static bool notify_ext_rec(struct mailbox_list_notify_index *inotify,
			   uint32_t uid)
{
	struct mailbox_list_notify *notify = &inotify->notify;

	switch (inotify->cur_ext) {
	case ILIST_EXT_NONE:
		i_unreached();
	case ILIST_EXT_BASE:
		/* UIDVALIDITY changed */
		if ((notify->mask & MAILBOX_LIST_NOTIFY_UIDVALIDITY) == 0)
			return FALSE;
		break;
	case ILIST_EXT_MSGS:
		/* APPEND, EXPUNGE, \Seen or \Recent flag change */
		if ((notify->mask & MAILBOX_LIST_NOTIFY_STATUS) == 0)
			return FALSE;
		break;
	case ILIST_EXT_HIGHESTMODSEQ:
		/* when this doesn't come with EXT_MSGS update,
		   it can only be a flag change or an explicit
		   modseq change */
		if ((notify->mask & MAILBOX_LIST_NOTIFY_MODSEQ_CHANGES) == 0)
			return FALSE;
		break;
	case ILIST_EXT_UNKNOWN:
		return FALSE;
	}
	seq_range_array_add(&inotify->changed_uids, uid);
	return TRUE;
}

static int
mailbox_list_index_notify_read_next(struct mailbox_list_notify_index *inotify)
{
	struct mailbox_list_notify *notify = &inotify->notify;
	struct mailbox_list_index *ilist = INDEX_LIST_CONTEXT(notify->list);
	const struct mail_transaction_header *hdr;
	const void *data;
	int ret;

	ret = mail_transaction_log_view_next(inotify->view->log_view,
					     &hdr, &data);
	if (ret <= 0)
		return ret;

	if ((hdr->type & MAIL_TRANSACTION_EXTERNAL) == 0) {
		/* all mailbox index updates are external */
		return 1;
	}
	switch (hdr->type & MAIL_TRANSACTION_TYPE_MASK) {
	case MAIL_TRANSACTION_APPEND: {
		/* mailbox added or renamed */
		const struct mail_index_record *rec, *end;

		if ((notify->mask & (MAILBOX_LIST_NOTIFY_CREATE |
				     MAILBOX_LIST_NOTIFY_RENAME)) == 0)
			break;

		end = CONST_PTR_OFFSET(data, hdr->size);
		for (rec = data; rec != end; rec++)
			seq_range_array_add(&inotify->new_uids, rec->uid);
		break;
	}
	case MAIL_TRANSACTION_EXPUNGE_GUID: {
		/* mailbox deleted or renamed */
		const struct mail_transaction_expunge_guid *rec, *end;

		if ((notify->mask & (MAILBOX_LIST_NOTIFY_DELETE |
				     MAILBOX_LIST_NOTIFY_RENAME)) == 0)
			break;

		end = CONST_PTR_OFFSET(data, hdr->size);
		for (rec = data; rec != end; rec++)
			seq_range_array_add(&inotify->expunged_uids, rec->uid);
		break;
	}
	case MAIL_TRANSACTION_EXT_INTRO: {
		struct mail_index_map *map = inotify->view->map;
		const struct mail_transaction_ext_intro *rec = data;
		const struct mail_index_ext *ext = NULL;
		const char *name;
		uint32_t ext_map_idx;

		if (!array_is_created(&map->extensions))
			break;
		/* we want to know what extension the future
		   ext-rec-updates are changing. we're assuming here that
		   there is only one ext-intro record before those,
		   which is true at least for now. */
		if (rec->ext_id != (uint32_t)-1 &&
		    rec->ext_id < array_count(&map->extensions)) {
			/* get extension by id */
			ext = array_idx(&map->extensions, rec->ext_id);
		} else if (rec->name_size > 0) {
			/* by name */
			name = t_strndup(rec+1, rec->name_size);
			if (mail_index_map_lookup_ext(map, name, &ext_map_idx))
				ext = array_idx(&map->extensions, ext_map_idx);
		}
		if (ext != NULL) {
			if (ext->index_idx == ilist->ext_id)
				inotify->cur_ext = ILIST_EXT_BASE;
			else if (ext->index_idx == ilist->msgs_ext_id)
				inotify->cur_ext = ILIST_EXT_MSGS;
			else if (ext->index_idx == ilist->hmodseq_ext_id)
				inotify->cur_ext = ILIST_EXT_HIGHESTMODSEQ;
			else
				inotify->cur_ext = ILIST_EXT_UNKNOWN;
			inotify->cur_ext_id = ext->index_idx;
		}
		break;
	}
	case MAIL_TRANSACTION_EXT_REC_UPDATE: {
		const struct mail_index_registered_ext *ext;
		const struct mail_transaction_ext_rec_update *rec;
		unsigned int i, record_size;

		if (inotify->cur_ext == ILIST_EXT_NONE) {
			i_error("%s: Missing ext-intro for ext-rec-update",
				ilist->index->filepath);
			break;
		}

		/* the record is padded to 32bits in the transaction log */
		ext = array_idx(&inotify->view->index->extensions,
				inotify->cur_ext_id);
		record_size = (sizeof(*rec) + ext->record_size + 3) & ~3;
		for (i = 0; i < hdr->size; i += record_size) {
			rec = CONST_PTR_OFFSET(data, i);

			if (i + record_size > hdr->size)
				break;
			if (!notify_ext_rec(inotify, rec->uid))
				break;
		}
		break;
	}
	}
	return 1;
}

static int
mailbox_list_inotify_entry_guid_cmp(const struct mailbox_list_inotify_entry *r1,
				    const struct mailbox_list_inotify_entry *r2)
{
	int ret;

	ret = memcmp(r1->guid, r2->guid, sizeof(r1->guid));
	if (ret != 0)
		return ret;

	if (r1->expunge == r2->expunge) {
		/* this really shouldn't happen */
		return 0;
	}
	return r1->expunge ? -1 : 1;
}

static void
mailbox_list_index_notify_find_renames(struct mailbox_list_notify_index *inotify)
{
	ARRAY(struct mailbox_list_inotify_entry) entries;
	struct mailbox_status status;
	struct mailbox_list_notify_rename *rename;
	struct mailbox_list_inotify_entry *entry;
	const struct mailbox_list_inotify_entry *e;
	unsigned int i, count;
	guid_128_t guid;
	uint32_t uid;

	/* first get all of the added and expunged GUIDs */
	t_array_init(&entries, array_count(&inotify->new_uids) +
		     array_count(&inotify->expunged_uids));
	while (seq_range_array_iter_nth(&inotify->expunged_uids_iter,
					inotify->expunged_uids_n++, &uid)) {
		if (notify_lookup_guid(inotify, inotify->old_view, uid,
				       0, &status, guid) != NULL &&
		    !guid_128_is_empty(guid)) {
			entry = array_append_space(&entries);
			entry->uid = uid;
			entry->expunge = TRUE;
			memcpy(entry->guid, guid, sizeof(entry->guid));
		}
	}

	(void)mailbox_list_index_parse(inotify->notify.list,
				       inotify->view, TRUE);
	while (seq_range_array_iter_nth(&inotify->new_uids_iter,
					inotify->new_uids_n++, &uid)) {
		if (notify_lookup_guid(inotify, inotify->view, uid,
				       0, &status, guid) != NULL &&
		    !guid_128_is_empty(guid)) {
			entry = array_append_space(&entries);
			entry->uid = uid;
			memcpy(entry->guid, guid, sizeof(entry->guid));
		}
	}

	/* now sort the entries by GUID and find those that have been both
	   added and expunged */
	array_sort(&entries, mailbox_list_inotify_entry_guid_cmp);

	e = array_get(&entries, &count);
	for (i = 1; i < count; i++) {
		if (e[i-1].expunge && !e[i].expunge &&
		    memcmp(e[i-1].guid, e[i].guid, sizeof(e[i].guid)) == 0) {
			rename = array_append_space(&inotify->renames);
			rename->old_uid = e[i-1].uid;
			rename->new_uid = e[i].uid;

			seq_range_array_remove(&inotify->expunged_uids,
					       rename->old_uid);
			seq_range_array_remove(&inotify->new_uids,
					       rename->new_uid);
		}
	}
}

static void
mailbox_list_index_notify_find_subscribes(struct mailbox_list_notify_index *inotify)
{
	struct mailbox_tree_iterate_context *old_iter, *new_iter;
	struct mailbox_tree_context *old_tree, *new_tree;
	const char *old_path = NULL, *new_path = NULL;
	pool_t pool;
	int ret;

	if (mailbox_list_iter_subscriptions_refresh(inotify->notify.list) < 0)
		return;
	mailbox_tree_sort(inotify->notify.list->subscriptions);

	old_tree = inotify->subscriptions;
	new_tree = mailbox_tree_dup(inotify->notify.list->subscriptions);

	old_iter = mailbox_tree_iterate_init(old_tree, NULL, MAILBOX_SUBSCRIBED);
	new_iter = mailbox_tree_iterate_init(new_tree, NULL, MAILBOX_SUBSCRIBED);

	pool = mailbox_tree_get_pool(new_tree);
	for (;;) {
		if (old_path == NULL) {
			if (mailbox_tree_iterate_next(old_iter, &old_path) == NULL)
				old_path = NULL;
		}
		if (new_path == NULL) {
			if (mailbox_tree_iterate_next(new_iter, &new_path) == NULL)
				new_path = NULL;
		}

		if (old_path == NULL) {
			if (new_path == NULL)
				break;
			ret = 1;
		} else if (new_path == NULL)
			ret = -1;
		else {
			ret = strcmp(old_path, new_path);
		}

		if (ret == 0) {
			old_path = NULL;
			new_path = NULL;
		} else if (ret > 0) {
			new_path = p_strdup(pool, new_path);
			array_append(&inotify->new_subscriptions, &new_path, 1);
			new_path = NULL;
		} else {
			old_path = p_strdup(pool, old_path);
			array_append(&inotify->new_unsubscriptions, &old_path, 1);
			old_path = NULL;
		}
	}
	mailbox_tree_iterate_deinit(&old_iter);
	mailbox_tree_iterate_deinit(&new_iter);

	mailbox_tree_deinit(&inotify->subscriptions);
	inotify->subscriptions = new_tree;
}

static void
mailbox_list_index_notify_reset_iters(struct mailbox_list_notify_index *inotify)
{
	seq_range_array_iter_init(&inotify->new_uids_iter,
				  &inotify->new_uids);
	seq_range_array_iter_init(&inotify->expunged_uids_iter,
				  &inotify->expunged_uids);
	seq_range_array_iter_init(&inotify->changed_uids_iter,
				  &inotify->changed_uids);
	inotify->changed_uids_n = 0;
	inotify->new_uids_n = 0;
	inotify->expunged_uids_n = 0;
	inotify->rename_idx = 0;
	inotify->subscription_idx = 0;
	inotify->unsubscription_idx = 0;
}

static void
mailbox_list_index_notify_read_init(struct mailbox_list_notify_index *inotify)
{
	bool b;
	int ret;

	mailbox_list_index_notify_sync_init(inotify);

	/* read all changes from .log file */
	while ((ret = mailbox_list_index_notify_read_next(inotify)) > 0) ;
	inotify->read_failed = ret < 0;

	(void)mail_index_view_sync_commit(&inotify->sync_ctx, &b);

	/* remove changes for already deleted mailboxes */
	seq_range_array_remove_seq_range(&inotify->new_uids,
					 &inotify->expunged_uids);
	seq_range_array_remove_seq_range(&inotify->changed_uids,
					 &inotify->expunged_uids);
	mailbox_list_index_notify_reset_iters(inotify);
	if (array_count(&inotify->new_uids) > 0 &&
	    array_count(&inotify->expunged_uids) > 0) {
		mailbox_list_index_notify_find_renames(inotify);
		mailbox_list_index_notify_reset_iters(inotify);
	}
	if (inotify->subscriptions != NULL)
		mailbox_list_index_notify_find_subscribes(inotify);

	inotify->initialized = TRUE;
}

static void
mailbox_list_index_notify_read_deinit(struct mailbox_list_notify_index *inotify)
{
	/* save the old view so we can look up expunged records */
	mail_index_view_close(&inotify->old_view);
	inotify->old_view = mail_index_view_dup_private(inotify->view);

	array_clear(&inotify->new_subscriptions);
	array_clear(&inotify->new_unsubscriptions);
	array_clear(&inotify->new_uids);
	array_clear(&inotify->expunged_uids);
	array_clear(&inotify->changed_uids);
	array_clear(&inotify->renames);

	inotify->initialized = FALSE;
}

static bool
mailbox_list_index_notify_lookup(struct mailbox_list_notify_index *inotify,
				 struct mail_index_view *view,
				 uint32_t uid, enum mailbox_status_items items,
				 struct mailbox_status *status_r,
				 struct mailbox_list_notify_rec **rec_r)
{
	struct mailbox_list_notify_rec *rec = &inotify->notify_rec;
	struct mailbox_list_index_node *index_node;
	const char *storage_name;
	char ns_sep = mailbox_list_get_hierarchy_sep(inotify->notify.list);

	memset(rec, 0, sizeof(*rec));
	index_node = notify_lookup_guid(inotify, view, uid,
					items, status_r, rec->guid);
	if (index_node == NULL)
		return FALSE;

	/* get storage_name */
	str_truncate(inotify->rec_name, 0);
	mailbox_list_index_node_get_path(index_node, ns_sep, inotify->rec_name);
	storage_name = str_c(inotify->rec_name);

	rec->storage_name = storage_name;
	rec->vname = mailbox_list_get_vname(inotify->notify.list,
					    rec->storage_name);
	*rec_r = rec;
	return TRUE;
}

static bool
mailbox_list_index_notify_rename(struct mailbox_list_notify_index *inotify,
				 unsigned int idx)
{
	const struct mailbox_list_notify_rename *rename;
	struct mailbox_list_notify_rec *rec;
	struct mailbox_status status;
	const char *old_vname;

	rename = array_idx(&inotify->renames, idx);

	/* lookup the old name */
	if (!mailbox_list_index_notify_lookup(inotify, inotify->old_view,
					      rename->old_uid, 0, &status, &rec))
		return FALSE;
	old_vname = t_strdup(rec->vname);

	/* return using the new name */
	if (!mailbox_list_index_notify_lookup(inotify, inotify->view,
					      rename->new_uid, 0, &status, &rec))
		return FALSE;

	rec->old_vname = old_vname;
	rec->events = MAILBOX_LIST_NOTIFY_RENAME;
	return TRUE;
}

static bool
mailbox_list_index_notify_subscribe(struct mailbox_list_notify_index *inotify,
				    unsigned int idx)
{
	struct mailbox_list_notify_rec *rec = &inotify->notify_rec;
	const char *const *vnamep;

	memset(rec, 0, sizeof(*rec));
	vnamep = array_idx(&inotify->new_subscriptions, idx);
	rec->vname = *vnamep;
	rec->storage_name = mailbox_list_get_storage_name(inotify->notify.list,
							  rec->vname);
	rec->events = MAILBOX_LIST_NOTIFY_SUBSCRIBE;
	return TRUE;
}

static bool
mailbox_list_index_notify_unsubscribe(struct mailbox_list_notify_index *inotify,
				      unsigned int idx)
{
	struct mailbox_list_notify_rec *rec = &inotify->notify_rec;
	const char *const *vnamep;

	memset(rec, 0, sizeof(*rec));
	vnamep = array_idx(&inotify->new_unsubscriptions, idx);
	rec->vname = *vnamep;
	rec->storage_name = mailbox_list_get_storage_name(inotify->notify.list,
							  rec->vname);
	rec->events = MAILBOX_LIST_NOTIFY_UNSUBSCRIBE;
	return TRUE;
}

static bool
mailbox_list_index_notify_expunge(struct mailbox_list_notify_index *inotify,
				  uint32_t uid)
{
	struct mailbox_list_notify_rec *rec;
	struct mailbox_status status;

	if (!mailbox_list_index_notify_lookup(inotify, inotify->old_view,
					      uid, 0, &status, &rec))
		return FALSE;
	rec->events = MAILBOX_LIST_NOTIFY_DELETE;
	return TRUE;
}

static bool
mailbox_list_index_notify_new(struct mailbox_list_notify_index *inotify,
			      uint32_t uid)
{
	struct mailbox_list_notify_rec *rec;
	struct mailbox_status status;

	if (!mailbox_list_index_notify_lookup(inotify, inotify->view,
					      uid, 0, &status, &rec))
		i_unreached();
	rec->events = MAILBOX_LIST_NOTIFY_CREATE;
	return TRUE;
}

static bool
mailbox_list_index_notify_change(struct mailbox_list_notify_index *inotify,
				 uint32_t uid)
{
	const enum mailbox_status_items status_items =
		STATUS_UIDVALIDITY | STATUS_UIDNEXT | STATUS_MESSAGES |
		STATUS_UNSEEN | STATUS_HIGHESTMODSEQ;
	struct mailbox_list_notify_rec *rec;
	struct mailbox_notify_node *nnode, empty_node;
	struct mailbox_status status;

	if (!mailbox_list_index_notify_lookup(inotify, inotify->view,
					      uid, status_items, &status, &rec))
		i_unreached();

	/* get the old status */
	nnode = mailbox_list_notify_tree_lookup(inotify->tree,
						rec->storage_name);
	if (nnode == NULL) {
		/* mailbox didn't exist earlier - report all events as new */
		memset(&empty_node, 0, sizeof(empty_node));
		nnode = &empty_node;
	}
	if (nnode->uidvalidity != status.uidvalidity)
		rec->events |= MAILBOX_LIST_NOTIFY_UIDVALIDITY;
	if (nnode->uidnext != status.uidnext)
		rec->events |= MAILBOX_LIST_NOTIFY_APPENDS;
	if (nnode->messages > status.messages) {
		/* NOTE: not entirely reliable, since there could be both
		   expunges and appends.. but it shouldn't make any difference
		   in practise, since anybody interested in expunges is most
		   likely also interested in appends. */
		rec->events |= MAILBOX_LIST_NOTIFY_EXPUNGES;
	}
	if (nnode->unseen != status.unseen)
		rec->events |= MAILBOX_LIST_NOTIFY_SEEN_CHANGES;
	if (nnode->highest_modseq < status.highest_modseq)
		rec->events |= MAILBOX_LIST_NOTIFY_MODSEQ_CHANGES;
	else {
		/* nothing changed */
		return FALSE;
	}

	/* update internal state */
	nnode->uidvalidity = status.uidvalidity;
	nnode->uidnext = status.uidnext;
	nnode->messages = status.messages;
	nnode->unseen = status.unseen;
	nnode->highest_modseq = status.highest_modseq;
	return TRUE;
}

static bool
mailbox_list_index_notify_try_next(struct mailbox_list_notify_index *inotify)
{
	uint32_t uid;

	/* first show mailbox deletes */
	if (seq_range_array_iter_nth(&inotify->expunged_uids_iter,
				     inotify->expunged_uids_n++, &uid))
		return mailbox_list_index_notify_expunge(inotify, uid);

	/* mailbox renames */
	if (inotify->rename_idx < array_count(&inotify->renames)) {
		return mailbox_list_index_notify_rename(inotify,
							inotify->rename_idx++);
	}

	/* next mailbox creates */
	if (seq_range_array_iter_nth(&inotify->new_uids_iter,
				     inotify->new_uids_n++, &uid))
		return mailbox_list_index_notify_new(inotify, uid);

	/* subscribes */
	if (inotify->subscription_idx < array_count(&inotify->new_subscriptions)) {
		return mailbox_list_index_notify_subscribe(inotify,
					inotify->subscription_idx++);
	}
	if (inotify->unsubscription_idx < array_count(&inotify->new_unsubscriptions)) {
		return mailbox_list_index_notify_unsubscribe(inotify,
					inotify->unsubscription_idx++);
	}

	/* STATUS updates */
	while (seq_range_array_iter_nth(&inotify->changed_uids_iter,
					inotify->changed_uids_n++, &uid)) {
		if (mailbox_list_index_notify_change(inotify, uid))
			return TRUE;
	}
	return FALSE;
}

int mailbox_list_index_notify_next(struct mailbox_list_notify *notify,
				   const struct mailbox_list_notify_rec **rec_r)
{
	struct mailbox_list_notify_index *inotify =
		(struct mailbox_list_notify_index *)notify;

	if (!inotify->initialized)
		mailbox_list_index_notify_read_init(inotify);
	if (mailbox_list_index_handle_corruption(notify->list) < 0)
		return -1;

	while (mailbox_list_index_notify_try_next(inotify)) {
		if ((inotify->notify_rec.events & inotify->notify.mask) != 0) {
			*rec_r = &inotify->notify_rec;
			return 1;
		} else {
			/* caller doesn't care about this change */
		}
	}
	if (inotify->inbox_event_pending) {
		inotify->inbox_event_pending = FALSE;
		memset(&inotify->notify_rec, 0, sizeof(inotify->notify_rec));
		inotify->notify_rec.vname = "INBOX";
		inotify->notify_rec.storage_name = "INBOX";
		/* Don't bother trying to figure out which event exactly this
		   is. Just send them all and let the caller handle it. */
		inotify->notify_rec.events = MAILBOX_LIST_NOTIFY_APPENDS |
			MAILBOX_LIST_NOTIFY_EXPUNGES |
			MAILBOX_LIST_NOTIFY_SEEN_CHANGES |
			MAILBOX_LIST_NOTIFY_MODSEQ_CHANGES;
		*rec_r = &inotify->notify_rec;
		return 1;
	}

	mailbox_list_index_notify_read_deinit(inotify);
	return inotify->read_failed ? -1 : 0;
}

static void notify_now_callback(struct mailbox_list_notify_index *inotify)
{
	timeout_remove(&inotify->to_notify);
	inotify->wait_callback(inotify->wait_context);
}

static void notify_callback(struct mailbox_list_notify_index *inotify)
{
#define INOTIFY_ST_CHANGED(last_st, prev_st) \
	((last_st).st_mtime != (prev_st).st_mtime || \
	 ST_MTIME_NSEC(last_st) != ST_MTIME_NSEC(prev_st) || \
	 (last_st).st_size != (prev_st).st_size || \
	 (last_st).st_ino != (prev_st).st_ino)
	struct stat list_prev_st = inotify->list_last_st;
	struct stat inbox_prev_st = inotify->inbox_last_st;
			 
	notify_update_stat(inotify);
	if (INOTIFY_ST_CHANGED(inotify->inbox_last_st, inbox_prev_st))
		inotify->inbox_event_pending = TRUE;
	if (inotify->inbox_event_pending ||
	    INOTIFY_ST_CHANGED(inotify->list_last_st, list_prev_st)) {
		/* log has changed. call the callback with a small delay
		   to allow bundling multiple changes together */
		if (inotify->to_notify != NULL) {
			/* already doing this */
			return;
		}
		inotify->to_notify =
			timeout_add_short(NOTIFY_DELAY_MSECS,
					  notify_now_callback, inotify);
	}
}

void mailbox_list_index_notify_wait(struct mailbox_list_notify *notify,
				    void (*callback)(void *context),
				    void *context)
{
	struct mailbox_list_notify_index *inotify =
		(struct mailbox_list_notify_index *)notify;
	unsigned int check_interval;

	inotify->wait_callback = callback;
	inotify->wait_context = context;

	if (callback == NULL) {
		if (inotify->io_wait != NULL)
			io_remove(&inotify->io_wait);
		if (inotify->io_wait_inbox != NULL)
			io_remove(&inotify->io_wait_inbox);
		if (inotify->to_wait != NULL)
			timeout_remove(&inotify->to_wait);
		if (inotify->to_notify != NULL)
			timeout_remove(&inotify->to_notify);
	} else if (inotify->to_wait == NULL) {
		(void)io_add_notify(inotify->list_log_path, notify_callback,
				    inotify, &inotify->io_wait);
		/* we need to check for INBOX explicitly, because INBOX changes
		   don't get added to mailbox.list.index.log */
		if (inotify->inbox_log_path != NULL) {
			(void)io_add_notify(inotify->inbox_log_path,
					    notify_callback, inotify,
					    &inotify->io_wait_inbox);
		}
		/* check with timeout as well, in case io_add_notify()
		   doesn't work (e.g. NFS) */
		check_interval = notify->list->mail_set->mailbox_idle_check_interval;
		i_assert(check_interval > 0);
		inotify->to_wait = timeout_add(check_interval * 1000,
					       notify_callback, inotify);
		notify_update_stat(inotify);
	}
}